From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-185.mta1.migadu.com (out-185.mta1.migadu.com [95.215.58.185]) (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 BADC2131BDD for ; Thu, 31 Oct 2024 05:27:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.185 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730352451; cv=none; b=E/XW0Nzrs+il0BXm/xe1TsRgVZII6/knvGH/tX0kwNPT4tHfAAVDYlC689RKNBgXi8U62ildjkpetlsHi6gdO03SSjv1Ne+LFX876KTtRv5WIXwVjwCLjpud8WJGAY9ONvcsCtnD5x/F5kxZBtJgGYtwUNnRXY8XioNip5qKS8w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730352451; c=relaxed/simple; bh=7G4Mzo3iB96zMi+5HCTVwzjdbbhW28GB2oQcs0wnwFw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DfhVoNuuJ8CKyCjWmsUOZBLhYInnIDrhFgB2Q7Yk587P0J4Yt8AjlpKQyS9LAe56rWidNtifqSuQYEMJcTUMpZ4We0jldYKR0T8olWUOc2eiEUz3u0TR1kZ5vdLsauLMo1QU+irSV9TzM56Batv9jatCaiCdaqWzwjCvDvjAF64= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=OcYh0j/j; arc=none smtp.client-ip=95.215.58.185 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="OcYh0j/j" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1730352444; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=s7GakDS8gXZDrITGXcw984pYrfx+sVRGojPXsl/D4XY=; b=OcYh0j/jj0ybNMxEg4z1Vj3mFE04UjLLc3VMNOW+0wrXcDP18Q9NrjTWP9hw0gXfGhDCMo cfxpHd76ynsFunn8w+3G1NLrnLQgcu0eRFgav5mt43xLVC0C90h91pJ0fHFxW3f/BscinI 1pmP6vZPr1whWZv+I43GUL4MuELcCho= Date: Thu, 31 Oct 2024 13:27:14 +0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf] bpf, bpftool: Fix incorrect disasm pc To: Quentin Monnet , Leon Hwang , bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kernel-patches-bot@fb.com, Stanislav Fomichev , Yonghong Song , Gray Liang References: <20241030094741.22929-1-hffilwlqm@gmail.com> <1b492a6f-c7e8-4dba-84dd-35aafb6c2ede@kernel.org> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Leon Hwang In-Reply-To: <1b492a6f-c7e8-4dba-84dd-35aafb6c2ede@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 2024/10/31 08:27, Quentin Monnet wrote: > 2024-10-30 17:47 UTC+0800 ~ Leon Hwang >> From: Leon Hwang >> >> This patch addresses the bpftool issue "Wrong callq address displayed"[0]. >> >> The issue stemmed from an incorrect program counter (PC) value used during >> disassembly with LLVM or libbfd. To calculate the correct address for >> relative calls, the PC argument must reflect the actual address in the >> kernel. >> >> [0] https://github.com/libbpf/bpftool/issues/109 >> >> Fixes: e1947c750ffe ("bpftool: Refactor disassembler for JIT-ed programs") >> Signed-off-by: Leon Hwang >> --- >> tools/bpf/bpftool/jit_disasm.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/tools/bpf/bpftool/jit_disasm.c b/tools/bpf/bpftool/jit_disasm.c >> index 7b8d9ec89ebd3..fe8fabba4b05f 100644 >> --- a/tools/bpf/bpftool/jit_disasm.c >> +++ b/tools/bpf/bpftool/jit_disasm.c >> @@ -114,8 +114,7 @@ disassemble_insn(disasm_ctx_t *ctx, unsigned char *image, ssize_t len, int pc) >> char buf[256]; >> int count; >> >> - count = LLVMDisasmInstruction(*ctx, image + pc, len - pc, pc, >> - buf, sizeof(buf)); >> + count = LLVMDisasmInstruction(*ctx, image, len, pc, buf, sizeof(buf)); >> if (json_output) >> printf_json(buf); >> else >> @@ -360,7 +359,8 @@ int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes, >> printf("%4x:" DISASM_SPACER, pc); >> } >> >> - count = disassemble_insn(&ctx, image, len, pc); >> + count = disassemble_insn(&ctx, image + pc, len - pc, >> + func_ksym + pc); > > Thanks a lot for looking into this! Your patch does solve the issue for > the LLVM disassembler (nice!), but it breaks the libbfd one: > > > $ ./bpftool version | grep features > features: libbfd > # ./bpftool prog dump j id 111 op > int xdp_redirect_map_0(struct xdp_md * xdp): > bpf_prog_a8f6f9c4be77b94c_xdp_redirect_map_0: > ; return bpf_redirect_map(&tx_port, 0, 0); > 0: Address 0xffffffffc01ae950 is out of bounds. > > I don't think we can change the PC in the case of libbfd, as far as I > can tell it needs to point to the first instruction to disassemble. Two > of the arguments we pass to disassemble_insn(), image and len, are > ignored by the libbfd disassembler; so it leaves only the ctx argument > that we can maybe update to pass the func_ksym, but I haven't found how > to do that yet (if possible at all). > > Thanks, > Quentin > Hi Quentin, After diving into the details of libbfd, I’ve found a way to correct the callq address. By adjusting the relative addresses using func_ksym within a custom info->print_addr_func, we can achieve accurate results. Here’s the updated patch: >From 687f165fe79b67ba457672bb682bde3d916ce0cd Mon Sep 17 00:00:00 2001 From: Leon Hwang Date: Thu, 31 Oct 2024 13:00:05 +0800 Subject: [PATCH bpf v2] bpf, bpftool: Fix incorrect disasm pc This patch addresses the bpftool issue "Wrong callq address displayed"[0]. The issue stemmed from an incorrect program counter (PC) value used during disassembly with LLVM or libbfd. For LLVM: The PC argument must represent the actual address in the kernel to compute the correct relative address. For libbfd: The relative address can be adjusted by adding func_ksym within the custom info->print_address_func to yield the correct address. [0] https://github.com/libbpf/bpftool/issues/109 Fixes: e1947c750ffe ("bpftool: Refactor disassembler for JIT-ed programs") Acked-by: Yonghong Song Signed-off-by: Leon Hwang --- tools/bpf/bpftool/jit_disasm.c | 40 ++++++++++++++++++++++++---------- 1 file changed, 29 insertions(+), 11 deletions(-) diff --git a/tools/bpf/bpftool/jit_disasm.c b/tools/bpf/bpftool/jit_disasm.c index 7b8d9ec89..f76d4bf0c 100644 --- a/tools/bpf/bpftool/jit_disasm.c +++ b/tools/bpf/bpftool/jit_disasm.c @@ -80,7 +80,8 @@ symbol_lookup_callback(__maybe_unused void *disasm_info, static int init_context(disasm_ctx_t *ctx, const char *arch, __maybe_unused const char *disassembler_options, - __maybe_unused unsigned char *image, __maybe_unused ssize_t len) + __maybe_unused unsigned char *image, __maybe_unused ssize_t len, + __maybe_unused __u64 func_ksym) { char *triple; @@ -109,12 +110,13 @@ static void destroy_context(disasm_ctx_t *ctx) } static int -disassemble_insn(disasm_ctx_t *ctx, unsigned char *image, ssize_t len, int pc) +disassemble_insn(disasm_ctx_t *ctx, unsigned char *image, ssize_t len, int pc, + __u64 func_ksym) { char buf[256]; int count; - count = LLVMDisasmInstruction(*ctx, image + pc, len - pc, pc, + count = LLVMDisasmInstruction(*ctx, image + pc, len - pc, func_ksym + pc, buf, sizeof(buf)); if (json_output) printf_json(buf); @@ -137,7 +139,20 @@ int disasm_init(void) #define DISASM_SPACER "\t" typedef struct { - struct disassemble_info *info; + struct disassemble_info info; + __u64 func_ksym; +} disasm_info; + +static void disasm_print_addr(bfd_vma addr, struct disassemble_info *info) +{ + disasm_info *dinfo = container_of(info, disasm_info, info); + + addr += dinfo->func_ksym; + generic_print_address(addr, info); +} + +typedef struct { + disasm_info *info; disassembler_ftype disassemble; bfd *bfdf; } disasm_ctx_t; @@ -215,7 +230,7 @@ static int fprintf_json_styled(void *out, static int init_context(disasm_ctx_t *ctx, const char *arch, const char *disassembler_options, - unsigned char *image, ssize_t len) + unsigned char *image, ssize_t len, __u64 func_ksym) { struct disassemble_info *info; char tpath[PATH_MAX]; @@ -238,12 +253,13 @@ static int init_context(disasm_ctx_t *ctx, const char *arch, } bfdf = ctx->bfdf; - ctx->info = malloc(sizeof(struct disassemble_info)); + ctx->info = malloc(sizeof(disasm_info)); if (!ctx->info) { p_err("mem alloc failed"); goto err_close; } - info = ctx->info; + ctx->info->func_ksym = func_ksym; + info = &ctx->info->info; if (json_output) init_disassemble_info_compat(info, stdout, @@ -272,6 +288,7 @@ static int init_context(disasm_ctx_t *ctx, const char *arch, info->disassembler_options = disassembler_options; info->buffer = image; info->buffer_length = len; + info->print_address_func = disasm_print_addr; disassemble_init_for_target(info); @@ -304,9 +321,10 @@ static void destroy_context(disasm_ctx_t *ctx) static int disassemble_insn(disasm_ctx_t *ctx, __maybe_unused unsigned char *image, - __maybe_unused ssize_t len, int pc) + __maybe_unused ssize_t len, __u64 pc, + __maybe_unused __u64 func_ksym) { - return ctx->disassemble(pc, ctx->info); + return ctx->disassemble(pc, &ctx->info->info); } int disasm_init(void) @@ -331,7 +349,7 @@ int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes, if (!len) return -1; - if (init_context(&ctx, arch, disassembler_options, image, len)) + if (init_context(&ctx, arch, disassembler_options, image, len, func_ksym)) return -1; if (json_output) @@ -360,7 +378,7 @@ int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes, printf("%4x:" DISASM_SPACER, pc); } - count = disassemble_insn(&ctx, image, len, pc); + count = disassemble_insn(&ctx, image, len, pc, func_ksym); if (json_output) { /* Operand array, was started in fprintf_json. Before -- 2.44.0 Thanks, Leon