linux-kernel - [PATCH 2/3] perf: build: Fix build feature-dwarf

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Message-Id: <20240806113210.1649909-3-yangjihong@bytedance.com>
Date: Tue,  6 Aug 2024 19:32:09 +0800
From: Yang Jihong <yangjihong@...edance.com>
To: peterz@...radead.org,
	mingo@...hat.com,
	acme@...nel.org,
	namhyung@...nel.org,
	mark.rutland@....com,
	alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org,
	irogers@...gle.com,
	adrian.hunter@...el.com,
	kan.liang@...ux.intel.com,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: yangjihong@...edance.com
Subject: [PATCH 2/3] perf: build: Fix build feature-dwarf_getlocations fail for old libdw

For libdw versions below 0.177, need to link libdl.a in addition to
libbebl.a during static compilation, otherwise feature-dwarf_getlocations
compilation will fail.

Before:

  $ make LDFLAGS=-static
    BUILD:   Doing 'make -j20' parallel build
  <SNIP>
  Makefile.config:483: Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157
  <SNIP>

  $ cat ../build/feature/test-dwarf_getlocations.make.output
  /usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libebl.a(eblclosebackend.o): in function `ebl_closebackend':
  (.text+0x20): undefined reference to `dlclose'
  collect2: error: ld returned 1 exit status

After:

  $ make LDFLAGS=-static
  <SNIP>
    Auto-detecting system features:
  ...                                   dwarf: [ on  ]
  <SNIP>

    $ ./perf probe
   Usage: perf probe [<options>] 'PROBEDEF' ['PROBEDEF' ...]
      or: perf probe [<options>] --add 'PROBEDEF' [--add 'PROBEDEF' ...]
      or: perf probe [<options>] --del '[GROUP:]EVENT' ...
      or: perf probe --list [GROUP:]EVENT ...
  <SNIP>

Fixes: 536661da6ea1 ("perf: build: Only link libebl.a for old libdw")
Signed-off-by: Yang Jihong <yangjihong@...edance.com>
---
 tools/build/feature/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index b18513ec4da6..1fc651cae9e5 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -179,7 +179,7 @@ ifeq ($(findstring -static,${LDFLAGS}),-static)
   # Elfutils merged libebl.a into libdw.a starting from version 0.177,
   # Link libebl.a only if libdw is older than this version.
   ifeq ($(shell test $(LIBDW_VERSION_2)0 -lt 1770; echo $$?),0)
-    DWARFLIBS += -lebl
+    DWARFLIBS += -lebl -ldl
   endif
 endif
 
-- 
2.25.1