Commit ae164807 authored by Jiang Liu's avatar Jiang Liu Committed by Catalin Marinas

arm64: introduce interfaces to hotpatch kernel and module code

Introduce three interfaces to patch kernel and module code:
aarch64_insn_patch_text_nosync():
	patch code without synchronization, it's caller's responsibility
	to synchronize all CPUs if needed.
aarch64_insn_patch_text_sync():
	patch code and always synchronize with stop_machine()
aarch64_insn_patch_text():
	patch code and synchronize with stop_machine() if needed
Reviewed-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarJiang Liu <liuj97@gmail.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent b11a64a4
......@@ -18,6 +18,9 @@
#define __ASM_INSN_H
#include <linux/types.h>
/* A64 instructions are always 32 bits. */
#define AARCH64_INSN_SIZE 4
/*
* ARM Architecture Reference Manual for ARMv8 Profile-A, Issue A.a
* Section C3.1 "A64 instruction index by encoding":
......@@ -70,8 +73,13 @@ __AARCH64_INSN_FUNCS(hint, 0xFFFFF01F, 0xD503201F)
bool aarch64_insn_is_nop(u32 insn);
int aarch64_insn_read(void *addr, u32 *insnp);
int aarch64_insn_write(void *addr, u32 insn);
enum aarch64_insn_encoding_class aarch64_get_insn_class(u32 insn);
bool aarch64_insn_hotpatch_safe(u32 old_insn, u32 new_insn);
int aarch64_insn_patch_text_nosync(void *addr, u32 insn);
int aarch64_insn_patch_text_sync(void *addrs[], u32 insns[], int cnt);
int aarch64_insn_patch_text(void *addrs[], u32 insns[], int cnt);
#endif /* __ASM_INSN_H */
......@@ -16,6 +16,10 @@
*/
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/stop_machine.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/insn.h>
static int aarch64_insn_encoding_class[] = {
......@@ -60,6 +64,28 @@ bool __kprobes aarch64_insn_is_nop(u32 insn)
}
}
/*
* In ARMv8-A, A64 instructions have a fixed length of 32 bits and are always
* little-endian.
*/
int __kprobes aarch64_insn_read(void *addr, u32 *insnp)
{
int ret;
u32 val;
ret = probe_kernel_read(&val, addr, AARCH64_INSN_SIZE);
if (!ret)
*insnp = le32_to_cpu(val);
return ret;
}
int __kprobes aarch64_insn_write(void *addr, u32 insn)
{
insn = cpu_to_le32(insn);
return probe_kernel_write(addr, &insn, AARCH64_INSN_SIZE);
}
static bool __kprobes __aarch64_insn_hotpatch_safe(u32 insn)
{
if (aarch64_get_insn_class(insn) != AARCH64_INSN_CLS_BR_SYS)
......@@ -89,3 +115,96 @@ bool __kprobes aarch64_insn_hotpatch_safe(u32 old_insn, u32 new_insn)
return __aarch64_insn_hotpatch_safe(old_insn) &&
__aarch64_insn_hotpatch_safe(new_insn);
}
int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
{
u32 *tp = addr;
int ret;
/* A64 instructions must be word aligned */
if ((uintptr_t)tp & 0x3)
return -EINVAL;
ret = aarch64_insn_write(tp, insn);
if (ret == 0)
flush_icache_range((uintptr_t)tp,
(uintptr_t)tp + AARCH64_INSN_SIZE);
return ret;
}
struct aarch64_insn_patch {
void **text_addrs;
u32 *new_insns;
int insn_cnt;
atomic_t cpu_count;
};
static int __kprobes aarch64_insn_patch_text_cb(void *arg)
{
int i, ret = 0;
struct aarch64_insn_patch *pp = arg;
/* The first CPU becomes master */
if (atomic_inc_return(&pp->cpu_count) == 1) {
for (i = 0; ret == 0 && i < pp->insn_cnt; i++)
ret = aarch64_insn_patch_text_nosync(pp->text_addrs[i],
pp->new_insns[i]);
/*
* aarch64_insn_patch_text_nosync() calls flush_icache_range(),
* which ends with "dsb; isb" pair guaranteeing global
* visibility.
*/
atomic_set(&pp->cpu_count, -1);
} else {
while (atomic_read(&pp->cpu_count) != -1)
cpu_relax();
isb();
}
return ret;
}
int __kprobes aarch64_insn_patch_text_sync(void *addrs[], u32 insns[], int cnt)
{
struct aarch64_insn_patch patch = {
.text_addrs = addrs,
.new_insns = insns,
.insn_cnt = cnt,
.cpu_count = ATOMIC_INIT(0),
};
if (cnt <= 0)
return -EINVAL;
return stop_machine(aarch64_insn_patch_text_cb, &patch,
cpu_online_mask);
}
int __kprobes aarch64_insn_patch_text(void *addrs[], u32 insns[], int cnt)
{
int ret;
u32 insn;
/* Unsafe to patch multiple instructions without synchronizaiton */
if (cnt == 1) {
ret = aarch64_insn_read(addrs[0], &insn);
if (ret)
return ret;
if (aarch64_insn_hotpatch_safe(insn, insns[0])) {
/*
* ARMv8 architecture doesn't guarantee all CPUs see
* the new instruction after returning from function
* aarch64_insn_patch_text_nosync(). So send IPIs to
* all other CPUs to achieve instruction
* synchronization.
*/
ret = aarch64_insn_patch_text_nosync(addrs[0], insns[0]);
kick_all_cpus_sync();
return ret;
}
}
return aarch64_insn_patch_text_sync(addrs, insns, cnt);
}
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