Re: [PATCH] perf tests vmlinux-kallsyms: ignore hidden symbols

[Michael Petlan <mpetlan@redhat.com>]

On Tue, 13 Jul 2021, Jiri Olsa wrote:
> On Thu, Jul 08, 2021 at 02:28:05PM +0200, Michael Petlan wrote:
> > Symbols containing particular prefixes are purposely hidden from kallsyms.
> > The prefixes are listed in scripts/kallsyms.c, using ignored_prefixes[]
> > string array. 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.
> 
> there's also other arrays like ignored_suffixes, ignored_matches ...
> should we have them as well? should we take the whole is_ignored_symbol
> function?

Well, maybe? There hasn't been a problem with the others yet... :-)

Arnaldo, should I do a v2 with the above?
> 
> > 
> > Let's add a filter to check if a symbol not found isn't one of these before
> > failing the test.
> > 
> > The ignored_prefixes[] array has been copied from scripts/kallsyms.c and needs
> > to be updated along with the original.
> > 
> > Signed-off-by: Michael Petlan <mpetlan@redhat.com>
> > ---
> >  tools/perf/tests/vmlinux-kallsyms.c | 41 +++++++++++++++++++++++++++++
> >  1 file changed, 41 insertions(+)
> > 
> > diff --git a/tools/perf/tests/vmlinux-kallsyms.c b/tools/perf/tests/vmlinux-kallsyms.c
> > index 193b7c91b4e2..11cd276ec8fd 100644
> > --- a/tools/perf/tests/vmlinux-kallsyms.c
> > +++ b/tools/perf/tests/vmlinux-kallsyms.c
> > @@ -14,6 +14,41 @@
> >  
> >  #define UM(x) kallsyms_map->unmap_ip(kallsyms_map, (x))
> >  
> > +/* Symbol names that begin with the following are ignored. (a copy from scripts/kallsyms.c) */
> > +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
> > +};
> > +
> > +static int has_prefix(const char *prefix, const char *string)
> > +{
> > +	while(*prefix)
> > +        if(*prefix++ != *string++)
> > +            return 0;
> > +
> > +	return 1;
> > +}
> > +
> > +static int should_be_hidden(const char *sym_name)
> > +{
> > +	int i;
> > +	for(i = 0; ignored_prefixes[i] != NULL; i++)
> > +		if(has_prefix(ignored_prefixes[i], sym_name))
> > +			return 1;
> > +
> > +	return 0;
> 
> please check your patch with scripts/checkpatch.pl before posting
> 
> thanks,
> jirka
> 
>