From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A45B7C77B60 for ; Wed, 26 Apr 2023 14:31:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241230AbjDZObE (ORCPT ); Wed, 26 Apr 2023 10:31:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241106AbjDZObB (ORCPT ); Wed, 26 Apr 2023 10:31:01 -0400 Received: from loongson.cn (mail.loongson.cn [114.242.206.163]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 5BB28449D; Wed, 26 Apr 2023 07:30:57 -0700 (PDT) Received: from loongson.cn (unknown [36.45.46.252]) by gateway (Coremail) with SMTP id _____8CxlfCdNUlkvxoBAA--.1954S3; Wed, 26 Apr 2023 22:30:53 +0800 (CST) Received: from [192.168.43.142] (unknown [36.45.46.252]) by localhost.localdomain (Coremail) with SMTP id AQAAf8CxKLKbNUlkbQo9AA--.17141S3; Wed, 26 Apr 2023 22:30:52 +0800 (CST) Message-ID: Date: Wed, 26 Apr 2023 22:30:51 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH 3/5] LoongArch: ftrace: Add direct call support To: Mark Rutland Cc: Huacai Chen , Steven Rostedt , Masami Hiramatsu , WANG Xuerui , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, loongarch@lists.linux.dev, loongson-kernel@lists.loongnix.cn, Qing Zhang References: <1682473754-25077-1-git-send-email-tangyouling@loongson.cn> <1682473754-25077-4-git-send-email-tangyouling@loongson.cn> From: Youling Tang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CM-TRANSID: AQAAf8CxKLKbNUlkbQo9AA--.17141S3 X-CM-SenderInfo: 5wdqw5prxox03j6o00pqjv00gofq/ X-Coremail-Antispam: 1Uk129KBjvJXoW3WFWkKFWxKF1UWw18Ar47Arb_yoW7ZFWkpr W7A3ZrtFWUuF4vk3sF9a48Wr4UXrWkX34fu3ZrAryFkr98Wryjvr48Ar98XFy0qw4kGrWI qF4rury5CF4aq37anT9S1TB71UUUUUJqnTZGkaVYY2UrUUUUj1kv1TuYvTs0mT0YCTnIWj qI5I8CrVACY4xI64kE6c02F40Ex7xfYxn0WfASr-VFAUDa7-sFnT9fnUUIcSsGvfJTRUUU bfAYFVCjjxCrM7AC8VAFwI0_Jr0_Gr1l1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s 1l1IIY67AEw4v_JrI_Jryl8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xv wVC0I7IYx2IY67AKxVWUJVWUCwA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVWUJVW8JwA2z4 x0Y4vEx4A2jsIE14v26r4UJVWxJr1l84ACjcxK6I8E87Iv6xkF7I0E14v26F4UJVW0owAa w2AFwI0_Jrv_JF1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqjxCEc2xF0cIa020Ex4CE44 I27wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jrv_JF1lYx0Ex4A2 jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvEwIxGrwCYjI0SjxkI62 AI1cAE67vIY487MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMxCIbckI 1I0E14v26r1Y6r17MI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_Jr Wlx4CE17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j 6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVWUJVW8JwCI42IY6xAIw20EY4v20xvaj40_Jr 0_JF4lIxAIcVC2z280aVAFwI0_Gr0_Cr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUv cSsGvfC2KfnxnUUI43ZEXa7IU8fsqJUUUUU== Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Mark On 2023/4/26 21:43, Mark Rutland wrote: > Hi, > > On Wed, Apr 26, 2023 at 09:49:12AM +0800, Youling Tang wrote: >> select the DYNAMIC_FTRACE_WITH_DIRECT_CALLS to provide the >> register_ftrace_direct[_multi] interfaces allowing users to register >> the customed trampoline (direct_caller) as the mcount for one or >> more target functions. And modify_ftrace_direct[_multi] are also >> provided for modifying direct_caller. >> >> There are a few cases to distinguish: >> - If a direct call ops is the only one tracing a function: >> - If the direct called trampoline is within the reach of a 'bl' >> instruction >> -> the ftrace patchsite jumps to the trampoline >> - Else >> -> the ftrace patchsite jumps to the ftrace_regs_caller trampoline >> which reads the ops pointer in the patchsite and jumps to the >> direct call address stored in the ops > I think you forgot to update this wording; there's no ops pointer in the > patchsite as you don't implement DYNAMIC_FTRACE_WITH_CALL_OPS. > > I think you can delete the "Else" case here, and replace the above with: > > - If a direct call ops is the only one tracing a function AND the direct called > trampoline is within the reach of a 'bl' instruction > -> the ftrace patchsite jumps to the trampoline > >> - Else >> -> the ftrace patchsite jumps to the ftrace_regs_caller trampoline and >> its ops literal points to ftrace_list_ops so it iterates over all >> registered ftrace ops, including the direct call ops and calls its >> call_direct_funcs handler which stores the direct called trampoline's >> address in the ftrace_regs and the ftrace_regs_caller trampoline will > Likewise here, there's no "ops literal" associated with the patchsite. Yes, thank you for pointing out, I will fix this description. Thanks, Youling. > > Otherwise, this looks sane to me. > > Mark. > >> return to that address instead of returning to the traced function >> >> Signed-off-by: Qing Zhang >> Signed-off-by: Youling Tang >> --- >> arch/loongarch/Kconfig | 1 + >> arch/loongarch/include/asm/ftrace.h | 12 ++++++++++++ >> arch/loongarch/kernel/ftrace_dyn.c | 8 ++++++++ >> arch/loongarch/kernel/mcount_dyn.S | 7 ++++++- >> 4 files changed, 27 insertions(+), 1 deletion(-) >> >> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig >> index 3ddde336e6a5..d6068a88d53f 100644 >> --- a/arch/loongarch/Kconfig >> +++ b/arch/loongarch/Kconfig >> @@ -92,6 +92,7 @@ config LOONGARCH >> select HAVE_DMA_CONTIGUOUS >> select HAVE_DYNAMIC_FTRACE >> select HAVE_DYNAMIC_FTRACE_WITH_ARGS >> + select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS >> select HAVE_DYNAMIC_FTRACE_WITH_REGS >> select HAVE_EBPF_JIT >> select HAVE_EFFICIENT_UNALIGNED_ACCESS if !ARCH_STRICT_ALIGN >> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h >> index 3418d32d4fc7..f789e680f633 100644 >> --- a/arch/loongarch/include/asm/ftrace.h >> +++ b/arch/loongarch/include/asm/ftrace.h >> @@ -57,6 +57,18 @@ static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs * >> #define ftrace_graph_func ftrace_graph_func >> void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, >> struct ftrace_ops *op, struct ftrace_regs *fregs); >> + >> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS >> +static inline void >> +__arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr) >> +{ >> + regs->regs[13] = addr; /* t1 */ >> +} >> + >> +#define arch_ftrace_set_direct_caller(fregs, addr) \ >> + __arch_ftrace_set_direct_caller(&(fregs)->regs, addr) >> +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ >> + >> #endif >> >> #endif /* __ASSEMBLY__ */ >> diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c >> index 3cc4f8159f48..4062a7e63137 100644 >> --- a/arch/loongarch/kernel/ftrace_dyn.c >> +++ b/arch/loongarch/kernel/ftrace_dyn.c >> @@ -66,6 +66,14 @@ static bool ftrace_find_callable_addr(struct dyn_ftrace *rec, struct module *mod >> unsigned long pc = rec->ip + LOONGARCH_INSN_SIZE; >> struct plt_entry *plt; >> >> + /* >> + * If a custom trampoline is unreachable, rely on the ftrace_regs_caller >> + * trampoline which knows how to indirectly reach that trampoline >> + * through ops->direct_call. >> + */ >> + if (*addr != FTRACE_ADDR && *addr != FTRACE_REGS_ADDR && !reachable_by_bl(*addr, pc)) >> + *addr = FTRACE_REGS_ADDR; >> + >> /* >> * When the target is within range of the 'bl' instruction, use 'addr' >> * as-is and branch to that directly. >> diff --git a/arch/loongarch/kernel/mcount_dyn.S b/arch/loongarch/kernel/mcount_dyn.S >> index bbabf06244c2..1008fbc3cabc 100644 >> --- a/arch/loongarch/kernel/mcount_dyn.S >> +++ b/arch/loongarch/kernel/mcount_dyn.S >> @@ -42,7 +42,6 @@ >> .if \allregs >> PTR_S tp, sp, PT_R2 >> PTR_S t0, sp, PT_R12 >> - PTR_S t1, sp, PT_R13 >> PTR_S t2, sp, PT_R14 >> PTR_S t3, sp, PT_R15 >> PTR_S t4, sp, PT_R16 >> @@ -64,6 +63,8 @@ >> PTR_S zero, sp, PT_R0 >> .endif >> PTR_S ra, sp, PT_ERA /* Save trace function ra at PT_ERA */ >> + move t1, zero >> + PTR_S t1, sp, PT_R13 >> PTR_ADDI t8, sp, PT_SIZE >> PTR_S t8, sp, PT_R3 >> .endm >> @@ -104,8 +105,12 @@ ftrace_common_return: >> PTR_L a7, sp, PT_R11 >> PTR_L fp, sp, PT_R22 >> PTR_L t0, sp, PT_ERA >> + PTR_L t1, sp, PT_R13 >> PTR_ADDI sp, sp, PT_SIZE >> + bnez t1,.Ldirect >> jr t0 >> +.Ldirect: >> + jr t1 >> SYM_CODE_END(ftrace_common) >> >> SYM_CODE_START(ftrace_caller) >> -- >> 2.37.1 >>