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, 81 insertions, 0 deletions

diff --git a/drivers/of/module.c b/drivers/of/module.c
new file mode 100644
index 000000000..1e735fc13
--- /dev/null
+++ b/drivers/of/module.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux kernel module helpers.
+ */
+
+#include <linux/of.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+ssize_t of_modalias(const struct device_node *np, char *str, ssize_t len)
+{
+	const char *compat;
+	char *c;
+	struct property *p;
+	ssize_t csize;
+	ssize_t tsize;
+
+	/*
+	 * Prevent a kernel oops in vsnprintf() -- it only allows passing a
+	 * NULL ptr when the length is also 0. Also filter out the negative
+	 * lengths...
+	 */
+	if ((len > 0 && !str) || len < 0)
+		return -EINVAL;
+
+	/* Name & Type */
+	/* %p eats all alphanum characters, so %c must be used here */
+	csize = snprintf(str, len, "of:N%pOFn%c%s", np, 'T',
+			 of_node_get_device_type(np));
+	tsize = csize;
+	if (csize >= len)
+		csize = len > 0 ? len - 1 : 0;
+	len -= csize;
+	str += csize;
+
+	of_property_for_each_string(np, "compatible", p, compat) {
+		csize = snprintf(str, len, "C%s", compat);
+		tsize += csize;
+		if (csize >= len)
+			continue;
+		for (c = str; c; ) {
+			c = strchr(c, ' ');
+			if (c)
+				*c++ = '_';
+		}
+		len -= csize;
+		str += csize;
+	}
+
+	return tsize;
+}
+
+int of_request_module(const struct device_node *np)
+{
+	char *str;
+	ssize_t size;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
+
+	size = of_modalias(np, NULL, 0);
+	if (size < 0)
+		return size;
+
+	/* Reserve an additional byte for the trailing '\0' */
+	size++;
+
+	str = kmalloc(size, GFP_KERNEL);
+	if (!str)
+		return -ENOMEM;
+
+	of_modalias(np, str, size);
+	str[size - 1] = '\0';
+	ret = request_module(str);
+	kfree(str);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(of_request_module);