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

[Jiri Olsa <jolsa@redhat.com>]

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?

> 
> 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