Hi Luis,
Thank you for the reviews and sorry for being a bit slow to respind.
On 11-10-2019 16:48, Luis Chamberlain wrote:
On Fri, Oct 04, 2019 at 04:50:50PM +0200, Hans de Goede wrote:
+static int __init efi_check_md_for_embedded_firmware(
+ efi_memory_desc_t *md, const struct efi_embedded_fw_desc *desc)
+{
+ const u64 prefix = *((u64 *)desc->prefix);
+ struct sha256_state sctx;
+ struct embedded_fw *fw;
+ u8 sha256[32];
+ u64 i, size;
+ void *map;
+
+ size = md->num_pages << EFI_PAGE_SHIFT;
+ map = memremap(md->phys_addr, size, MEMREMAP_WB);
Since our limitaiton is the init process must have mostly finished,
it implies early x86 boot code cannot use this, what measures can we
take to prevent / check for such conditions to be detected and
gracefully errored out?
As with all (EFI) early boot code, there simply is a certain order
in which things need to be done. This needs to happen after the basic
mm is setup, but before efi_free_boot_services() gets called, there
isn't really a way to check for all these conditions. As with all
early boot code, people making changes need to be careful to not
break stuff.
+ if (!map) {
+ pr_err("Error mapping EFI mem at %#llx\n", md->phys_addr);
+ return -ENOMEM;
+ }
+
+ size -= desc->length;
Remind me again, why we decrement the size here?
Basically this is another way of writing:
for (i = 0; (i + desc->length) < size; i += 8) {
I was going to ask if we didn't need a:
if (desc->length > size) {
memunmap(map);
return -EINVAL;
}
That is a good point, unlikely but still a good point,
so I guess that writing:
for (i = 0; (i + desc->length) < size; i += 8) {
Instead would better as that avoids the need for that check.
I will fix this for the next version.
Regards,
Hans
+ for (i = 0; i < size; i += 8) {
+ u64 *mem = map + i;
+
+ if (*mem != prefix)
+ continue;
+
+ sha256_init(&sctx);
+ sha256_update(&sctx, map + i, desc->length);
+ sha256_final(&sctx, sha256);
+ if (memcmp(sha256, desc->sha256, 32) == 0)
+ break;
+ }
+ if (i >= size) {
+ memunmap(map);
+ return -ENOENT;
+ }
+
+ pr_info("Found EFI embedded fw '%s'\n", desc->name);
Otherwise looks good.
Luis
