420 lines
11 KiB
C
420 lines
11 KiB
C
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// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/sched.h>
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#include <linux/sched/task.h>
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#include <linux/sched/task_stack.h>
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#include <linux/interrupt.h>
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#include <asm/sections.h>
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#include <asm/ptrace.h>
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#include <asm/bitops.h>
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#include <asm/stacktrace.h>
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#include <asm/unwind.h>
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#define FRAME_HEADER_SIZE (sizeof(long) * 2)
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unsigned long unwind_get_return_address(struct unwind_state *state)
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{
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if (unwind_done(state))
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return 0;
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return __kernel_text_address(state->ip) ? state->ip : 0;
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}
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EXPORT_SYMBOL_GPL(unwind_get_return_address);
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unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
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{
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if (unwind_done(state))
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return NULL;
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return state->regs ? &state->regs->ip : state->bp + 1;
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}
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static void unwind_dump(struct unwind_state *state)
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{
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static bool dumped_before = false;
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bool prev_zero, zero = false;
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unsigned long word, *sp;
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struct stack_info stack_info = {0};
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unsigned long visit_mask = 0;
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if (dumped_before)
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return;
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dumped_before = true;
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printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n",
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state->stack_info.type, state->stack_info.next_sp,
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state->stack_mask, state->graph_idx);
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for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp;
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sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
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if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
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break;
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for (; sp < stack_info.end; sp++) {
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word = READ_ONCE_NOCHECK(*sp);
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prev_zero = zero;
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zero = word == 0;
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if (zero) {
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if (!prev_zero)
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printk_deferred("%p: %0*x ...\n",
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sp, BITS_PER_LONG/4, 0);
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continue;
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}
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printk_deferred("%p: %0*lx (%pB)\n",
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sp, BITS_PER_LONG/4, word, (void *)word);
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}
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}
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}
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static bool in_entry_code(unsigned long ip)
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{
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char *addr = (char *)ip;
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return addr >= __entry_text_start && addr < __entry_text_end;
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}
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static inline unsigned long *last_frame(struct unwind_state *state)
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{
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return (unsigned long *)task_pt_regs(state->task) - 2;
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}
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static bool is_last_frame(struct unwind_state *state)
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{
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return state->bp == last_frame(state);
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}
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#ifdef CONFIG_X86_32
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#define GCC_REALIGN_WORDS 3
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#else
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#define GCC_REALIGN_WORDS 1
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#endif
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static inline unsigned long *last_aligned_frame(struct unwind_state *state)
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{
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return last_frame(state) - GCC_REALIGN_WORDS;
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}
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static bool is_last_aligned_frame(struct unwind_state *state)
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{
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unsigned long *last_bp = last_frame(state);
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unsigned long *aligned_bp = last_aligned_frame(state);
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/*
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* GCC can occasionally decide to realign the stack pointer and change
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* the offset of the stack frame in the prologue of a function called
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* by head/entry code. Examples:
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*
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* <start_secondary>:
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* push %edi
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* lea 0x8(%esp),%edi
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* and $0xfffffff8,%esp
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* pushl -0x4(%edi)
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* push %ebp
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* mov %esp,%ebp
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*
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* <x86_64_start_kernel>:
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* lea 0x8(%rsp),%r10
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* and $0xfffffffffffffff0,%rsp
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* pushq -0x8(%r10)
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* push %rbp
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* mov %rsp,%rbp
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*
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* After aligning the stack, it pushes a duplicate copy of the return
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* address before pushing the frame pointer.
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*/
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return (state->bp == aligned_bp && *(aligned_bp + 1) == *(last_bp + 1));
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}
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static bool is_last_ftrace_frame(struct unwind_state *state)
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{
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unsigned long *last_bp = last_frame(state);
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unsigned long *last_ftrace_bp = last_bp - 3;
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/*
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* When unwinding from an ftrace handler of a function called by entry
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* code, the stack layout of the last frame is:
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*
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* bp
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* parent ret addr
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* bp
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* function ret addr
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* parent ret addr
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* pt_regs
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* -----------------
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*/
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return (state->bp == last_ftrace_bp &&
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*state->bp == *(state->bp + 2) &&
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*(state->bp + 1) == *(state->bp + 4));
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}
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static bool is_last_task_frame(struct unwind_state *state)
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{
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return is_last_frame(state) || is_last_aligned_frame(state) ||
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is_last_ftrace_frame(state);
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}
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/*
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* This determines if the frame pointer actually contains an encoded pointer to
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* pt_regs on the stack. See ENCODE_FRAME_POINTER.
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*/
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#ifdef CONFIG_X86_64
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static struct pt_regs *decode_frame_pointer(unsigned long *bp)
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{
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unsigned long regs = (unsigned long)bp;
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if (!(regs & 0x1))
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return NULL;
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return (struct pt_regs *)(regs & ~0x1);
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}
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#else
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static struct pt_regs *decode_frame_pointer(unsigned long *bp)
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{
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unsigned long regs = (unsigned long)bp;
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if (regs & 0x80000000)
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return NULL;
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return (struct pt_regs *)(regs | 0x80000000);
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}
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#endif
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/*
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* While walking the stack, KMSAN may stomp on stale locals from other
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* functions that were marked as uninitialized upon function exit, and
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* now hold the call frame information for the current function (e.g. the frame
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* pointer). Because KMSAN does not specifically mark call frames as
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* initialized, false positive reports are possible. To prevent such reports,
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* we mark the functions scanning the stack (here and below) with
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* __no_kmsan_checks.
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*/
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__no_kmsan_checks
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static bool update_stack_state(struct unwind_state *state,
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unsigned long *next_bp)
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{
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struct stack_info *info = &state->stack_info;
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enum stack_type prev_type = info->type;
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struct pt_regs *regs;
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unsigned long *frame, *prev_frame_end, *addr_p, addr;
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size_t len;
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if (state->regs)
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prev_frame_end = (void *)state->regs + sizeof(*state->regs);
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else
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prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE;
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/* Is the next frame pointer an encoded pointer to pt_regs? */
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regs = decode_frame_pointer(next_bp);
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if (regs) {
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frame = (unsigned long *)regs;
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len = sizeof(*regs);
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state->got_irq = true;
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} else {
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frame = next_bp;
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len = FRAME_HEADER_SIZE;
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}
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/*
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* If the next bp isn't on the current stack, switch to the next one.
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*
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* We may have to traverse multiple stacks to deal with the possibility
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* that info->next_sp could point to an empty stack and the next bp
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* could be on a subsequent stack.
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*/
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while (!on_stack(info, frame, len))
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if (get_stack_info(info->next_sp, state->task, info,
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&state->stack_mask))
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return false;
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/* Make sure it only unwinds up and doesn't overlap the prev frame: */
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if (state->orig_sp && state->stack_info.type == prev_type &&
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frame < prev_frame_end)
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return false;
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/* Move state to the next frame: */
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if (regs) {
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state->regs = regs;
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state->bp = NULL;
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} else {
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state->bp = next_bp;
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state->regs = NULL;
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}
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/* Save the return address: */
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if (state->regs && user_mode(state->regs))
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state->ip = 0;
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else {
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addr_p = unwind_get_return_address_ptr(state);
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addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
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state->ip = unwind_recover_ret_addr(state, addr, addr_p);
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}
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/* Save the original stack pointer for unwind_dump(): */
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if (!state->orig_sp)
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state->orig_sp = frame;
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return true;
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}
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__no_kmsan_checks
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bool unwind_next_frame(struct unwind_state *state)
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{
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struct pt_regs *regs;
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unsigned long *next_bp;
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if (unwind_done(state))
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return false;
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/* Have we reached the end? */
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if (state->regs && user_mode(state->regs))
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goto the_end;
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if (is_last_task_frame(state)) {
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regs = task_pt_regs(state->task);
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/*
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* kthreads (other than the boot CPU's idle thread) have some
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* partial regs at the end of their stack which were placed
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* there by copy_thread(). But the regs don't have any
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* useful information, so we can skip them.
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*
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* This user_mode() check is slightly broader than a PF_KTHREAD
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* check because it also catches the awkward situation where a
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* newly forked kthread transitions into a user task by calling
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* kernel_execve(), which eventually clears PF_KTHREAD.
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*/
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if (!user_mode(regs))
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goto the_end;
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/*
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* We're almost at the end, but not quite: there's still the
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* syscall regs frame. Entry code doesn't encode the regs
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* pointer for syscalls, so we have to set it manually.
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*/
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state->regs = regs;
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state->bp = NULL;
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state->ip = 0;
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return true;
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}
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/* Get the next frame pointer: */
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if (state->next_bp) {
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next_bp = state->next_bp;
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state->next_bp = NULL;
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} else if (state->regs) {
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next_bp = (unsigned long *)state->regs->bp;
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} else {
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next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp);
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}
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/* Move to the next frame if it's safe: */
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if (!update_stack_state(state, next_bp))
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goto bad_address;
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return true;
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bad_address:
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state->error = true;
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/*
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* When unwinding a non-current task, the task might actually be
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* running on another CPU, in which case it could be modifying its
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* stack while we're reading it. This is generally not a problem and
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* can be ignored as long as the caller understands that unwinding
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* another task will not always succeed.
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*/
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if (state->task != current)
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goto the_end;
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/*
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* Don't warn if the unwinder got lost due to an interrupt in entry
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* code or in the C handler before the first frame pointer got set up:
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*/
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if (state->got_irq && in_entry_code(state->ip))
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goto the_end;
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if (state->regs &&
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state->regs->sp >= (unsigned long)last_aligned_frame(state) &&
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state->regs->sp < (unsigned long)task_pt_regs(state->task))
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goto the_end;
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/*
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* There are some known frame pointer issues on 32-bit. Disable
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* unwinder warnings on 32-bit until it gets objtool support.
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*/
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if (IS_ENABLED(CONFIG_X86_32))
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goto the_end;
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if (state->task != current)
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goto the_end;
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if (state->regs) {
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printk_deferred_once(KERN_WARNING
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"WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
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state->regs, state->task->comm,
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state->task->pid, next_bp);
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unwind_dump(state);
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} else {
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printk_deferred_once(KERN_WARNING
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"WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n",
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state->bp, state->task->comm,
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state->task->pid, next_bp);
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unwind_dump(state);
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}
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the_end:
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state->stack_info.type = STACK_TYPE_UNKNOWN;
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return false;
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}
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EXPORT_SYMBOL_GPL(unwind_next_frame);
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void __unwind_start(struct unwind_state *state, struct task_struct *task,
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struct pt_regs *regs, unsigned long *first_frame)
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{
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unsigned long *bp;
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memset(state, 0, sizeof(*state));
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state->task = task;
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state->got_irq = (regs);
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/* Don't even attempt to start from user mode regs: */
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if (regs && user_mode(regs)) {
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||
|
|
state->stack_info.type = STACK_TYPE_UNKNOWN;
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
bp = get_frame_pointer(task, regs);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* If we crash with IP==0, the last successfully executed instruction
|
||
|
|
* was probably an indirect function call with a NULL function pointer.
|
||
|
|
* That means that SP points into the middle of an incomplete frame:
|
||
|
|
* *SP is a return pointer, and *(SP-sizeof(unsigned long)) is where we
|
||
|
|
* would have written a frame pointer if we hadn't crashed.
|
||
|
|
* Pretend that the frame is complete and that BP points to it, but save
|
||
|
|
* the real BP so that we can use it when looking for the next frame.
|
||
|
|
*/
|
||
|
|
if (regs && regs->ip == 0 && (unsigned long *)regs->sp >= first_frame) {
|
||
|
|
state->next_bp = bp;
|
||
|
|
bp = ((unsigned long *)regs->sp) - 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Initialize stack info and make sure the frame data is accessible: */
|
||
|
|
get_stack_info(bp, state->task, &state->stack_info,
|
||
|
|
&state->stack_mask);
|
||
|
|
update_stack_state(state, bp);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* The caller can provide the address of the first frame directly
|
||
|
|
* (first_frame) or indirectly (regs->sp) to indicate which stack frame
|
||
|
|
* to start unwinding at. Skip ahead until we reach it.
|
||
|
|
*/
|
||
|
|
while (!unwind_done(state) &&
|
||
|
|
(!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
|
||
|
|
(state->next_bp == NULL && state->bp < first_frame)))
|
||
|
|
unwind_next_frame(state);
|
||
|
|
}
|
||
|
|
EXPORT_SYMBOL_GPL(__unwind_start);
|