Commit d5cdf4cf authored by Arvind Sankar's avatar Arvind Sankar Committed by Ingo Molnar

efi/x86: Don't relocate the kernel unless necessary

Add alignment slack to the PE image size, so that we can realign the
decompression buffer within the space allocated for the image.

Only relocate the kernel if it has been loaded at an unsuitable address:

 - Below LOAD_PHYSICAL_ADDR, or
 - Above 64T for 64-bit and 512MiB for 32-bit

For 32-bit, the upper limit is conservative, but the exact limit can be
difficult to calculate.
Signed-off-by: default avatarArvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200303221205.4048668-6-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-20-ardb@kernel.org
parent 964124a9
...@@ -238,21 +238,17 @@ static void update_pecoff_text(unsigned int text_start, unsigned int file_sz, ...@@ -238,21 +238,17 @@ static void update_pecoff_text(unsigned int text_start, unsigned int file_sz,
pe_header = get_unaligned_le32(&buf[0x3c]); pe_header = get_unaligned_le32(&buf[0x3c]);
#ifdef CONFIG_EFI_MIXED
/* /*
* In mixed mode, we will execute startup_32() at whichever offset in * The PE/COFF loader may load the image at an address which is
* memory it happened to land when the PE/COFF loader loaded the image, * misaligned with respect to the kernel_alignment field in the setup
* which may be misaligned with respect to the kernel_alignment field * header.
* in the setup header.
* *
* In order for startup_32 to safely execute in place at this offset, * In order to avoid relocating the kernel to correct the misalignment,
* we need to ensure that the CONFIG_PHYSICAL_ALIGN aligned allocation * add slack to allow the buffer to be aligned within the declared size
* it creates for the page tables does not extend beyond the declared * of the image.
* size of the image in the PE/COFF header. So add the required slack.
*/ */
bss_sz += CONFIG_PHYSICAL_ALIGN; bss_sz += CONFIG_PHYSICAL_ALIGN;
init_sz += CONFIG_PHYSICAL_ALIGN; init_sz += CONFIG_PHYSICAL_ALIGN;
#endif
/* /*
* Size of code: Subtract the size of the first sector (512 bytes) * Size of code: Subtract the size of the first sector (512 bytes)
......
...@@ -17,6 +17,9 @@ ...@@ -17,6 +17,9 @@
#include "efistub.h" #include "efistub.h"
/* Maximum physical address for 64-bit kernel with 4-level paging */
#define MAXMEM_X86_64_4LEVEL (1ull << 46)
static efi_system_table_t *sys_table; static efi_system_table_t *sys_table;
extern const bool efi_is64; extern const bool efi_is64;
extern u32 image_offset; extern u32 image_offset;
...@@ -718,6 +721,7 @@ unsigned long efi_main(efi_handle_t handle, ...@@ -718,6 +721,7 @@ unsigned long efi_main(efi_handle_t handle,
struct boot_params *boot_params) struct boot_params *boot_params)
{ {
unsigned long bzimage_addr = (unsigned long)startup_32; unsigned long bzimage_addr = (unsigned long)startup_32;
unsigned long buffer_start, buffer_end;
struct setup_header *hdr = &boot_params->hdr; struct setup_header *hdr = &boot_params->hdr;
efi_status_t status; efi_status_t status;
unsigned long cmdline_paddr; unsigned long cmdline_paddr;
...@@ -729,10 +733,33 @@ unsigned long efi_main(efi_handle_t handle, ...@@ -729,10 +733,33 @@ unsigned long efi_main(efi_handle_t handle,
efi_exit(handle, EFI_INVALID_PARAMETER); efi_exit(handle, EFI_INVALID_PARAMETER);
/* /*
* If the kernel isn't already loaded at the preferred load * If the kernel isn't already loaded at a suitable address,
* address, relocate it. * relocate it.
*
* It must be loaded above LOAD_PHYSICAL_ADDR.
*
* The maximum address for 64-bit is 1 << 46 for 4-level paging. This
* is defined as the macro MAXMEM, but unfortunately that is not a
* compile-time constant if 5-level paging is configured, so we instead
* define our own macro for use here.
*
* For 32-bit, the maximum address is complicated to figure out, for
* now use KERNEL_IMAGE_SIZE, which will be 512MiB, the same as what
* KASLR uses.
*
* Also relocate it if image_offset is zero, i.e. we weren't loaded by
* LoadImage, but we are not aligned correctly.
*/ */
if (bzimage_addr - image_offset != hdr->pref_address) {
buffer_start = ALIGN(bzimage_addr - image_offset,
hdr->kernel_alignment);
buffer_end = buffer_start + hdr->init_size;
if ((buffer_start < LOAD_PHYSICAL_ADDR) ||
(IS_ENABLED(CONFIG_X86_32) && buffer_end > KERNEL_IMAGE_SIZE) ||
(IS_ENABLED(CONFIG_X86_64) && buffer_end > MAXMEM_X86_64_4LEVEL) ||
(image_offset == 0 && !IS_ALIGNED(bzimage_addr,
hdr->kernel_alignment))) {
status = efi_relocate_kernel(&bzimage_addr, status = efi_relocate_kernel(&bzimage_addr,
hdr->init_size, hdr->init_size, hdr->init_size, hdr->init_size,
hdr->pref_address, hdr->pref_address,
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment