linux-kernel - [PATCH v2 1/3] perf: build: Fix static compilation error when libdw is not installed

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Message-Id: <20240806114801.1652417-2-yangjihong@bytedance.com>
Date: Tue,  6 Aug 2024 19:47:59 +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 v2 1/3] perf: build: Fix static compilation error when libdw is not installed

If libdw is not installed in build environment, the output of
'pkg-config --modversion libdw' is empty, causing LIBDW_VERSION_2
to be empty and the shell test will have the following error:

  /bin/sh: 1: test: -lt: unexpected operator

Before:

  $ pkg-config --modversion libdw
  Package libdw was not found in the pkg-config search path.
  Perhaps you should add the directory containing `libdw.pc'
  to the PKG_CONFIG_PATH environment variable
  No package 'libdw' found
  $ make LDFLAGS=-static -j16
    BUILD:   Doing 'make -j20' parallel build
  <SNIP>
  Package libdw was not found in the pkg-config search path.
  Perhaps you should add the directory containing `libdw.pc'
  to the PKG_CONFIG_PATH environment variable
  No package 'libdw' found
  /bin/sh: 1: test: -lt: unexpected operator

After:

  1. libdw is not installed:

  $ pkg-config --modversion libdw
  Package libdw was not found in the pkg-config search path.
  Perhaps you should add the directory containing `libdw.pc'
  to the PKG_CONFIG_PATH environment variable
  No package 'libdw' found
  $ make LDFLAGS=-static -j16
    BUILD:   Doing 'make -j20' parallel build
  <SNIP>
  Package libdw was not found in the pkg-config search path.
  Perhaps you should add the directory containing `libdw.pc'
  to the PKG_CONFIG_PATH environment variable
  No package 'libdw' found
  Makefile.config:473: No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR

  2. libdw version is lower than 0.177

  $ pkg-config --modversion libdw
  0.176
  $ make LDFLAGS=-static -j16
    BUILD:   Doing 'make -j20' parallel build
  <SNIP>

  Auto-detecting system features:
  ...                                   dwarf: [ on  ]
  <SNIP>
    INSTALL libsubcmd_headers
    INSTALL libapi_headers
    INSTALL libperf_headers
    INSTALL libsymbol_headers
    INSTALL libbpf_headers
    LINK    perf

  3. libdw version is higher than 0.177

  $ pkg-config --modversion libdw
  0.186
  $ make LDFLAGS=-static -j16
    BUILD:   Doing 'make -j20' parallel build
  <SNIP>

  Auto-detecting system features:
  ...                                   dwarf: [ on  ]
  <SNIP>
    CC      util/bpf-utils.o
    CC      util/pfm.o
    LD      util/perf-util-in.o
    LD      perf-util-in.o
    AR      libperf-util.a
    LINK    perf

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

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 12796808f07a..b18513ec4da6 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -178,7 +178,7 @@ 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) -lt 177; echo $$?),0)
+  ifeq ($(shell test $(LIBDW_VERSION_2)0 -lt 1770; echo $$?),0)
     DWARFLIBS += -lebl
   endif
 endif
diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index fa679db61f62..7d1003d2efb2 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -160,7 +160,7 @@ 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) -lt 177; echo $$?),0)
+  ifeq ($(shell test $(LIBDW_VERSION_2)0 -lt 1770; echo $$?),0)
     DWARFLIBS += -lebl
   endif
 endif
-- 
2.25.1