diff options
author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2016-01-26 13:48:29 (GMT) |
---|---|---|
committer | Catalin Marinas <catalin.marinas@arm.com> | 2016-02-24 14:57:29 (GMT) |
commit | 2b5fe07a78a09a32002642b8a823428ade611f16 (patch) | |
tree | db8929655f2d9de7827d68fbfad1ea08d1cd0e29 /drivers/firmware/efi | |
parent | 48fcb2d0216103d15306caa4814e2381104df6d8 (diff) | |
download | linux-2b5fe07a78a09a32002642b8a823428ade611f16.tar.xz |
arm64: efi: invoke EFI_RNG_PROTOCOL to supply KASLR randomness
Since arm64 does not use a decompressor that supplies an execution
environment where it is feasible to some extent to provide a source of
randomness, the arm64 KASLR kernel depends on the bootloader to supply
some random bits in the /chosen/kaslr-seed DT property upon kernel entry.
On UEFI systems, we can use the EFI_RNG_PROTOCOL, if supplied, to obtain
some random bits. At the same time, use it to randomize the offset of the
kernel Image in physical memory.
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'drivers/firmware/efi')
-rw-r--r-- | drivers/firmware/efi/libstub/arm-stub.c | 40 | ||||
-rw-r--r-- | drivers/firmware/efi/libstub/arm64-stub.c | 78 | ||||
-rw-r--r-- | drivers/firmware/efi/libstub/fdt.c | 14 |
3 files changed, 97 insertions, 35 deletions
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c index 3397902..4deb3e7 100644 --- a/drivers/firmware/efi/libstub/arm-stub.c +++ b/drivers/firmware/efi/libstub/arm-stub.c @@ -18,6 +18,8 @@ #include "efistub.h" +bool __nokaslr; + static int efi_secureboot_enabled(efi_system_table_t *sys_table_arg) { static efi_guid_t const var_guid = EFI_GLOBAL_VARIABLE_GUID; @@ -207,14 +209,6 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, pr_efi_err(sys_table, "Failed to find DRAM base\n"); goto fail; } - status = handle_kernel_image(sys_table, image_addr, &image_size, - &reserve_addr, - &reserve_size, - dram_base, image); - if (status != EFI_SUCCESS) { - pr_efi_err(sys_table, "Failed to relocate kernel\n"); - goto fail; - } /* * Get the command line from EFI, using the LOADED_IMAGE @@ -224,7 +218,28 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, cmdline_ptr = efi_convert_cmdline(sys_table, image, &cmdline_size); if (!cmdline_ptr) { pr_efi_err(sys_table, "getting command line via LOADED_IMAGE_PROTOCOL\n"); - goto fail_free_image; + goto fail; + } + + /* check whether 'nokaslr' was passed on the command line */ + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { + static const u8 default_cmdline[] = CONFIG_CMDLINE; + const u8 *str, *cmdline = cmdline_ptr; + + if (IS_ENABLED(CONFIG_CMDLINE_FORCE)) + cmdline = default_cmdline; + str = strstr(cmdline, "nokaslr"); + if (str == cmdline || (str > cmdline && *(str - 1) == ' ')) + __nokaslr = true; + } + + status = handle_kernel_image(sys_table, image_addr, &image_size, + &reserve_addr, + &reserve_size, + dram_base, image); + if (status != EFI_SUCCESS) { + pr_efi_err(sys_table, "Failed to relocate kernel\n"); + goto fail_free_cmdline; } status = efi_parse_options(cmdline_ptr); @@ -244,7 +259,7 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, if (status != EFI_SUCCESS) { pr_efi_err(sys_table, "Failed to load device tree!\n"); - goto fail_free_cmdline; + goto fail_free_image; } } @@ -286,12 +301,11 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table, efi_free(sys_table, initrd_size, initrd_addr); efi_free(sys_table, fdt_size, fdt_addr); -fail_free_cmdline: - efi_free(sys_table, cmdline_size, (unsigned long)cmdline_ptr); - fail_free_image: efi_free(sys_table, image_size, *image_addr); efi_free(sys_table, reserve_size, reserve_addr); +fail_free_cmdline: + efi_free(sys_table, cmdline_size, (unsigned long)cmdline_ptr); fail: return EFI_ERROR; } diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c index 78dfbd3..e0e6b74 100644 --- a/drivers/firmware/efi/libstub/arm64-stub.c +++ b/drivers/firmware/efi/libstub/arm64-stub.c @@ -13,6 +13,10 @@ #include <asm/efi.h> #include <asm/sections.h> +#include "efistub.h" + +extern bool __nokaslr; + efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg, unsigned long *image_addr, unsigned long *image_size, @@ -23,26 +27,52 @@ efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg, { efi_status_t status; unsigned long kernel_size, kernel_memsize = 0; - unsigned long nr_pages; void *old_image_addr = (void *)*image_addr; unsigned long preferred_offset; + u64 phys_seed = 0; + + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { + if (!__nokaslr) { + status = efi_get_random_bytes(sys_table_arg, + sizeof(phys_seed), + (u8 *)&phys_seed); + if (status == EFI_NOT_FOUND) { + pr_efi(sys_table_arg, "EFI_RNG_PROTOCOL unavailable, no randomness supplied\n"); + } else if (status != EFI_SUCCESS) { + pr_efi_err(sys_table_arg, "efi_get_random_bytes() failed\n"); + return status; + } + } else { + pr_efi(sys_table_arg, "KASLR disabled on kernel command line\n"); + } + } /* * The preferred offset of the kernel Image is TEXT_OFFSET bytes beyond * a 2 MB aligned base, which itself may be lower than dram_base, as * long as the resulting offset equals or exceeds it. */ - preferred_offset = round_down(dram_base, SZ_2M) + TEXT_OFFSET; + preferred_offset = round_down(dram_base, MIN_KIMG_ALIGN) + TEXT_OFFSET; if (preferred_offset < dram_base) - preferred_offset += SZ_2M; + preferred_offset += MIN_KIMG_ALIGN; - /* Relocate the image, if required. */ kernel_size = _edata - _text; - if (*image_addr != preferred_offset) { - kernel_memsize = kernel_size + (_end - _edata); + kernel_memsize = kernel_size + (_end - _edata); + + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) { + /* + * If KASLR is enabled, and we have some randomness available, + * locate the kernel at a randomized offset in physical memory. + */ + *reserve_size = kernel_memsize + TEXT_OFFSET; + status = efi_random_alloc(sys_table_arg, *reserve_size, + MIN_KIMG_ALIGN, reserve_addr, + phys_seed); + *image_addr = *reserve_addr + TEXT_OFFSET; + } else { /* - * First, try a straight allocation at the preferred offset. + * Else, try a straight allocation at the preferred offset. * This will work around the issue where, if dram_base == 0x0, * efi_low_alloc() refuses to allocate at 0x0 (to prevent the * address of the allocation to be mistaken for a FAIL return @@ -52,27 +82,31 @@ efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg, * Mustang), we can still place the kernel at the address * 'dram_base + TEXT_OFFSET'. */ + if (*image_addr == preferred_offset) + return EFI_SUCCESS; + *image_addr = *reserve_addr = preferred_offset; - nr_pages = round_up(kernel_memsize, EFI_ALLOC_ALIGN) / - EFI_PAGE_SIZE; + *reserve_size = round_up(kernel_memsize, EFI_ALLOC_ALIGN); + status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS, - EFI_LOADER_DATA, nr_pages, + EFI_LOADER_DATA, + *reserve_size / EFI_PAGE_SIZE, (efi_physical_addr_t *)reserve_addr); - if (status != EFI_SUCCESS) { - kernel_memsize += TEXT_OFFSET; - status = efi_low_alloc(sys_table_arg, kernel_memsize, - SZ_2M, reserve_addr); + } - if (status != EFI_SUCCESS) { - pr_efi_err(sys_table_arg, "Failed to relocate kernel\n"); - return status; - } - *image_addr = *reserve_addr + TEXT_OFFSET; + if (status != EFI_SUCCESS) { + *reserve_size = kernel_memsize + TEXT_OFFSET; + status = efi_low_alloc(sys_table_arg, *reserve_size, + MIN_KIMG_ALIGN, reserve_addr); + + if (status != EFI_SUCCESS) { + pr_efi_err(sys_table_arg, "Failed to relocate kernel\n"); + *reserve_size = 0; + return status; } - memcpy((void *)*image_addr, old_image_addr, kernel_size); - *reserve_size = kernel_memsize; + *image_addr = *reserve_addr + TEXT_OFFSET; } - + memcpy((void *)*image_addr, old_image_addr, kernel_size); return EFI_SUCCESS; } diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c index cf7b7d4..6dba78a 100644 --- a/drivers/firmware/efi/libstub/fdt.c +++ b/drivers/firmware/efi/libstub/fdt.c @@ -147,6 +147,20 @@ efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt, if (status) goto fdt_set_fail; + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) { + efi_status_t efi_status; + + efi_status = efi_get_random_bytes(sys_table, sizeof(fdt_val64), + (u8 *)&fdt_val64); + if (efi_status == EFI_SUCCESS) { + status = fdt_setprop(fdt, node, "kaslr-seed", + &fdt_val64, sizeof(fdt_val64)); + if (status) + goto fdt_set_fail; + } else if (efi_status != EFI_NOT_FOUND) { + return efi_status; + } + } return EFI_SUCCESS; fdt_set_fail: |