[PATCH v2 5/7] riscv: Pass patch_text() the length in bytes

Samuel Holland
2024-03-27T16:05:29Z

patch_text_nosync() already handles an arbitrary length of code, so this
removes a superfluous loop and reduces the number of icache flushes.

Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

Changes in v2:
- Remove unnecessary line wrapping

arch/riscv/include/asm/patch.h | 2 +-
arch/riscv/kernel/patch.c | 14 +++++---------
arch/riscv/kernel/probes/kprobes.c | 18 ++++++++++--------
arch/riscv/net/bpf_jit_comp64.c | 7 ++++---
4 files changed, 20 insertions(+), 21 deletions(-)

diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h
index 9f5d6e14c405..7228e266b9a1 100644
--- a/arch/riscv/include/asm/patch.h
+++ b/arch/riscv/include/asm/patch.h
@@ -9,7 +9,7 @@
int patch_insn_write(void *addr, const void *insn, size_t len);
int patch_text_nosync(void *addr, const void *insns, size_t len);
int patch_text_set_nosync(void *addr, u8 c, size_t len);
-int patch_text(void *addr, u32 *insns, int ninsns);
+int patch_text(void *addr, u32 *insns, size_t len);

extern int riscv_patch_in_stop_machine;

diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
index 0d1700d1934c..243e1573410b 100644
--- a/arch/riscv/kernel/patch.c
+++ b/arch/riscv/kernel/patch.c
@@ -19,7 +19,7 @@
struct patch_insn {
void *addr;
u32 *insns;
- int ninsns;
+ size_t len;
atomic_t cpu_count;
};

@@ -231,14 +231,10 @@ NOKPROBE_SYMBOL(patch_text_nosync);
static int patch_text_cb(void *data)
{
struct patch_insn *patch = data;
- unsigned long len;
- int i, ret = 0;
+ int 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_insn_write(patch->addr + i * len, &patch->insns[i], len);
- }
+ ret = patch_insn_write(patch->addr, patch->insns, patch->len);
/*
* Make sure the patching store is effective *before* we
* increment the counter which releases all waiting CPUs
@@ -258,13 +254,13 @@ static int patch_text_cb(void *data)
}
NOKPROBE_SYMBOL(patch_text_cb);

-int patch_text(void *addr, u32 *insns, int ninsns)
+int patch_text(void *addr, u32 *insns, size_t len)
{
int ret;
struct patch_insn patch = {
.addr = addr,
.insns = insns,
- .ninsns = ninsns,
+ .len = len,
.cpu_count = ATOMIC_INIT(0),
};

diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index fecbbcf40ac3..f3cbc3ec9e6a 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -23,13 +23,13 @@ post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);

static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
{
+ size_t len = GET_INSN_LENGTH(p->opcode);
u32 insn = __BUG_INSN_32;
- unsigned long offset = GET_INSN_LENGTH(p->opcode);

- p->ainsn.api.restore = (unsigned long)p->addr + offset;
+ p->ainsn.api.restore = (unsigned long)p->addr + len;

- patch_text_nosync(p->ainsn.api.insn, &p->opcode, 1);
- patch_text_nosync(p->ainsn.api.insn + offset, &insn, 1);
+ patch_text_nosync(p->ainsn.api.insn, &p->opcode, len);
+ patch_text_nosync(p->ainsn.api.insn + len, &insn, GET_INSN_LENGTH(insn));
}

static void __kprobes arch_prepare_simulate(struct kprobe *p)
@@ -116,16 +116,18 @@ void *alloc_insn_page(void)
/* install breakpoint in text */
void __kprobes arch_arm_kprobe(struct kprobe *p)
{
- u32 insn = (p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32 ?
- __BUG_INSN_32 : __BUG_INSN_16;
+ size_t len = GET_INSN_LENGTH(p->opcode);
+ u32 insn = len == 4 ? __BUG_INSN_32 : __BUG_INSN_16;

- patch_text(p->addr, &insn, 1);
+ patch_text(p->addr, &insn, len);
}

/* remove breakpoint from text */
void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
- patch_text(p->addr, &p->opcode, 1);
+ size_t len = GET_INSN_LENGTH(p->opcode);
+
+ patch_text(p->addr, &p->opcode, len);
}

void __kprobes arch_remove_kprobe(struct kprobe *p)
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index aac190085472..6ed4035a8136 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -15,6 +15,7 @@
#include "bpf_jit.h"

#define RV_FENTRY_NINSNS 2
+#define RV_FENTRY_NBYTES (RV_FENTRY_NINSNS * 4)

#define RV_REG_TCC RV_REG_A6
#define RV_REG_TCC_SAVED RV_REG_S6 /* Store A6 in S6 if program do calls */
@@ -663,7 +664,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
if (ret)
return ret;

- if (memcmp(ip, old_insns, RV_FENTRY_NINSNS * 4))
+ if (memcmp(ip, old_insns, RV_FENTRY_NBYTES))
return -EFAULT;

ret = gen_jump_or_nops(new_addr, ip, new_insns, is_call);
@@ -672,8 +673,8 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,

cpus_read_lock();
mutex_lock(&text_mutex);
- if (memcmp(ip, new_insns, RV_FENTRY_NINSNS * 4))
- ret = patch_text(ip, new_insns, RV_FENTRY_NINSNS);
+ if (memcmp(ip, new_insns, RV_FENTRY_NBYTES))
+ ret = patch_text(ip, new_insns, RV_FENTRY_NBYTES);
mutex_unlock(&text_mutex);
cpus_read_unlock();

--
2.43.1