firmware_loader: formalize built-in firmware API

Now that we have a kconfig entry to represent built-in firmware
support, formalize its use witha a proper API. This can later be
used by other callers where all they need is built-in firmware.

We export the firmware_request_builtin() call for now only
under the TEST_FIRMWARE symbol namespace as there are no
direct modular users for it. If they pop up they are free
to export it generally. Built-in code always gets access to
the callers and we'll demonstrate a hidden user which has been
lurking in the kernel for a while and the reason why using a
proper API was better long term.

Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

5 files changed, 74 insertions, 64 deletions

diff --git a/drivers/base/firmware_loader/builtin/Makefile b/drivers/base/firmware_loader/builtin/Makefile
index 101754ad48d91..eb4be452062a0 100644
--- a/drivers/base/firmware_loader/builtin/Makefile
+++ b/drivers/base/firmware_loader/builtin/Makefile
@@ -1,11 +1,13 @@
 # SPDX-License-Identifier: GPL-2.0
+obj-y  += main.o
 
 # Create $(fwdir) from $(CONFIG_EXTRA_FIRMWARE_DIR) -- if it doesn't have a
 # leading /, it's relative to $(srctree).
 fwdir := $(subst $(quote),,$(CONFIG_EXTRA_FIRMWARE_DIR))
 fwdir := $(addprefix $(srctree)/,$(filter-out /%,$(fwdir)))$(filter /%,$(fwdir))
 
-obj-y  := $(addsuffix .gen.o, $(subst $(quote),,$(CONFIG_EXTRA_FIRMWARE)))
+firmware  := $(addsuffix .gen.o, $(subst $(quote),,$(CONFIG_EXTRA_FIRMWARE)))
+obj-y += $(firmware)
 
 FWNAME    = $(patsubst $(obj)/%.gen.S,%,$@)
 FWSTR     = $(subst $(comma),_,$(subst /,_,$(subst .,_,$(subst -,_,$(FWNAME)))))
@@ -34,7 +36,7 @@ $(obj)/%.gen.S: FORCE
 	$(call filechk,fwbin)
 
 # The .o files depend on the binaries directly; the .S files don't.
-$(addprefix $(obj)/, $(obj-y)): $(obj)/%.gen.o: $(fwdir)/%
+$(addprefix $(obj)/, $(firmware)): $(obj)/%.gen.o: $(fwdir)/%
 
 targets := $(patsubst $(obj)/%,%, \
                                 $(shell find $(obj) -name \*.gen.S 2>/dev/null))
diff --git a/drivers/base/firmware_loader/builtin/main.c b/drivers/base/firmware_loader/builtin/main.c
new file mode 100644
index 0000000000000..385cf8379378a
--- /dev/null
+++ b/drivers/base/firmware_loader/builtin/main.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Builtin firmware support */
+
+#include <linux/firmware.h>
+
+extern struct builtin_fw __start_builtin_fw[];
+extern struct builtin_fw __end_builtin_fw[];
+
+static void fw_copy_to_prealloc_buf(struct firmware *fw,
+				    void *buf, size_t size)
+{
+	if (!buf || size < fw->size)
+		return;
+	memcpy(buf, fw->data, fw->size);
+}
+
+bool firmware_request_builtin(struct firmware *fw, const char *name,
+			      void *buf, size_t size)
+{
+	struct builtin_fw *b_fw;
+
+	for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++) {
+		if (strcmp(name, b_fw->name) == 0) {
+			fw->size = b_fw->size;
+			fw->data = b_fw->data;
+			fw_copy_to_prealloc_buf(fw, buf, size);
+
+			return true;
+		}
+	}
+
+	return false;
+}
+EXPORT_SYMBOL_NS_GPL(firmware_request_builtin, TEST_FIRMWARE);
+
+bool firmware_is_builtin(const struct firmware *fw)
+{
+	struct builtin_fw *b_fw;
+
+	for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++)
+		if (fw->data == b_fw->data)
+			return true;
+
+	return false;
+}
diff --git a/drivers/base/firmware_loader/firmware.h b/drivers/base/firmware_loader/firmware.h
index a3014e9e2c852..5da4364879017 100644
--- a/drivers/base/firmware_loader/firmware.h
+++ b/drivers/base/firmware_loader/firmware.h
@@ -151,6 +151,15 @@ static inline void fw_state_done(struct fw_priv *fw_priv)
 
 int assign_fw(struct firmware *fw, struct device *device);
 
+#ifdef CONFIG_FW_LOADER_BUILTIN
+bool firmware_is_builtin(const struct firmware *fw);
+#else
+static inline bool firmware_is_builtin(const struct firmware *fw)
+{
+	return false;
+}
+#endif
+
 #ifdef CONFIG_FW_LOADER_PAGED_BUF
 void fw_free_paged_buf(struct fw_priv *fw_priv);
 int fw_grow_paged_buf(struct fw_priv *fw_priv, int pages_needed);
diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index 9dcd07be7a2f1..0b6f3d1ef1dc4 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -93,65 +93,6 @@ DEFINE_MUTEX(fw_lock);
 
 static struct firmware_cache fw_cache;
 
-/* Builtin firmware support */
-
-#ifdef CONFIG_FW_LOADER_BUILTIN
-
-extern struct builtin_fw __start_builtin_fw[];
-extern struct builtin_fw __end_builtin_fw[];
-
-static void fw_copy_to_prealloc_buf(struct firmware *fw,
-				    void *buf, size_t size)
-{
-	if (!buf || size < fw->size)
-		return;
-	memcpy(buf, fw->data, fw->size);
-}
-
-static bool fw_get_builtin_firmware(struct firmware *fw, const char *name,
-				    void *buf, size_t size)
-{
-	struct builtin_fw *b_fw;
-
-	for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++) {
-		if (strcmp(name, b_fw->name) == 0) {
-			fw->size = b_fw->size;
-			fw->data = b_fw->data;
-			fw_copy_to_prealloc_buf(fw, buf, size);
-
-			return true;
-		}
-	}
-
-	return false;
-}
-
-static bool fw_is_builtin_firmware(const struct firmware *fw)
-{
-	struct builtin_fw *b_fw;
-
-	for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++)
-		if (fw->data == b_fw->data)
-			return true;
-
-	return false;
-}
-
-#else
-
-static inline bool fw_get_builtin_firmware(struct firmware *fw,
-					   const char *name, void *buf,
-					   size_t size)
-{
-	return false;
-}
-
-static inline bool fw_is_builtin_firmware(const struct firmware *fw)
-{
-	return false;
-}
-#endif
-
 static void fw_state_init(struct fw_priv *fw_priv)
 {
 	struct fw_state *fw_st = &fw_priv->fw_st;
@@ -736,7 +677,7 @@ _request_firmware_prepare(struct firmware **firmware_p, const char *name,
 		return -ENOMEM;
 	}
 
-	if (fw_get_builtin_firmware(firmware, name, dbuf, size)) {
+	if (firmware_request_builtin(firmware, name, dbuf, size)) {
 		dev_dbg(device, "using built-in %s\n", name);
 		return 0; /* assigned */
 	}
@@ -1051,7 +992,7 @@ EXPORT_SYMBOL(request_partial_firmware_into_buf);
 void release_firmware(const struct firmware *fw)
 {
 	if (fw) {
-		if (!fw_is_builtin_firmware(fw))
+		if (!firmware_is_builtin(fw))
 			firmware_free_data(fw);
 		kfree(fw);
 	}
@@ -1215,7 +1156,7 @@ static int uncache_firmware(const char *fw_name)
 
 	pr_debug("%s: %s\n", __func__, fw_name);
 
-	if (fw_get_builtin_firmware(&fw, fw_name, NULL, 0))
+	if (firmware_request_builtin(&fw, fw_name, NULL, 0))
 		return 0;
 
 	fw_priv = lookup_fw_priv(fw_name);
diff --git a/include/linux/firmware.h b/include/linux/firmware.h
index 25109192cebec..1f8df57ecacff 100644
--- a/include/linux/firmware.h
+++ b/include/linux/firmware.h
@@ -20,12 +20,16 @@ struct firmware {
 struct module;
 struct device;
 
+#ifdef CONFIG_FW_LOADER_BUILTIN
 struct builtin_fw {
 	char *name;
 	void *data;
 	unsigned long size;
 };
 
+bool firmware_request_builtin(struct firmware *fw, const char *name,
+			      void *buf, size_t size);
+
 /* We have to play tricks here much like stringify() to get the
    __COUNTER__ macro to be expanded as we want it */
 #define __fw_concat1(x, y) x##y
@@ -38,6 +42,15 @@ struct builtin_fw {
 	static const struct builtin_fw __fw_concat(__builtin_fw,__COUNTER__) \
 	__used __section(".builtin_fw") = { name, blob, size }
 
+#else
+static inline bool firmware_request_builtin(struct firmware *fw,
+					    const char *name,
+					    void *buf, size_t size)
+{
+	return false;
+}
+#endif
+
 #if defined(CONFIG_FW_LOADER) || (defined(CONFIG_FW_LOADER_MODULE) && defined(MODULE))
 int request_firmware(const struct firmware **fw, const char *name,
 		     struct device *device);