From mboxrd@z Thu Jan 1 00:00:00 1970 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 10BE818EB0; Wed, 8 Jan 2025 04:52:20 +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=1736311941; cv=none; b=izvRYn5WGZHgs0HhHAans0MEPtwQfcUcnZ/mqdzYfi+2pDw2iusgFf2FLDY5gOeLvE5Ohp4Lyn3MgdUcHFD7YrNSCnL3//vIlVBiGMULNsDckVbLvlGq0QV/nXlf1ycEtQMjDZ54NVcPSz18LsxkHopkBEXMIqNtIecycHet2i0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736311941; c=relaxed/simple; bh=D1PhWHZp6We3lr7kB99PxDSEro3BDLrjugvo4kINodU=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=aET6iJRlkKzLukY4eI6OtE9tVd6ylHPkf9t+q6iI8BBRfIRsD22f48r4E3rDucl8CDeLOtrGDWhelOThJqsPWwTQYurs0fSvEWl4JupeDXMNAUha6lRzEJ411CoLAf/JwWwugx576TFZAUzUwiUGPtsrgd86jjvPr0wd+VPButk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=G3xHI011; 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="G3xHI011" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 94B7EC4CED0; Wed, 8 Jan 2025 04:52:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736311940; bh=D1PhWHZp6We3lr7kB99PxDSEro3BDLrjugvo4kINodU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=G3xHI011+ui/VTEAVoPJqf+lbvbeMZkCu1YPLBPK40W2Jws/lvEi9sP1YaZ1LJlkA Gy78ufGq+CkPO+m66r0EqwwhMnExEh2gbDFvHY1UwaUlrTycxFAfJMCsgmZY0HNdNn 1x5SXwfKOhde+qw4crp++MKO1l26wstLJvtAffCf6dHn/gYTIYINlq2z2ZbcqDicMK eB+AK0y8K0XcrR10EwPHvv/hX4RpKojdn91lsbSXPzSwVlRhkFgwkEZSioDo149//3 8l53F0fh8jyAT3ptqP6+i0cElf/5KhKrAE/xMK7BT5iGnANhDPTQ2Dh0IBSyIw4rxv fd3KhGgdFECHw== Date: Wed, 8 Jan 2025 13:52:17 +0900 From: Masami Hiramatsu (Google) To: Donglin Peng Cc: Steven Rostedt , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Sven Schnelle , Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren , Zheng Yejian , bpf@vger.kernel.org Subject: Re: [PATCH v2 1/4] ftrace: Add print_function_args() Message-Id: <20250108135217.9db8d131835acfb6ce4baa88@kernel.org> In-Reply-To: References: <20241223201347.609298489@goodmis.org> <20241223201541.898496620@goodmis.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Wed, 8 Jan 2025 10:30:08 +0800 Donglin Peng wrote: > Steven Rostedt 于2024年12月24日 周二04:14写道： > > > From: Sven Schnelle > > > > Add a function to decode argument types with the help of BTF. Will > > be used to display arguments in the function and function graph > > tracer. > > > > It can only handle simply arguments and up to FTRACE_REGS_MAX_ARGS number > > of arguments. When it hits a max, it will print ", ...": > > > > page_to_skb(vi=0xffff8d53842dc980, rq=0xffff8d53843a0800, > > page=0xfffffc2e04337c00, offset=6160, len=64, truesize=1536, ...) > > > > And if it hits an argument that is not recognized, it will print the raw > > value and the type of argument it is: > > > > make_vfsuid(idmap=0xffffffff87f99db8, fs_userns=0xffffffff87e543c0, > > kuid=0x0 (STRUCT)) > > __pti_set_user_pgtbl(pgdp=0xffff8d5384ab47f8, pgd=0x110e74067 (STRUCT)) > > > > Co-developed-by: Steven Rostedt (Google) > > Signed-off-by: Sven Schnelle > > Signed-off-by: Steven Rostedt (Google) > > --- > > Changes since v1: > > https://lore.kernel.org/20240904065908.1009086-5-svens@linux.ibm.com > > > > - Added Config option FUNCTION_TRACE_ARGS to this patch > > (unconditional if dependencies are met) > > > > - Changed the print_function_args() function to take an array of > > unsigned long args and not the ftrace_regs pointer. The ftrace_regs > > should be opaque from generic code. > > > > - Have the function print the name of an BTF type that is not supported. > > > > - Added FTRACE_REGS_MAX_ARGS as the number of arguments saved in > > the event and printed out. > > > > - Print "...," if the number of arguments goes past FTRACE_REGS_MAX_ARGS. > > > > include/linux/ftrace_regs.h | 5 +++ > > kernel/trace/Kconfig | 6 +++ > > kernel/trace/trace_output.c | 78 +++++++++++++++++++++++++++++++++++++ > > kernel/trace/trace_output.h | 9 +++++ > > 4 files changed, 98 insertions(+) > > > > diff --git a/include/linux/ftrace_regs.h b/include/linux/ftrace_regs.h > > index bbc1873ca6b8..15627ceea9bc 100644 > > --- a/include/linux/ftrace_regs.h > > +++ b/include/linux/ftrace_regs.h > > @@ -35,4 +35,9 @@ struct ftrace_regs; > > > > #endif /* HAVE_ARCH_FTRACE_REGS */ > > > > +/* This can be overridden by the architectures */ > > +#ifndef FTRACE_REGS_MAX_ARGS > > +# define FTRACE_REGS_MAX_ARGS 6 > > +#endif > > + > > #endif /* _LINUX_FTRACE_REGS_H */ > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > > index d570b8b9c0a9..60412c1012ef 100644 > > --- a/kernel/trace/Kconfig > > +++ b/kernel/trace/Kconfig > > @@ -263,6 +263,12 @@ config FUNCTION_GRAPH_RETADDR > > the function is called. This feature is off by default, and you > > can > > enable it via the trace option funcgraph-retaddr. > > > > +config FUNCTION_TRACE_ARGS > > + bool > > + depends on HAVE_FUNCTION_ARG_ACCESS_API > > + depends on DEBUG_INFO_BTF > > + default y > > + > > config DYNAMIC_FTRACE > > bool "enable/disable function tracing dynamically" > > depends on FUNCTION_TRACER > > diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c > > index da748b7cbc4d..40d6c7a9e0c4 100644 > > --- a/kernel/trace/trace_output.c > > +++ b/kernel/trace/trace_output.c > > @@ -12,8 +12,11 @@ > > #include > > #include > > #include > > +#include > > +#include > > > > #include "trace_output.h" > > +#include "trace_btf.h" > > > > /* must be a power of 2 */ > > #define EVENT_HASHSIZE 128 > > @@ -680,6 +683,81 @@ int trace_print_lat_context(struct trace_iterator > > *iter) > > return !trace_seq_has_overflowed(s); > > } > > > > +#ifdef CONFIG_FUNCTION_TRACE_ARGS > > +void print_function_args(struct trace_seq *s, unsigned long *args, > > + unsigned long func) > > +{ > > + const struct btf_param *param; > > + const struct btf_type *t; > > + const char *param_name; > > + char name[KSYM_NAME_LEN]; > > + unsigned long arg; > > + struct btf *btf; > > + s32 tid, nr = 0; > > + int i; > > + > > + trace_seq_printf(s, "("); > > + > > + if (!args) > > + goto out; > > + if (lookup_symbol_name(func, name)) > > + goto out; > > + > > + btf = bpf_get_btf_vmlinux(); > > + if (IS_ERR_OR_NULL(btf)) > > + goto out; > > > There is no need to the retrieve the BTF of vmlinux, as btf_find_func_proto > will return the correct BTF via its second parameter. Good catch! The second parameter of btf_find_func_proto() is output. Thank you, > > — donglin > > > > + > > + t = btf_find_func_proto(name, &btf); > > + if (IS_ERR_OR_NULL(t)) > > + goto out; > > + > > + param = btf_get_func_param(t, &nr); > > + if (!param) > > + goto out_put; > > + > > + for (i = 0; i < nr; i++) { > > + /* This only prints what the arch allows (6 args by > > default) */ > > + if (i == FTRACE_REGS_MAX_ARGS) { > > + trace_seq_puts(s, "..."); > > + break; > > + } > > + > > + arg = args[i]; > > + > > + param_name = btf_name_by_offset(btf, param[i].name_off); > > + if (param_name) > > + trace_seq_printf(s, "%s=", param_name); > > + t = btf_type_skip_modifiers(btf, param[i].type, &tid); > > + > > + switch (t ? BTF_INFO_KIND(t->info) : BTF_KIND_UNKN) { > > + case BTF_KIND_UNKN: > > + trace_seq_putc(s, '?'); > > + /* Still print unknown type values */ > > + fallthrough; > > + case BTF_KIND_PTR: > > + trace_seq_printf(s, "0x%lx", arg); > > + break; > > + case BTF_KIND_INT: > > + trace_seq_printf(s, "%ld", arg); > > + break; > > + case BTF_KIND_ENUM: > > + trace_seq_printf(s, "%ld", arg); > > + break; > > + default: > > + /* This does not handle complex arguments */ > > + trace_seq_printf(s, "0x%lx (%s)", arg, > > btf_type_str(t)); > > + break; > > + } > > + if (i < nr - 1) > > + trace_seq_printf(s, ", "); > > + } > > +out_put: > > + btf_put(btf); > > +out: > > + trace_seq_printf(s, ")"); > > +} > > +#endif > > + > > /** > > * ftrace_find_event - find a registered event > > * @type: the type of event to look for > > diff --git a/kernel/trace/trace_output.h b/kernel/trace/trace_output.h > > index dca40f1f1da4..2e305364f2a9 100644 > > --- a/kernel/trace/trace_output.h > > +++ b/kernel/trace/trace_output.h > > @@ -41,5 +41,14 @@ extern struct rw_semaphore trace_event_sem; > > #define SEQ_PUT_HEX_FIELD(s, x) \ > > trace_seq_putmem_hex(s, &(x), sizeof(x)) > > > > +#ifdef CONFIG_FUNCTION_TRACE_ARGS > > +void print_function_args(struct trace_seq *s, unsigned long *args, > > + unsigned long func); > > +#else > > +static inline void print_function_args(struct trace_seq *s, unsigned long > > *args, > > + unsigned long func) { > > + trace_seq_puts(s, "()"); > > +} > > +#endif > > #endif > > > > -- > > 2.45.2 > > > > > > -- Masami Hiramatsu (Google)