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

Commit Message

Samuel Holland March 27, 2024, 4:04 p.m. UTC

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 <[e-mail]>
Signed-off-by: Samuel Holland <[e-mail]>
---

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(-)

Comments

Conor Dooley April 24, 2024, 10:49 a.m. UTC | #1

On Wed, Mar 27, 2024 at 09:04:44AM -0700, Samuel Holland wrote:
> 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 <[e-mail]>
> Signed-off-by: Samuel Holland <[e-mail]>

Reviewed-by: Conor Dooley <[e-mail]>

Patch

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();