diff options
| -rw-r--r-- | hw/arm/boot.c | 6 | ||||
| -rw-r--r-- | hw/core/loader.c | 91 | ||||
| -rw-r--r-- | include/hw/loader.h | 19 |
3 files changed, 116 insertions, 0 deletions
diff --git a/hw/arm/boot.c b/hw/arm/boot.c index 1e021c4a34..50e5141116 100644 --- a/hw/arm/boot.c +++ b/hw/arm/boot.c @@ -926,6 +926,12 @@ static uint64_t load_aarch64_image(const char *filename, hwaddr mem_base, return -1; } size = len; + + /* Unpack the image if it is a EFI zboot image */ + if (unpack_efi_zboot_image(&buffer, &size) < 0) { + g_free(buffer); + return -1; + } } /* check the arm64 magic header value -- very old kernels may not have it */ diff --git a/hw/core/loader.c b/hw/core/loader.c index 173f8f67f6..cd53235fed 100644 --- a/hw/core/loader.c +++ b/hw/core/loader.c @@ -857,6 +857,97 @@ ssize_t load_image_gzipped(const char *filename, hwaddr addr, uint64_t max_sz) return bytes; } +/* The PE/COFF MS-DOS stub magic number */ +#define EFI_PE_MSDOS_MAGIC "MZ" + +/* + * The Linux header magic number for a EFI PE/COFF + * image targetting an unspecified architecture. + */ +#define EFI_PE_LINUX_MAGIC "\xcd\x23\x82\x81" + +/* + * Bootable Linux kernel images may be packaged as EFI zboot images, which are + * self-decompressing executables when loaded via EFI. The compressed payload + * can also be extracted from the image and decompressed by a non-EFI loader. + * + * The de facto specification for this format is at the following URL: + * + * https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/efi/libstub/zboot-header.S + * + * This definition is based on Linux upstream commit 29636a5ce87beba. + */ +struct linux_efi_zboot_header { + uint8_t msdos_magic[2]; /* PE/COFF 'MZ' magic number */ + uint8_t reserved0[2]; + uint8_t zimg[4]; /* "zimg" for Linux EFI zboot images */ + uint32_t payload_offset; /* LE offset to compressed payload */ + uint32_t payload_size; /* LE size of the compressed payload */ + uint8_t reserved1[8]; + char compression_type[32]; /* Compression type, NUL terminated */ + uint8_t linux_magic[4]; /* Linux header magic */ + uint32_t pe_header_offset; /* LE offset to the PE header */ +}; + +/* + * Check whether *buffer points to a Linux EFI zboot image in memory. + * + * If it does, attempt to decompress it to a new buffer, and free the old one. + * If any of this fails, return an error to the caller. + * + * If the image is not a Linux EFI zboot image, do nothing and return success. + */ +ssize_t unpack_efi_zboot_image(uint8_t **buffer, int *size) +{ + const struct linux_efi_zboot_header *header; + uint8_t *data = NULL; + int ploff, plsize; + ssize_t bytes; + + /* ignore if this is too small to be a EFI zboot image */ + if (*size < sizeof(*header)) { + return 0; + } + + header = (struct linux_efi_zboot_header *)*buffer; + + /* ignore if this is not a Linux EFI zboot image */ + if (memcmp(&header->msdos_magic, EFI_PE_MSDOS_MAGIC, 2) != 0 || + memcmp(&header->zimg, "zimg", 4) != 0 || + memcmp(&header->linux_magic, EFI_PE_LINUX_MAGIC, 4) != 0) { + return 0; + } + + if (strcmp(header->compression_type, "gzip") != 0) { + fprintf(stderr, + "unable to handle EFI zboot image with \"%.*s\" compression\n", + (int)sizeof(header->compression_type) - 1, + header->compression_type); + return -1; + } + + ploff = ldl_le_p(&header->payload_offset); + plsize = ldl_le_p(&header->payload_size); + + if (ploff < 0 || plsize < 0 || ploff + plsize > *size) { + fprintf(stderr, "unable to handle corrupt EFI zboot image\n"); + return -1; + } + + data = g_malloc(LOAD_IMAGE_MAX_GUNZIP_BYTES); + bytes = gunzip(data, LOAD_IMAGE_MAX_GUNZIP_BYTES, *buffer + ploff, plsize); + if (bytes < 0) { + fprintf(stderr, "failed to decompress EFI zboot image\n"); + g_free(data); + return -1; + } + + g_free(*buffer); + *buffer = g_realloc(data, bytes); + *size = bytes; + return bytes; +} + /* * Functions for reboot-persistent memory regions. * - used for vga bios and option roms. diff --git a/include/hw/loader.h b/include/hw/loader.h index 1384796a4b..c4c14170ea 100644 --- a/include/hw/loader.h +++ b/include/hw/loader.h @@ -86,6 +86,25 @@ ssize_t load_image_gzipped_buffer(const char *filename, uint64_t max_sz, uint8_t **buffer); ssize_t load_image_gzipped(const char *filename, hwaddr addr, uint64_t max_sz); +/** + * unpack_efi_zboot_image: + * @buffer: pointer to a variable holding the address of a buffer containing the + * image + * @size: pointer to a variable holding the size of the buffer + * + * Check whether the buffer contains a EFI zboot image, and if it does, extract + * the compressed payload and decompress it into a new buffer. If successful, + * the old buffer is freed, and the *buffer and size variables pointed to by the + * function arguments are updated to refer to the newly populated buffer. + * + * Returns 0 if the image could not be identified as a EFI zboot image. + * Returns -1 if the buffer contents were identified as a EFI zboot image, but + * unpacking failed for any reason. + * Returns the size of the decompressed payload if decompression was performed + * successfully. + */ +ssize_t unpack_efi_zboot_image(uint8_t **buffer, int *size); + #define ELF_LOAD_FAILED -1 #define ELF_LOAD_NOT_ELF -2 #define ELF_LOAD_WRONG_ARCH -3 |