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, 121 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap-mdio.c b/drivers/base/regmap/regmap-mdio.c
new file mode 100644
index 000000000..9573bf3b5
--- /dev/null
+++ b/drivers/base/regmap/regmap-mdio.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/errno.h>
+#include <linux/mdio.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define REGVAL_MASK		GENMASK(15, 0)
+#define REGNUM_C22_MASK		GENMASK(4, 0)
+/* Clause-45 mask includes the device type (5 bit) and actual register number (16 bit) */
+#define REGNUM_C45_MASK		GENMASK(20, 0)
+
+static int regmap_mdio_c22_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct mdio_device *mdio_dev = context;
+	int ret;
+
+	if (unlikely(reg & ~REGNUM_C22_MASK))
+		return -ENXIO;
+
+	ret = mdiodev_read(mdio_dev, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret & REGVAL_MASK;
+
+	return 0;
+}
+
+static int regmap_mdio_c22_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct mdio_device *mdio_dev = context;
+
+	if (unlikely(reg & ~REGNUM_C22_MASK))
+		return -ENXIO;
+
+	return mdiodev_write(mdio_dev, reg, val);
+}
+
+static const struct regmap_bus regmap_mdio_c22_bus = {
+	.reg_write = regmap_mdio_c22_write,
+	.reg_read = regmap_mdio_c22_read,
+};
+
+static int regmap_mdio_c45_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct mdio_device *mdio_dev = context;
+	unsigned int devad;
+	int ret;
+
+	if (unlikely(reg & ~REGNUM_C45_MASK))
+		return -ENXIO;
+
+	devad = reg >> REGMAP_MDIO_C45_DEVAD_SHIFT;
+	reg = reg & REGMAP_MDIO_C45_REGNUM_MASK;
+
+	ret = mdiodev_c45_read(mdio_dev, devad, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret & REGVAL_MASK;
+
+	return 0;
+}
+
+static int regmap_mdio_c45_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct mdio_device *mdio_dev = context;
+	unsigned int devad;
+
+	if (unlikely(reg & ~REGNUM_C45_MASK))
+		return -ENXIO;
+
+	devad = reg >> REGMAP_MDIO_C45_DEVAD_SHIFT;
+	reg = reg & REGMAP_MDIO_C45_REGNUM_MASK;
+
+	return mdiodev_c45_write(mdio_dev, devad, reg, val);
+}
+
+static const struct regmap_bus regmap_mdio_c45_bus = {
+	.reg_write = regmap_mdio_c45_write,
+	.reg_read = regmap_mdio_c45_read,
+};
+
+struct regmap *__regmap_init_mdio(struct mdio_device *mdio_dev,
+	const struct regmap_config *config, struct lock_class_key *lock_key,
+	const char *lock_name)
+{
+	const struct regmap_bus *bus;
+
+	if (config->reg_bits == 5 && config->val_bits == 16)
+		bus = &regmap_mdio_c22_bus;
+	else if (config->reg_bits == 21 && config->val_bits == 16)
+		bus = &regmap_mdio_c45_bus;
+	else
+		return ERR_PTR(-EOPNOTSUPP);
+
+	return __regmap_init(&mdio_dev->dev, bus, mdio_dev, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__regmap_init_mdio);
+
+struct regmap *__devm_regmap_init_mdio(struct mdio_device *mdio_dev,
+	const struct regmap_config *config, struct lock_class_key *lock_key,
+	const char *lock_name)
+{
+	const struct regmap_bus *bus;
+
+	if (config->reg_bits == 5 && config->val_bits == 16)
+		bus = &regmap_mdio_c22_bus;
+	else if (config->reg_bits == 21 && config->val_bits == 16)
+		bus = &regmap_mdio_c45_bus;
+	else
+		return ERR_PTR(-EOPNOTSUPP);
+
+	return __devm_regmap_init(&mdio_dev->dev, bus, mdio_dev, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_mdio);
+
+MODULE_AUTHOR("Sander Vanheule <sander@svanheule.net>");
+MODULE_DESCRIPTION("regmap MDIO Module");
+MODULE_LICENSE("GPL v2");