From: Arnaldo Carvalho de Melo <acme@redhat.com>
Date: Tue, 8 Apr 2025 14:37:20 +0000 (-0300)
Subject: perf build: Warn when libdebuginfod devel files are not available
X-Git-Tag: v6.16-rc1~57^2~203
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4fce4b91fd1aabb326c46e237eb4b19ab72598f8;p=thirdparty%2Flinux.git

perf build: Warn when libdebuginfod devel files are not available

While working on 'perf version --build-options' I noticed that:

  $ perf version --build-options
  perf version 6.15.rc1.g312a07a00d31
                   aio: [ on  ]  # HAVE_AIO_SUPPORT
                   bpf: [ on  ]  # HAVE_LIBBPF_SUPPORT
         bpf_skeletons: [ on  ]  # HAVE_BPF_SKEL
            debuginfod: [ OFF ]  # HAVE_DEBUGINFOD_SUPPORT
  <SNIP>

And looking at tools/perf/Makefile.config I also noticed that it is not
opt-in, meaning we will attempt to build with it in all normal cases.

So add the usual warning at build time to let the user know that
something recommended is missing, now we see:

  Makefile.config:563: No elfutils/debuginfod.h found, no debuginfo server support, please install elfutils-debuginfod-client-devel or equivalent

And after following the recommendation:

  $ perf check feature debuginfod
            debuginfod: [ on  ]  # HAVE_DEBUGINFOD_SUPPORT
  $ ldd ~/bin/perf | grep debuginfo
	libdebuginfod.so.1 => /lib64/libdebuginfod.so.1 (0x00007fee5cf5f000)
  $

With this feature on several perf tools will fetch what is needed and
not require all the contents of the debuginfo packages, for instance:

  # rpm -qa | grep kernel-debuginfo
  # pahole --running_kernel_vmlinux
  pahole: couldn't find a vmlinux that matches the running kernel
  HINT: Maybe you're inside a container or missing a debuginfo package?
  #
  # perf trace -e open* perf probe --vars icmp_rcv
      0.000 ( 0.005 ms): perf/97391 openat(dfd: CWD, filename: "/etc/ld.so.cache", flags: RDONLY|CLOEXEC) = 3
      0.014 ( 0.004 ms): perf/97391 openat(dfd: CWD, filename: "/lib64/libm.so.6", flags: RDONLY|CLOEXEC) = 3
  <SNIP>
  32130.100 ( 0.008 ms): perf/97391 openat(dfd: CWD, filename: "/root/.cache/debuginfod_client/aa3c82b4a13f9c0e0301bebb20fe958c4db6f362/debuginfo") = 3
  <SNIP>
  Available variables at icmp_rcv
        @<icmp_rcv+0>
                struct sk_buff* skb
  <SNIP>
  #
  # pahole --running_kernel_vmlinux
  /root/.cache/debuginfod_client/aa3c82b4a13f9c0e0301bebb20fe958c4db6f362/debuginfo
  # file /root/.cache/debuginfod_client/aa3c82b4a13f9c0e0301bebb20fe958c4db6f362/debuginfo
  /root/.cache/debuginfod_client/aa3c82b4a13f9c0e0301bebb20fe958c4db6f362/debuginfo: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=aa3c82b4a13f9c0e0301bebb20fe958c4db6f362, with debug_info, not stripped
  # ls -la /root/.cache/debuginfod_client/aa3c82b4a13f9c0e0301bebb20fe958c4db6f362/debuginfo
  -r--------. 1 root root 475401512 Mar 27 21:00 /root/.cache/debuginfod_client/aa3c82b4a13f9c0e0301bebb20fe958c4db6f362/debuginfo
  #

Then, cached:

  # perf stat --null perf probe --vars icmp_rcv
  Available variables at icmp_rcv
        @<icmp_rcv+0>
                struct sk_buff* skb

   Performance counter stats for 'perf probe --vars icmp_rcv':

       0.671389041 seconds time elapsed

       0.519176000 seconds user
       0.150860000 seconds sys

Fixes: c7a14fdcb3fa7736 ("perf build-ids: Fall back to debuginfod query if debuginfo not found")
Tested-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Link: https://lore.kernel.org/r/Z_dkNDj9EPFwPqq1@gmail.com
[ Folded patch from Ingo to have the debian/ubuntu devel package added build warning message ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 8ff1d8ade73fc..9f08a6e96b351 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -559,6 +559,8 @@ ifndef NO_LIBELF
     ifeq ($(feature-libdebuginfod), 1)
       CFLAGS += -DHAVE_DEBUGINFOD_SUPPORT
       EXTLIBS += -ldebuginfod
+    else
+      $(warning No elfutils/debuginfod.h found, no debuginfo server support, please install libdebuginfod-dev/elfutils-debuginfod-client-devel or equivalent)
     endif
   endif