From patchwork Fri Jun 28 11:47:46 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andy Chiu X-Patchwork-Id: 13716000 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4897FC2BBCA for ; Fri, 28 Jun 2024 11:48:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:In-Reply-To:References:Message-Id :MIME-Version:Subject:Date:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=LBkh1rxwavZj0gyCgChuTbH/0B4PMmhfpxq/e9F5Ld8=; b=V88pujW6vBikcQ iNVqQhx23+oSwqbIR/hKW9vF4cQ7pfuOLCE25a0KuRtQNOvuUQ2P3hFzzeXwuXLFgQxnF6QEfAg0v ZSVlbM/0ShtWbGS2lA9rG2c2IfAzuwP+Z+kllJ1XIsZAMVnKAlCj5XEBIBCAGv2z51l03HZQ4yqNT CStpt9B/LQ5JiUzPI79objfItgqnazL1xqPw+jgwVjK0EYvioJBno7Erpx5oOUybnUOO25q9Vy1uo 32aQJfLnOYVcL4yMLwpicq0sK1hNyGd4lZ+ikc4mZzzjVeTmUEB70UmUKo2V/Ky08+8JykJSJypap 2c56A7XC6eXPM8cguTow==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sNA5d-0000000DZz7-1gRa; Fri, 28 Jun 2024 11:48:29 +0000 Received: from mail-pf1-x42d.google.com ([2607:f8b0:4864:20::42d]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sNA5b-0000000DZxU-0hsZ for linux-riscv@lists.infradead.org; Fri, 28 Jun 2024 11:48:28 +0000 Received: by mail-pf1-x42d.google.com with SMTP id d2e1a72fcca58-7066a4a611dso337365b3a.3 for ; Fri, 28 Jun 2024 04:48:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sifive.com; s=google; t=1719575306; x=1720180106; darn=lists.infradead.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=VRfKgP0f/b5byy3Hsr+xfWPWy/6xoLq7KDU6P/HKJkA=; b=Q8inDCZdTNPCgbe0ctbXsa2o97drQKgEqR0cfltA0J80Iatyn8f4OGgDFJHud0UfYw EG0uIWv35sqM8Lrlhi6/rWUOHQysTukq6sN9HLtSGnmysLvYpXfWl3SNPOlXXafl1hLC fv/Ycvlnyo7Qb+O5XDjB4uuNzV4J8Mu/jlbzSSBzJoW+KArYhkkeDxohxIukfHf/F826 JN83ChWOMY3x25u6dr3ml8VRbtQAq+KnHt/+vifZH9nTF5hrVEVk3yZApgHk4Wki4M5W qLLnPd/B0/ILzDIXwhhzauE2b0uTYcXNRkv9SQhVrdwv8BiuMTiR0u4Ao70FxIXmZ7wB rDZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719575306; x=1720180106; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=VRfKgP0f/b5byy3Hsr+xfWPWy/6xoLq7KDU6P/HKJkA=; b=l3qGNHiCNieSwgqqSu01TmjtD4KdKxhoBP0fxr37N3fMMbebYN5XCxsNDFJeCWc/hT w6AFsKNbkQUfsLvFZcN4YOU+s9x+FGxJ9y2dnI3jW82+oAGLQ9eP88f5ZEqrgojHoIAk 9v/EHlk6NdKGmHJcn7ih6+7u1/jKShzY1P86rqAfYt8jMnd/aSq6TMKrJXbrohA5X8+Q 4ZJrX5Uwf4ARmX+xU3xtEYMmC85R1C8nfhQOpAUyaQqCQn5hQVi9mkceOuOo3NxypqF2 7txwWOGdP5mvu5GyPQcFk8RFqYAKCU9Kpcgpcpguf8QGUHUB2t4WVVpu6dwP+wf4rbW1 apJA== X-Forwarded-Encrypted: i=1; AJvYcCUZEQ4CwFqi05UMI9scTgcA+orJzLWLKdGyOhs16xowVSw25e5WoLZKALgBDUvP9uclaGGqP6tDE7iEvY9KTp6wwzDo7U00YK6HkHI9GmDF X-Gm-Message-State: AOJu0Yz8Ax06e9vn286TWCkW9exME4BJHRY39MueqJlSadpP+tAmUTuc mk3mNK9cLUUvsDvf261mqhmDCuVIhTn/jEO1HY1b6KuAwEOpC4NqsPpU87yzrDk= X-Google-Smtp-Source: AGHT+IEAymT/KibkJ2rVnqkBCpfqAUN3Ax4XLYgVI1XP9yFZGQfCsMCsbNKadorxrzTjX8uUzgoyYQ== X-Received: by 2002:a05:6a00:2e96:b0:706:8cc6:7471 with SMTP id d2e1a72fcca58-7068cc67611mr15622161b3a.34.1719575306121; Fri, 28 Jun 2024 04:48:26 -0700 (PDT) Received: from [127.0.1.1] (59-124-168-89.hinet-ip.hinet.net. [59.124.168.89]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-70803ecfb90sm1377775b3a.139.2024.06.28.04.48.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Jun 2024 04:48:25 -0700 (PDT) From: Andy Chiu Date: Fri, 28 Jun 2024 19:47:46 +0800 Subject: [PATCH v2 3/6] riscv: ftrace: prepare ftrace for atomic code patching MIME-Version: 1.0 Message-Id: <20240628-dev-andyc-dyn-ftrace-v4-v2-3-1e5f4cb1f049@sifive.com> References: <20240628-dev-andyc-dyn-ftrace-v4-v2-0-1e5f4cb1f049@sifive.com> In-Reply-To: <20240628-dev-andyc-dyn-ftrace-v4-v2-0-1e5f4cb1f049@sifive.com> To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Zong Li , Steven Rostedt , Masami Hiramatsu , Mark Rutland , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Puranjay Mohan Cc: Palmer Dabbelt , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, llvm@lists.linux.dev, Andy Chiu X-Mailer: b4 0.12.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240628_044827_250585_4AA5FB47 X-CRM114-Status: GOOD ( 21.68 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org We use an AUIPC+JALR pair to jump into a ftrace trampoline. Since instruction fetch can break down to 4 byte at a time, it is impossible to update two instructions without a race. In order to mitigate it, we initialize the patchable entry to AUIPC + NOP4. Then, the run-time code patching can change NOP4 to JALR to eable/disable ftrcae from a function. This limits the reach of each ftrace entry to +-2KB displacing from ftrace_caller. Starting from the trampoline, we add a level of indirection for it to reach ftrace caller target. Now, it loads the target address from a memory location, then perform the jump. This enable the kernel to update the target atomically. The ordering of reading/updating the targert address should be guarded by generic ftrace code, where it sends smp_rmb ipi. Signed-off-by: Andy Chiu --- arch/riscv/include/asm/ftrace.h | 4 +++ arch/riscv/kernel/ftrace.c | 80 ++++++++++++++++++++++++++--------------- arch/riscv/kernel/mcount-dyn.S | 9 +++-- 3 files changed, 62 insertions(+), 31 deletions(-) diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h index 5f81c53dbfd9..7199383f8c02 100644 --- a/arch/riscv/include/asm/ftrace.h +++ b/arch/riscv/include/asm/ftrace.h @@ -81,6 +81,7 @@ struct dyn_arch_ftrace { #define JALR_T0 (0x000282e7) #define AUIPC_T0 (0x00000297) #define NOP4 (0x00000013) +#define JALR_RANGE (JALR_SIGN_MASK - 1) #define to_jalr_t0(offset) \ (((offset & JALR_OFFSET_MASK) << JALR_SHIFT) | JALR_T0) @@ -118,6 +119,9 @@ do { \ * Let auipc+jalr be the basic *mcount unit*, so we make it 8 bytes here. */ #define MCOUNT_INSN_SIZE 8 +#define MCOUNT_AUIPC_SIZE 4 +#define MCOUNT_JALR_SIZE 4 +#define MCOUNT_NOP4_SIZE 4 #ifndef __ASSEMBLY__ struct dyn_ftrace; diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c index 4b95c574fd04..5ebe412280ef 100644 --- a/arch/riscv/kernel/ftrace.c +++ b/arch/riscv/kernel/ftrace.c @@ -64,42 +64,64 @@ static int ftrace_check_current_call(unsigned long hook_pos, return 0; } -static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target, - bool enable, bool ra) +static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target, bool validate) { unsigned int call[2]; - unsigned int nops[2] = {NOP4, NOP4}; + unsigned int replaced[2]; + + make_call_t0(hook_pos, target, call); - if (ra) - make_call_ra(hook_pos, target, call); - else - make_call_t0(hook_pos, target, call); + if (validate) { + /* + * Read the text we want to modify; + * return must be -EFAULT on read error + */ + if (copy_from_kernel_nofault(replaced, (void *)hook_pos, + MCOUNT_INSN_SIZE)) + return -EFAULT; + + if (replaced[0] != call[0]) { + pr_err("%p: expected (%08x) but got (%08x)\n", + (void *)hook_pos, call[0], replaced[0]); + return -EINVAL; + } + } - /* Replace the auipc-jalr pair at once. Return -EPERM on write error. */ - if (patch_insn_write((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE)) + /* Replace the jalr at once. Return -EPERM on write error. */ + if (patch_insn_write((void *)(hook_pos + MCOUNT_AUIPC_SIZE), call + 1, MCOUNT_JALR_SIZE)) return -EPERM; return 0; } -int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) +static int __ftrace_modify_call_site(ftrace_func_t *hook_pos, ftrace_func_t target, bool enable) { - unsigned int call[2]; + ftrace_func_t call = target; + ftrace_func_t nops = &ftrace_stub; - make_call_t0(rec->ip, addr, call); - - if (patch_insn_write((void *)rec->ip, call, MCOUNT_INSN_SIZE)) - return -EPERM; + WRITE_ONCE(*hook_pos, enable ? call : nops); return 0; } +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long distance, orig_addr; + + orig_addr = (unsigned long)&ftrace_caller; + distance = addr > orig_addr ? addr - orig_addr : orig_addr - addr; + if (distance > JALR_RANGE) + return -EINVAL; + + return __ftrace_modify_call(rec->ip, addr, false); +} + int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { - unsigned int nops[2] = {NOP4, NOP4}; + unsigned int nops[1] = {NOP4}; - if (patch_insn_write((void *)rec->ip, nops, MCOUNT_INSN_SIZE)) + if (patch_insn_write((void *)(rec->ip + MCOUNT_AUIPC_SIZE), nops, MCOUNT_NOP4_SIZE)) return -EPERM; return 0; @@ -114,21 +136,23 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, */ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) { + unsigned int nops[2]; int out; + make_call_t0(rec->ip, &ftrace_caller, nops); + nops[1] = NOP4; + mutex_lock(&text_mutex); - out = ftrace_make_nop(mod, rec, MCOUNT_ADDR); + out = patch_insn_write((void *)rec->ip, nops, MCOUNT_INSN_SIZE); mutex_unlock(&text_mutex); return out; } +ftrace_func_t ftrace_call_dest = ftrace_stub; int ftrace_update_ftrace_func(ftrace_func_t func) { - int ret = __ftrace_modify_call((unsigned long)&ftrace_call, - (unsigned long)func, true, true); - - return ret; + return __ftrace_modify_call_site(&ftrace_call_dest, func, true); } struct ftrace_modify_param { @@ -182,7 +206,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, if (ret) return ret; - return __ftrace_modify_call(caller, addr, true, false); + return __ftrace_modify_call(caller, addr, true); } #endif @@ -217,17 +241,17 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, prepare_ftrace_return(&fregs->ra, ip, fregs->s0); } #else /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */ -extern void ftrace_graph_call(void); +ftrace_func_t ftrace_graph_call_dest = ftrace_stub; int ftrace_enable_ftrace_graph_caller(void) { - return __ftrace_modify_call((unsigned long)&ftrace_graph_call, - (unsigned long)&prepare_ftrace_return, true, true); + return __ftrace_modify_call_site(&ftrace_graph_call_dest, + &prepare_ftrace_return, true); } int ftrace_disable_ftrace_graph_caller(void) { - return __ftrace_modify_call((unsigned long)&ftrace_graph_call, - (unsigned long)&prepare_ftrace_return, false, true); + return __ftrace_modify_call_site(&ftrace_graph_call_dest, + &prepare_ftrace_return, false); } #endif /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */ #endif /* CONFIG_DYNAMIC_FTRACE */ diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S index e988bd26b28b..bc06e8ab81cf 100644 --- a/arch/riscv/kernel/mcount-dyn.S +++ b/arch/riscv/kernel/mcount-dyn.S @@ -162,7 +162,8 @@ SYM_FUNC_START(ftrace_caller) mv a3, sp SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) - call ftrace_stub + REG_L ra, ftrace_call_dest + jalr 0(ra) #ifdef CONFIG_FUNCTION_GRAPH_TRACER addi a0, sp, ABI_RA @@ -172,7 +173,8 @@ SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) mv a2, s0 #endif SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) - call ftrace_stub + REG_L ra, ftrace_graph_call_dest + jalr 0(ra) #endif RESTORE_ABI jr t0 @@ -185,7 +187,8 @@ SYM_FUNC_START(ftrace_caller) PREPARE_ARGS SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) - call ftrace_stub + REG_L ra, ftrace_call_dest + jalr 0(ra) RESTORE_ABI_REGS bnez t1, .Ldirect