From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Michael Petlan <mpetlan@redhat.com>, Ian Rogers <irogers@google.com>
Cc: linux-perf-users@vger.kernel.org, Jiri Olsa <jolsa@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] perf tests vmlinux-kallsyms: ignore hidden symbols
Date: Wed, 29 Sep 2021 18:10:33 -0300 [thread overview]
Message-ID: <YVTWSXjThbbZbE0L@kernel.org> (raw)
In-Reply-To: <CAP-5=fUN_fYmgm69ruBvp6E+nkLKsTvZwHqGzaRd471MhMRykA@mail.gmail.com>
Em Wed, Sep 22, 2021 at 09:36:11AM -0700, Ian Rogers escreveu:
> On Wed, Sep 22, 2021 at 8:27 AM Michael Petlan <mpetlan@redhat.com> wrote:
> >
> > Certain kernel symbols are purposely hidden from kallsyms. The function
> > is_ignored_symbol() from scripts/kallsyms.c decides if a symbol should
> > be hidden or not.
> >
> > The perf test "vmlinux symtab matches kallsyms" fails in case perf finds
> > some of the hidden symbols in its machine image and can't match them to
> > kallsyms.
> >
> > Let's add a filter to check if a symbol not found isn't one of these
> > before failing the test.
> >
> > The function is_ignored_symbol() has been copied from scripts/kallsyms.c
> > and needs to be updated along with the original.
> >
> > Signed-off-by: Michael Petlan <mpetlan@redhat.com>
>
> Acked-by: Ian Rogers <irogers@google.com>
>
> It is a shame this can't be a library to ensure the function is kept in sync.
We can adapt :-)
⬢[acme@toolbox perf]$ sed -n -e '/static bool is_ignored_symbol.*/,/^}.*/ p' scripts/kallsyms.c > original
⬢[acme@toolbox perf]$ sed -n -e '/static bool is_ignored_symbol.*/,/^}.*/ p' tools/perf/tests/vmlinux-kallsyms.c > copy
⬢[acme@toolbox perf]$ diff -u original copy
⬢[acme@toolbox perf]$
⬢[acme@toolbox perf]$ sed -n -e '/static bool is_ignored_symbol.*/,/^}.*/ p' scripts/kallsyms.c
static bool is_ignored_symbol(const char *name, char type)
{
/* Symbol names that exactly match to the following are ignored.*/
static const char * const ignored_symbols[] = {
/*
* Symbols which vary between passes. Passes 1 and 2 must have
* identical symbol lists. The kallsyms_* symbols below are
* only added after pass 1, they would be included in pass 2
* when --all-symbols is specified so exclude them to get a
* stable symbol list.
*/
"kallsyms_addresses",
"kallsyms_offsets",
"kallsyms_relative_base",
"kallsyms_num_syms",
"kallsyms_names",
"kallsyms_markers",
"kallsyms_token_table",
"kallsyms_token_index",
/* Exclude linker generated symbols which vary between passes */
"_SDA_BASE_", /* ppc */
"_SDA2_BASE_", /* ppc */
NULL
};
/* Symbol names that begin with the following are ignored.*/
static const char * const ignored_prefixes[] = {
"$", /* local symbols for ARM, MIPS, etc. */
".LASANPC", /* s390 kasan local symbols */
"__crc_", /* modversions */
"__efistub_", /* arm64 EFI stub namespace */
"__kvm_nvhe_", /* arm64 non-VHE KVM namespace */
"__AArch64ADRPThunk_", /* arm64 lld */
"__ARMV5PILongThunk_", /* arm lld */
"__ARMV7PILongThunk_",
"__ThumbV7PILongThunk_",
"__LA25Thunk_", /* mips lld */
"__microLA25Thunk_",
NULL
};
/* Symbol names that end with the following are ignored.*/
static const char * const ignored_suffixes[] = {
"_from_arm", /* arm */
"_from_thumb", /* arm */
"_veneer", /* arm */
NULL
};
/* Symbol names that contain the following are ignored.*/
static const char * const ignored_matches[] = {
".long_branch.", /* ppc stub */
".plt_branch.", /* ppc stub */
NULL
};
const char * const *p;
for (p = ignored_symbols; *p; p++)
if (!strcmp(name, *p))
return true;
for (p = ignored_prefixes; *p; p++)
if (!strncmp(name, *p, strlen(*p)))
return true;
for (p = ignored_suffixes; *p; p++) {
int l = strlen(name) - strlen(*p);
if (l >= 0 && !strcmp(name + l, *p))
return true;
}
for (p = ignored_matches; *p; p++) {
if (strstr(name, *p))
return true;
}
if (type == 'U' || type == 'u')
return true;
/* exclude debugging symbols */
if (type == 'N' || type == 'n')
return true;
if (toupper(type) == 'A') {
/* Keep these useful absolute symbols */
if (strcmp(name, "__kernel_syscall_via_break") &&
strcmp(name, "__kernel_syscall_via_epc") &&
strcmp(name, "__kernel_sigtramp") &&
strcmp(name, "__gp"))
return true;
}
return false;
}
⬢[acme@toolbox perf]$
This should be added to tools/perf/check-headers.sh as a new
function_check() function that receives three parameters:
function_check scripts/kallsyms.c tools/perf/tests/vmlinux-kallsyms.c is_ignored_symbol
The regexps can also be tightened up a bit.
Michael, can you cook up a patch for this?
Thanks,
- Arnaldo
next prev parent reply other threads:[~2021-09-29 21:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-22 15:27 [PATCH] perf tests vmlinux-kallsyms: ignore hidden symbols Michael Petlan
2021-09-22 16:36 ` Ian Rogers
2021-09-29 17:14 ` Arnaldo Carvalho de Melo
2021-09-29 21:10 ` Arnaldo Carvalho de Melo [this message]
-- strict thread matches above, loose matches on Subject: below --
2021-07-08 12:28 Michael Petlan
2021-07-13 9:57 ` Jiri Olsa
2021-07-23 8:54 ` Michael Petlan
2021-07-23 9:03 ` Michael Petlan
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