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, 34 insertions, 0 deletions

diff --git a/Documentation/admin-guide/sysctl/abi.rst b/Documentation/admin-guide/sysctl/abi.rst
new file mode 100644
index 000000000..4e6db0a2a
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/abi.rst
@@ -0,0 +1,34 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+================================
+Documentation for /proc/sys/abi/
+================================
+
+.. See scripts/check-sysctl-docs to keep this up to date:
+.. scripts/check-sysctl-docs -vtable="abi" \
+..         Documentation/admin-guide/sysctl/abi.rst \
+..         $(git grep -l register_sysctl_)
+
+Copyright (c) 2020, Stephen Kitt
+
+For general info, see Documentation/admin-guide/sysctl/index.rst.
+
+------------------------------------------------------------------------------
+
+The files in ``/proc/sys/abi`` can be used to see and modify
+ABI-related settings.
+
+Currently, these files might (depending on your configuration)
+show up in ``/proc/sys/kernel``:
+
+.. contents:: :local:
+
+vsyscall32 (x86)
+================
+
+Determines whether the kernels maps a vDSO page into 32-bit processes;
+can be set to 1 to enable, or 0 to disable. Defaults to enabled if
+``CONFIG_COMPAT_VDSO`` is set, disabled otherwise.
+
+This controls the same setting as the ``vdso32`` kernel boot
+parameter.