From 7e61560628d17ea6b1d8ee370f6d42694cff8758 Mon Sep 17 00:00:00 2001
From: Ulises Mendez Martinez <umendez@google.com>
Date: Fri, 4 Sep 2026 15:07:09 +0000
Subject: objtool: Validate disassembler headers in libopcodes probe

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>
---
 scripts/atomic/gen-atomic-instrumented.sh | 184 ++++++++++++++++++++++++++++++
 1 file changed, 184 insertions(+)
 create mode 100755 scripts/atomic/gen-atomic-instrumented.sh

(limited to 'scripts/atomic/gen-atomic-instrumented.sh')

diff --git a/scripts/atomic/gen-atomic-instrumented.sh b/scripts/atomic/gen-atomic-instrumented.sh
new file mode 100755
index 000000000..9c1d53f81
--- /dev/null
+++ b/scripts/atomic/gen-atomic-instrumented.sh
@@ -0,0 +1,184 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+ATOMICDIR=$(dirname $0)
+
+. ${ATOMICDIR}/atomic-tbl.sh
+
+#gen_param_check(meta, arg)
+gen_param_check()
+{
+	local meta="$1"; shift
+	local arg="$1"; shift
+	local type="${arg%%:*}"
+	local name="$(gen_param_name "${arg}")"
+	local rw="atomic_write"
+
+	case "${type#c}" in
+	i) return;;
+	esac
+
+	if [ ${type#c} != ${type} ]; then
+		# We don't write to constant parameters.
+		rw="atomic_read"
+	elif [ "${type}" = "p" ] ; then
+		# The "old" argument in try_cmpxchg() gets accessed non-atomically
+		rw="read_write"
+	elif [ "${meta}" != "s" ]; then
+		# An atomic RMW: if this parameter is not a constant, and this atomic is
+		# not just a 's'tore, this parameter is both read from and written to.
+		rw="atomic_read_write"
+	fi
+
+	printf "\tinstrument_${rw}(${name}, sizeof(*${name}));\n"
+}
+
+#gen_params_checks(meta, arg...)
+gen_params_checks()
+{
+	local meta="$1"; shift
+	local order="$1"; shift
+
+	if [ "${order}" = "_release" ]; then
+		printf "\tkcsan_release();\n"
+	elif [ -z "${order}" ] && ! meta_in "$meta" "slv"; then
+		# RMW with return value is fully ordered
+		printf "\tkcsan_mb();\n"
+	fi
+
+	while [ "$#" -gt 0 ]; do
+		gen_param_check "$meta" "$1"
+		shift;
+	done
+}
+
+#gen_proto_order_variant(meta, pfx, name, sfx, order, atomic, int, arg...)
+gen_proto_order_variant()
+{
+	local meta="$1"; shift
+	local pfx="$1"; shift
+	local name="$1"; shift
+	local sfx="$1"; shift
+	local order="$1"; shift
+	local atomic="$1"; shift
+	local int="$1"; shift
+
+	local atomicname="${atomic}_${pfx}${name}${sfx}${order}"
+
+	local ret="$(gen_ret_type "${meta}" "${int}")"
+	local params="$(gen_params "${int}" "${atomic}" "$@")"
+	local checks="$(gen_params_checks "${meta}" "${order}" "$@")"
+	local args="$(gen_args "$@")"
+	local retstmt="$(gen_ret_stmt "${meta}")"
+
+	gen_kerneldoc "" "${meta}" "${pfx}" "${name}" "${sfx}" "${order}" "${atomic}" "${int}" "$@"
+
+cat <<EOF
+static __always_inline ${ret}
+${atomicname}(${params})
+{
+${checks}
+	${retstmt}raw_${atomicname}(${args});
+}
+EOF
+
+	printf "\n"
+}
+
+gen_xchg()
+{
+	local xchg="$1"; shift
+	local order="$1"; shift
+
+	kcsan_barrier=""
+	if [ "${xchg%_local}" = "${xchg}" ]; then
+		case "$order" in
+		_release)	kcsan_barrier="kcsan_release()" ;;
+		"")			kcsan_barrier="kcsan_mb()" ;;
+		esac
+	fi
+
+	if [ "${xchg%${xchg#try_cmpxchg}}" = "try_cmpxchg" ] ; then
+
+cat <<EOF
+#define ${xchg}${order}(ptr, oldp, ...) \\
+({ \\
+	typeof(ptr) __ai_ptr = (ptr); \\
+	typeof(oldp) __ai_oldp = (oldp); \\
+EOF
+[ -n "$kcsan_barrier" ] && printf "\t${kcsan_barrier}; \\\\\n"
+cat <<EOF
+	instrument_atomic_read_write(__ai_ptr, sizeof(*__ai_ptr)); \\
+	instrument_read_write(__ai_oldp, sizeof(*__ai_oldp)); \\
+	raw_${xchg}${order}(__ai_ptr, __ai_oldp, __VA_ARGS__); \\
+})
+EOF
+
+	else
+
+cat <<EOF
+#define ${xchg}${order}(ptr, ...) \\
+({ \\
+	typeof(ptr) __ai_ptr = (ptr); \\
+EOF
+[ -n "$kcsan_barrier" ] && printf "\t${kcsan_barrier}; \\\\\n"
+cat <<EOF
+	instrument_atomic_read_write(__ai_ptr, sizeof(*__ai_ptr)); \\
+	raw_${xchg}${order}(__ai_ptr, __VA_ARGS__); \\
+})
+EOF
+
+	fi
+}
+
+cat << EOF
+// SPDX-License-Identifier: GPL-2.0
+
+// Generated by $0
+// DO NOT MODIFY THIS FILE DIRECTLY
+
+/*
+ * This file provoides atomic operations with explicit instrumentation (e.g.
+ * KASAN, KCSAN), which should be used unless it is necessary to avoid
+ * instrumentation. Where it is necessary to aovid instrumenation, the
+ * raw_atomic*() operations should be used.
+ */
+#ifndef _LINUX_ATOMIC_INSTRUMENTED_H
+#define _LINUX_ATOMIC_INSTRUMENTED_H
+
+#include <linux/build_bug.h>
+#include <linux/compiler.h>
+#include <linux/instrumented.h>
+
+EOF
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" "atomic" "int" ${args}
+done
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" "atomic64" "s64" ${args}
+done
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" "atomic_long" "long" ${args}
+done
+
+
+for xchg in "xchg" "cmpxchg" "cmpxchg64" "cmpxchg128" "try_cmpxchg" "try_cmpxchg64" "try_cmpxchg128"; do
+	for order in "" "_acquire" "_release" "_relaxed"; do
+		gen_xchg "${xchg}" "${order}"
+		printf "\n"
+	done
+done
+
+for xchg in "cmpxchg_local" "cmpxchg64_local" "cmpxchg128_local" "sync_cmpxchg" \
+	    "try_cmpxchg_local" "try_cmpxchg64_local" "try_cmpxchg128_local" "sync_try_cmpxchg"; do
+	gen_xchg "${xchg}" ""
+	printf "\n"
+done
+
+cat <<EOF
+
+#endif /* _LINUX_ATOMIC_INSTRUMENTED_H */
+EOF
-- 
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