[PATCH v5 8/9] riscv/kprobe: Patch AUIPC/JALR pair to optimize kprobe

Chen Guokai
2022-12-24T15:22:17Z

From: Liao Chang <liaochang1@huawei.com>

The patch optimize 'EBREAK' with 'AUIPC/JALR', introduce new patching
function to modify multiple instructions.

Signed-off-by: Liao Chang <liaochang1@huawei.com>
Co-developed-by: Chen Guokai <chenguokai17@mails.ucas.ac.cn>
Signed-off-by: Chen Guokai <chenguokai17@mails.ucas.ac.cn>
---
arch/riscv/include/asm/patch.h | 1 +
arch/riscv/kernel/patch.c | 23 ++++++++++---
arch/riscv/kernel/probes/opt.c | 63 ++++++++++++++++++++++++++++++++--
3 files changed, 81 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h
index 9a7d7346001e..ee31539de65f 100644
--- a/arch/riscv/include/asm/patch.h
+++ b/arch/riscv/include/asm/patch.h
@@ -8,5 +8,6 @@

int patch_text_nosync(void *addr, const void *insns, size_t len);
int patch_text(void *addr, u32 insn);
+int patch_text_batch(void *addr, const void *insn, size_t size);

#endif /* _ASM_RISCV_PATCH_H */
diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
index 765004b60513..ce324b6a6998 100644
--- a/arch/riscv/kernel/patch.c
+++ b/arch/riscv/kernel/patch.c
@@ -15,7 +15,8 @@

struct patch_insn {
void *addr;
- u32 insn;
+ const void *insn;
+ size_t size;
atomic_t cpu_count;
};

@@ -106,8 +107,7 @@ static int patch_text_cb(void *data)

if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
ret =
- patch_text_nosync(patch->addr, &patch->insn,
- GET_INSN_LENGTH(patch->insn));
+ patch_text_nosync(patch->addr, patch->insn, patch->size);
atomic_inc(&patch->cpu_count);
} else {
while (atomic_read(&patch->cpu_count) <= num_online_cpus())
@@ -123,7 +123,8 @@ int patch_text(void *addr, u32 insn)
{
struct patch_insn patch = {
.addr = addr,
- .insn = insn,
+ .insn = &insn,
+ .size = GET_INSN_LENGTH(insn),
.cpu_count = ATOMIC_INIT(0),
};

@@ -131,3 +132,17 @@ int patch_text(void *addr, u32 insn)
&patch, cpu_online_mask);
}
NOKPROBE_SYMBOL(patch_text);
+
+int patch_text_batch(void *addr, const void *insn, size_t size)
+{
+ struct patch_insn patch = {
+ .addr = addr,
+ .insn = insn,
+ .size = size,
+ .cpu_count = ATOMIC_INIT(0),
+ };
+
+ return stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
+}
+
+NOKPROBE_SYMBOL(patch_text_batch);
diff --git a/arch/riscv/kernel/probes/opt.c b/arch/riscv/kernel/probes/opt.c
index bc232fce5b39..1c0e9d218f6f 100644
--- a/arch/riscv/kernel/probes/opt.c
+++ b/arch/riscv/kernel/probes/opt.c
@@ -448,11 +448,19 @@ static bool can_optimize(unsigned long paddr, struct optimized_kprobe *op)

int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
{
- return 0;
+ return optinsn->length;
}

int arch_check_optimized_kprobe(struct optimized_kprobe *op)
{
+ unsigned long i;
+ struct kprobe *p;
+
+ for (i = RVC_INSN_LEN; i < op->optinsn.length; i += RVC_INSN_LEN) {
+ p = get_kprobe(op->kp.addr + i);
+ if (p && !kprobe_disabled(p))
+ return -EEXIST;
+ }
return 0;
}

@@ -521,23 +529,74 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,

void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
{
+ if (op->optinsn.insn) {
+ free_optinsn_slot(op->optinsn.insn, 1);
+ op->optinsn.insn = NULL;
+ op->optinsn.length = 0;
+ }
}

void arch_optimize_kprobes(struct list_head *oplist)
{
+ long offs;
+ kprobe_opcode_t insn[3];
+ struct optimized_kprobe *op, *tmp;
+
+ list_for_each_entry_safe(op, tmp, oplist, list) {
+ WARN_ON(kprobe_disabled(&op->kp));
+
+ /* Backup instructions which will be replaced by jump address */
+ memcpy(op->optinsn.copied_insn,
+ DETOUR_ADDR(op->kp.addr, GET_INSN_LENGTH(op->kp.opcode)),
+ op->optinsn.length - GET_INSN_LENGTH(op->kp.opcode));
+
+ /*
+ * After patch, it should be:
+ * auipc free_register, %hi(detour_buffer)
+ * jalr free_register, free_register, %lo(detour_buffer)
+ * where free_register will eventually save the return address
+ */
+ offs = (unsigned long)op->optinsn.insn -
+ (unsigned long)op->kp.addr;
+ insn[0] = rv_auipc(op->optinsn.rd, (offs + (1 << 11)) >> 12);
+ insn[1] = rv_jalr(op->optinsn.rd, op->optinsn.rd, offs & 0xFFF);
+ /* For 3 RVC + 1 RVI scenario, need C.NOP for padding */
+ if (op->optinsn.length > 2 * RVI_INSN_LEN)
+ insn[2] = rvc_addi(0, 0);
+
+ patch_text_batch(op->kp.addr, insn, op->optinsn.length);
+ if (memcmp(op->kp.addr, insn, op->optinsn.length))
+ continue;
+
+ list_del_init(&op->list);
+ }
}

void arch_unoptimize_kprobes(struct list_head *oplist,
struct list_head *done_list)
{
+ struct optimized_kprobe *op, *tmp;
+
+ list_for_each_entry_safe(op, tmp, oplist, list) {
+ arch_unoptimize_kprobe(op);
+ list_move(&op->list, done_list);
+ }
}

void arch_unoptimize_kprobe(struct optimized_kprobe *op)
{
+ kprobe_opcode_t buf[MAX_COPIED_INSN];
+ unsigned long offset = GET_INSN_LENGTH(op->kp.opcode);
+
+ buf[0] = (offset == RVI_INSN_LEN) ? __BUG_INSN_32 : __BUG_INSN_16;
+ memcpy(DETOUR_ADDR(buf, offset), op->optinsn.copied_insn,
+ op->optinsn.length - offset);
+ patch_text_batch(op->kp.addr, buf, op->optinsn.length);
}

int arch_within_optimized_kprobe(struct optimized_kprobe *op,
kprobe_opcode_t *addr)
{
- return 0;
+ return (op->kp.addr <= addr &&
+ op->kp.addr + op->optinsn.length > addr);
}
--
2.34.1