1370 lines
48 KiB
C
1370 lines
48 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* KCSAN core runtime.
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*
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* Copyright (C) 2019, Google LLC.
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*/
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#define pr_fmt(fmt) "kcsan: " fmt
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#include <linux/atomic.h>
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#include <linux/bug.h>
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#include <linux/delay.h>
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#include <linux/export.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/minmax.h>
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#include <linux/moduleparam.h>
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#include <linux/percpu.h>
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#include <linux/preempt.h>
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#include <linux/sched.h>
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#include <linux/string.h>
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#include <linux/uaccess.h>
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#include "encoding.h"
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#include "kcsan.h"
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#include "permissive.h"
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static bool kcsan_early_enable = IS_ENABLED(CONFIG_KCSAN_EARLY_ENABLE);
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unsigned int kcsan_udelay_task = CONFIG_KCSAN_UDELAY_TASK;
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unsigned int kcsan_udelay_interrupt = CONFIG_KCSAN_UDELAY_INTERRUPT;
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static long kcsan_skip_watch = CONFIG_KCSAN_SKIP_WATCH;
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static bool kcsan_interrupt_watcher = IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER);
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#ifdef MODULE_PARAM_PREFIX
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#undef MODULE_PARAM_PREFIX
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#endif
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#define MODULE_PARAM_PREFIX "kcsan."
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module_param_named(early_enable, kcsan_early_enable, bool, 0);
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module_param_named(udelay_task, kcsan_udelay_task, uint, 0644);
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module_param_named(udelay_interrupt, kcsan_udelay_interrupt, uint, 0644);
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module_param_named(skip_watch, kcsan_skip_watch, long, 0644);
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module_param_named(interrupt_watcher, kcsan_interrupt_watcher, bool, 0444);
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#ifdef CONFIG_KCSAN_WEAK_MEMORY
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static bool kcsan_weak_memory = true;
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module_param_named(weak_memory, kcsan_weak_memory, bool, 0644);
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#else
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#define kcsan_weak_memory false
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#endif
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bool kcsan_enabled;
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/* Per-CPU kcsan_ctx for interrupts */
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static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
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.scoped_accesses = {LIST_POISON1, NULL},
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};
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/*
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* Helper macros to index into adjacent slots, starting from address slot
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* itself, followed by the right and left slots.
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*
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* The purpose is 2-fold:
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*
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* 1. if during insertion the address slot is already occupied, check if
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* any adjacent slots are free;
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* 2. accesses that straddle a slot boundary due to size that exceeds a
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* slot's range may check adjacent slots if any watchpoint matches.
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*
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* Note that accesses with very large size may still miss a watchpoint; however,
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* given this should be rare, this is a reasonable trade-off to make, since this
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* will avoid:
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*
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* 1. excessive contention between watchpoint checks and setup;
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* 2. larger number of simultaneous watchpoints without sacrificing
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* performance.
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*
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* Example: SLOT_IDX values for KCSAN_CHECK_ADJACENT=1, where i is [0, 1, 2]:
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*
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* slot=0: [ 1, 2, 0]
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* slot=9: [10, 11, 9]
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* slot=63: [64, 65, 63]
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*/
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#define SLOT_IDX(slot, i) (slot + ((i + KCSAN_CHECK_ADJACENT) % NUM_SLOTS))
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/*
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* SLOT_IDX_FAST is used in the fast-path. Not first checking the address's primary
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* slot (middle) is fine if we assume that races occur rarely. The set of
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* indices {SLOT_IDX(slot, i) | i in [0, NUM_SLOTS)} is equivalent to
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* {SLOT_IDX_FAST(slot, i) | i in [0, NUM_SLOTS)}.
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*/
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#define SLOT_IDX_FAST(slot, i) (slot + i)
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/*
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* Watchpoints, with each entry encoded as defined in encoding.h: in order to be
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* able to safely update and access a watchpoint without introducing locking
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* overhead, we encode each watchpoint as a single atomic long. The initial
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* zero-initialized state matches INVALID_WATCHPOINT.
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*
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* Add NUM_SLOTS-1 entries to account for overflow; this helps avoid having to
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* use more complicated SLOT_IDX_FAST calculation with modulo in the fast-path.
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*/
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static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1];
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/*
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* Instructions to skip watching counter, used in should_watch(). We use a
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* per-CPU counter to avoid excessive contention.
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*/
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static DEFINE_PER_CPU(long, kcsan_skip);
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/* For kcsan_prandom_u32_max(). */
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static DEFINE_PER_CPU(u32, kcsan_rand_state);
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static __always_inline atomic_long_t *find_watchpoint(unsigned long addr,
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size_t size,
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bool expect_write,
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long *encoded_watchpoint)
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{
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const int slot = watchpoint_slot(addr);
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const unsigned long addr_masked = addr & WATCHPOINT_ADDR_MASK;
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atomic_long_t *watchpoint;
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unsigned long wp_addr_masked;
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size_t wp_size;
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bool is_write;
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int i;
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BUILD_BUG_ON(CONFIG_KCSAN_NUM_WATCHPOINTS < NUM_SLOTS);
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for (i = 0; i < NUM_SLOTS; ++i) {
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watchpoint = &watchpoints[SLOT_IDX_FAST(slot, i)];
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*encoded_watchpoint = atomic_long_read(watchpoint);
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if (!decode_watchpoint(*encoded_watchpoint, &wp_addr_masked,
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&wp_size, &is_write))
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continue;
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if (expect_write && !is_write)
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continue;
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/* Check if the watchpoint matches the access. */
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if (matching_access(wp_addr_masked, wp_size, addr_masked, size))
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return watchpoint;
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}
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return NULL;
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}
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static inline atomic_long_t *
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insert_watchpoint(unsigned long addr, size_t size, bool is_write)
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{
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const int slot = watchpoint_slot(addr);
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const long encoded_watchpoint = encode_watchpoint(addr, size, is_write);
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atomic_long_t *watchpoint;
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int i;
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/* Check slot index logic, ensuring we stay within array bounds. */
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BUILD_BUG_ON(SLOT_IDX(0, 0) != KCSAN_CHECK_ADJACENT);
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BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT+1) != 0);
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BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT) != ARRAY_SIZE(watchpoints)-1);
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BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT+1) != ARRAY_SIZE(watchpoints) - NUM_SLOTS);
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for (i = 0; i < NUM_SLOTS; ++i) {
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long expect_val = INVALID_WATCHPOINT;
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/* Try to acquire this slot. */
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watchpoint = &watchpoints[SLOT_IDX(slot, i)];
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if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val, encoded_watchpoint))
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return watchpoint;
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}
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return NULL;
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}
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/*
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* Return true if watchpoint was successfully consumed, false otherwise.
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*
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* This may return false if:
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*
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* 1. another thread already consumed the watchpoint;
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* 2. the thread that set up the watchpoint already removed it;
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* 3. the watchpoint was removed and then re-used.
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*/
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static __always_inline bool
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try_consume_watchpoint(atomic_long_t *watchpoint, long encoded_watchpoint)
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{
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return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint, CONSUMED_WATCHPOINT);
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}
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/* Return true if watchpoint was not touched, false if already consumed. */
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static inline bool consume_watchpoint(atomic_long_t *watchpoint)
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{
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return atomic_long_xchg_relaxed(watchpoint, CONSUMED_WATCHPOINT) != CONSUMED_WATCHPOINT;
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}
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/* Remove the watchpoint -- its slot may be reused after. */
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static inline void remove_watchpoint(atomic_long_t *watchpoint)
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{
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atomic_long_set(watchpoint, INVALID_WATCHPOINT);
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}
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static __always_inline struct kcsan_ctx *get_ctx(void)
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{
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/*
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* In interrupts, use raw_cpu_ptr to avoid unnecessary checks, that would
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* also result in calls that generate warnings in uaccess regions.
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*/
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return in_task() ? ¤t->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx);
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}
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static __always_inline void
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check_access(const volatile void *ptr, size_t size, int type, unsigned long ip);
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/* Check scoped accesses; never inline because this is a slow-path! */
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static noinline void kcsan_check_scoped_accesses(void)
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{
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struct kcsan_ctx *ctx = get_ctx();
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struct kcsan_scoped_access *scoped_access;
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if (ctx->disable_scoped)
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return;
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ctx->disable_scoped++;
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list_for_each_entry(scoped_access, &ctx->scoped_accesses, list) {
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check_access(scoped_access->ptr, scoped_access->size,
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scoped_access->type, scoped_access->ip);
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}
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ctx->disable_scoped--;
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}
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/* Rules for generic atomic accesses. Called from fast-path. */
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static __always_inline bool
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is_atomic(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size, int type)
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{
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if (type & KCSAN_ACCESS_ATOMIC)
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return true;
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/*
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* Unless explicitly declared atomic, never consider an assertion access
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* as atomic. This allows using them also in atomic regions, such as
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* seqlocks, without implicitly changing their semantics.
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*/
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if (type & KCSAN_ACCESS_ASSERT)
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return false;
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if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) &&
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(type & KCSAN_ACCESS_WRITE) && size <= sizeof(long) &&
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!(type & KCSAN_ACCESS_COMPOUND) && IS_ALIGNED((unsigned long)ptr, size))
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return true; /* Assume aligned writes up to word size are atomic. */
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if (ctx->atomic_next > 0) {
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/*
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* Because we do not have separate contexts for nested
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* interrupts, in case atomic_next is set, we simply assume that
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* the outer interrupt set atomic_next. In the worst case, we
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* will conservatively consider operations as atomic. This is a
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* reasonable trade-off to make, since this case should be
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* extremely rare; however, even if extremely rare, it could
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* lead to false positives otherwise.
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*/
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if ((hardirq_count() >> HARDIRQ_SHIFT) < 2)
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--ctx->atomic_next; /* in task, or outer interrupt */
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return true;
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}
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return ctx->atomic_nest_count > 0 || ctx->in_flat_atomic;
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}
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static __always_inline bool
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should_watch(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size, int type)
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{
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/*
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* Never set up watchpoints when memory operations are atomic.
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*
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* Need to check this first, before kcsan_skip check below: (1) atomics
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* should not count towards skipped instructions, and (2) to actually
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* decrement kcsan_atomic_next for consecutive instruction stream.
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*/
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if (is_atomic(ctx, ptr, size, type))
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return false;
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if (this_cpu_dec_return(kcsan_skip) >= 0)
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return false;
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/*
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* NOTE: If we get here, kcsan_skip must always be reset in slow path
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* via reset_kcsan_skip() to avoid underflow.
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*/
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/* this operation should be watched */
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return true;
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}
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/*
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* Returns a pseudo-random number in interval [0, ep_ro). Simple linear
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* congruential generator, using constants from "Numerical Recipes".
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*/
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static u32 kcsan_prandom_u32_max(u32 ep_ro)
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{
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u32 state = this_cpu_read(kcsan_rand_state);
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state = 1664525 * state + 1013904223;
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this_cpu_write(kcsan_rand_state, state);
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return state % ep_ro;
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}
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static inline void reset_kcsan_skip(void)
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{
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long skip_count = kcsan_skip_watch -
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(IS_ENABLED(CONFIG_KCSAN_SKIP_WATCH_RANDOMIZE) ?
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kcsan_prandom_u32_max(kcsan_skip_watch) :
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0);
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this_cpu_write(kcsan_skip, skip_count);
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}
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static __always_inline bool kcsan_is_enabled(struct kcsan_ctx *ctx)
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{
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return READ_ONCE(kcsan_enabled) && !ctx->disable_count;
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}
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/* Introduce delay depending on context and configuration. */
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static void delay_access(int type)
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{
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unsigned int delay = in_task() ? kcsan_udelay_task : kcsan_udelay_interrupt;
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/* For certain access types, skew the random delay to be longer. */
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unsigned int skew_delay_order =
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(type & (KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_ASSERT)) ? 1 : 0;
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delay -= IS_ENABLED(CONFIG_KCSAN_DELAY_RANDOMIZE) ?
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kcsan_prandom_u32_max(delay >> skew_delay_order) :
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0;
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udelay(delay);
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}
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/*
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* Reads the instrumented memory for value change detection; value change
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* detection is currently done for accesses up to a size of 8 bytes.
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*/
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static __always_inline u64 read_instrumented_memory(const volatile void *ptr, size_t size)
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{
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/*
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* In the below we don't necessarily need the read of the location to
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* be atomic, and we don't use READ_ONCE(), since all we need for race
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* detection is to observe 2 different values.
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*
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* Furthermore, on certain architectures (such as arm64), READ_ONCE()
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* may turn into more complex instructions than a plain load that cannot
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* do unaligned accesses.
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*/
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switch (size) {
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case 1: return *(const volatile u8 *)ptr;
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case 2: return *(const volatile u16 *)ptr;
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case 4: return *(const volatile u32 *)ptr;
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case 8: return *(const volatile u64 *)ptr;
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default: return 0; /* Ignore; we do not diff the values. */
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}
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}
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void kcsan_save_irqtrace(struct task_struct *task)
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{
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#ifdef CONFIG_TRACE_IRQFLAGS
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task->kcsan_save_irqtrace = task->irqtrace;
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#endif
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}
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void kcsan_restore_irqtrace(struct task_struct *task)
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{
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#ifdef CONFIG_TRACE_IRQFLAGS
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task->irqtrace = task->kcsan_save_irqtrace;
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#endif
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}
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static __always_inline int get_kcsan_stack_depth(void)
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{
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#ifdef CONFIG_KCSAN_WEAK_MEMORY
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return current->kcsan_stack_depth;
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#else
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BUILD_BUG();
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return 0;
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#endif
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}
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static __always_inline void add_kcsan_stack_depth(int val)
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{
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#ifdef CONFIG_KCSAN_WEAK_MEMORY
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current->kcsan_stack_depth += val;
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#else
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BUILD_BUG();
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#endif
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}
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static __always_inline struct kcsan_scoped_access *get_reorder_access(struct kcsan_ctx *ctx)
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{
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#ifdef CONFIG_KCSAN_WEAK_MEMORY
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return ctx->disable_scoped ? NULL : &ctx->reorder_access;
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#else
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return NULL;
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#endif
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}
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static __always_inline bool
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find_reorder_access(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size,
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int type, unsigned long ip)
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{
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struct kcsan_scoped_access *reorder_access = get_reorder_access(ctx);
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if (!reorder_access)
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return false;
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/*
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* Note: If accesses are repeated while reorder_access is identical,
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* never matches the new access, because !(type & KCSAN_ACCESS_SCOPED).
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*/
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return reorder_access->ptr == ptr && reorder_access->size == size &&
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reorder_access->type == type && reorder_access->ip == ip;
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}
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static inline void
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set_reorder_access(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size,
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int type, unsigned long ip)
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{
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struct kcsan_scoped_access *reorder_access = get_reorder_access(ctx);
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if (!reorder_access || !kcsan_weak_memory)
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return;
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/*
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* To avoid nested interrupts or scheduler (which share kcsan_ctx)
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* reading an inconsistent reorder_access, ensure that the below has
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* exclusive access to reorder_access by disallowing concurrent use.
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*/
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ctx->disable_scoped++;
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barrier();
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reorder_access->ptr = ptr;
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reorder_access->size = size;
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reorder_access->type = type | KCSAN_ACCESS_SCOPED;
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reorder_access->ip = ip;
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reorder_access->stack_depth = get_kcsan_stack_depth();
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barrier();
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ctx->disable_scoped--;
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}
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/*
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* Pull everything together: check_access() below contains the performance
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* critical operations; the fast-path (including check_access) functions should
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* all be inlinable by the instrumentation functions.
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*
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* The slow-path (kcsan_found_watchpoint, kcsan_setup_watchpoint) are
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* non-inlinable -- note that, we prefix these with "kcsan_" to ensure they can
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* be filtered from the stacktrace, as well as give them unique names for the
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* UACCESS whitelist of objtool. Each function uses user_access_save/restore(),
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* since they do not access any user memory, but instrumentation is still
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* emitted in UACCESS regions.
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*/
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static noinline void kcsan_found_watchpoint(const volatile void *ptr,
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size_t size,
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int type,
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unsigned long ip,
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atomic_long_t *watchpoint,
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long encoded_watchpoint)
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{
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const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
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struct kcsan_ctx *ctx = get_ctx();
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unsigned long flags;
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bool consumed;
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/*
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* We know a watchpoint exists. Let's try to keep the race-window
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* between here and finally consuming the watchpoint below as small as
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* possible -- avoid unneccessarily complex code until consumed.
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*/
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if (!kcsan_is_enabled(ctx))
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return;
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/*
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* The access_mask check relies on value-change comparison. To avoid
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* reporting a race where e.g. the writer set up the watchpoint, but the
|
|
* reader has access_mask!=0, we have to ignore the found watchpoint.
|
|
*
|
|
* reorder_access is never created from an access with access_mask set.
|
|
*/
|
|
if (ctx->access_mask && !find_reorder_access(ctx, ptr, size, type, ip))
|
|
return;
|
|
|
|
/*
|
|
* If the other thread does not want to ignore the access, and there was
|
|
* a value change as a result of this thread's operation, we will still
|
|
* generate a report of unknown origin.
|
|
*
|
|
* Use CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN=n to filter.
|
|
*/
|
|
if (!is_assert && kcsan_ignore_address(ptr))
|
|
return;
|
|
|
|
/*
|
|
* Consuming the watchpoint must be guarded by kcsan_is_enabled() to
|
|
* avoid erroneously triggering reports if the context is disabled.
|
|
*/
|
|
consumed = try_consume_watchpoint(watchpoint, encoded_watchpoint);
|
|
|
|
/* keep this after try_consume_watchpoint */
|
|
flags = user_access_save();
|
|
|
|
if (consumed) {
|
|
kcsan_save_irqtrace(current);
|
|
kcsan_report_set_info(ptr, size, type, ip, watchpoint - watchpoints);
|
|
kcsan_restore_irqtrace(current);
|
|
} else {
|
|
/*
|
|
* The other thread may not print any diagnostics, as it has
|
|
* already removed the watchpoint, or another thread consumed
|
|
* the watchpoint before this thread.
|
|
*/
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_REPORT_RACES]);
|
|
}
|
|
|
|
if (is_assert)
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
|
|
else
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_DATA_RACES]);
|
|
|
|
user_access_restore(flags);
|
|
}
|
|
|
|
static noinline void
|
|
kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned long ip)
|
|
{
|
|
const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
|
|
const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
|
|
atomic_long_t *watchpoint;
|
|
u64 old, new, diff;
|
|
enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE;
|
|
bool interrupt_watcher = kcsan_interrupt_watcher;
|
|
unsigned long ua_flags = user_access_save();
|
|
struct kcsan_ctx *ctx = get_ctx();
|
|
unsigned long access_mask = ctx->access_mask;
|
|
unsigned long irq_flags = 0;
|
|
bool is_reorder_access;
|
|
|
|
/*
|
|
* Always reset kcsan_skip counter in slow-path to avoid underflow; see
|
|
* should_watch().
|
|
*/
|
|
reset_kcsan_skip();
|
|
|
|
if (!kcsan_is_enabled(ctx))
|
|
goto out;
|
|
|
|
/*
|
|
* Check to-ignore addresses after kcsan_is_enabled(), as we may access
|
|
* memory that is not yet initialized during early boot.
|
|
*/
|
|
if (!is_assert && kcsan_ignore_address(ptr))
|
|
goto out;
|
|
|
|
if (!check_encodable((unsigned long)ptr, size)) {
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_UNENCODABLE_ACCESSES]);
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* The local CPU cannot observe reordering of its own accesses, and
|
|
* therefore we need to take care of 2 cases to avoid false positives:
|
|
*
|
|
* 1. Races of the reordered access with interrupts. To avoid, if
|
|
* the current access is reorder_access, disable interrupts.
|
|
* 2. Avoid races of scoped accesses from nested interrupts (below).
|
|
*/
|
|
is_reorder_access = find_reorder_access(ctx, ptr, size, type, ip);
|
|
if (is_reorder_access)
|
|
interrupt_watcher = false;
|
|
/*
|
|
* Avoid races of scoped accesses from nested interrupts (or scheduler).
|
|
* Assume setting up a watchpoint for a non-scoped (normal) access that
|
|
* also conflicts with a current scoped access. In a nested interrupt,
|
|
* which shares the context, it would check a conflicting scoped access.
|
|
* To avoid, disable scoped access checking.
|
|
*/
|
|
ctx->disable_scoped++;
|
|
|
|
/*
|
|
* Save and restore the IRQ state trace touched by KCSAN, since KCSAN's
|
|
* runtime is entered for every memory access, and potentially useful
|
|
* information is lost if dirtied by KCSAN.
|
|
*/
|
|
kcsan_save_irqtrace(current);
|
|
if (!interrupt_watcher)
|
|
local_irq_save(irq_flags);
|
|
|
|
watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
|
|
if (watchpoint == NULL) {
|
|
/*
|
|
* Out of capacity: the size of 'watchpoints', and the frequency
|
|
* with which should_watch() returns true should be tweaked so
|
|
* that this case happens very rarely.
|
|
*/
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_NO_CAPACITY]);
|
|
goto out_unlock;
|
|
}
|
|
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_SETUP_WATCHPOINTS]);
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
|
|
|
|
/*
|
|
* Read the current value, to later check and infer a race if the data
|
|
* was modified via a non-instrumented access, e.g. from a device.
|
|
*/
|
|
old = is_reorder_access ? 0 : read_instrumented_memory(ptr, size);
|
|
|
|
/*
|
|
* Delay this thread, to increase probability of observing a racy
|
|
* conflicting access.
|
|
*/
|
|
delay_access(type);
|
|
|
|
/*
|
|
* Re-read value, and check if it is as expected; if not, we infer a
|
|
* racy access.
|
|
*/
|
|
if (!is_reorder_access) {
|
|
new = read_instrumented_memory(ptr, size);
|
|
} else {
|
|
/*
|
|
* Reordered accesses cannot be used for value change detection,
|
|
* because the memory location may no longer be accessible and
|
|
* could result in a fault.
|
|
*/
|
|
new = 0;
|
|
access_mask = 0;
|
|
}
|
|
|
|
diff = old ^ new;
|
|
if (access_mask)
|
|
diff &= access_mask;
|
|
|
|
/*
|
|
* Check if we observed a value change.
|
|
*
|
|
* Also check if the data race should be ignored (the rules depend on
|
|
* non-zero diff); if it is to be ignored, the below rules for
|
|
* KCSAN_VALUE_CHANGE_MAYBE apply.
|
|
*/
|
|
if (diff && !kcsan_ignore_data_race(size, type, old, new, diff))
|
|
value_change = KCSAN_VALUE_CHANGE_TRUE;
|
|
|
|
/* Check if this access raced with another. */
|
|
if (!consume_watchpoint(watchpoint)) {
|
|
/*
|
|
* Depending on the access type, map a value_change of MAYBE to
|
|
* TRUE (always report) or FALSE (never report).
|
|
*/
|
|
if (value_change == KCSAN_VALUE_CHANGE_MAYBE) {
|
|
if (access_mask != 0) {
|
|
/*
|
|
* For access with access_mask, we require a
|
|
* value-change, as it is likely that races on
|
|
* ~access_mask bits are expected.
|
|
*/
|
|
value_change = KCSAN_VALUE_CHANGE_FALSE;
|
|
} else if (size > 8 || is_assert) {
|
|
/* Always assume a value-change. */
|
|
value_change = KCSAN_VALUE_CHANGE_TRUE;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* No need to increment 'data_races' counter, as the racing
|
|
* thread already did.
|
|
*
|
|
* Count 'assert_failures' for each failed ASSERT access,
|
|
* therefore both this thread and the racing thread may
|
|
* increment this counter.
|
|
*/
|
|
if (is_assert && value_change == KCSAN_VALUE_CHANGE_TRUE)
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
|
|
|
|
kcsan_report_known_origin(ptr, size, type, ip,
|
|
value_change, watchpoint - watchpoints,
|
|
old, new, access_mask);
|
|
} else if (value_change == KCSAN_VALUE_CHANGE_TRUE) {
|
|
/* Inferring a race, since the value should not have changed. */
|
|
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN]);
|
|
if (is_assert)
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
|
|
|
|
if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert) {
|
|
kcsan_report_unknown_origin(ptr, size, type, ip,
|
|
old, new, access_mask);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Remove watchpoint; must be after reporting, since the slot may be
|
|
* reused after this point.
|
|
*/
|
|
remove_watchpoint(watchpoint);
|
|
atomic_long_dec(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
|
|
|
|
out_unlock:
|
|
if (!interrupt_watcher)
|
|
local_irq_restore(irq_flags);
|
|
kcsan_restore_irqtrace(current);
|
|
ctx->disable_scoped--;
|
|
|
|
/*
|
|
* Reordered accesses cannot be used for value change detection,
|
|
* therefore never consider for reordering if access_mask is set.
|
|
* ASSERT_EXCLUSIVE are not real accesses, ignore them as well.
|
|
*/
|
|
if (!access_mask && !is_assert)
|
|
set_reorder_access(ctx, ptr, size, type, ip);
|
|
out:
|
|
user_access_restore(ua_flags);
|
|
}
|
|
|
|
static __always_inline void
|
|
check_access(const volatile void *ptr, size_t size, int type, unsigned long ip)
|
|
{
|
|
atomic_long_t *watchpoint;
|
|
long encoded_watchpoint;
|
|
|
|
/*
|
|
* Do nothing for 0 sized check; this comparison will be optimized out
|
|
* for constant sized instrumentation (__tsan_{read,write}N).
|
|
*/
|
|
if (unlikely(size == 0))
|
|
return;
|
|
|
|
again:
|
|
/*
|
|
* Avoid user_access_save in fast-path: find_watchpoint is safe without
|
|
* user_access_save, as the address that ptr points to is only used to
|
|
* check if a watchpoint exists; ptr is never dereferenced.
|
|
*/
|
|
watchpoint = find_watchpoint((unsigned long)ptr, size,
|
|
!(type & KCSAN_ACCESS_WRITE),
|
|
&encoded_watchpoint);
|
|
/*
|
|
* It is safe to check kcsan_is_enabled() after find_watchpoint in the
|
|
* slow-path, as long as no state changes that cause a race to be
|
|
* detected and reported have occurred until kcsan_is_enabled() is
|
|
* checked.
|
|
*/
|
|
|
|
if (unlikely(watchpoint != NULL))
|
|
kcsan_found_watchpoint(ptr, size, type, ip, watchpoint, encoded_watchpoint);
|
|
else {
|
|
struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */
|
|
|
|
if (unlikely(should_watch(ctx, ptr, size, type))) {
|
|
kcsan_setup_watchpoint(ptr, size, type, ip);
|
|
return;
|
|
}
|
|
|
|
if (!(type & KCSAN_ACCESS_SCOPED)) {
|
|
struct kcsan_scoped_access *reorder_access = get_reorder_access(ctx);
|
|
|
|
if (reorder_access) {
|
|
/*
|
|
* reorder_access check: simulates reordering of
|
|
* the access after subsequent operations.
|
|
*/
|
|
ptr = reorder_access->ptr;
|
|
type = reorder_access->type;
|
|
ip = reorder_access->ip;
|
|
/*
|
|
* Upon a nested interrupt, this context's
|
|
* reorder_access can be modified (shared ctx).
|
|
* We know that upon return, reorder_access is
|
|
* always invalidated by setting size to 0 via
|
|
* __tsan_func_exit(). Therefore we must read
|
|
* and check size after the other fields.
|
|
*/
|
|
barrier();
|
|
size = READ_ONCE(reorder_access->size);
|
|
if (size)
|
|
goto again;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Always checked last, right before returning from runtime;
|
|
* if reorder_access is valid, checked after it was checked.
|
|
*/
|
|
if (unlikely(ctx->scoped_accesses.prev))
|
|
kcsan_check_scoped_accesses();
|
|
}
|
|
}
|
|
|
|
/* === Public interface ===================================================== */
|
|
|
|
void __init kcsan_init(void)
|
|
{
|
|
int cpu;
|
|
|
|
BUG_ON(!in_task());
|
|
|
|
for_each_possible_cpu(cpu)
|
|
per_cpu(kcsan_rand_state, cpu) = (u32)get_cycles();
|
|
|
|
/*
|
|
* We are in the init task, and no other tasks should be running;
|
|
* WRITE_ONCE without memory barrier is sufficient.
|
|
*/
|
|
if (kcsan_early_enable) {
|
|
pr_info("enabled early\n");
|
|
WRITE_ONCE(kcsan_enabled, true);
|
|
}
|
|
|
|
if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) ||
|
|
IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) ||
|
|
IS_ENABLED(CONFIG_KCSAN_PERMISSIVE) ||
|
|
IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) {
|
|
pr_warn("non-strict mode configured - use CONFIG_KCSAN_STRICT=y to see all data races\n");
|
|
} else {
|
|
pr_info("strict mode configured\n");
|
|
}
|
|
}
|
|
|
|
/* === Exported interface =================================================== */
|
|
|
|
void kcsan_disable_current(void)
|
|
{
|
|
++get_ctx()->disable_count;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_disable_current);
|
|
|
|
void kcsan_enable_current(void)
|
|
{
|
|
if (get_ctx()->disable_count-- == 0) {
|
|
/*
|
|
* Warn if kcsan_enable_current() calls are unbalanced with
|
|
* kcsan_disable_current() calls, which causes disable_count to
|
|
* become negative and should not happen.
|
|
*/
|
|
kcsan_disable_current(); /* restore to 0, KCSAN still enabled */
|
|
kcsan_disable_current(); /* disable to generate warning */
|
|
WARN(1, "Unbalanced %s()", __func__);
|
|
kcsan_enable_current();
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(kcsan_enable_current);
|
|
|
|
void kcsan_enable_current_nowarn(void)
|
|
{
|
|
if (get_ctx()->disable_count-- == 0)
|
|
kcsan_disable_current();
|
|
}
|
|
EXPORT_SYMBOL(kcsan_enable_current_nowarn);
|
|
|
|
void kcsan_nestable_atomic_begin(void)
|
|
{
|
|
/*
|
|
* Do *not* check and warn if we are in a flat atomic region: nestable
|
|
* and flat atomic regions are independent from each other.
|
|
* See include/linux/kcsan.h: struct kcsan_ctx comments for more
|
|
* comments.
|
|
*/
|
|
|
|
++get_ctx()->atomic_nest_count;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_nestable_atomic_begin);
|
|
|
|
void kcsan_nestable_atomic_end(void)
|
|
{
|
|
if (get_ctx()->atomic_nest_count-- == 0) {
|
|
/*
|
|
* Warn if kcsan_nestable_atomic_end() calls are unbalanced with
|
|
* kcsan_nestable_atomic_begin() calls, which causes
|
|
* atomic_nest_count to become negative and should not happen.
|
|
*/
|
|
kcsan_nestable_atomic_begin(); /* restore to 0 */
|
|
kcsan_disable_current(); /* disable to generate warning */
|
|
WARN(1, "Unbalanced %s()", __func__);
|
|
kcsan_enable_current();
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(kcsan_nestable_atomic_end);
|
|
|
|
void kcsan_flat_atomic_begin(void)
|
|
{
|
|
get_ctx()->in_flat_atomic = true;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_flat_atomic_begin);
|
|
|
|
void kcsan_flat_atomic_end(void)
|
|
{
|
|
get_ctx()->in_flat_atomic = false;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_flat_atomic_end);
|
|
|
|
void kcsan_atomic_next(int n)
|
|
{
|
|
get_ctx()->atomic_next = n;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_atomic_next);
|
|
|
|
void kcsan_set_access_mask(unsigned long mask)
|
|
{
|
|
get_ctx()->access_mask = mask;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_set_access_mask);
|
|
|
|
struct kcsan_scoped_access *
|
|
kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type,
|
|
struct kcsan_scoped_access *sa)
|
|
{
|
|
struct kcsan_ctx *ctx = get_ctx();
|
|
|
|
check_access(ptr, size, type, _RET_IP_);
|
|
|
|
ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
|
|
|
|
INIT_LIST_HEAD(&sa->list);
|
|
sa->ptr = ptr;
|
|
sa->size = size;
|
|
sa->type = type;
|
|
sa->ip = _RET_IP_;
|
|
|
|
if (!ctx->scoped_accesses.prev) /* Lazy initialize list head. */
|
|
INIT_LIST_HEAD(&ctx->scoped_accesses);
|
|
list_add(&sa->list, &ctx->scoped_accesses);
|
|
|
|
ctx->disable_count--;
|
|
return sa;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_begin_scoped_access);
|
|
|
|
void kcsan_end_scoped_access(struct kcsan_scoped_access *sa)
|
|
{
|
|
struct kcsan_ctx *ctx = get_ctx();
|
|
|
|
if (WARN(!ctx->scoped_accesses.prev, "Unbalanced %s()?", __func__))
|
|
return;
|
|
|
|
ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
|
|
|
|
list_del(&sa->list);
|
|
if (list_empty(&ctx->scoped_accesses))
|
|
/*
|
|
* Ensure we do not enter kcsan_check_scoped_accesses()
|
|
* slow-path if unnecessary, and avoids requiring list_empty()
|
|
* in the fast-path (to avoid a READ_ONCE() and potential
|
|
* uaccess warning).
|
|
*/
|
|
ctx->scoped_accesses.prev = NULL;
|
|
|
|
ctx->disable_count--;
|
|
|
|
check_access(sa->ptr, sa->size, sa->type, sa->ip);
|
|
}
|
|
EXPORT_SYMBOL(kcsan_end_scoped_access);
|
|
|
|
void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
|
|
{
|
|
check_access(ptr, size, type, _RET_IP_);
|
|
}
|
|
EXPORT_SYMBOL(__kcsan_check_access);
|
|
|
|
#define DEFINE_MEMORY_BARRIER(name, order_before_cond) \
|
|
void __kcsan_##name(void) \
|
|
{ \
|
|
struct kcsan_scoped_access *sa = get_reorder_access(get_ctx()); \
|
|
if (!sa) \
|
|
return; \
|
|
if (order_before_cond) \
|
|
sa->size = 0; \
|
|
} \
|
|
EXPORT_SYMBOL(__kcsan_##name)
|
|
|
|
DEFINE_MEMORY_BARRIER(mb, true);
|
|
DEFINE_MEMORY_BARRIER(wmb, sa->type & (KCSAN_ACCESS_WRITE | KCSAN_ACCESS_COMPOUND));
|
|
DEFINE_MEMORY_BARRIER(rmb, !(sa->type & KCSAN_ACCESS_WRITE) || (sa->type & KCSAN_ACCESS_COMPOUND));
|
|
DEFINE_MEMORY_BARRIER(release, true);
|
|
|
|
/*
|
|
* KCSAN uses the same instrumentation that is emitted by supported compilers
|
|
* for ThreadSanitizer (TSAN).
|
|
*
|
|
* When enabled, the compiler emits instrumentation calls (the functions
|
|
* prefixed with "__tsan" below) for all loads and stores that it generated;
|
|
* inline asm is not instrumented.
|
|
*
|
|
* Note that, not all supported compiler versions distinguish aligned/unaligned
|
|
* accesses, but e.g. recent versions of Clang do. We simply alias the unaligned
|
|
* version to the generic version, which can handle both.
|
|
*/
|
|
|
|
#define DEFINE_TSAN_READ_WRITE(size) \
|
|
void __tsan_read##size(void *ptr); \
|
|
void __tsan_read##size(void *ptr) \
|
|
{ \
|
|
check_access(ptr, size, 0, _RET_IP_); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_read##size); \
|
|
void __tsan_unaligned_read##size(void *ptr) \
|
|
__alias(__tsan_read##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_read##size); \
|
|
void __tsan_write##size(void *ptr); \
|
|
void __tsan_write##size(void *ptr) \
|
|
{ \
|
|
check_access(ptr, size, KCSAN_ACCESS_WRITE, _RET_IP_); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_write##size); \
|
|
void __tsan_unaligned_write##size(void *ptr) \
|
|
__alias(__tsan_write##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_write##size); \
|
|
void __tsan_read_write##size(void *ptr); \
|
|
void __tsan_read_write##size(void *ptr) \
|
|
{ \
|
|
check_access(ptr, size, \
|
|
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE, \
|
|
_RET_IP_); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_read_write##size); \
|
|
void __tsan_unaligned_read_write##size(void *ptr) \
|
|
__alias(__tsan_read_write##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_read_write##size)
|
|
|
|
DEFINE_TSAN_READ_WRITE(1);
|
|
DEFINE_TSAN_READ_WRITE(2);
|
|
DEFINE_TSAN_READ_WRITE(4);
|
|
DEFINE_TSAN_READ_WRITE(8);
|
|
DEFINE_TSAN_READ_WRITE(16);
|
|
|
|
void __tsan_read_range(void *ptr, size_t size);
|
|
void __tsan_read_range(void *ptr, size_t size)
|
|
{
|
|
check_access(ptr, size, 0, _RET_IP_);
|
|
}
|
|
EXPORT_SYMBOL(__tsan_read_range);
|
|
|
|
void __tsan_write_range(void *ptr, size_t size);
|
|
void __tsan_write_range(void *ptr, size_t size)
|
|
{
|
|
check_access(ptr, size, KCSAN_ACCESS_WRITE, _RET_IP_);
|
|
}
|
|
EXPORT_SYMBOL(__tsan_write_range);
|
|
|
|
/*
|
|
* Use of explicit volatile is generally disallowed [1], however, volatile is
|
|
* still used in various concurrent context, whether in low-level
|
|
* synchronization primitives or for legacy reasons.
|
|
* [1] https://lwn.net/Articles/233479/
|
|
*
|
|
* We only consider volatile accesses atomic if they are aligned and would pass
|
|
* the size-check of compiletime_assert_rwonce_type().
|
|
*/
|
|
#define DEFINE_TSAN_VOLATILE_READ_WRITE(size) \
|
|
void __tsan_volatile_read##size(void *ptr); \
|
|
void __tsan_volatile_read##size(void *ptr) \
|
|
{ \
|
|
const bool is_atomic = size <= sizeof(long long) && \
|
|
IS_ALIGNED((unsigned long)ptr, size); \
|
|
if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic) \
|
|
return; \
|
|
check_access(ptr, size, is_atomic ? KCSAN_ACCESS_ATOMIC : 0, \
|
|
_RET_IP_); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_volatile_read##size); \
|
|
void __tsan_unaligned_volatile_read##size(void *ptr) \
|
|
__alias(__tsan_volatile_read##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_volatile_read##size); \
|
|
void __tsan_volatile_write##size(void *ptr); \
|
|
void __tsan_volatile_write##size(void *ptr) \
|
|
{ \
|
|
const bool is_atomic = size <= sizeof(long long) && \
|
|
IS_ALIGNED((unsigned long)ptr, size); \
|
|
if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic) \
|
|
return; \
|
|
check_access(ptr, size, \
|
|
KCSAN_ACCESS_WRITE | \
|
|
(is_atomic ? KCSAN_ACCESS_ATOMIC : 0), \
|
|
_RET_IP_); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_volatile_write##size); \
|
|
void __tsan_unaligned_volatile_write##size(void *ptr) \
|
|
__alias(__tsan_volatile_write##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_volatile_write##size)
|
|
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(1);
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(2);
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(4);
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(8);
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(16);
|
|
|
|
/*
|
|
* Function entry and exit are used to determine the validty of reorder_access.
|
|
* Reordering of the access ends at the end of the function scope where the
|
|
* access happened. This is done for two reasons:
|
|
*
|
|
* 1. Artificially limits the scope where missing barriers are detected.
|
|
* This minimizes false positives due to uninstrumented functions that
|
|
* contain the required barriers but were missed.
|
|
*
|
|
* 2. Simplifies generating the stack trace of the access.
|
|
*/
|
|
void __tsan_func_entry(void *call_pc);
|
|
noinline void __tsan_func_entry(void *call_pc)
|
|
{
|
|
if (!IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
|
|
return;
|
|
|
|
add_kcsan_stack_depth(1);
|
|
}
|
|
EXPORT_SYMBOL(__tsan_func_entry);
|
|
|
|
void __tsan_func_exit(void);
|
|
noinline void __tsan_func_exit(void)
|
|
{
|
|
struct kcsan_scoped_access *reorder_access;
|
|
|
|
if (!IS_ENABLED(CONFIG_KCSAN_WEAK_MEMORY))
|
|
return;
|
|
|
|
reorder_access = get_reorder_access(get_ctx());
|
|
if (!reorder_access)
|
|
goto out;
|
|
|
|
if (get_kcsan_stack_depth() <= reorder_access->stack_depth) {
|
|
/*
|
|
* Access check to catch cases where write without a barrier
|
|
* (supposed release) was last access in function: because
|
|
* instrumentation is inserted before the real access, a data
|
|
* race due to the write giving up a c-s would only be caught if
|
|
* we do the conflicting access after.
|
|
*/
|
|
check_access(reorder_access->ptr, reorder_access->size,
|
|
reorder_access->type, reorder_access->ip);
|
|
reorder_access->size = 0;
|
|
reorder_access->stack_depth = INT_MIN;
|
|
}
|
|
out:
|
|
add_kcsan_stack_depth(-1);
|
|
}
|
|
EXPORT_SYMBOL(__tsan_func_exit);
|
|
|
|
void __tsan_init(void);
|
|
void __tsan_init(void)
|
|
{
|
|
}
|
|
EXPORT_SYMBOL(__tsan_init);
|
|
|
|
/*
|
|
* Instrumentation for atomic builtins (__atomic_*, __sync_*).
|
|
*
|
|
* Normal kernel code _should not_ be using them directly, but some
|
|
* architectures may implement some or all atomics using the compilers'
|
|
* builtins.
|
|
*
|
|
* Note: If an architecture decides to fully implement atomics using the
|
|
* builtins, because they are implicitly instrumented by KCSAN (and KASAN,
|
|
* etc.), implementing the ARCH_ATOMIC interface (to get instrumentation via
|
|
* atomic-instrumented) is no longer necessary.
|
|
*
|
|
* TSAN instrumentation replaces atomic accesses with calls to any of the below
|
|
* functions, whose job is to also execute the operation itself.
|
|
*/
|
|
|
|
static __always_inline void kcsan_atomic_builtin_memorder(int memorder)
|
|
{
|
|
if (memorder == __ATOMIC_RELEASE ||
|
|
memorder == __ATOMIC_SEQ_CST ||
|
|
memorder == __ATOMIC_ACQ_REL)
|
|
__kcsan_release();
|
|
}
|
|
|
|
#define DEFINE_TSAN_ATOMIC_LOAD_STORE(bits) \
|
|
u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder); \
|
|
u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder) \
|
|
{ \
|
|
kcsan_atomic_builtin_memorder(memorder); \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC, _RET_IP_); \
|
|
} \
|
|
return __atomic_load_n(ptr, memorder); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_load); \
|
|
void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder); \
|
|
void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder) \
|
|
{ \
|
|
kcsan_atomic_builtin_memorder(memorder); \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, \
|
|
KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC, _RET_IP_); \
|
|
} \
|
|
__atomic_store_n(ptr, v, memorder); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_store)
|
|
|
|
#define DEFINE_TSAN_ATOMIC_RMW(op, bits, suffix) \
|
|
u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder); \
|
|
u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder) \
|
|
{ \
|
|
kcsan_atomic_builtin_memorder(memorder); \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, \
|
|
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
|
|
KCSAN_ACCESS_ATOMIC, _RET_IP_); \
|
|
} \
|
|
return __atomic_##op##suffix(ptr, v, memorder); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_##op)
|
|
|
|
/*
|
|
* Note: CAS operations are always classified as write, even in case they
|
|
* fail. We cannot perform check_access() after a write, as it might lead to
|
|
* false positives, in cases such as:
|
|
*
|
|
* T0: __atomic_compare_exchange_n(&p->flag, &old, 1, ...)
|
|
*
|
|
* T1: if (__atomic_load_n(&p->flag, ...)) {
|
|
* modify *p;
|
|
* p->flag = 0;
|
|
* }
|
|
*
|
|
* The only downside is that, if there are 3 threads, with one CAS that
|
|
* succeeds, another CAS that fails, and an unmarked racing operation, we may
|
|
* point at the wrong CAS as the source of the race. However, if we assume that
|
|
* all CAS can succeed in some other execution, the data race is still valid.
|
|
*/
|
|
#define DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strength, weak) \
|
|
int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp, \
|
|
u##bits val, int mo, int fail_mo); \
|
|
int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp, \
|
|
u##bits val, int mo, int fail_mo) \
|
|
{ \
|
|
kcsan_atomic_builtin_memorder(mo); \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, \
|
|
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
|
|
KCSAN_ACCESS_ATOMIC, _RET_IP_); \
|
|
} \
|
|
return __atomic_compare_exchange_n(ptr, exp, val, weak, mo, fail_mo); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_##strength)
|
|
|
|
#define DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits) \
|
|
u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
|
|
int mo, int fail_mo); \
|
|
u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
|
|
int mo, int fail_mo) \
|
|
{ \
|
|
kcsan_atomic_builtin_memorder(mo); \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, \
|
|
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
|
|
KCSAN_ACCESS_ATOMIC, _RET_IP_); \
|
|
} \
|
|
__atomic_compare_exchange_n(ptr, &exp, val, 0, mo, fail_mo); \
|
|
return exp; \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_val)
|
|
|
|
#define DEFINE_TSAN_ATOMIC_OPS(bits) \
|
|
DEFINE_TSAN_ATOMIC_LOAD_STORE(bits); \
|
|
DEFINE_TSAN_ATOMIC_RMW(exchange, bits, _n); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_add, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_sub, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_and, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_or, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_xor, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_nand, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strong, 0); \
|
|
DEFINE_TSAN_ATOMIC_CMPXCHG(bits, weak, 1); \
|
|
DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits)
|
|
|
|
DEFINE_TSAN_ATOMIC_OPS(8);
|
|
DEFINE_TSAN_ATOMIC_OPS(16);
|
|
DEFINE_TSAN_ATOMIC_OPS(32);
|
|
DEFINE_TSAN_ATOMIC_OPS(64);
|
|
|
|
void __tsan_atomic_thread_fence(int memorder);
|
|
void __tsan_atomic_thread_fence(int memorder)
|
|
{
|
|
kcsan_atomic_builtin_memorder(memorder);
|
|
__atomic_thread_fence(memorder);
|
|
}
|
|
EXPORT_SYMBOL(__tsan_atomic_thread_fence);
|
|
|
|
/*
|
|
* In instrumented files, we emit instrumentation for barriers by mapping the
|
|
* kernel barriers to an __atomic_signal_fence(), which is interpreted specially
|
|
* and otherwise has no relation to a real __atomic_signal_fence(). No known
|
|
* kernel code uses __atomic_signal_fence().
|
|
*
|
|
* Since fsanitize=thread instrumentation handles __atomic_signal_fence(), which
|
|
* are turned into calls to __tsan_atomic_signal_fence(), such instrumentation
|
|
* can be disabled via the __no_kcsan function attribute (vs. an explicit call
|
|
* which could not). When __no_kcsan is requested, __atomic_signal_fence()
|
|
* generates no code.
|
|
*
|
|
* Note: The result of using __atomic_signal_fence() with KCSAN enabled is
|
|
* potentially limiting the compiler's ability to reorder operations; however,
|
|
* if barriers were instrumented with explicit calls (without LTO), the compiler
|
|
* couldn't optimize much anyway. The result of a hypothetical architecture
|
|
* using __atomic_signal_fence() in normal code would be KCSAN false negatives.
|
|
*/
|
|
void __tsan_atomic_signal_fence(int memorder);
|
|
noinline void __tsan_atomic_signal_fence(int memorder)
|
|
{
|
|
switch (memorder) {
|
|
case __KCSAN_BARRIER_TO_SIGNAL_FENCE_mb:
|
|
__kcsan_mb();
|
|
break;
|
|
case __KCSAN_BARRIER_TO_SIGNAL_FENCE_wmb:
|
|
__kcsan_wmb();
|
|
break;
|
|
case __KCSAN_BARRIER_TO_SIGNAL_FENCE_rmb:
|
|
__kcsan_rmb();
|
|
break;
|
|
case __KCSAN_BARRIER_TO_SIGNAL_FENCE_release:
|
|
__kcsan_release();
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(__tsan_atomic_signal_fence);
|
|
|
|
#ifdef __HAVE_ARCH_MEMSET
|
|
void *__tsan_memset(void *s, int c, size_t count);
|
|
noinline void *__tsan_memset(void *s, int c, size_t count)
|
|
{
|
|
/*
|
|
* Instead of not setting up watchpoints where accessed size is greater
|
|
* than MAX_ENCODABLE_SIZE, truncate checked size to MAX_ENCODABLE_SIZE.
|
|
*/
|
|
size_t check_len = min_t(size_t, count, MAX_ENCODABLE_SIZE);
|
|
|
|
check_access(s, check_len, KCSAN_ACCESS_WRITE, _RET_IP_);
|
|
return memset(s, c, count);
|
|
}
|
|
#else
|
|
void *__tsan_memset(void *s, int c, size_t count) __alias(memset);
|
|
#endif
|
|
EXPORT_SYMBOL(__tsan_memset);
|
|
|
|
#ifdef __HAVE_ARCH_MEMMOVE
|
|
void *__tsan_memmove(void *dst, const void *src, size_t len);
|
|
noinline void *__tsan_memmove(void *dst, const void *src, size_t len)
|
|
{
|
|
size_t check_len = min_t(size_t, len, MAX_ENCODABLE_SIZE);
|
|
|
|
check_access(dst, check_len, KCSAN_ACCESS_WRITE, _RET_IP_);
|
|
check_access(src, check_len, 0, _RET_IP_);
|
|
return memmove(dst, src, len);
|
|
}
|
|
#else
|
|
void *__tsan_memmove(void *dst, const void *src, size_t len) __alias(memmove);
|
|
#endif
|
|
EXPORT_SYMBOL(__tsan_memmove);
|
|
|
|
#ifdef __HAVE_ARCH_MEMCPY
|
|
void *__tsan_memcpy(void *dst, const void *src, size_t len);
|
|
noinline void *__tsan_memcpy(void *dst, const void *src, size_t len)
|
|
{
|
|
size_t check_len = min_t(size_t, len, MAX_ENCODABLE_SIZE);
|
|
|
|
check_access(dst, check_len, KCSAN_ACCESS_WRITE, _RET_IP_);
|
|
check_access(src, check_len, 0, _RET_IP_);
|
|
return memcpy(dst, src, len);
|
|
}
|
|
#else
|
|
void *__tsan_memcpy(void *dst, const void *src, size_t len) __alias(memcpy);
|
|
#endif
|
|
EXPORT_SYMBOL(__tsan_memcpy);
|