From patchwork Fri Dec 6 00:12:40 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13896114 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8979914F90; Fri, 6 Dec 2024 00:12:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733443966; cv=none; b=ZTABAvvzX/49wSnA7BQueAvp/tfj48CylvBp8Cfm1m25E2H1N190XJRD9CBJEWXhLMce9QTzwKfaZBdsDyvbgTBXGyMfDqjeLRHkcSG+I8Rh/dXk/PDBMA3d1q1MfCJvGbHMyQh3QWgeUf0s56C6WimQgFo+HLFo39kcIdqoKt8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733443966; c=relaxed/simple; bh=o30VIrd/1GcGRTzhKdK9PfjKtWuWZz4RS9+3nBbYnyo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=KzSoJlgL8TDpMP4KxZYEKLKCZUtxl/aedq4z76SxKlhy1IaZYeBEPSfPRiKPZc52nDkM2454WiAbUnEisYy8NT7q7lUMvDvGGErO5yiUabG0qW4l6KfreZWyVJB0wynULak1KvwU5tEMm25395KjBdoO1opRJp8MW040HrkzZAg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZoksD5GG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZoksD5GG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3489DC4CED1; Fri, 6 Dec 2024 00:12:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733443966; bh=o30VIrd/1GcGRTzhKdK9PfjKtWuWZz4RS9+3nBbYnyo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZoksD5GGVzUkG8+ATYpuytJVfHKQiEZqbDtoujxfhMe4HFr1LLIDC70Puyb/2hLVg bn+/5dshwosjHa/BhX2FTjFhJFZG4wjcasYQuEYwDeT3ywFq9PELg3/rj4XgRL3VmA gB1YimakxYMgf1hZbKYTTfvZCdm0Jkk3FxiTI9DI3tDDmJoMb8Kj0wL3JpV6DHw6Ry GHZarWozjgZSTUO2zLkuFfxZEE2XGA4anp8r4pUN1rAt8iaonpFgNyYtEdXmUJ0KUO fUJXPMUC3ne3jh5cvrdBFZ48ntAbp0r26P0BY3FeZtI2NmQihdcAwtC7uySbOrLigg F7f72Cdsr0ivQ== From: "Masami Hiramatsu (Google)" To: Alexei Starovoitov , Steven Rostedt , Florent Revest Cc: linux-trace-kernel@vger.kernel.org, LKML , Martin KaFai Lau , bpf , Alexei Starovoitov , Jiri Olsa , Alan Maguire , Mark Rutland , linux-arch@vger.kernel.org Subject: [PATCH v20 18/19] ftrace: Add ftrace_get_symaddr to convert fentry_ip to symaddr Date: Fri, 6 Dec 2024 09:12:40 +0900 Message-ID: <173344396077.50709.15571140954397859402.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <173344373580.50709.5332611753907139634.stgit@devnote2> References: <173344373580.50709.5332611753907139634.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Masami Hiramatsu (Google) This introduces ftrace_get_symaddr() which tries to convert fentry_ip passed by ftrace or fgraph callback to symaddr without calling kallsyms API. It returns the symbol address or 0 if it fails to convert it. Signed-off-by: Masami Hiramatsu (Google) --- Changes in v19: - Newly added. --- arch/arm64/include/asm/ftrace.h | 2 + arch/arm64/kernel/ftrace.c | 63 +++++++++++++++++++++++++++++++++++++++ arch/x86/include/asm/ftrace.h | 21 +++++++++++++ include/linux/ftrace.h | 13 ++++++++ 4 files changed, 99 insertions(+) diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h index 876e88ad4119..f08e70bf09ea 100644 --- a/arch/arm64/include/asm/ftrace.h +++ b/arch/arm64/include/asm/ftrace.h @@ -52,6 +52,8 @@ extern unsigned long ftrace_graph_call; extern void return_to_handler(void); unsigned long ftrace_call_adjust(unsigned long addr); +unsigned long arch_ftrace_call_adjust(unsigned long fentry_ip); +#define ftrace_call_adjust(fentry_ip) arch_ftrace_call_adjust(fentry_ip) #ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS #define HAVE_ARCH_FTRACE_REGS diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c index 570c38be833c..d7c0d023dfe5 100644 --- a/arch/arm64/kernel/ftrace.c +++ b/arch/arm64/kernel/ftrace.c @@ -143,6 +143,69 @@ unsigned long ftrace_call_adjust(unsigned long addr) return addr; } +/* Convert fentry_ip to the symbol address without kallsyms */ +unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip) +{ + u32 insn; + + /* + * When using patchable-function-entry without pre-function NOPS, ftrace + * entry is the address of the first NOP after the function entry point. + * + * The compiler has either generated: + * + * func+00: func: NOP // To be patched to MOV X9, LR + * func+04: NOP // To be patched to BL + * + * Or: + * + * func-04: BTI C + * func+00: func: NOP // To be patched to MOV X9, LR + * func+04: NOP // To be patched to BL + * + * The fentry_ip is the address of `BL ` which is at `func + 4` + * bytes in either case. + */ + if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS)) + return fentry_ip - AARCH64_INSN_SIZE; + + /* + * When using patchable-function-entry with pre-function NOPs, BTI is + * a bit different. + * + * func+00: func: NOP // To be patched to MOV X9, LR + * func+04: NOP // To be patched to BL + * + * Or: + * + * func+00: func: BTI C + * func+04: NOP // To be patched to MOV X9, LR + * func+08: NOP // To be patched to BL + * + * The fentry_ip is the address of `BL ` which is at either + * `func + 4` or `func + 8` depends on whether there is a BTI. + */ + + /* If there is no BTI, the func address should be one instruction before. */ + if (!IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)) + return fentry_ip - AARCH64_INSN_SIZE; + + /* We want to be extra safe in case entry ip is on the page edge, + * but otherwise we need to avoid get_kernel_nofault()'s overhead. + */ + if ((fentry_ip & ~PAGE_MASK) < AARCH64_INSN_SIZE * 2) { + if (get_kernel_nofault(insn, (u32 *)(fentry_ip - AARCH64_INSN_SIZE * 2))) + return 0; + } else { + insn = *(u32 *)(fentry_ip - AARCH64_INSN_SIZE * 2); + } + + if (aarch64_insn_is_bti(le32_to_cpu((__le32)insn))) + return fentry_ip - AARCH64_INSN_SIZE * 2; + + return fentry_ip - AARCH64_INSN_SIZE; +} + /* * Replace a single instruction, which may be a branch or NOP. * If @validate == true, a replaced instruction is checked against 'old'. diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h index cc92c99ef276..f9cb4d07df58 100644 --- a/arch/x86/include/asm/ftrace.h +++ b/arch/x86/include/asm/ftrace.h @@ -34,6 +34,27 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) return addr; } +static inline unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip) +{ +#ifdef CONFIG_X86_KERNEL_IBT + u32 instr; + + /* We want to be extra safe in case entry ip is on the page edge, + * but otherwise we need to avoid get_kernel_nofault()'s overhead. + */ + if ((fentry_ip & ~PAGE_MASK) < ENDBR_INSN_SIZE) { + if (get_kernel_nofault(instr, (u32 *)(fentry_ip - ENDBR_INSN_SIZE))) + return fentry_ip; + } else { + instr = *(u32 *)(fentry_ip - ENDBR_INSN_SIZE); + } + if (is_endbr(instr)) + fentry_ip -= ENDBR_INSN_SIZE; +#endif + return fentry_ip; +} +#define ftrace_get_symaddr(fentry_ip) arch_ftrace_get_symaddr(fentry_ip) + #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS #include diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 4c553fe9c026..9659bb2cd76c 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -652,6 +652,19 @@ struct ftrace_ops *ftrace_ops_trampoline(unsigned long addr); bool is_ftrace_trampoline(unsigned long addr); +/* Arches can override ftrace_get_symaddr() to convert fentry_ip to symaddr. */ +#ifndef ftrace_get_symaddr +/** + * ftrace_get_symaddr - return the symbol address from fentry_ip + * @fentry_ip: the address of ftrace location + * + * Get the symbol address from @fentry_ip (fast path). If there is no fast + * search path, this returns 0. + * User may need to use kallsyms API to find the symbol address. + */ +#define ftrace_get_symaddr(fentry_ip) (0) +#endif + /* * The dyn_ftrace record's flags field is split into two parts. * the first part which is '0-FTRACE_REF_MAX' is a counter of