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, 72 insertions, 0 deletions

diff --git a/drivers/regulator/dummy.c b/drivers/regulator/dummy.c
new file mode 100644
index 000000000..c3e416fd3
--- /dev/null
+++ b/drivers/regulator/dummy.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * dummy.c
+ *
+ * Copyright 2010 Wolfson Microelectronics PLC.
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ *
+ * This is useful for systems with mixed controllable and
+ * non-controllable regulators, as well as for allowing testing on
+ * systems with no controllable regulators.
+ */
+
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/device/faux.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/machine.h>
+
+#include "dummy.h"
+
+struct regulator_dev *dummy_regulator_rdev;
+
+static const struct regulator_init_data dummy_initdata = {
+	.constraints = {
+		.always_on = 1,
+	},
+};
+
+static const struct regulator_ops dummy_ops;
+
+static const struct regulator_desc dummy_desc = {
+	.name = "regulator-dummy",
+	.id = -1,
+	.type = REGULATOR_VOLTAGE,
+	.owner = THIS_MODULE,
+	.ops = &dummy_ops,
+};
+
+static int dummy_regulator_probe(struct faux_device *fdev)
+{
+	struct regulator_config config = { };
+	int ret;
+
+	config.dev = &fdev->dev;
+	config.init_data = &dummy_initdata;
+
+	dummy_regulator_rdev = devm_regulator_register(&fdev->dev, &dummy_desc,
+						       &config);
+	if (IS_ERR(dummy_regulator_rdev)) {
+		ret = PTR_ERR(dummy_regulator_rdev);
+		pr_err("Failed to register regulator: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static struct faux_device_ops dummy_regulator_driver = {
+	.probe = dummy_regulator_probe,
+};
+
+static struct faux_device *dummy_fdev;
+
+void __init regulator_dummy_init(void)
+{
+	dummy_fdev = faux_device_create("reg-dummy", NULL, &dummy_regulator_driver);
+	if (!dummy_fdev) {
+		pr_err("Failed to allocate dummy regulator device\n");
+		return;
+	}
+}