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, 56 insertions, 0 deletions

diff --git a/lib/compat_audit.c b/lib/compat_audit.c
new file mode 100644
index 000000000..fee1dfccd
--- /dev/null
+++ b/lib/compat_audit.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/audit_arch.h>
+#include <asm/unistd32.h>
+
+unsigned int compat_dir_class[] = {
+#include <asm-generic/audit_dir_write.h>
+~0U
+};
+
+unsigned int compat_read_class[] = {
+#include <asm-generic/audit_read.h>
+~0U
+};
+
+unsigned int compat_write_class[] = {
+#include <asm-generic/audit_write.h>
+~0U
+};
+
+unsigned int compat_chattr_class[] = {
+#include <asm-generic/audit_change_attr.h>
+~0U
+};
+
+unsigned int compat_signal_class[] = {
+#include <asm-generic/audit_signal.h>
+~0U
+};
+
+int audit_classify_compat_syscall(int abi, unsigned int syscall)
+{
+	switch (syscall) {
+#ifdef __NR_open
+	case __NR_open:
+		return AUDITSC_OPEN;
+#endif
+#ifdef __NR_openat
+	case __NR_openat:
+		return AUDITSC_OPENAT;
+#endif
+#ifdef __NR_socketcall
+	case __NR_socketcall:
+		return AUDITSC_SOCKETCALL;
+#endif
+	case __NR_execve:
+		return AUDITSC_EXECVE;
+#ifdef __NR_openat2
+	case __NR_openat2:
+		return AUDITSC_OPENAT2;
+#endif
+	default:
+		return AUDITSC_COMPAT;
+	}
+}