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, 117 insertions, 0 deletions

diff --git a/drivers/usb/gadget/functions.c b/drivers/usb/gadget/functions.c
new file mode 100644
index 000000000..203361a64
--- /dev/null
+++ b/drivers/usb/gadget/functions.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/err.h>
+
+#include <linux/usb/composite.h>
+
+static LIST_HEAD(func_list);
+static DEFINE_MUTEX(func_lock);
+
+static struct usb_function_instance *try_get_usb_function_instance(const char *name)
+{
+	struct usb_function_driver *fd;
+	struct usb_function_instance *fi;
+
+	fi = ERR_PTR(-ENOENT);
+	mutex_lock(&func_lock);
+	list_for_each_entry(fd, &func_list, list) {
+
+		if (strcmp(name, fd->name))
+			continue;
+
+		if (!try_module_get(fd->mod)) {
+			fi = ERR_PTR(-EBUSY);
+			break;
+		}
+		fi = fd->alloc_inst();
+		if (IS_ERR(fi))
+			module_put(fd->mod);
+		else
+			fi->fd = fd;
+		break;
+	}
+	mutex_unlock(&func_lock);
+	return fi;
+}
+
+struct usb_function_instance *usb_get_function_instance(const char *name)
+{
+	struct usb_function_instance *fi;
+	int ret;
+
+	fi = try_get_usb_function_instance(name);
+	if (!IS_ERR(fi))
+		return fi;
+	ret = PTR_ERR(fi);
+	if (ret != -ENOENT)
+		return fi;
+	ret = request_module("usbfunc:%s", name);
+	if (ret < 0)
+		return ERR_PTR(ret);
+	return try_get_usb_function_instance(name);
+}
+EXPORT_SYMBOL_GPL(usb_get_function_instance);
+
+struct usb_function *usb_get_function(struct usb_function_instance *fi)
+{
+	struct usb_function *f;
+
+	f = fi->fd->alloc_func(fi);
+	if (IS_ERR(f))
+		return f;
+	f->fi = fi;
+	return f;
+}
+EXPORT_SYMBOL_GPL(usb_get_function);
+
+void usb_put_function_instance(struct usb_function_instance *fi)
+{
+	struct module *mod;
+
+	if (!fi)
+		return;
+
+	mod = fi->fd->mod;
+	fi->free_func_inst(fi);
+	module_put(mod);
+}
+EXPORT_SYMBOL_GPL(usb_put_function_instance);
+
+void usb_put_function(struct usb_function *f)
+{
+	if (!f)
+		return;
+
+	f->free_func(f);
+}
+EXPORT_SYMBOL_GPL(usb_put_function);
+
+int usb_function_register(struct usb_function_driver *newf)
+{
+	struct usb_function_driver *fd;
+	int ret;
+
+	ret = -EEXIST;
+
+	mutex_lock(&func_lock);
+	list_for_each_entry(fd, &func_list, list) {
+		if (!strcmp(fd->name, newf->name))
+			goto out;
+	}
+	ret = 0;
+	list_add_tail(&newf->list, &func_list);
+out:
+	mutex_unlock(&func_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(usb_function_register);
+
+void usb_function_unregister(struct usb_function_driver *fd)
+{
+	mutex_lock(&func_lock);
+	list_del(&fd->list);
+	mutex_unlock(&func_lock);
+}
+EXPORT_SYMBOL_GPL(usb_function_unregister);