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[image] Add the concept of a static image

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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>
This commit is contained in:
Michael Brown
2025-04-30 13:22:54 +01:00
parent 3303910010
commit cd803ff2e2
9 changed files with 68 additions and 8 deletions
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44
src/core/image.c
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@@ -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++ );