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 93FDB1E492; Wed, 19 Jun 2024 13:44:24 +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=1718804664; cv=none; b=SWyysccYEJyLa972ZHdu+5k0dneX1c65NspsMo38hLattT/OKDbLerfF7UP32dNpporWahikOOhECDS3BLjZEB8hJtOAcw6G4u55zjf80WZdOUsBeK7fgPKW7XvgiPuICg9vPx1rW0d1YMCZ1jjKk7u6TE+joes2/CzGslVZ6Z0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718804664; c=relaxed/simple; bh=Wkexoc0cDdq8jJKOXWR0FU3hrNxUSmtW5T6O6D7F3Yw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mV7jZXVS+bwDoo/T0RL7LJg1YJXNy7vNt3mTmpC5AAbQfQqmElVbfNQGdr6/q7jnyjAGe4gvxgk90w8NsdYUXJZe2xBw5r1d+bXUyBVizXTkEP49baGR2315S9oxRUn8JW8P7AwRBtYrQGTZQWNM2yQu4o0xM1mI/NeKpJtWrGU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ObJ/Z1FC; 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="ObJ/Z1FC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8BA67C32781; Wed, 19 Jun 2024 13:44:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1718804664; bh=Wkexoc0cDdq8jJKOXWR0FU3hrNxUSmtW5T6O6D7F3Yw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ObJ/Z1FCQR6mn0JbTmkcT53fSUEgKgpO/D9aU5ce1jKEF+Ht6qH3Ut7hpkgNvs5aJ Lzb54kmMWEcq9nQV9PqrReJMnFs6bgYfBCmAdHwVCtC+PJNXKfuH8ISGbnmmXoQBbj spgVjR6ZGn6/O8kRGUsDfgmEevnk6IDLD3ZEtfSPYdg893QirSIF2tvW4EaoirFzPt nrJWe29+ObJuD3GkkQ4WjymWrpDhWrh9UZkKNs4K6po8TQtqPR1z1Jk/dMrEeGGWZO 8IBXYfGk/Bk+Pwt+u/767WJFT3NXjEI2AsAmGF/0rWrfNlTmMsQVL6zx7e9BG7h92V JqEpmWLZtGw/Q== Date: Wed, 19 Jun 2024 10:44:18 -0300 From: Arnaldo Carvalho de Melo To: Howard Chu Cc: Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , Kan Liang , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: Re: [PATCH v2 2/5] perf trace: Augment enum syscall arguments with BTF Message-ID: References: <20240619082042.4173621-1-howardchu95@gmail.com> <20240619082042.4173621-3-howardchu95@gmail.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240619082042.4173621-3-howardchu95@gmail.com> On Wed, Jun 19, 2024 at 04:20:39PM +0800, Howard Chu wrote: > This is a feature implemented on the basis of the previous bug fix > https://lore.kernel.org/linux-perf-users/d18a9606-ac9f-4ca7-afaf-fcf4c951cb90@web.de/T/#t > > In this patch, BTF is used to turn enum value to the corresponding > enum variable name. There is only one system call that uses enum value > as its argument, that is `landlock_add_rule()`. > > The vmlinux btf is loaded lazily, when user decided to trace the > `landlock_add_rule` syscall. But if one decides to run `perf trace` > without any arguments, the behaviour is to trace `landlock_add_rule`, > so vmlinux btf will be loaded by default. > > before: > > ``` > perf $ ./perf trace -e landlock_add_rule > 0.000 ( 0.008 ms): ldlck-test/438194 landlock_add_rule(rule_type: 2) = -1 EBADFD (File descriptor in bad state) > 0.010 ( 0.001 ms): ldlck-test/438194 landlock_add_rule(rule_type: 1) = -1 EBADFD (File descriptor in bad state) > ``` > > after: > > ``` > perf $ ./perf trace -e landlock_add_rule > 0.000 ( 0.029 ms): ldlck-test/438194 landlock_add_rule(rule_type: LANDLOCK_RULE_NET_PORT) = -1 EBADFD (File descriptor in bad state) > 0.036 ( 0.004 ms): ldlck-test/438194 landlock_add_rule(rule_type: LANDLOCK_RULE_PATH_BENEATH) = -1 EBADFD (File descriptor in bad state) > ``` > Tested-by: Arnaldo Carvalho de Melo > Suggested-by: Arnaldo Carvalho de Melo > Reviewed-by: Arnaldo Carvalho de Melo > Signed-off-by: Howard Chu > --- > tools/perf/builtin-trace.c | 96 ++++++++++++++++++++++++++++++++++++-- > 1 file changed, 91 insertions(+), 5 deletions(-) > > diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c > index c4fa8191253d..d93f34e9af74 100644 > --- a/tools/perf/builtin-trace.c > +++ b/tools/perf/builtin-trace.c > @@ -19,6 +19,7 @@ > #ifdef HAVE_LIBBPF_SUPPORT > #include > #include > +#include > #ifdef HAVE_BPF_SKEL > #include "bpf_skel/augmented_raw_syscalls.skel.h" > #endif > @@ -110,6 +111,11 @@ struct syscall_arg_fmt { > const char *name; > u16 nr_entries; // for arrays > bool show_zero; > + bool is_enum; > + struct { > + void *entries; > + u16 nr_entries; > + } btf_entry; > }; > > struct syscall_fmt { > @@ -140,6 +146,7 @@ struct trace { > #ifdef HAVE_BPF_SKEL > struct augmented_raw_syscalls_bpf *skel; > #endif > + struct btf *btf; > struct record_opts opts; > struct evlist *evlist; > struct machine *host; > @@ -897,6 +904,56 @@ static size_t syscall_arg__scnprintf_getrandom_flags(char *bf, size_t size, > .strtoul = STUL_STRARRAY_FLAGS, \ > .parm = &strarray__##array, } > > +static int btf_enum_find_entry(struct btf *btf, char *type, struct syscall_arg_fmt *arg_fmt) > +{ > + const struct btf_type *bt; > + char enum_prefix[][16] = { "enum", "const enum" }, *ep; > + int id; > + size_t i; > + > + for (i = 0; i < ARRAY_SIZE(enum_prefix); i++) { > + ep = enum_prefix[i]; > + if (strlen(type) > strlen(ep) + 1 && strstarts(type, ep)) No need for the strlen test? I.e. plain using strstarts() should be enough? > + type += strlen(ep) + 1; > + } > + > + id = btf__find_by_name(btf, type); > + if (id < 0) > + return -1; > + > + bt = btf__type_by_id(btf, id); > + if (bt == NULL) a pr_debug() stating that something that tracefs says should be in BTF and isn't found there seems to be of value here. > + return -1; > + > + arg_fmt->btf_entry.entries = btf_enum(bt); > + arg_fmt->btf_entry.nr_entries = btf_vlen(bt); > + > + return 0; > +} > + > +static size_t btf_enum_scnprintf(char *bf, size_t size, int val, struct btf *btf, char *type, > + struct syscall_arg_fmt *arg_fmt) > +{ > + struct btf_enum *be; > + int i; > + > + /* if btf_entry is NULL, find and save it to arg_fmt */ > + if (arg_fmt->btf_entry.entries == NULL) > + if (btf_enum_find_entry(btf, type, arg_fmt)) > + return 0; > + > + be = (struct btf_enum *)arg_fmt->btf_entry.entries; struct btf_enum *be = (struct btf_enum *)arg_fmt->btf_entry.entries; arg_fmt->btf_entry.entries is (void *), so we don't need the (struct btf_enum *) cast here, removing it makes the code more compact. And since we move the declaration to the same line, the info about its type is there as well. > + > + for (i = 0; i < arg_fmt->btf_entry.nr_entries; ++i, ++be) { for (int i = 0; i < arg_fmt->btf_entry.nr_entries; ++i, ++be) { ⬢[acme@toolbox perf-tools-next]$ git grep 'for (int ' tools/perf/ | wc -l 99 ⬢[acme@toolbox perf-tools-next]$ Doing it this way makes the code more compact and is allowed even in kernel code since some time ago: ⬢[acme@toolbox perf-tools-next]$ git grep 'for (int ' drivers/ | wc -l 294 ⬢[acme@toolbox perf-tools-next]$ git grep 'for (int ' kernel/ | wc -l 12 ⬢[acme@toolbox perf-tools-next]$ git grep 'for (int ' net/ | wc -l 3 ⬢[acme@toolbox perf-tools-next]$ git grep 'for (int ' mm/ | wc -l 21 ⬢[acme@toolbox perf-tools-next]$ > + if (be->val == val) { > + return scnprintf(bf, size, "%s", > + btf__name_by_offset(btf, be->name_off)); > + } > + } > + > + return 0; > +} > + > #include "trace/beauty/arch_errno_names.c" > #include "trace/beauty/eventfd.c" > #include "trace/beauty/futex_op.c" > @@ -1699,6 +1756,15 @@ static void trace__symbols__exit(struct trace *trace) > symbol__exit(); > } > > +static void trace__load_vmlinux_btf(struct trace *trace) > +{ > + trace->btf = btf__load_vmlinux_btf(); > + if (verbose > 0) { > + fprintf(trace->output, trace->btf ? "vmlinux BTF loaded\n" : > + "Failed to load vmlinux BTF\n"); > + } > +} > + > static int syscall__alloc_arg_fmts(struct syscall *sc, int nr_args) > { > int idx; > @@ -1744,7 +1810,7 @@ static const struct syscall_arg_fmt *syscall_arg_fmt__find_by_name(const char *n > } > > static struct tep_format_field * > -syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field *field) > +syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field *field, bool *use_btf) > { > struct tep_format_field *last_field = NULL; > int len; > @@ -1782,6 +1848,8 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field > * 7 unsigned long > */ > arg->scnprintf = SCA_FD; > + } else if (strstr(field->type, "enum") && use_btf != NULL) { > + *use_btf = arg->is_enum = true; Here you have to check if use_btf is NULL, as you, in this patch, later call syscall_arg_fmt__init_array(arg, field, NULL) in evsel__init_tp_arg_scnprintf(), probably you tested it all at the end of the patch series, we have to make sure that it works after each patch, so that we keep the codebase bisectable. > } else { > const struct syscall_arg_fmt *fmt = > syscall_arg_fmt__find_by_name(field->name); > @@ -1796,9 +1864,10 @@ syscall_arg_fmt__init_array(struct syscall_arg_fmt *arg, struct tep_format_field > return last_field; > } > > -static int syscall__set_arg_fmts(struct syscall *sc) > +static int syscall__set_arg_fmts(struct syscall *sc, bool *use_btf) > { > - struct tep_format_field *last_field = syscall_arg_fmt__init_array(sc->arg_fmt, sc->args); > + struct tep_format_field *last_field = syscall_arg_fmt__init_array(sc->arg_fmt, sc->args, > + use_btf); > > if (last_field) > sc->args_size = last_field->offset + last_field->size; > @@ -1810,7 +1879,9 @@ static int trace__read_syscall_info(struct trace *trace, int id) > { > char tp_name[128]; > struct syscall *sc; > + int err; > const char *name = syscalltbl__name(trace->sctbl, id); > + bool use_btf = false; > > #ifdef HAVE_SYSCALL_TABLE_SUPPORT > if (trace->syscalls.table == NULL) { > @@ -1883,7 +1954,12 @@ static int trace__read_syscall_info(struct trace *trace, int id) > sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit"); > sc->is_open = !strcmp(name, "open") || !strcmp(name, "openat"); > > - return syscall__set_arg_fmts(sc); > + err = syscall__set_arg_fmts(sc, &use_btf); > + > + if (use_btf && trace->btf == NULL) > + trace__load_vmlinux_btf(trace); > + > + return err; > } > > static int evsel__init_tp_arg_scnprintf(struct evsel *evsel) > @@ -1891,7 +1967,7 @@ static int evsel__init_tp_arg_scnprintf(struct evsel *evsel) > struct syscall_arg_fmt *fmt = evsel__syscall_arg_fmt(evsel); > > if (fmt != NULL) { > - syscall_arg_fmt__init_array(fmt, evsel->tp_format->format.fields); > + syscall_arg_fmt__init_array(fmt, evsel->tp_format->format.fields, NULL); > return 0; > } > > @@ -2103,6 +2179,16 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size, > if (trace->show_arg_names) > printed += scnprintf(bf + printed, size - printed, "%s: ", field->name); > > + if (sc->arg_fmt[arg.idx].is_enum && trace->btf) { > + size_t p = btf_enum_scnprintf(bf + printed, size - printed, val, > + trace->btf, field->type, > + &sc->arg_fmt[arg.idx]); > + if (p) { > + printed += p; > + continue; > + } > + } > + > printed += syscall_arg_fmt__scnprintf_val(&sc->arg_fmt[arg.idx], > bf + printed, size - printed, &arg, val); > } > -- > 2.45.2 >