Messages in this thread | | | Subject | Re: [PATCH v7 2/8] efi: Add embedded peripheral firmware support | From | Hans de Goede <> | Date | Thu, 14 Nov 2019 12:27:01 +0100 |
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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 >
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