/* SPDX-License-Identifier: LGPL-2.1-or-later */ /* * x86 specific code to for EFI handover boot protocol * Linux kernels version 5.8 and newer support providing the initrd by * LINUX_INITRD_MEDIA_GUID DevicePath. In order to support older kernels too, * this x86 specific linux_exec function passes the initrd by setting the * corresponding fields in the setup_header struct. * * see https://docs.kernel.org/x86/boot.html */ #include #include #include "initrd.h" #include "linux.h" #include "macro-fundamental.h" #include "util.h" #define KERNEL_SECTOR_SIZE 512u #define BOOT_FLAG_MAGIC 0xAA55u #define SETUP_MAGIC 0x53726448u /* "HdrS" */ #define SETUP_VERSION_2_11 0x20bu #define SETUP_VERSION_2_12 0x20cu #define SETUP_VERSION_2_15 0x20fu #define CMDLINE_PTR_MAX 0xA0000u enum { XLF_KERNEL_64 = 1 << 0, XLF_CAN_BE_LOADED_ABOVE_4G = 1 << 1, XLF_EFI_HANDOVER_32 = 1 << 2, XLF_EFI_HANDOVER_64 = 1 << 3, #ifdef __x86_64__ XLF_EFI_HANDOVER = XLF_EFI_HANDOVER_64, #else XLF_EFI_HANDOVER = XLF_EFI_HANDOVER_32, #endif }; typedef struct { uint8_t setup_sects; uint16_t root_flags; uint32_t syssize; uint16_t ram_size; uint16_t vid_mode; uint16_t root_dev; uint16_t boot_flag; uint8_t jump; /* We split the 2-byte jump field from the spec in two for convenience. */ uint8_t setup_size; uint32_t header; uint16_t version; uint32_t realmode_swtch; uint16_t start_sys_seg; uint16_t kernel_version; uint8_t type_of_loader; uint8_t loadflags; uint16_t setup_move_size; uint32_t code32_start; uint32_t ramdisk_image; uint32_t ramdisk_size; uint32_t bootsect_kludge; uint16_t heap_end_ptr; uint8_t ext_loader_ver; uint8_t ext_loader_type; uint32_t cmd_line_ptr; uint32_t initrd_addr_max; uint32_t kernel_alignment; uint8_t relocatable_kernel; uint8_t min_alignment; uint16_t xloadflags; uint32_t cmdline_size; uint32_t hardware_subarch; uint64_t hardware_subarch_data; uint32_t payload_offset; uint32_t payload_length; uint64_t setup_data; uint64_t pref_address; uint32_t init_size; uint32_t handover_offset; } _packed_ SetupHeader; /* We really only care about a few fields, but we still have to provide a full page otherwise. */ typedef struct { uint8_t pad[192]; uint32_t ext_ramdisk_image; uint32_t ext_ramdisk_size; uint32_t ext_cmd_line_ptr; uint8_t pad2[293]; SetupHeader hdr; uint8_t pad3[3480]; } _packed_ BootParams; assert_cc(offsetof(BootParams, ext_ramdisk_image) == 0x0C0); assert_cc(sizeof(BootParams) == 4096); #ifdef __i386__ # define __regparm0__ __attribute__((regparm(0))) #else # define __regparm0__ #endif typedef void (*handover_f)(void *parent, EFI_SYSTEM_TABLE *table, BootParams *params) __regparm0__ __attribute__((sysv_abi)); static void linux_efi_handover(EFI_HANDLE parent, uintptr_t kernel, BootParams *params) { assert(params); kernel += (params->hdr.setup_sects + 1) * KERNEL_SECTOR_SIZE; /* 32bit entry address. */ /* Old kernels needs this set, while newer ones seem to ignore this. Note that this gets truncated on * above 4G boots, which is fine as long as we do not use the value to jump to kernel entry. */ params->hdr.code32_start = kernel; #ifdef __x86_64__ kernel += KERNEL_SECTOR_SIZE; /* 64bit entry address. */ #endif kernel += params->hdr.handover_offset; /* 32/64bit EFI handover address. */ /* Note in EFI mixed mode this now points to the correct 32bit handover entry point, allowing a 64bit * kernel to be booted from a 32bit sd-stub. */ handover_f handover = (handover_f) kernel; handover(parent, ST, params); } EFI_STATUS linux_exec_efi_handover( EFI_HANDLE parent, const char16_t *cmdline, const void *linux_buffer, size_t linux_length, const void *initrd_buffer, size_t initrd_length) { assert(parent); assert(linux_buffer); assert(initrd_buffer || initrd_length == 0); if (linux_length < sizeof(BootParams)) return EFI_LOAD_ERROR; const BootParams *image_params = (const BootParams *) linux_buffer; if (image_params->hdr.header != SETUP_MAGIC || image_params->hdr.boot_flag != BOOT_FLAG_MAGIC) return log_error_status_stall(EFI_UNSUPPORTED, u"Unsupported kernel image."); if (image_params->hdr.version < SETUP_VERSION_2_11) return log_error_status_stall(EFI_UNSUPPORTED, u"Kernel too old."); if (!image_params->hdr.relocatable_kernel) return log_error_status_stall(EFI_UNSUPPORTED, u"Kernel is not relocatable."); /* The xloadflags were added in version 2.12+ of the boot protocol but the handover support predates * that, so we cannot safety-check this for 2.11. */ if (image_params->hdr.version >= SETUP_VERSION_2_12 && !FLAGS_SET(image_params->hdr.xloadflags, XLF_EFI_HANDOVER)) return log_error_status_stall(EFI_UNSUPPORTED, u"Kernel does not support EFI handover protocol."); bool can_4g = image_params->hdr.version >= SETUP_VERSION_2_12 && FLAGS_SET(image_params->hdr.xloadflags, XLF_CAN_BE_LOADED_ABOVE_4G); if (!can_4g && POINTER_TO_PHYSICAL_ADDRESS(linux_buffer) + linux_length > UINT32_MAX) return log_error_status_stall( EFI_UNSUPPORTED, u"Unified kernel image was loaded above 4G, but kernel lacks support."); if (!can_4g && POINTER_TO_PHYSICAL_ADDRESS(initrd_buffer) + initrd_length > UINT32_MAX) return log_error_status_stall( EFI_UNSUPPORTED, u"Initrd is above 4G, but kernel lacks support."); _cleanup_pages_ Pages boot_params_page = xmalloc_pages( can_4g ? AllocateAnyPages : AllocateMaxAddress, EfiLoaderData, EFI_SIZE_TO_PAGES(sizeof(BootParams)), UINT32_MAX /* Below the 4G boundary */); BootParams *boot_params = PHYSICAL_ADDRESS_TO_POINTER(boot_params_page.addr); *boot_params = (BootParams){}; /* Setup size is determined by offset 0x0202 + byte value at offset 0x0201, which is the same as * offset of the header field and the target from the jump field (which we split for this reason). */ memcpy(&boot_params->hdr, &image_params->hdr, offsetof(SetupHeader, header) + image_params->hdr.setup_size); boot_params->hdr.type_of_loader = 0xff; /* Spec says: For backwards compatibility, if the setup_sects field contains 0, the real value is 4. */ if (boot_params->hdr.setup_sects == 0) boot_params->hdr.setup_sects = 4; _cleanup_pages_ Pages cmdline_pages = {}; if (cmdline) { size_t len = MIN(strlen16(cmdline), image_params->hdr.cmdline_size); cmdline_pages = xmalloc_pages( can_4g ? AllocateAnyPages : AllocateMaxAddress, EfiLoaderData, EFI_SIZE_TO_PAGES(len + 1), CMDLINE_PTR_MAX); /* Convert cmdline to ASCII. */ char *cmdline8 = PHYSICAL_ADDRESS_TO_POINTER(cmdline_pages.addr); for (size_t i = 0; i < len; i++) cmdline8[i] = cmdline[i] <= 0x7E ? cmdline[i] : ' '; cmdline8[len] = '\0'; boot_params->hdr.cmd_line_ptr = (uint32_t) cmdline_pages.addr; boot_params->ext_cmd_line_ptr = cmdline_pages.addr >> 32; assert(can_4g || cmdline_pages.addr <= CMDLINE_PTR_MAX); } boot_params->hdr.ramdisk_image = (uintptr_t) initrd_buffer; boot_params->ext_ramdisk_image = POINTER_TO_PHYSICAL_ADDRESS(initrd_buffer) >> 32; boot_params->hdr.ramdisk_size = initrd_length; boot_params->ext_ramdisk_size = ((uint64_t) initrd_length) >> 32; linux_efi_handover(parent, (uintptr_t) linux_buffer, boot_params); return EFI_LOAD_ERROR; }