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efi: libstub: remove DT dependency from generic stub

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Refactor the generic EFI stub entry code so that all the dependencies on
device tree are abstracted and hidden behind a generic efi_boot_kernel()
routine that can also be implemented in other ways. This allows users of
the generic stub to avoid using FDT for passing information to the core
kernel.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Ard Biesheuvel 2022-09-16 18:51:36 +02:00
parent f4dc7fffa9
commit 4fc8e738ff
3 changed files with 60 additions and 61 deletions
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53
drivers/firmware/efi/libstub/efi-stub.c
View File

@ -10,7 +10,6 @@
*/
#include <linux/efi.h>
#include <linux/libfdt.h>
#include <asm/efi.h>
#include "efistub.h"
@ -132,14 +131,11 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
unsigned long image_addr;
unsigned long image_size = 0;
/* addr/point and size pairs for memory management*/
unsigned long fdt_addr = 0; /* Original DTB */
unsigned long fdt_size = 0;
char *cmdline_ptr = NULL;
int cmdline_size = 0;
efi_guid_t loaded_image_proto = LOADED_IMAGE_PROTOCOL_GUID;
unsigned long reserve_addr = 0;
unsigned long reserve_size = 0;
enum efi_secureboot_mode secure_boot;
struct screen_info *si;
efi_properties_table_t *prop_tbl;
@ -215,38 +211,6 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
/* Ask the firmware to clear memory on unclean shutdown */
efi_enable_reset_attack_mitigation();
secure_boot = efi_get_secureboot();
/*
* Unauthenticated device tree data is a security hazard, so ignore
* 'dtb=' unless UEFI Secure Boot is disabled. We assume that secure
* boot is enabled if we can't determine its state.
*/
if (!IS_ENABLED(CONFIG_EFI_ARMSTUB_DTB_LOADER) ||
secure_boot != efi_secureboot_mode_disabled) {
if (strstr(cmdline_ptr, "dtb="))
efi_err("Ignoring DTB from command line.\n");
} else {
status = efi_load_dtb(image, &fdt_addr, &fdt_size);
if (status != EFI_SUCCESS && status != EFI_NOT_READY) {
efi_err("Failed to load device tree!\n");
goto fail_free_image;
}
}
if (fdt_addr) {
efi_info("Using DTB from command line\n");
} else {
/* Look for a device tree configuration table entry. */
fdt_addr = (uintptr_t)get_fdt(&fdt_size);
if (fdt_addr)
efi_info("Using DTB from configuration table\n");
}
if (!fdt_addr)
efi_info("Generating empty DTB\n");
efi_load_initrd(image, ULONG_MAX, efi_get_max_initrd_addr(image_addr),
NULL);
@ -290,23 +254,8 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
install_memreserve_table();
status = allocate_new_fdt_and_exit_boot(handle, &fdt_addr, cmdline_ptr,
fdt_addr, fdt_size);
if (status != EFI_SUCCESS)
goto fail_free_fdt;
status = efi_boot_kernel(handle, image, image_addr, cmdline_ptr);
if (IS_ENABLED(CONFIG_ARM))
efi_handle_post_ebs_state();
efi_enter_kernel(image_addr, fdt_addr, fdt_totalsize((void *)fdt_addr));
/* not reached */
fail_free_fdt:
efi_err("Failed to update FDT and exit boot services\n");
efi_free(fdt_size, fdt_addr);
fail_free_image:
efi_free(image_size, image_addr);
efi_free(reserve_size, reserve_addr);
fail_free_screeninfo:

7
drivers/firmware/efi/libstub/efistub.h
View File

@ -844,11 +844,8 @@ typedef efi_status_t (*efi_exit_boot_map_processing)(
efi_status_t efi_exit_boot_services(void *handle, void *priv,
efi_exit_boot_map_processing priv_func);
efi_status_t allocate_new_fdt_and_exit_boot(void *handle,
unsigned long *new_fdt_addr,
char *cmdline_ptr,
unsigned long fdt_addr,
unsigned long fdt_size);
efi_status_t efi_boot_kernel(void *handle, efi_loaded_image_t *image,
unsigned long kernel_addr, char *cmdline_ptr);
void *get_fdt(unsigned long *fdt_size);

61
drivers/firmware/efi/libstub/fdt.c
View File

@ -219,17 +219,18 @@ static efi_status_t exit_boot_func(struct efi_boot_memmap *map, void *priv)
* exit_boot_services() call, so the exiting of boot services is very tightly
* tied to the creation of the FDT with the final memory map in it.
*/
static
efi_status_t allocate_new_fdt_and_exit_boot(void *handle,
efi_loaded_image_t *image,
unsigned long *new_fdt_addr,
char *cmdline_ptr,
unsigned long fdt_addr,
unsigned long fdt_size)
char *cmdline_ptr)
{
unsigned long desc_size;
u32 desc_ver;
efi_status_t status;
struct exit_boot_struct priv;
unsigned long fdt_addr = 0;
unsigned long fdt_size = 0;
if (!efi_novamap) {
status = efi_alloc_virtmap(&priv.runtime_map, &desc_size,
@ -240,6 +241,36 @@ efi_status_t allocate_new_fdt_and_exit_boot(void *handle,
}
}
/*
* Unauthenticated device tree data is a security hazard, so ignore
* 'dtb=' unless UEFI Secure Boot is disabled. We assume that secure
* boot is enabled if we can't determine its state.
*/
if (!IS_ENABLED(CONFIG_EFI_ARMSTUB_DTB_LOADER) ||
efi_get_secureboot() != efi_secureboot_mode_disabled) {
if (strstr(cmdline_ptr, "dtb="))
efi_err("Ignoring DTB from command line.\n");
} else {
status = efi_load_dtb(image, &fdt_addr, &fdt_size);
if (status != EFI_SUCCESS && status != EFI_NOT_READY) {
efi_err("Failed to load device tree!\n");
goto fail;
}
}
if (fdt_addr) {
efi_info("Using DTB from command line\n");
} else {
/* Look for a device tree configuration table entry. */
fdt_addr = (uintptr_t)get_fdt(&fdt_size);
if (fdt_addr)
efi_info("Using DTB from configuration table\n");
}
if (!fdt_addr)
efi_info("Generating empty DTB\n");
efi_info("Exiting boot services...\n");
status = efi_allocate_pages(MAX_FDT_SIZE, new_fdt_addr, ULONG_MAX);
@ -303,11 +334,33 @@ fail_free_new_fdt:
efi_free(MAX_FDT_SIZE, *new_fdt_addr);
fail:
efi_free(fdt_size, fdt_addr);
efi_bs_call(free_pool, priv.runtime_map);
return EFI_LOAD_ERROR;
}
efi_status_t efi_boot_kernel(void *handle, efi_loaded_image_t *image,
unsigned long kernel_addr, char *cmdline_ptr)
{
unsigned long fdt_addr;
efi_status_t status;
status = allocate_new_fdt_and_exit_boot(handle, image, &fdt_addr,
cmdline_ptr);
if (status != EFI_SUCCESS) {
efi_err("Failed to update FDT and exit boot services\n");
return status;
}
if (IS_ENABLED(CONFIG_ARM))
efi_handle_post_ebs_state();
efi_enter_kernel(kernel_addr, fdt_addr, fdt_totalsize((void *)fdt_addr));
/* not reached */
}
void *get_fdt(unsigned long *fdt_size)
{
void *fdt;