[PATCH bpf-next] selftests/bpf: remove unnecessary link dependencies

[PATCH bpf-next] selftests/bpf: remove unnecessary link dependencies

[Mykyta Yatsenko]

From: Mykyta Yatsenko <yatsenko@meta.com>

Remove llvm dependencies from binaries that do not use llvm libraries.
Filter out libxml2 from llvm dependencies, as it seems that
it is not actually used. This patch reduced link dependencies
for BPF selftests.
The next line was adding llvm dependencies to every target in the
makefile, while the only targets that require those are test
runnners (test_progs, test_progs-no_alu32,...):
```
$(OUTPUT)/$(TRUNNER_BINARY): LDLIBS += $$(LLVM_LDLIBS)
```

Before this change:
ldd linux/tools/testing/selftests/bpf/veristat
    linux-vdso.so.1 (0x00007ffd2c3fd000)
    libelf.so.1 => /lib64/libelf.so.1 (0x00007fe1dcf89000)
    libz.so.1 => /lib64/libz.so.1 (0x00007fe1dcf6f000)
    libm.so.6 => /lib64/libm.so.6 (0x00007fe1dce94000)
    libzstd.so.1 => /lib64/libzstd.so.1 (0x00007fe1dcddd000)
    libxml2.so.2 => /lib64/libxml2.so.2 (0x00007fe1dcc54000)
    libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fe1dca00000)
    libc.so.6 => /lib64/libc.so.6 (0x00007fe1dc600000)
    /lib64/ld-linux-x86-64.so.2 (0x00007fe1dcfb1000)
    liblzma.so.5 => /lib64/liblzma.so.5 (0x00007fe1dc9d4000)
    libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fe1dcc38000)

After:
ldd linux/tools/testing/selftests/bpf/veristat
    linux-vdso.so.1 (0x00007ffc83370000)
    libelf.so.1 => /lib64/libelf.so.1 (0x00007f4b87515000)
    libz.so.1 => /lib64/libz.so.1 (0x00007f4b874fb000)
    libc.so.6 => /lib64/libc.so.6 (0x00007f4b87200000)
    libzstd.so.1 => /lib64/libzstd.so.1 (0x00007f4b87444000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f4b8753d000)

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
---
 tools/testing/selftests/bpf/Makefile | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 0d04cf54068e..27db3bf20c21 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -180,7 +180,7 @@ ifeq ($(feature-llvm),1)
   # Prefer linking statically if it's available, otherwise fallback to shared
   ifeq ($(shell $(LLVM_CONFIG) --link-static --libs >/dev/null 2>&1 && echo static),static)
     LLVM_LDLIBS  += $(shell $(LLVM_CONFIG) --link-static --libs $(LLVM_CONFIG_LIB_COMPONENTS))
-    LLVM_LDLIBS  += $(shell $(LLVM_CONFIG) --link-static --system-libs $(LLVM_CONFIG_LIB_COMPONENTS))
+    LLVM_LDLIBS  += $(filter-out -lxml2,$(shell $(LLVM_CONFIG) --link-static --system-libs $(LLVM_CONFIG_LIB_COMPONENTS)))
     LLVM_LDLIBS  += -lstdc++
   else
     LLVM_LDLIBS  += $(shell $(LLVM_CONFIG) --link-shared --libs $(LLVM_CONFIG_LIB_COMPONENTS))
@@ -675,9 +675,6 @@ ifneq ($2:$(OUTPUT),:$(shell pwd))
 	$(Q)rsync -aq $$^ $(TRUNNER_OUTPUT)/
 endif
 
-$(OUTPUT)/$(TRUNNER_BINARY): LDLIBS += $$(LLVM_LDLIBS)
-$(OUTPUT)/$(TRUNNER_BINARY): LDFLAGS += $$(LLVM_LDFLAGS)
-
 # some X.test.o files have runtime dependencies on Y.bpf.o files
 $(OUTPUT)/$(TRUNNER_BINARY): | $(TRUNNER_BPF_OBJS)
 
@@ -688,7 +685,7 @@ $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TEST_OBJS)			\
 			     $(OUTPUT)/veristat				\
 			     | $(TRUNNER_BINARY)-extras
 	$$(call msg,BINARY,,$$@)
-	$(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) $$(LDFLAGS) -o $$@
+	$(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) $$(LLVM_LDLIBS) $$(LDFLAGS) $$(LLVM_LDFLAGS) -o $$@
 	$(Q)$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@
 	$(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/$(USE_BOOTSTRAP)bpftool \
 		   $(OUTPUT)/$(if $2,$2/)bpftool
-- 
2.49.0

Re: [PATCH bpf-next] selftests/bpf: remove unnecessary link dependencies

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Fri, 16 May 2025 20:55:22 +0100 you wrote:
> From: Mykyta Yatsenko <yatsenko@meta.com>
> 
> Remove llvm dependencies from binaries that do not use llvm libraries.
> Filter out libxml2 from llvm dependencies, as it seems that
> it is not actually used. This patch reduced link dependencies
> for BPF selftests.
> The next line was adding llvm dependencies to every target in the
> makefile, while the only targets that require those are test
> runnners (test_progs, test_progs-no_alu32,...):
> ```
> $(OUTPUT)/$(TRUNNER_BINARY): LDLIBS += $$(LLVM_LDLIBS)
> ```
> 
> [...]

Here is the summary with links:
  - [bpf-next] selftests/bpf: remove unnecessary link dependencies
    https://git.kernel.org/bpf/bpf-next/c/b615ce5fbefb

You are awesome, thank you!
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