[image] Add the concept of a static image

Not all images are allocated via alloc_image().  For example: embedded
images, the static images created to hold a runtime command line, and
the images used by unit tests are all static structures.

Using image_set_cmdline() (via e.g. the "imgargs" command) to set the
command-line arguments of a static image will succeed but will leak
memory, since nothing will ever free the allocated command line.
There are no code paths that can lead to calling image_set_len() on a
static image, but there is no safety check against future code paths
attempting this.

Define a flag IMAGE_STATIC to mark an image as statically allocated,
generalise free_image() to also handle freeing dynamically allocated
portions of static images (such as the command line), and expose
free_image() for use by static images.

Define a related flag IMAGE_STATIC_NAME to mark the name as statically
allocated.  Allow a statically allocated name to be replaced with a
dynamically allocated name since this is a potentially valid use case
(e.g. if "imgdecrypt --name <name>" is used on an embedded image).

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86/core/runtime.c

@@ -70,6 +70,7 @@ static void cmdline_image_free ( struct refcnt *refcnt ) {
 	struct image *image = container_of ( refcnt, struct image, refcnt );
 
 	DBGC ( image, "RUNTIME freeing command line\n" );
+	free_image ( refcnt );
 	free ( cmdline_copy );
 }
 
@@ -77,6 +78,7 @@ static void cmdline_image_free ( struct refcnt *refcnt ) {
 static struct image cmdline_image = {
 	.refcnt = REF_INIT ( cmdline_image_free ),
 	.name = "<CMDLINE>",
+	.flags = ( IMAGE_STATIC | IMAGE_STATIC_NAME ),
 	.type = &script_image_type,
 };
 

src/core/image.c

@@ -76,22 +76,41 @@ static int require_trusted_images_permanent = 0;
  * Free executable image
  *
  * @v refcnt		Reference counter
+ *
+ * Image consumers must call image_put() rather than calling
+ * free_image() directly.  This function is exposed for use only by
+ * static images.
  */
-static void free_image ( struct refcnt *refcnt ) {
+void free_image ( struct refcnt *refcnt ) {
 	struct image *image = container_of ( refcnt, struct image, refcnt );
 	struct image_tag *tag;
 
+	/* Sanity check: free_image() should not be called directly on
+	 * dynamically allocated images.
+	 */
+	assert ( refcnt->count < 0 );
 	DBGC ( image, "IMAGE %s freed\n", image->name );
+
+	/* Clear any tag weak references */
 	for_each_table_entry ( tag, IMAGE_TAGS ) {
 		if ( tag->image == image )
 			tag->image = NULL;
 	}
-	free ( image->name );
+
+	/* Free dynamic allocations used by both static and dynamic images */
 	free ( image->cmdline );
 	uri_put ( image->uri );
-	ufree ( image->data );
 	image_put ( image->replacement );
-	free ( image );
+
+	/* Free image name, if dynamically allocated */
+	if ( ! ( image->flags & IMAGE_STATIC_NAME ) )
+		free ( image->name );
+
+	/* Free image data and image itself, if dynamically allocated */
+	if ( ! ( image->flags & IMAGE_STATIC ) ) {
+		ufree ( image->data );
+		free ( image );
+	}
 }
 
 /**
@@ -165,9 +184,13 @@ int image_set_name ( struct image *image, const char *name ) {
 	if ( ! name_copy )
 		return -ENOMEM;
 
+	/* Free existing name, if not statically allocated */
+	if ( ! ( image->flags & IMAGE_STATIC_NAME ) )
+		free ( image->name );
+
 	/* Replace existing name */
-	free ( image->name );
 	image->name = name_copy;
+	image->flags &= ~IMAGE_STATIC_NAME;
 
 	return 0;
 }
@@ -220,6 +243,10 @@ int image_set_cmdline ( struct image *image, const char *cmdline ) {
 int image_set_len ( struct image *image, size_t len ) {
 	void *new;
 
+	/* Refuse to reallocate static images */
+	if ( image->flags & IMAGE_STATIC )
+		return -ENOTTY;
+
 	/* (Re)allocate image data */
 	new = urealloc ( image->data, len );
 	if ( ! new )
@@ -288,6 +315,13 @@ int register_image ( struct image *image ) {
 	char name[8]; /* "imgXXXX" */
 	int rc;
 
+	/* Sanity checks */
+	if ( image->flags & IMAGE_STATIC ) {
+		assert ( ( image->name == NULL ) ||
+			 ( image->flags & IMAGE_STATIC_NAME ) );
+		assert ( image->cmdline == NULL );
+	}
+
 	/* Create image name if it doesn't already have one */
 	if ( ! image->name ) {
 		snprintf ( name, sizeof ( name ), "img%d", imgindex++ );

src/image/embedded.c

@@ -31,8 +31,9 @@ EMBED_ALL
 /* Image structures for all embedded images */
 #undef EMBED
 #define EMBED( _index, _path, _name ) {					\
-	.refcnt = REF_INIT ( ref_no_free ),				\
+	.refcnt = REF_INIT ( free_image ),				\
 	.name = _name,							\
+	.flags = ( IMAGE_STATIC | IMAGE_STATIC_NAME ),			\
 	.data = ( userptr_t ) ( embedded_image_ ## _index ## _data ),	\
 	.len = ( size_t ) embedded_image_ ## _index ## _len,		\
 },

src/include/ipxe/image.h

@@ -30,14 +30,22 @@ struct image {
 
 	/** URI of image */
 	struct uri *uri;
-	/** Name */
+	/** Name
+	 *
+	 * If the @c IMAGE_STATIC_NAME flag is set, then this is a
+	 * statically allocated string.
+	 */
 	char *name;
 	/** Flags */
 	unsigned int flags;
 
 	/** Command line to pass to image */
 	char *cmdline;
-	/** Raw file image */
+	/** Raw file image
+	 *
+	 * If the @c IMAGE_STATIC flag is set, then this is a
+	 * statically allocated image.
+	 */
 	void *data;
 	/** Length of raw file image */
 	size_t len;
@@ -72,6 +80,12 @@ struct image {
 /** Image will be hidden from enumeration */
 #define IMAGE_HIDDEN 0x0008
 
+/** Image is statically allocated */
+#define IMAGE_STATIC 0x0010
+
+/** Image name is statically allocated */
+#define IMAGE_STATIC_NAME 0x0020
+
 /** An executable image type */
 struct image_type {
 	/** Name of this image type */
@@ -185,6 +199,7 @@ static inline struct image * first_image ( void ) {
 	return list_first_entry ( &images, struct image, list );
 }
 
+extern void free_image ( struct refcnt *refcnt );
 extern struct image * alloc_image ( struct uri *uri );
 extern int image_set_uri ( struct image *image, struct uri *uri );
 extern int image_set_name ( struct image *image, const char *name );

src/interface/efi/efi_cmdline.c

@@ -58,6 +58,7 @@ static void efi_cmdline_free ( struct refcnt *refcnt ) {
 	struct image *image = container_of ( refcnt, struct image, refcnt );
 
 	DBGC ( image, "CMDLINE freeing command line\n" );
+	free_image ( refcnt );
 	free ( efi_cmdline_copy );
 }
 
@@ -65,6 +66,7 @@ static void efi_cmdline_free ( struct refcnt *refcnt ) {
 static struct image efi_cmdline_image = {
 	.refcnt = REF_INIT ( efi_cmdline_free ),
 	.name = "<CMDLINE>",
+	.flags = ( IMAGE_STATIC | IMAGE_STATIC_NAME ),
 	.type = &script_image_type,
 };
 

src/tests/asn1_test.h

@@ -46,6 +46,7 @@ struct asn1_test {
 	static struct image _name ## __image = {			\
 		.refcnt = REF_INIT ( ref_no_free ),			\
 		.name = #_name,						\
+		.flags = ( IMAGE_STATIC | IMAGE_STATIC_NAME ),		\
 		.data = ( userptr_t ) ( _name ## __file ),		\
 		.len = sizeof ( _name ## __file ),			\
 	};								\

src/tests/cms_test.c

@@ -85,6 +85,7 @@ struct cms_test_keypair {
 		.image = {						\
 			.refcnt = REF_INIT ( ref_no_free ),		\
 			.name = #NAME,					\
+			.flags = ( IMAGE_STATIC | IMAGE_STATIC_NAME ),	\
 			.data = ( userptr_t ) ( NAME ## _data ),	\
 			.len = sizeof ( NAME ## _data ),		\
 		},							\
@@ -97,6 +98,7 @@ struct cms_test_keypair {
 		.image = {						\
 			.refcnt = REF_INIT ( ref_no_free ),		\
 			.name = #NAME,					\
+			.flags = ( IMAGE_STATIC | IMAGE_STATIC_NAME ),	\
 			.data = ( userptr_t ) ( NAME ## _data ),	\
 			.len = sizeof ( NAME ## _data ),		\
 		},							\
@@ -109,6 +111,7 @@ struct cms_test_keypair {
 		.image = {						\
 			.refcnt = REF_INIT ( ref_no_free ),		\
 			.name = #NAME,					\
+			.flags = ( IMAGE_STATIC | IMAGE_STATIC_NAME ),	\
 			.type = &der_image_type,			\
 			.data = ( userptr_t ) ( NAME ## _data ),	\
 			.len = sizeof ( NAME ## _data ),		\

src/tests/pixbuf_test.h

@@ -41,6 +41,7 @@ struct pixel_buffer_test {
 	static struct image _name ## __image = {			\
 		.refcnt = REF_INIT ( ref_no_free ),			\
 		.name = #_name,						\
+		.flags = ( IMAGE_STATIC | IMAGE_STATIC_NAME ),		\
 		.data = ( userptr_t ) ( _name ## __file ),		\
 		.len = sizeof ( _name ## __file ),			\
 	};								\

src/tests/test.c

@@ -162,6 +162,7 @@ static struct image_type test_image_type = {
 static struct image test_image = {
 	.refcnt = REF_INIT ( ref_no_free ),
 	.name = "<TESTS>",
+	.flags = ( IMAGE_STATIC | IMAGE_STATIC_NAME ),
 	.type = &test_image_type,
 };