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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2020 SiFive
*/
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/memory.h>
#include <linux/uaccess.h>
#include <linux/stop_machine.h>
#include <asm/kprobes.h>
#include <asm/cacheflush.h>
#include <asm/fixmap.h>
#include <asm/ftrace.h>
#include <asm/patch.h>
struct patch_insn {
void *addr;
u32 *insns;
int ninsns;
atomic_t cpu_count;
};
int riscv_patch_in_stop_machine = false;
#ifdef CONFIG_MMU
/*
* The fix_to_virt(, idx) needs a const value (not a dynamic variable of
* reg-a0) or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".
* So use '__always_inline' and 'const unsigned int fixmap' here.
*/
static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
{
uintptr_t uintaddr = (uintptr_t) addr;
struct page *page;
if (core_kernel_text(uintaddr))
page = phys_to_page(__pa_symbol(addr));
else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
page = vmalloc_to_page(addr);
else
return addr;
BUG_ON(!page);
return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
(uintaddr & ~PAGE_MASK));
}
static void patch_unmap(int fixmap)
{
clear_fixmap(fixmap);
}
NOKPROBE_SYMBOL(patch_unmap);
static int __patch_insn_write(void *addr, const void *insn, size_t len)
{
void *waddr = addr;
bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE;
int ret;
/*
* Only two pages can be mapped at a time for writing.
*/
if (len + offset_in_page(addr) > 2 * PAGE_SIZE)
return -EINVAL;
/*
* Before reaching here, it was expected to lock the text_mutex
* already, so we don't need to give another lock here and could
* ensure that it was safe between each cores.
*
* We're currently using stop_machine() for ftrace & kprobes, and while
* that ensures text_mutex is held before installing the mappings it
* does not ensure text_mutex is held by the calling thread. That's
* safe but triggers a lockdep failure, so just elide it for that
* specific case.
*/
if (!riscv_patch_in_stop_machine)
lockdep_assert_held(&text_mutex);
if (across_pages)
patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);
waddr = patch_map(addr, FIX_TEXT_POKE0);
ret = copy_to_kernel_nofault(waddr, insn, len);
patch_unmap(FIX_TEXT_POKE0);
if (across_pages)
patch_unmap(FIX_TEXT_POKE1);
return ret;
}
NOKPROBE_SYMBOL(__patch_insn_write);
#else
static int __patch_insn_write(void *addr, const void *insn, size_t len)
{
return copy_to_kernel_nofault(addr, insn, len);
}
NOKPROBE_SYMBOL(__patch_insn_write);
#endif /* CONFIG_MMU */
static int patch_insn_write(void *addr, const void *insn, size_t len)
{
size_t patched = 0;
size_t size;
int ret = 0;
/*
* Copy the instructions to the destination address, two pages at a time
* because __patch_insn_write() can only handle len <= 2 * PAGE_SIZE.
*/
while (patched < len && !ret) {
size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched);
ret = __patch_insn_write(addr + patched, insn + patched, size);
patched += size;
}
return ret;
}
NOKPROBE_SYMBOL(patch_insn_write);
int patch_text_nosync(void *addr, const void *insns, size_t len)
{
u32 *tp = addr;
int ret;
ret = patch_insn_write(tp, insns, len);
if (!ret)
flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len);
return ret;
}
NOKPROBE_SYMBOL(patch_text_nosync);
static int patch_text_cb(void *data)
{
struct patch_insn *patch = data;
unsigned long len;
int i, ret = 0;
if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
for (i = 0; ret == 0 && i < patch->ninsns; i++) {
len = GET_INSN_LENGTH(patch->insns[i]);
ret = patch_text_nosync(patch->addr + i * len,
&patch->insns[i], len);
}
atomic_inc(&patch->cpu_count);
} else {
while (atomic_read(&patch->cpu_count) <= num_online_cpus())
cpu_relax();
smp_mb();
}
return ret;
}
NOKPROBE_SYMBOL(patch_text_cb);
int patch_text(void *addr, u32 *insns, int ninsns)
{
int ret;
struct patch_insn patch = {
.addr = addr,
.insns = insns,
.ninsns = ninsns,
.cpu_count = ATOMIC_INIT(0),
};
/*
* kprobes takes text_mutex, before calling patch_text(), but as we call
* calls stop_machine(), the lockdep assertion in patch_insn_write()
* gets confused by the context in which the lock is taken.
* Instead, ensure the lock is held before calling stop_machine(), and
* set riscv_patch_in_stop_machine to skip the check in
* patch_insn_write().
*/
lockdep_assert_held(&text_mutex);
riscv_patch_in_stop_machine = true;
ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
riscv_patch_in_stop_machine = false;
return ret;
}
NOKPROBE_SYMBOL(patch_text);
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