objtool: Validate disassembler headers in libopcodes probegrafted

commit 3f2de814c059 ("objtool: Fix libopcodes linking with static libraries")
tested for libopcodes availability by linking a test snippet with a forward
declaration of disassemble_init_for_target().

However, testing symbol linkage with an extern declaration only verifies
the presence of the library (.so/.a) and bypasses checking for development
headers (binutils-dev). On systems where libopcodes is present without
development headers installed, the probe succeeds, enabling BUILD_DISAS.
Subsequent compilation of objtool then fails:

  fatal error: 'bfd.h' file not found
    113 | #include <bfd.h>

Additionally, the probe invokes $(HOSTCC) without $(HOSTCFLAGS), ignoring
any sysroot or include flags specified for the host compiler.

Fix this by including <bfd.h> and <dis-asm.h> directly in the test snippet,
passing $(HOSTCFLAGS) so host compiler options are respected, and defining
PACKAGE="objtool" to satisfy the configuration check in <bfd.h>.

Fixes: 3f2de814c059 ("objtool: Fix libopcodes linking with static libraries")
Fixes: 436326bc525d ("objtool: fix build failure due to missing libopcodes check")
Reported-by: Alice Ryhl <aliceryhl@google.com>
Assisted-by: Antigravity:Gemini-Next
Signed-off-by: Ulises Mendez Martinez <umendez@google.com>
Link: https://patch.msgid.link/20260904150710.2997558-1-umendez@google.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

1 files changed, 51 insertions, 0 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
new file mode 100644
index 000000000..b15122aa2
--- /dev/null
+++ b/fs/btrfs/Makefile
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# Subset of W=1 warnings
+subdir-ccflags-y += -Wextra -Wunused -Wno-unused-parameter
+subdir-ccflags-y += -Wmissing-declarations
+subdir-ccflags-y += -Wmissing-format-attribute
+subdir-ccflags-y += -Wmissing-prototypes
+subdir-ccflags-y += -Wold-style-definition
+subdir-ccflags-y += -Wmissing-include-dirs
+condflags := \
+	$(call cc-option, -Wunused-but-set-variable)		\
+	$(call cc-option, -Wunused-const-variable)		\
+	$(call cc-option, -Wpacked-not-aligned)			\
+	$(call cc-option, -Wstringop-truncation)		\
+	$(call cc-option, -Wmaybe-uninitialized)
+subdir-ccflags-y += $(condflags)
+# The following turn off the warnings enabled by -Wextra
+subdir-ccflags-y += -Wno-missing-field-initializers
+subdir-ccflags-y += -Wno-sign-compare
+subdir-ccflags-y += -Wno-shift-negative-value
+
+obj-$(CONFIG_BTRFS_FS) := btrfs.o
+
+btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
+	   file-item.o inode-item.o disk-io.o \
+	   transaction.o inode.o file.o defrag.o \
+	   extent_map.o sysfs.o accessors.o xattr.o ordered-data.o \
+	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
+	   export.o tree-log.o free-space-cache.o zlib.o lzo.o zstd.o \
+	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
+	   backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o \
+	   uuid-tree.o props.o free-space-tree.o tree-checker.o space-info.o \
+	   block-rsv.o delalloc-space.o block-group.o discard.o reflink.o \
+	   subpage.o tree-mod-log.o extent-io-tree.o fs.o messages.o bio.o \
+	   lru_cache.o raid-stripe-tree.o fiemap.o direct-io.o
+
+btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
+btrfs-$(CONFIG_BTRFS_DEBUG) += ref-verify.o
+btrfs-$(CONFIG_BLK_DEV_ZONED) += zoned.o
+btrfs-$(CONFIG_FS_VERITY) += verity.o
+
+btrfs-$(CONFIG_BTRFS_FS_RUN_SANITY_TESTS) += tests/free-space-tests.o \
+	tests/extent-buffer-tests.o tests/btrfs-tests.o \
+	tests/extent-io-tests.o tests/inode-tests.o tests/qgroup-tests.o \
+	tests/free-space-tree-tests.o tests/extent-map-tests.o \
+	tests/raid-stripe-tree-tests.o tests/delayed-refs-tests.o \
+	tests/chunk-allocation-tests.o
+
+ifeq ($(CONFIG_BLK_DEV_ZONED),y)
+btrfs-$(CONFIG_BTRFS_FS_RUN_SANITY_TESTS) += tests/zoned-tests.o
+endif