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/virtio/virtio_debug.c b/drivers/virtio/virtio_debug.c
new file mode 100644
index 000000000..ccf1955a1
--- /dev/null
+++ b/drivers/virtio/virtio_debug.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/debugfs.h>
+
+static struct dentry *virtio_debugfs_dir;
+
+static int virtio_debug_device_features_show(struct seq_file *s, void *data)
+{
+	u64 device_features[VIRTIO_FEATURES_U64S];
+	struct virtio_device *dev = s->private;
+	unsigned int i;
+
+	virtio_get_features(dev, device_features);
+	for (i = 0; i < VIRTIO_FEATURES_BITS; i++) {
+		if (virtio_features_test_bit(device_features, i))
+			seq_printf(s, "%u\n", i);
+	}
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(virtio_debug_device_features);
+
+static int virtio_debug_filter_features_show(struct seq_file *s, void *data)
+{
+	struct virtio_device *dev = s->private;
+	unsigned int i;
+
+	for (i = 0; i < VIRTIO_FEATURES_BITS; i++) {
+		if (virtio_features_test_bit(dev->debugfs_filter_features, i))
+			seq_printf(s, "%u\n", i);
+	}
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(virtio_debug_filter_features);
+
+static int virtio_debug_filter_features_clear(void *data, u64 val)
+{
+	struct virtio_device *dev = data;
+
+	if (val == 1)
+		virtio_features_zero(dev->debugfs_filter_features);
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(virtio_debug_filter_features_clear_fops, NULL,
+			 virtio_debug_filter_features_clear, "%llu\n");
+
+static int virtio_debug_filter_feature_add(void *data, u64 val)
+{
+	struct virtio_device *dev = data;
+
+	if (val >= VIRTIO_FEATURES_BITS)
+		return -EINVAL;
+
+	virtio_features_set_bit(dev->debugfs_filter_features, val);
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(virtio_debug_filter_feature_add_fops, NULL,
+			 virtio_debug_filter_feature_add, "%llu\n");
+
+static int virtio_debug_filter_feature_del(void *data, u64 val)
+{
+	struct virtio_device *dev = data;
+
+	if (val >= VIRTIO_FEATURES_BITS)
+		return -EINVAL;
+
+	virtio_features_clear_bit(dev->debugfs_filter_features, val);
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(virtio_debug_filter_feature_del_fops, NULL,
+			 virtio_debug_filter_feature_del, "%llu\n");
+
+void virtio_debug_device_init(struct virtio_device *dev)
+{
+	dev->debugfs_dir = debugfs_create_dir(dev_name(&dev->dev),
+					      virtio_debugfs_dir);
+	debugfs_create_file("device_features", 0400, dev->debugfs_dir, dev,
+			    &virtio_debug_device_features_fops);
+	debugfs_create_file("filter_features", 0400, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_features_fops);
+	debugfs_create_file("filter_features_clear", 0200, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_features_clear_fops);
+	debugfs_create_file("filter_feature_add", 0200, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_feature_add_fops);
+	debugfs_create_file("filter_feature_del", 0200, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_feature_del_fops);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_device_init);
+
+void virtio_debug_device_filter_features(struct virtio_device *dev)
+{
+	virtio_features_andnot(dev->features_array, dev->features_array,
+			       dev->debugfs_filter_features);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_device_filter_features);
+
+void virtio_debug_device_exit(struct virtio_device *dev)
+{
+	debugfs_remove_recursive(dev->debugfs_dir);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_device_exit);
+
+void virtio_debug_init(void)
+{
+	virtio_debugfs_dir = debugfs_create_dir("virtio", NULL);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_init);
+
+void virtio_debug_exit(void)
+{
+	debugfs_remove_recursive(virtio_debugfs_dir);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_exit);