linux-kernel - Re: [PATCH 09/52] perf probe: Convert to check dwarf

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Message-Id: <20231110192550.53b4daa1325c83da7f88417f@kernel.org>
Date:   Fri, 10 Nov 2023 19:25:50 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Stephane Eranian <eranian@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-trace-devel@...r.kernel.org, linux-toolchains@...r.kernel.org
Subject: Re: [PATCH 09/52] perf probe: Convert to check dwarf_getcfi feature

On Thu,  9 Nov 2023 15:59:28 -0800
Namhyung Kim <namhyung@...nel.org> wrote:

> Now it has a feature check for the dwarf_getcfi(), use it and convert
> the code to check HAVE_DWARF_CFI_SUPPORT definition.
> 

Looks good to me!

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks!

> Suggested-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/Makefile.config     | 5 +++++
>  tools/perf/util/probe-finder.c | 8 ++++----
>  2 files changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 8b6cffbc4858..aa55850fbc21 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -476,6 +476,11 @@ else
>        else
>          CFLAGS += -DHAVE_DWARF_GETLOCATIONS_SUPPORT
>        endif # dwarf_getlocations
> +      ifneq ($(feature-dwarf_getcfi), 1)
> +        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.142);
> +      else
> +        CFLAGS += -DHAVE_DWARF_CFI_SUPPORT
> +      endif # dwarf_getcfi
>      endif # Dwarf support
>    endif # libelf support
>  endif # NO_LIBELF
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 8d3dd85f9ff4..c8923375e30d 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -604,7 +604,7 @@ static int call_probe_finder(Dwarf_Die *sc_die, struct probe_finder *pf)
>  	ret = dwarf_getlocation_addr(&fb_attr, pf->addr, &pf->fb_ops, &nops, 1);
>  	if (ret <= 0 || nops == 0) {
>  		pf->fb_ops = NULL;
> -#if _ELFUTILS_PREREQ(0, 142)
> +#ifdef HAVE_DWARF_CFI_SUPPORT
>  	} else if (nops == 1 && pf->fb_ops[0].atom == DW_OP_call_frame_cfa &&
>  		   (pf->cfi_eh != NULL || pf->cfi_dbg != NULL)) {
>  		if ((dwarf_cfi_addrframe(pf->cfi_eh, pf->addr, &frame) != 0 &&
> @@ -615,7 +615,7 @@ static int call_probe_finder(Dwarf_Die *sc_die, struct probe_finder *pf)
>  			free(frame);
>  			return -ENOENT;
>  		}
> -#endif
> +#endif /* HAVE_DWARF_CFI_SUPPORT */
>  	}
>  
>  	/* Call finder's callback handler */
> @@ -1140,7 +1140,7 @@ static int debuginfo__find_probes(struct debuginfo *dbg,
>  
>  	pf->machine = ehdr.e_machine;
>  
> -#if _ELFUTILS_PREREQ(0, 142)
> +#ifdef HAVE_DWARF_CFI_SUPPORT
>  	do {
>  		GElf_Shdr shdr;
>  
> @@ -1150,7 +1150,7 @@ static int debuginfo__find_probes(struct debuginfo *dbg,
>  
>  		pf->cfi_dbg = dwarf_getcfi(dbg->dbg);
>  	} while (0);
> -#endif
> +#endif /* HAVE_DWARF_CFI_SUPPORT */
>  
>  	ret = debuginfo__find_probe_location(dbg, pf);
>  	return ret;
> -- 
> 2.42.0.869.gea05f2083d-goog
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>