161 lines
3.9 KiB
C
161 lines
3.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2020 SiFive
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*/
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#include <linux/spinlock.h>
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#include <linux/mm.h>
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#include <linux/memory.h>
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#include <linux/uaccess.h>
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#include <linux/stop_machine.h>
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#include <asm/kprobes.h>
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#include <asm/cacheflush.h>
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#include <asm/fixmap.h>
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#include <asm/ftrace.h>
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#include <asm/patch.h>
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struct patch_insn {
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void *addr;
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u32 *insns;
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int ninsns;
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atomic_t cpu_count;
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};
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int riscv_patch_in_stop_machine = false;
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#ifdef CONFIG_MMU
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/*
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* The fix_to_virt(, idx) needs a const value (not a dynamic variable of
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* reg-a0) or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".
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* So use '__always_inline' and 'const unsigned int fixmap' here.
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*/
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static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
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{
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uintptr_t uintaddr = (uintptr_t) addr;
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struct page *page;
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if (core_kernel_text(uintaddr))
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page = phys_to_page(__pa_symbol(addr));
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else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
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page = vmalloc_to_page(addr);
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else
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return addr;
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BUG_ON(!page);
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return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
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(uintaddr & ~PAGE_MASK));
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}
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static void patch_unmap(int fixmap)
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{
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clear_fixmap(fixmap);
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}
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NOKPROBE_SYMBOL(patch_unmap);
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static int patch_insn_write(void *addr, const void *insn, size_t len)
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{
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void *waddr = addr;
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bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE;
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int ret;
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/*
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* Before reaching here, it was expected to lock the text_mutex
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* already, so we don't need to give another lock here and could
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* ensure that it was safe between each cores.
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*
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* We're currently using stop_machine() for ftrace & kprobes, and while
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* that ensures text_mutex is held before installing the mappings it
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* does not ensure text_mutex is held by the calling thread. That's
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* safe but triggers a lockdep failure, so just elide it for that
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* specific case.
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*/
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if (!riscv_patch_in_stop_machine)
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lockdep_assert_held(&text_mutex);
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if (across_pages)
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patch_map(addr + len, FIX_TEXT_POKE1);
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waddr = patch_map(addr, FIX_TEXT_POKE0);
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ret = copy_to_kernel_nofault(waddr, insn, len);
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patch_unmap(FIX_TEXT_POKE0);
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if (across_pages)
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patch_unmap(FIX_TEXT_POKE1);
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return ret;
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}
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NOKPROBE_SYMBOL(patch_insn_write);
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#else
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static int patch_insn_write(void *addr, const void *insn, size_t len)
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{
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return copy_to_kernel_nofault(addr, insn, len);
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}
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NOKPROBE_SYMBOL(patch_insn_write);
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#endif /* CONFIG_MMU */
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int patch_text_nosync(void *addr, const void *insns, size_t len)
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{
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u32 *tp = addr;
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int ret;
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ret = patch_insn_write(tp, insns, len);
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if (!ret)
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flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len);
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return ret;
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}
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NOKPROBE_SYMBOL(patch_text_nosync);
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static int patch_text_cb(void *data)
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{
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struct patch_insn *patch = data;
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unsigned long len;
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int i, ret = 0;
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if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
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for (i = 0; ret == 0 && i < patch->ninsns; i++) {
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len = GET_INSN_LENGTH(patch->insns[i]);
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ret = patch_text_nosync(patch->addr + i * len,
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&patch->insns[i], len);
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}
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atomic_inc(&patch->cpu_count);
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} else {
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while (atomic_read(&patch->cpu_count) <= num_online_cpus())
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cpu_relax();
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smp_mb();
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}
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return ret;
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}
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NOKPROBE_SYMBOL(patch_text_cb);
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int patch_text(void *addr, u32 *insns, int ninsns)
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{
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int ret;
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struct patch_insn patch = {
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.addr = addr,
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.insns = insns,
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.ninsns = ninsns,
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.cpu_count = ATOMIC_INIT(0),
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};
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/*
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* kprobes takes text_mutex, before calling patch_text(), but as we call
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* calls stop_machine(), the lockdep assertion in patch_insn_write()
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* gets confused by the context in which the lock is taken.
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* Instead, ensure the lock is held before calling stop_machine(), and
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* set riscv_patch_in_stop_machine to skip the check in
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* patch_insn_write().
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*/
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lockdep_assert_held(&text_mutex);
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riscv_patch_in_stop_machine = true;
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ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
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riscv_patch_in_stop_machine = false;
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return ret;
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}
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NOKPROBE_SYMBOL(patch_text);
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