[PATCH v3 0/4] tools build: Fixes for libbfd -lzstd dependency

[PATCH v3 0/4] tools build: Fixes for libbfd -lzstd dependency

[Ian Rogers]

This series addresses build problems when linking against static
libbfd/libopcodes on distributions like Fedora where binutils is built
with zstd section decompression support (requiring '-liberty -lz -lzstd'
together).

In v2, commit 89d001d48ec7 ("tools build: Add zstd to the binutils
library feature tests") landed in tools/build/feature/Makefile at the
same time, creating a merge conflict and only adding '|| $(BUILD_BFD)
-lzstd' without '-liberty -lz' or the corresponding
libbfd-liberty-z-zstd feature check in perf and bpftool (so even if
test-libbfd.bin passed with -lzstd, perf and bpftool would link only
'-lbfd -lopcodes' without '-lzstd').

v3 rebases onto perf-tools-next (v7.4-rc1), fixes commit 89d001d48ec7 in
patch 1/4, collects the Acked-by tags from Quentin Monnet and Peter
Zijlstra, updates the LIBOPCODES_LIBS comment in tools/objtool/Makefile,
and moves the AI assistance disclosure from commit trailers to the cover
letter.

v2: https://lore.kernel.org/all/20260909204122.1993010-1-irogers@google.com/
v1: https://lore.kernel.org/linux-perf-users/20260909181030.1870496-1-irogers@google.com/

AI Assistance Disclosure (per Documentation/process/coding-assistants.rst):
- Tools used: Antigravity coding assistant and Sashiko automated patch
  review.
- Summary of prompts and assistance: Rebased the 4-patch series onto
  perf-tools-next, resolved the conflict with commit 89d001d48ec7 in
  tools/build/feature/Makefile, incorporated review feedback and
  Acked-by tags, and verified with scripts/checkpatch.pl.

Ian Rogers (4):
  tools build: Add explicitly sequenced -lzstd to libbfd feature
    fallback
  perf build: Add explicitly sequenced -lzstd to libbfd feature fallback
  bpftool: Add explicitly sequenced -lzstd to libbfd feature fallback
  objtool: Add explicitly sequenced -lzstd to libopcodes fallback

 tools/bpf/bpftool/Makefile   |  4 ++++
 tools/build/Makefile.feature |  3 ++-
 tools/build/feature/Makefile | 19 +++++++++++++------
 tools/objtool/Makefile       |  7 ++++---
 tools/perf/Makefile.config   |  3 +++
 5 files changed, 26 insertions(+), 10 deletions(-)

-- 
2.56.0.385.gac671c819a-goog

[PATCH v3 1/4] tools build: Add explicitly sequenced -lzstd to libbfd feature fallback

[Ian Rogers]

Distributions like Fedora ship a statically compiled binutils libbfd
that depends on zstd (along with libiberty and zlib) to decompress
sections (e.g. undefined reference to 'ZSTD_decompress').

Commit 89d001d48ec7 ("tools build: Add zstd to the binutils library
feature tests") added '|| $(BUILD_BFD) -lzstd' directly to
test-libbfd.bin, test-libbfd-threadsafe.bin, and
test-disassembler-four-args.bin. However, static libbfd requires
'-liberty -lz -lzstd' together, and setting feature-libbfd=1 when extra
libraries are needed causes callers (perf, bpftool) to link only '-lbfd
-lopcodes' without '-lzstd'.

Restore test-libbfd.bin to test only $(BUILD_BFD), add the
test-libbfd-liberty-z-zstd.bin feature test and
FEATURE_GROUP_MEMBERS-libbfd entry, and append the '-liberty -lz -lzstd'
fallback to test-libbfd-threadsafe.bin, test-disassembler-four-args.bin,
and test-disassembler-init-styled.bin.

Fixes: 89d001d48ec7 ("tools build: Add zstd to the binutils library feature tests")
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/build/Makefile.feature |  3 ++-
 tools/build/feature/Makefile | 19 +++++++++++++------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 4d37d11f674c..c010049d9720 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -121,6 +121,7 @@ FEATURE_TESTS_EXTRA :=                  \
          libcheck                       \
          libbfd-liberty                 \
          libbfd-liberty-z               \
+         libbfd-liberty-z-zstd          \
          libopencsd                     \
          llvm                           \
          libbpf                         \
@@ -160,7 +161,7 @@ FEATURE_DISPLAY ?=              \
 # Declare group members of a feature to display the logical OR of the detection
 # result instead of each member result.
 #
-FEATURE_GROUP_MEMBERS-libbfd = libbfd-liberty libbfd-liberty-z
+FEATURE_GROUP_MEMBERS-libbfd = libbfd-liberty libbfd-liberty-z libbfd-liberty-z-zstd
 
 #
 # Declare list of feature dependency packages that provide pkg-config files.
diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index 10340a537224..359da8b98bc5 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -20,6 +20,7 @@ FILES=                                          \
          test-reallocarray.bin			\
          test-libbfd-liberty.bin                \
          test-libbfd-liberty-z.bin              \
+         test-libbfd-liberty-z-zstd.bin         \
          test-cplus-demangle.bin                \
          test-cxa-demangle.bin                  \
          test-libcap.bin			\
@@ -249,18 +250,21 @@ $(OUTPUT)test-python-module.bin:
 	$(BUILD) $(FLAGS_PYTHON_EMBED)
 
 $(OUTPUT)test-libbfd.bin:
-	$(BUILD_BFD) || $(BUILD_BFD) -lzstd
+	$(BUILD_BFD)
 
 $(OUTPUT)test-libbfd-threadsafe.bin:
-	$(BUILD_BFD) || $(BUILD_BFD) -lzstd || $(BUILD_BFD) -liberty || $(BUILD_BFD) -liberty -lz
+	$(BUILD_BFD) || $(BUILD_BFD) -liberty || $(BUILD_BFD) -liberty -lz || \
+	$(BUILD_BFD) -liberty -lz -lzstd
 
 $(OUTPUT)test-disassembler-four-args.bin:
-	$(BUILD_BFD) -lopcodes || $(BUILD_BFD) -lopcodes -lzstd || $(BUILD_BFD) -lopcodes -liberty || \
-	$(BUILD_BFD) -lopcodes -liberty -lz
+	$(BUILD_BFD) -lopcodes || $(BUILD_BFD) -lopcodes -liberty || \
+	$(BUILD_BFD) -lopcodes -liberty -lz || \
+	$(BUILD_BFD) -lopcodes -liberty -lz -lzstd
 
 $(OUTPUT)test-disassembler-init-styled.bin:
-	$(BUILD_BFD) -lopcodes ||  $(BUILD_BFD) -lopcodes -liberty || \
-	$(BUILD_BFD) -lopcodes -liberty -lz
+	$(BUILD_BFD) -lopcodes || $(BUILD_BFD) -lopcodes -liberty || \
+	$(BUILD_BFD) -lopcodes -liberty -lz || \
+	$(BUILD_BFD) -lopcodes -liberty -lz -lzstd
 
 $(OUTPUT)test-reallocarray.bin:
 	$(BUILD)
@@ -271,6 +275,9 @@ $(OUTPUT)test-libbfd-liberty.bin:
 $(OUTPUT)test-libbfd-liberty-z.bin:
 	$(CC) $(CFLAGS) -Wall -Werror -o $@ test-libbfd.c -DPACKAGE='"perf"' $(LDFLAGS) -lbfd -ldl -liberty -lz
 
+$(OUTPUT)test-libbfd-liberty-z-zstd.bin:
+	$(CC) $(CFLAGS) -Wall -Werror -o $@ test-libbfd.c -DPACKAGE='"perf"' $(LDFLAGS) -lbfd -ldl -liberty -lz -lzstd
+
 $(OUTPUT)test-cplus-demangle.bin:
 	$(BUILD) -liberty
 
-- 
2.56.0.385.gac671c819a-goog

[PATCH v3 2/4] perf build: Add explicitly sequenced -lzstd to libbfd feature fallback

[Ian Rogers]

Distributions like Fedora ship a statically compiled binutils libbfd
that depends on zstd to decompress sections (e.g. undefined reference to
'ZSTD_decompress').

Since libbfd does not reliably distribute a .pc file for pkg-config,
perf probes manual linker flag combinations in fallback chains (-lbfd
-ldl -liberty -lz).

Extend the testing cascade in tools/perf/Makefile.config to check
libbfd-liberty-z-zstd and append '-lbfd -lopcodes -liberty -lz -lzstd'
when detected.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/Makefile.config | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index b4764f69f47f..78423b0dcc73 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -896,6 +896,7 @@ ifdef BUILD_NONDISTRO
   $(call feature_check,libbfd-threadsafe)
   $(call feature_check,libbfd-liberty)
   $(call feature_check,libbfd-liberty-z)
+  $(call feature_check,libbfd-liberty-z-zstd)
 
   ifneq ($(feature-libbfd-threadsafe), 1)
     $(error binutils-dev(el) 2.42 or later is required for non-distro builds)
@@ -909,6 +910,8 @@ ifdef BUILD_NONDISTRO
     EXTLIBS += -lbfd -lopcodes -liberty
   else ifeq ($(feature-libbfd-liberty-z), 1)
     EXTLIBS += -lbfd -lopcodes -liberty -lz
+  else ifeq ($(feature-libbfd-liberty-z-zstd), 1)
+    EXTLIBS += -lbfd -lopcodes -liberty -lz -lzstd
   endif
 
   CFLAGS += -DHAVE_LIBBFD_SUPPORT
-- 
2.56.0.385.gac671c819a-goog

[PATCH v3 3/4] bpftool: Add explicitly sequenced -lzstd to libbfd feature fallback

[Ian Rogers]

Distributions like Fedora ship a statically compiled binutils libbfd
that depends on zstd to decompress sections (e.g. undefined reference to
'ZSTD_decompress').

Add libbfd-liberty-z-zstd to FEATURE_TESTS and FEATURE_DISPLAY in
tools/bpf/bpftool/Makefile and append the '-lbfd -ldl -lopcodes -liberty
-lz -lzstd' branch to the libbfd fallback chain.

Acked-by: Quentin Monnet <qmo@kernel.org>
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/bpf/bpftool/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index b0f7168e7943..1cac4508eb0c 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -125,6 +125,7 @@ FEATURE_TESTS += libcap
 FEATURE_TESTS += libbfd
 FEATURE_TESTS += libbfd-liberty
 FEATURE_TESTS += libbfd-liberty-z
+FEATURE_TESTS += libbfd-liberty-z-zstd
 FEATURE_TESTS += disassembler-four-args
 FEATURE_TESTS += disassembler-init-styled
 FEATURE_TESTS += libelf-zstd
@@ -135,6 +136,7 @@ FEATURE_DISPLAY += libcap
 FEATURE_DISPLAY += libbfd
 FEATURE_DISPLAY += libbfd-liberty
 FEATURE_DISPLAY += libbfd-liberty-z
+FEATURE_DISPLAY += libbfd-liberty-z-zstd
 endif
 
 check_feat := 1
@@ -201,6 +203,8 @@ else
     LIBS += -lbfd -ldl -lopcodes -liberty
   else ifeq ($(feature-libbfd-liberty-z),1)
     LIBS += -lbfd -ldl -lopcodes -liberty -lz
+  else ifeq ($(feature-libbfd-liberty-z-zstd),1)
+    LIBS += -lbfd -ldl -lopcodes -liberty -lz -lzstd
   endif
 
   # If one of the above feature combinations is set, we support libbfd
-- 
2.56.0.385.gac671c819a-goog

[PATCH v3 4/4] objtool: Add explicitly sequenced -lzstd to libopcodes fallback

[Ian Rogers]

Distributions like Fedora ship a statically compiled binutils libbfd (an
intrinsic dependency of libopcodes) that uses zstd to decompress
sections.

Because objtool resolves host dependencies sequentially via a manual
HOSTCC shell loop, linking against static binutils fails with undefined
references to 'ZSTD_decompress' unless the loop probes for -lzstd.

Add the '-lopcodes -lbfd -liberty -lz -lzstd' combination to the
LIBOPCODES_LIBS fallback chain.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/objtool/Makefile | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index db99c4759b2c..238da6fd277f 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -81,14 +81,15 @@ HOST_OVERRIDES := CC="$(HOSTCC)" LD="$(HOSTLD)" AR="$(HOSTAR)"
 #
 # When using shared libraries, -lopcodes is sufficient as dependencies are
 # resolved automatically. With static libraries, we must explicitly link
-# against libopcodes' dependencies: libbfd, libiberty, and sometimes libz.
-# Try each combination and use the first one that succeeds.
+# against libopcodes' dependencies: libbfd, libiberty, and sometimes libz
+# and libzstd. Try each combination and use the first one that succeeds.
 #
 LIBOPCODES_LIBS := $(shell \
 	for libs in "-lopcodes" \
 		    "-lopcodes -lbfd" \
 		    "-lopcodes -lbfd -liberty" \
-		    "-lopcodes -lbfd -liberty -lz"; do \
+		    "-lopcodes -lbfd -liberty -lz" \
+		    "-lopcodes -lbfd -liberty -lz -lzstd"; do \
 		printf '%s\n' \
 		       '$(pound)include <bfd.h>' \
 		       '$(pound)include <dis-asm.h>' \
-- 
2.56.0.385.gac671c819a-goog

Re: [PATCH v3 1/4] tools build: Add explicitly sequenced -lzstd to libbfd feature fallback

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 2680 bytes --]

> tools build: Add explicitly sequenced -lzstd to libbfd feature fallback

TL;DR: Possible build break at this commit: the libbfd -lzstd fallback is
removed but no consumer uses the new feature test yet, so perf may fail to
link and bpftool may lose JIT disassembly.

> diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
> --- a/tools/build/feature/Makefile
> +++ b/tools/build/feature/Makefile

[ ... ]

> @@ -249,18 +250,21 @@ $(OUTPUT)test-python-module.bin:
>  	$(BUILD) $(FLAGS_PYTHON_EMBED)
>  
>  $(OUTPUT)test-libbfd.bin:
> -	$(BUILD_BFD) || $(BUILD_BFD) -lzstd
> +	$(BUILD_BFD)
>  
>  $(OUTPUT)test-libbfd-threadsafe.bin:
> -	$(BUILD_BFD) || $(BUILD_BFD) -lzstd || $(BUILD_BFD) -liberty || $(BUILD_BFD) -liberty -lz
> +	$(BUILD_BFD) || $(BUILD_BFD) -liberty || $(BUILD_BFD) -liberty -lz || \
> +	$(BUILD_BFD) -liberty -lz -lzstd

Can this leave perf and bpftool unable to link libbfd at this commit?

Nothing here reads the new libbfd-liberty-z-zstd result.  Neither
tools/perf/Makefile.config nor tools/bpf/bpftool/Makefile calls
feature_check for it or has a branch that uses it.

On a system where "-lbfd -ldl" fails but "-lbfd -ldl -lzstd" links, the
parent commit gave feature-libbfd=1 through the removed fallback.  Here
feature-libbfd, feature-libbfd-liberty and feature-libbfd-liberty-z are
all 0, while feature-libbfd-threadsafe is 1 through the new
"-liberty -lz -lzstd" fallback.

With BUILD_NONDISTRO=1, perf's Makefile.config then passes the threadsafe
check but takes none of the EXTLIBS branches:

  ifeq ($(feature-libbfd), 1)
    EXTLIBS += -lbfd -lopcodes
  else ifeq ($(feature-libbfd-liberty), 1)
    EXTLIBS += -lbfd -lopcodes -liberty
  else ifeq ($(feature-libbfd-liberty-z), 1)
    EXTLIBS += -lbfd -lopcodes -liberty -lz
  endif

  CFLAGS += -DHAVE_LIBBFD_SUPPORT

util/libbfd.o is still built, so the perf link can fail with undefined
references to bfd_openr(), bfd_check_format() and disassembler().  bpftool
goes down the same chain, silently drops -lbfd and -DHAVE_LIBBFD_SUPPORT,
and loses JIT disassembly.

The consumers are added later in the series:

  6eb66acc776f ("perf build: Add explicitly sequenced -lzstd to libbfd
  feature fallback")
  155513d3a59d ("bpftool: Add explicitly sequenced -lzstd to libbfd
  feature fallback")

Would it be better to keep the old -lzstd fallback until those consumers
land, or to reorder or squash so that each commit remains buildable?


---
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CI run summary: https://github.com/kernel-patches/bpf/actions/runs/41774922004