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, 39 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-generic.c b/drivers/rtc/rtc-generic.c
new file mode 100644
index 000000000..89ae78e93
--- /dev/null
+++ b/drivers/rtc/rtc-generic.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* rtc-generic: RTC driver using the generic RTC abstraction
+ *
+ * Copyright (C) 2008 Kyle McMartin <kyle@mcmartin.ca>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/time.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+
+static int __init generic_rtc_probe(struct platform_device *dev)
+{
+	struct rtc_device *rtc;
+	const struct rtc_class_ops *ops = dev_get_platdata(&dev->dev);
+
+	rtc = devm_rtc_device_register(&dev->dev, "rtc-generic",
+					ops, THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	platform_set_drvdata(dev, rtc);
+
+	return 0;
+}
+
+static struct platform_driver generic_rtc_driver = {
+	.driver = {
+		.name = "rtc-generic",
+	},
+};
+
+module_platform_driver_probe(generic_rtc_driver, generic_rtc_probe);
+
+MODULE_AUTHOR("Kyle McMartin <kyle@mcmartin.ca>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Generic RTC driver");
+MODULE_ALIAS("platform:rtc-generic");