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Message-Id: <20230126161559.1467374-1-guoren@kernel.org> Date: Thu, 26 Jan 2023 11:15:59 -0500 From: guoren@...nel.org To: guoren@...nel.org, palmer@...belt.com, paul.walmsley@...ive.com, mhiramat@...nel.org, conor.dooley@...rochip.com, penberg@...nel.org, mark.rutland@....com Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, Guo Ren <guoren@...ux.alibaba.com> Subject: [PATCH] riscv: kprobe: Optimize kprobe with accurate atomicity From: Guo Ren <guoren@...ux.alibaba.com> The previous implementation was based on the stop_matchine mechanism, which reduced the speed of arm/disarm_kprobe. Using minimum ebreak instruction would get accurate atomicity. This patch removes the patch_text of riscv, which is based on stop_machine. Then riscv only reserved patch_text_nosync, and developers need to be more careful in dealing with patch_text atomicity. When CONFIG_RISCV_ISA_C=n, the ebreak could replace the whole instruction. When CONFIG_RISCV_ISA_C=y, the patch uses 16-bit length c.ebreak instruction, which may occupy the first part of the 32-bit instruction and leave half the rest of the broken instruction. Because ebreak could detour the flow to skip it, leaving it in the kernel text memory is okay. Signed-off-by: Guo Ren <guoren@...ux.alibaba.com> Signed-off-by: Guo Ren <guoren@...nel.org> --- arch/riscv/include/asm/patch.h | 1 - arch/riscv/kernel/patch.c | 33 ------------------------------ arch/riscv/kernel/probes/kprobes.c | 29 ++++++++++++++++++-------- 3 files changed, 21 insertions(+), 42 deletions(-) diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h index 9a7d7346001e..2500782e6f5b 100644 --- a/arch/riscv/include/asm/patch.h +++ b/arch/riscv/include/asm/patch.h @@ -7,6 +7,5 @@ #define _ASM_RISCV_PATCH_H int patch_text_nosync(void *addr, const void *insns, size_t len); -int patch_text(void *addr, u32 insn); #endif /* _ASM_RISCV_PATCH_H */ diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 765004b60513..8bd51ed8b806 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -98,36 +98,3 @@ int patch_text_nosync(void *addr, const void *insns, size_t 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) == num_online_cpus()) { - 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); diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c index 475989f06d6d..27f8960c321c 100644 --- a/arch/riscv/kernel/probes/kprobes.c +++ b/arch/riscv/kernel/probes/kprobes.c @@ -24,12 +24,18 @@ post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *); static void __kprobes arch_prepare_ss_slot(struct kprobe *p) { unsigned long offset = GET_INSN_LENGTH(p->opcode); +#ifdef CONFIG_RISCV_ISA_C + u32 opcode = __BUG_INSN_16; +#else + u32 opcode = __BUG_INSN_32; +#endif p->ainsn.api.restore = (unsigned long)p->addr + offset; - patch_text(p->ainsn.api.insn, p->opcode); - patch_text((void *)((unsigned long)(p->ainsn.api.insn) + offset), - __BUG_INSN_32); + patch_text_nosync(p->ainsn.api.insn, &p->opcode, offset); + patch_text_nosync((void *)((unsigned long)(p->ainsn.api.insn) + offset), + &opcode, GET_INSN_LENGTH(opcode)); + } static void __kprobes arch_prepare_simulate(struct kprobe *p) @@ -114,16 +120,23 @@ void *alloc_insn_page(void) /* install breakpoint in text */ void __kprobes arch_arm_kprobe(struct kprobe *p) { - if ((p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32) - patch_text(p->addr, __BUG_INSN_32); - else - patch_text(p->addr, __BUG_INSN_16); +#ifdef CONFIG_RISCV_ISA_C + u32 opcode = __BUG_INSN_16; +#else + u32 opcode = __BUG_INSN_32; +#endif + patch_text_nosync(p->addr, &opcode, GET_INSN_LENGTH(opcode)); } /* remove breakpoint from text */ void __kprobes arch_disarm_kprobe(struct kprobe *p) { - patch_text(p->addr, p->opcode); +#ifdef CONFIG_RISCV_ISA_C + u32 opcode = __BUG_INSN_16; +#else + u32 opcode = __BUG_INSN_32; +#endif + patch_text_nosync(p->addr, &p->opcode, GET_INSN_LENGTH(opcode)); } void __kprobes arch_remove_kprobe(struct kprobe *p) -- 2.36.1
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