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, 87 insertions, 0 deletions

diff --git a/rust/helpers/atomic_ext.c b/rust/helpers/atomic_ext.c
new file mode 100644
index 000000000..c267d5190
--- /dev/null
+++ b/rust/helpers/atomic_ext.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <asm/barrier.h>
+#include <asm/rwonce.h>
+#include <linux/atomic.h>
+
+#define GEN_READ_HELPER(tname, type)						\
+__rust_helper type rust_helper_atomic_##tname##_read(type *ptr)			\
+{										\
+	return READ_ONCE(*ptr);							\
+}
+
+#define GEN_SET_HELPER(tname, type)						\
+__rust_helper void rust_helper_atomic_##tname##_set(type *ptr, type val)	\
+{										\
+	WRITE_ONCE(*ptr, val);							\
+}
+
+#define GEN_READ_ACQUIRE_HELPER(tname, type)					\
+__rust_helper type rust_helper_atomic_##tname##_read_acquire(type *ptr)		\
+{										\
+	return smp_load_acquire(ptr);						\
+}
+
+#define GEN_SET_RELEASE_HELPER(tname, type)					\
+__rust_helper void rust_helper_atomic_##tname##_set_release(type *ptr, type val)\
+{										\
+	smp_store_release(ptr, val);						\
+}
+
+#define GEN_READ_SET_HELPERS(tname, type)					\
+	GEN_READ_HELPER(tname, type)						\
+	GEN_SET_HELPER(tname, type)						\
+	GEN_READ_ACQUIRE_HELPER(tname, type)					\
+	GEN_SET_RELEASE_HELPER(tname, type)					\
+
+GEN_READ_SET_HELPERS(i8, s8)
+GEN_READ_SET_HELPERS(i16, s16)
+GEN_READ_SET_HELPERS(ptr, const void *)
+
+/*
+ * xchg helpers depend on ARCH_SUPPORTS_ATOMIC_RMW and on the
+ * architecture provding xchg() support for i8 and i16.
+ *
+ * The architectures that currently support Rust (x86_64, armv7,
+ * arm64, riscv, and loongarch) satisfy these requirements.
+ */
+#define GEN_XCHG_HELPER(tname, type, suffix)					\
+__rust_helper type								\
+rust_helper_atomic_##tname##_xchg##suffix(type *ptr, type new)			\
+{										\
+	return xchg##suffix(ptr, new);					\
+}
+
+#define GEN_XCHG_HELPERS(tname, type)						\
+	GEN_XCHG_HELPER(tname, type, )						\
+	GEN_XCHG_HELPER(tname, type, _acquire)					\
+	GEN_XCHG_HELPER(tname, type, _release)					\
+	GEN_XCHG_HELPER(tname, type, _relaxed)					\
+
+GEN_XCHG_HELPERS(i8, s8)
+GEN_XCHG_HELPERS(i16, s16)
+GEN_XCHG_HELPERS(ptr, const void *)
+
+/*
+ * try_cmpxchg helpers depend on ARCH_SUPPORTS_ATOMIC_RMW and on the
+ * architecture provding try_cmpxchg() support for i8 and i16.
+ *
+ * The architectures that currently support Rust (x86_64, armv7,
+ * arm64, riscv, and loongarch) satisfy these requirements.
+ */
+#define GEN_TRY_CMPXCHG_HELPER(tname, type, suffix)				\
+__rust_helper bool								\
+rust_helper_atomic_##tname##_try_cmpxchg##suffix(type *ptr, type *old, type new)\
+{										\
+	return try_cmpxchg##suffix(ptr, old, new);				\
+}
+
+#define GEN_TRY_CMPXCHG_HELPERS(tname, type)					\
+	GEN_TRY_CMPXCHG_HELPER(tname, type, )					\
+	GEN_TRY_CMPXCHG_HELPER(tname, type, _acquire)				\
+	GEN_TRY_CMPXCHG_HELPER(tname, type, _release)				\
+	GEN_TRY_CMPXCHG_HELPER(tname, type, _relaxed)				\
+
+GEN_TRY_CMPXCHG_HELPERS(i8, s8)
+GEN_TRY_CMPXCHG_HELPERS(i16, s16)
+GEN_TRY_CMPXCHG_HELPERS(ptr, const void *)