From: Ard Biesheuvel ardb@kernel.org
[ Commit 7e50262229faad0c7b8c54477cd1c883f31cc4a7 upstream ]
The native EFI entrypoint does not take a struct boot_params from the loader, but instead, it constructs one from scratch, using the setup header data placed at the start of the image.
This setup header is placed in a way that permits legacy loaders to manipulate the contents (i.e., to pass the kernel command line or the address and size of an initial ramdisk), but EFI boot does not use it in that way - it only copies the contents that were placed there at build time, but EFI loaders will not (and should not) manipulate the setup header to configure the boot. (Commit 63bf28ceb3ebbe76 "efi: x86: Wipe setup_data on pure EFI boot" deals with some of the fallout of using setup_data in a way that breaks EFI boot.)
Given that none of the non-zero values that are copied from the setup header into the EFI stub's struct boot_params are relevant to the boot now that the EFI stub no longer enters via the legacy decompressor, the copy can be omitted altogether.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lore.kernel.org/r/20230912090051.4014114-19-ardb@google.com Signed-off-by: Ard Biesheuvel ardb@kernel.org --- drivers/firmware/efi/libstub/x86-stub.c | 46 +++----------------- 1 file changed, 6 insertions(+), 40 deletions(-)
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index dc50dda40239..c592ecd40dab 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -426,9 +426,8 @@ void __noreturn efi_stub_entry(efi_handle_t handle, efi_status_t __efiapi efi_pe_entry(efi_handle_t handle, efi_system_table_t *sys_table_arg) { - struct boot_params *boot_params; - struct setup_header *hdr; - void *image_base; + static struct boot_params boot_params __page_aligned_bss; + struct setup_header *hdr = &boot_params.hdr; efi_guid_t proto = LOADED_IMAGE_PROTOCOL_GUID; int options_size = 0; efi_status_t status; @@ -449,30 +448,9 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle, efi_exit(handle, status); }
- image_base = efi_table_attr(image, image_base); - - status = efi_allocate_pages(sizeof(struct boot_params), - (unsigned long *)&boot_params, ULONG_MAX); - if (status != EFI_SUCCESS) { - efi_err("Failed to allocate lowmem for boot params\n"); - efi_exit(handle, status); - } - - memset(boot_params, 0x0, sizeof(struct boot_params)); - - hdr = &boot_params->hdr; - - /* Copy the setup header from the second sector to boot_params */ - memcpy(&hdr->jump, image_base + 512, - sizeof(struct setup_header) - offsetof(struct setup_header, jump)); - - /* - * Fill out some of the header fields ourselves because the - * EFI firmware loader doesn't load the first sector. - */ + /* Assign the setup_header fields that the kernel actually cares about */ hdr->root_flags = 1; hdr->vid_mode = 0xffff; - hdr->boot_flag = 0xAA55;
hdr->type_of_loader = 0x21;
@@ -481,25 +459,13 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle, if (!cmdline_ptr) goto fail;
- efi_set_u64_split((unsigned long)cmdline_ptr, - &hdr->cmd_line_ptr, &boot_params->ext_cmd_line_ptr); - - hdr->ramdisk_image = 0; - hdr->ramdisk_size = 0; - - /* - * Disregard any setup data that was provided by the bootloader: - * setup_data could be pointing anywhere, and we have no way of - * authenticating or validating the payload. - */ - hdr->setup_data = 0; + efi_set_u64_split((unsigned long)cmdline_ptr, &hdr->cmd_line_ptr, + &boot_params.ext_cmd_line_ptr);
- efi_stub_entry(handle, sys_table_arg, boot_params); + efi_stub_entry(handle, sys_table_arg, &boot_params); /* not reached */
fail: - efi_free(sizeof(struct boot_params), (unsigned long)boot_params); - efi_exit(handle, status); }