objtool: Fix libopcodes linking with static libraries

3f2de814 · Sasha Levin <[email protected]> · 2026-01-21 11:25:32 -05:00

Commit 436326bc525d ("objtool: fix build failure due to missing libopcodes
check") tests for libopcodes using an empty main(), which passes even when
static libraries lack their dependencies. This causes undefined reference
errors (xmalloc, bfd_get_bits, etc.) when linking against static libopcodes
without its required libbfd and libiberty.

Fix by testing with an actual libopcodes symbol and trying increasingly
complete library combinations until one succeeds.

Fixes: 436326bc525d ("objtool: fix build failure due to missing libopcodes check")
Reported-by: Rafael J. Wysocki <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Rafael J. Wysocki (Intel) <[email protected]>
Link: https://patch.msgid.link/[email protected]

Commit: 3f2de814c0597c97d5abe09a1635d8c4e2fddaf2
Parents: 24d479d2

Changes

1 files changed · +17 −4

File	Status	Add	Del	Content
tools/objtool/Makefile	modified	+17	−4	View file

tools/objtool/Makefile

View file

diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 9b45031..a40f302 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -77,8 +77,21 @@ HOST_OVERRIDES := CC="$(HOSTCC)" LD="$(HOSTLD)" AR="$(HOSTAR)"
 # We check using HOSTCC directly rather than the shared feature framework
 # because objtool is a host tool that links against host libraries.
 #
-HAVE_LIBOPCODES := $(shell echo 'int main(void) { return 0; }' | \
-			$(HOSTCC) -xc - -o /dev/null -lopcodes 2>/dev/null && echo y)
+# 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.
+#
+LIBOPCODES_LIBS := $(shell \
+	for libs in "-lopcodes" \
+		    "-lopcodes -lbfd" \
+		    "-lopcodes -lbfd -liberty" \
+		    "-lopcodes -lbfd -liberty -lz"; do \
+		echo 'extern void disassemble_init_for_target(void *);' \
+		     'int main(void) { disassemble_init_for_target(0); return 0; }' | \
+			$(HOSTCC) -xc - -o /dev/null $$libs 2>/dev/null && \
+			echo "$$libs" && break; \
+	done)
 
 # Styled disassembler support requires binutils >= 2.39
 HAVE_DISASM_STYLED := $(shell echo '$(pound)include <dis-asm.h>' | \
@@ -86,10 +99,10 @@ HAVE_DISASM_STYLED := $(shell echo '$(pound)include <dis-asm.h>' | \
 
 BUILD_DISAS := n
 
-ifeq ($(HAVE_LIBOPCODES),y)
+ifneq ($(LIBOPCODES_LIBS),)
 	BUILD_DISAS := y
 	OBJTOOL_CFLAGS += -DDISAS -DPACKAGE='"objtool"'
-	OBJTOOL_LDFLAGS += -lopcodes
+	OBJTOOL_LDFLAGS += $(LIBOPCODES_LIBS)
 ifeq ($(HAVE_DISASM_STYLED),y)
 	OBJTOOL_CFLAGS += -DDISASM_INIT_STYLED
 endif