0ff7c3b331
We don't need the additional lock protection when patching the text.
There are two patching interfaces here:
- patch_text: patch code and always synchronize with stop_machine()
- patch_text_nosync: patch code without synchronization, it's caller's
responsibility to synchronize all CPUs if needed.
For the first one, stop_machine() is protected by its own mutex, and
also the irq is already disabled here.
For the second one, in risc-v real case now, it would be used to ftrace
patching the mcount function, since it already running under
kstop_machine(), no other thread will run, so we could use text_mutex
on ftrace side.
Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
129 lines
2.6 KiB
C
129 lines
2.6 KiB
C
// 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>
|
|
|
|
struct patch_insn {
|
|
void *addr;
|
|
u32 insn;
|
|
atomic_t cpu_count;
|
|
};
|
|
|
|
#ifdef CONFIG_MMU
|
|
static void *patch_map(void *addr, 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));
|
|
}
|
|
NOKPROBE_SYMBOL(patch_map);
|
|
|
|
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;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
lockdep_assert_held(&text_mutex);
|
|
|
|
if (across_pages)
|
|
patch_map(addr + len, FIX_TEXT_POKE1);
|
|
|
|
waddr = patch_map(addr, FIX_TEXT_POKE0);
|
|
|
|
ret = probe_kernel_write(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 probe_kernel_write(addr, insn, len);
|
|
}
|
|
NOKPROBE_SYMBOL(patch_insn_write);
|
|
#endif /* CONFIG_MMU */
|
|
|
|
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;
|
|
int ret = 0;
|
|
|
|
if (atomic_inc_return(&patch->cpu_count) == 1) {
|
|
ret =
|
|
patch_text_nosync(patch->addr, &patch->insn,
|
|
GET_INSN_LENGTH(patch->insn));
|
|
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 insn)
|
|
{
|
|
struct patch_insn patch = {
|
|
.addr = addr,
|
|
.insn = insn,
|
|
.cpu_count = ATOMIC_INIT(0),
|
|
};
|
|
|
|
return stop_machine_cpuslocked(patch_text_cb,
|
|
&patch, cpu_online_mask);
|
|
}
|
|
NOKPROBE_SYMBOL(patch_text);
|