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[92.145.124.62]) by smtp.gmail.com with ESMTPSA id n12-20020a05600c500c00b00412abfb0ed0sm2880142wmr.0.2024.02.28.09.53.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Feb 2024 09:53:56 -0800 (PST) From: Alexandre Ghiti To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrea Parri , Anup Patel , Steven Rostedt , Masami Hiramatsu , Mark Rutland , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Alexandre Ghiti , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= Subject: [PATCH 2/2] riscv: Fix text patching when IPI are used Date: Wed, 28 Feb 2024 18:51:49 +0100 Message-Id: <20240228175149.162646-3-alexghiti@rivosinc.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240228175149.162646-1-alexghiti@rivosinc.com> References: <20240228175149.162646-1-alexghiti@rivosinc.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1792166217112775087 X-GMAIL-MSGID: 1792166217112775087 For now, we use stop_machine() to patch the text and when we use IPIs for remote icache flushes (which is emitted in patch_text_nosync()), the system hangs. So instead, make sure every cpu executes the stop_machine() patching function and emit a local icache flush there. Co-developed-by: Björn Töpel Signed-off-by: Björn Töpel Signed-off-by: Alexandre Ghiti Reviewed-by: Andrea Parri --- arch/riscv/include/asm/patch.h | 1 + arch/riscv/kernel/ftrace.c | 42 ++++++++++++++++++++++++++++++---- arch/riscv/kernel/patch.c | 18 +++++++++------ 3 files changed, 50 insertions(+), 11 deletions(-) diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h index e88b52d39eac..9f5d6e14c405 100644 --- a/arch/riscv/include/asm/patch.h +++ b/arch/riscv/include/asm/patch.h @@ -6,6 +6,7 @@ #ifndef _ASM_RISCV_PATCH_H #define _ASM_RISCV_PATCH_H +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); diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c index f5aa24d9e1c1..5654966c4e7d 100644 --- a/arch/riscv/kernel/ftrace.c +++ b/arch/riscv/kernel/ftrace.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include @@ -75,8 +76,7 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target, make_call_t0(hook_pos, target, call); /* Replace the auipc-jalr pair at once. Return -EPERM on write error. */ - if (patch_text_nosync - ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE)) + if (patch_insn_write((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE)) return -EPERM; return 0; @@ -88,7 +88,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) make_call_t0(rec->ip, addr, call); - if (patch_text_nosync((void *)rec->ip, call, MCOUNT_INSN_SIZE)) + if (patch_insn_write((void *)rec->ip, call, MCOUNT_INSN_SIZE)) return -EPERM; return 0; @@ -99,7 +99,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, { unsigned int nops[2] = {NOP4, NOP4}; - if (patch_text_nosync((void *)rec->ip, nops, MCOUNT_INSN_SIZE)) + if (patch_insn_write((void *)rec->ip, nops, MCOUNT_INSN_SIZE)) return -EPERM; return 0; @@ -134,6 +134,40 @@ int ftrace_update_ftrace_func(ftrace_func_t func) return ret; } + +struct ftrace_modify_param { + int command; + atomic_t cpu_count; +}; + +static int __ftrace_modify_code(void *data) +{ + struct ftrace_modify_param *param = data; + + if (atomic_inc_return(¶m->cpu_count) == num_online_cpus()) { + ftrace_modify_all_code(param->command); + /* + * Make sure the patching store is effective *before* we + * increment the counter which releases all waiting cpus + * by using the release version of atomic increment. + */ + atomic_inc_return_release(¶m->cpu_count); + } else { + while (atomic_read(¶m->cpu_count) <= num_online_cpus()) + cpu_relax(); + } + + local_flush_icache_all(); + + return 0; +} + +void arch_ftrace_update_code(int command) +{ + struct ftrace_modify_param param = { command, ATOMIC_INIT(0) }; + + stop_machine(__ftrace_modify_code, ¶m, cpu_online_mask); +} #endif #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 0b5c16dfe3f4..82d8508c765b 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -188,7 +188,7 @@ int patch_text_set_nosync(void *addr, u8 c, size_t len) } NOKPROBE_SYMBOL(patch_text_set_nosync); -static int patch_insn_write(void *addr, const void *insn, size_t len) +int patch_insn_write(void *addr, const void *insn, size_t len) { size_t patched = 0; size_t size; @@ -211,11 +211,9 @@ NOKPROBE_SYMBOL(patch_insn_write); int patch_text_nosync(void *addr, const void *insns, size_t len) { - u32 *tp = addr; int ret; - ret = patch_insn_write(tp, insns, len); - + ret = patch_insn_write(addr, insns, len); if (!ret) flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len); @@ -232,15 +230,21 @@ static int patch_text_cb(void *data) 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_text_nosync(patch->addr + i * len, - &patch->insns[i], len); + ret = patch_insn_write(patch->addr + i * len, &patch->insns[i], len); } - atomic_inc(&patch->cpu_count); + /* + * Make sure the patching store is effective *before* we + * increment the counter which releases all waiting cpus + * by using the release version of atomic increment. + */ + atomic_inc_return_release(&patch->cpu_count); } else { while (atomic_read(&patch->cpu_count) <= num_online_cpus()) cpu_relax(); } + local_flush_icache_all(); + return ret; } NOKPROBE_SYMBOL(patch_text_cb);