[PATCH] disk: efi_loader: Add function to detect disk image type
Javier Tia
javier.tia at linaro.org
Thu Jul 31 23:40:07 CEST 2025
Hi Heinrich,
On Thu, Jul 31, 2025, at 8:05 AM, Heinrich Schuchardt wrote:
> On 31.07.25 00:49, Javier Tia wrote:
>> This commit introduces a new function, detect_disk_image_type(), which
>> checks if a buffer contains a disk image. This function is used to
>> detect disk images based on their headers, rather than relying on file
>> extensions.
>>
>> The function checks for ISO 9660, DOS MBR, and GPT protective MBR
>> signatures. It returns 1 if a disk image is detected, and 0 otherwise.
>>
>> This function is then used in the efi_bootmgr.c file to determine if a
>> downloaded file is a PE-COFF image or a disk image. This change
>> improves the reliability of disk image detection, as it no longer
>> relies on file extensions, which can be easily changed or omitted.
>>
>> Signed-off-by: Javier Tia <javier.tia at linaro.org>
>
> It would be easier to use efi_check_pe() to identify if the downloaded
> file is a PE-COFF image. Otherwise try booting it as a disk image.
>
> You could use part_driver_lookup_type() to determine the partition type.
I have addressed your comments in the next patch: https://lore.kernel.org/u-boot/20250731213547.654823-1-javier.tia@linaro.org/T/#u.
Thanks.
> Best regards
>
> Heinrich
>
>> ---
>> disk/part.c | 46 ++++++++++++++++++++++++++++++++++++
>> include/part.h | 9 +++++++
>> lib/efi_loader/efi_bootmgr.c | 29 ++++++++++-------------
>> 3 files changed, 68 insertions(+), 16 deletions(-)
>>
>> diff --git a/disk/part.c b/disk/part.c
>> index 66e2b3a7219..9d9483b216c 100644
>> --- a/disk/part.c
>> +++ b/disk/part.c
>> @@ -855,3 +855,49 @@ int part_get_bootable(struct blk_desc *desc)
>>
>> return 0;
>> }
>> +
>> +/**
>> +* detect_disk_image_type() - Detect if buffer contains a disk image
>> +*
>> +* @buffer: Buffer containing potential disk image data
>> +* @size: Size of the buffer
>> +* Return: 1 if disk image detected, 0 otherwise
>> +*/
>> +int detect_disk_image_type(void *buffer, size_t size)
>> +{
>> + unsigned char *buf = (unsigned char *)buffer;
>> +
>> + /* Need at least 512 bytes for basic checks */
>> + if (!buffer || size < 512)
>> + return 0;
>> +
>> +#if IS_ENABLED(CONFIG_ISO_PARTITION)
>> + /* Check for ISO 9660 signature "CD001" at offset 0x8001 */
>> + if (size > 0x8005) {
>> + if (buf[0x8001] == 'C' && buf[0x8002] == 'D' &&
>> + buf[0x8003] == '0' && buf[0x8004] == '0' &&
>> + buf[0x8005] == '1') {
>> + return 1;
>> + }
>> + }
>> +#endif
>> +
>> +#if IS_ENABLED(CONFIG_DOS_PARTITION)
>> + /* Check for DOS MBR signature 0x55AA at offset 0x1FE */
>> + if (buf[0x1FE] == 0x55 && buf[0x1FF] == 0xAA) {
>> + return 1;
>> + }
>> +#endif
>> +
>> +#if IS_ENABLED(CONFIG_EFI_PARTITION)
>> + /* Check for GPT protective MBR */
>> + if (buf[0x1FE] == 0x55 && buf[0x1FF] == 0xAA) {
>> + /* Check if partition type is 0xEE (GPT protective) */
>> + if (buf[0x1C2] == 0xEE) {
>> + return 1;
>> + }
>> + }
>> +#endif
>> +
>> + return 0;
>> +}
>> diff --git a/include/part.h b/include/part.h
>> index b772fb34c8a..39c04e0c8f7 100644
>> --- a/include/part.h
>> +++ b/include/part.h
>> @@ -727,6 +727,15 @@ int part_get_type_by_name(const char *name);
>> */
>> int part_get_bootable(struct blk_desc *desc);
>>
>> +/**
>> + * detect_disk_image_type() - Detect if buffer contains a disk image
>> + *
>> + * @buffer: Buffer containing potential disk image data
>> + * @size: Size of the buffer
>> + * Return: 1 if disk image detected, 0 otherwise
>> + */
>> +int detect_disk_image_type(void *buffer, size_t size);
>> +
>> #else
>> static inline int part_driver_get_count(void)
>> { return 0; }
>> diff --git a/lib/efi_loader/efi_bootmgr.c b/lib/efi_loader/efi_bootmgr.c
>> index 662993fb809..da63ad41b40 100644
>> --- a/lib/efi_loader/efi_bootmgr.c
>> +++ b/lib/efi_loader/efi_bootmgr.c
>> @@ -17,6 +17,7 @@
>> #include <log.h>
>> #include <malloc.h>
>> #include <net.h>
>> +#include <part.h>
>> #include <efi_loader.h>
>> #include <efi_variable.h>
>> #include <asm/unaligned.h>
>> @@ -407,7 +408,7 @@ static efi_status_t efi_bootmgr_release_uridp(struct uridp_context *ctx)
>> if (!ctx)
>> return ret;
>>
>> - /* cleanup for iso or img image */
>> + /* cleanup for image file */
>> if (ctx->ramdisk_blk_dev) {
>> ret = efi_add_memory_map(ctx->image_addr, ctx->image_size,
>> EFI_CONVENTIONAL_MEMORY);
>> @@ -466,7 +467,6 @@ static efi_status_t try_load_from_uri_path(struct efi_device_path_uri *uridp,
>> {
>> char *s;
>> int err;
>> - int uri_len;
>> efi_status_t ret;
>> void *source_buffer;
>> efi_uintn_t source_size;
>> @@ -516,21 +516,10 @@ static efi_status_t try_load_from_uri_path(struct efi_device_path_uri *uridp,
>> image_size = ALIGN(image_size, SZ_2M);
>>
>> /*
>> - * If the file extension is ".iso" or ".img", mount it and try to load
>> - * the default file.
>> - * If the file is PE-COFF image, load the downloaded file.
>> + * Check if the downloaded file is a PE-COFF image or a disk image.
>> + * Use header-based detection instead of file extensions.
>> */
>> - uri_len = strlen(uridp->uri);
>> - if (!strncmp(&uridp->uri[uri_len - 4], ".iso", 4) ||
>> - !strncmp(&uridp->uri[uri_len - 4], ".img", 4)) {
>> - ret = prepare_loaded_image(lo_label, image_addr, image_size,
>> - &loaded_dp, &blk);
>> - if (ret != EFI_SUCCESS)
>> - goto err;
>> -
>> - source_buffer = NULL;
>> - source_size = 0;
>> - } else if (efi_check_pe((void *)image_addr, image_size, NULL) == EFI_SUCCESS) {
>> + if (efi_check_pe((void *)image_addr, image_size, NULL) == EFI_SUCCESS) {
>> /*
>> * loaded_dp must exist until efi application returns,
>> * will be freed in return_to_efibootmgr event callback.
>> @@ -544,6 +533,14 @@ static efi_status_t try_load_from_uri_path(struct efi_device_path_uri *uridp,
>>
>> source_buffer = (void *)image_addr;
>> source_size = image_size;
>> + } else if (detect_disk_image_type((void *)image_addr, image_size)) {
>> + ret = prepare_loaded_image(lo_label, image_addr, image_size,
>> + &loaded_dp, &blk);
>> + if (ret != EFI_SUCCESS)
>> + goto err;
>> +
>> + source_buffer = NULL;
>> + source_size = 0;
>> } else {
>> log_err("Error: file type is not supported\n");
>> ret = EFI_UNSUPPORTED;
--
» Javier Tia ✍
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