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, 36 insertions, 0 deletions

diff --git a/include/uapi/asm-generic/Kbuild b/include/uapi/asm-generic/Kbuild
new file mode 100644
index 000000000..ebb180aac
--- /dev/null
+++ b/include/uapi/asm-generic/Kbuild
@@ -0,0 +1,36 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Headers that are mandatory in usr/include/asm/
+# (This file is not included when SRCARCH=um since UML does not support UAPI.)
+
+mandatory-y += auxvec.h
+mandatory-y += bitsperlong.h
+mandatory-y += bpf_perf_event.h
+mandatory-y += byteorder.h
+mandatory-y += errno.h
+mandatory-y += fcntl.h
+mandatory-y += ioctl.h
+mandatory-y += ioctls.h
+mandatory-y += ipcbuf.h
+mandatory-y += mman.h
+mandatory-y += msgbuf.h
+mandatory-y += param.h
+mandatory-y += poll.h
+mandatory-y += posix_types.h
+mandatory-y += ptrace.h
+mandatory-y += resource.h
+mandatory-y += sembuf.h
+mandatory-y += setup.h
+mandatory-y += shmbuf.h
+mandatory-y += sigcontext.h
+mandatory-y += siginfo.h
+mandatory-y += signal.h
+mandatory-y += socket.h
+mandatory-y += sockios.h
+mandatory-y += stat.h
+mandatory-y += statfs.h
+mandatory-y += swab.h
+mandatory-y += termbits.h
+mandatory-y += termios.h
+mandatory-y += types.h
+mandatory-y += unistd.h