1c761ee9da
Currently the EFI stub prints a diagnostic on boot saying that KASLR will be disabled if it is unable to use the EFI RNG protocol to obtain a seed for KASLR. With the addition of support for v8.5-RNG and the SMCCC RNG protocol it is now possible for KASLR to obtain entropy even if the EFI RNG protocol is unsupported in the system, and the main kernel now explicitly says if KASLR is active itself. This can result in a boot log where the stub says KASLR has been disabled and the main kernel says that it is enabled which is confusing for users. Remove the explicit reference to KASLR from the diagnostics, the warnings are still useful as EFI is the only source of entropy the stub uses when randomizing the physical address of the kernel and the other sources may not be available. Signed-off-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20210120163810.14973-1-broonie@kernel.org Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
120 lines
3.2 KiB
C
120 lines
3.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2013, 2014 Linaro Ltd; <roy.franz@linaro.org>
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*
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* This file implements the EFI boot stub for the arm64 kernel.
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* Adapted from ARM version by Mark Salter <msalter@redhat.com>
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*/
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#include <linux/efi.h>
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#include <asm/efi.h>
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#include <asm/memory.h>
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#include <asm/sections.h>
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#include <asm/sysreg.h>
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#include "efistub.h"
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efi_status_t check_platform_features(void)
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{
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u64 tg;
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/* UEFI mandates support for 4 KB granularity, no need to check */
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if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
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return EFI_SUCCESS;
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tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_TGRAN_SHIFT) & 0xf;
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if (tg != ID_AA64MMFR0_TGRAN_SUPPORTED) {
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if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
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efi_err("This 64 KB granular kernel is not supported by your CPU\n");
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else
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efi_err("This 16 KB granular kernel is not supported by your CPU\n");
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return EFI_UNSUPPORTED;
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}
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return EFI_SUCCESS;
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}
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/*
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* Although relocatable kernels can fix up the misalignment with respect to
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* MIN_KIMG_ALIGN, the resulting virtual text addresses are subtly out of
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* sync with those recorded in the vmlinux when kaslr is disabled but the
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* image required relocation anyway. Therefore retain 2M alignment unless
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* KASLR is in use.
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*/
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static u64 min_kimg_align(void)
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{
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return efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN;
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}
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efi_status_t handle_kernel_image(unsigned long *image_addr,
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unsigned long *image_size,
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unsigned long *reserve_addr,
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unsigned long *reserve_size,
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efi_loaded_image_t *image)
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{
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efi_status_t status;
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unsigned long kernel_size, kernel_memsize = 0;
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u32 phys_seed = 0;
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if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
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if (!efi_nokaslr) {
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status = efi_get_random_bytes(sizeof(phys_seed),
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(u8 *)&phys_seed);
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if (status == EFI_NOT_FOUND) {
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efi_info("EFI_RNG_PROTOCOL unavailable\n");
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efi_nokaslr = true;
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} else if (status != EFI_SUCCESS) {
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efi_err("efi_get_random_bytes() failed (0x%lx)\n",
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status);
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efi_nokaslr = true;
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}
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} else {
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efi_info("KASLR disabled on kernel command line\n");
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}
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}
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if (image->image_base != _text)
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efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n");
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kernel_size = _edata - _text;
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kernel_memsize = kernel_size + (_end - _edata);
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*reserve_size = kernel_memsize;
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if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
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/*
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* If KASLR is enabled, and we have some randomness available,
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* locate the kernel at a randomized offset in physical memory.
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*/
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status = efi_random_alloc(*reserve_size, min_kimg_align(),
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reserve_addr, phys_seed);
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} else {
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status = EFI_OUT_OF_RESOURCES;
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}
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if (status != EFI_SUCCESS) {
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if (IS_ALIGNED((u64)_text, min_kimg_align())) {
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/*
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* Just execute from wherever we were loaded by the
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* UEFI PE/COFF loader if the alignment is suitable.
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*/
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*image_addr = (u64)_text;
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*reserve_size = 0;
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return EFI_SUCCESS;
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}
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status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
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ULONG_MAX, min_kimg_align());
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if (status != EFI_SUCCESS) {
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efi_err("Failed to relocate kernel\n");
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*reserve_size = 0;
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return status;
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}
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}
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*image_addr = *reserve_addr;
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memcpy((void *)*image_addr, _text, kernel_size);
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return EFI_SUCCESS;
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}
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