efi/x86: Decompress at start of PE image load address
When booted via PE loader, define image_offset to hold the offset of
startup_32() from the start of the PE image, and use it as the start of
the decompression buffer.
[ mingo: Fixed the grammar in the comments. ]
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200303221205.4048668-3-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-17-ardb@kernel.org
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 69a942f..3e1bc8a 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -19,6 +19,7 @@
static efi_system_table_t *sys_table;
extern const bool efi_is64;
+extern u32 image_offset;
__pure efi_system_table_t *efi_system_table(void)
{
@@ -365,6 +366,7 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
struct boot_params *boot_params;
struct setup_header *hdr;
efi_loaded_image_t *image;
+ void *image_base;
efi_guid_t proto = LOADED_IMAGE_PROTOCOL_GUID;
int options_size = 0;
efi_status_t status;
@@ -385,7 +387,10 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
efi_exit(handle, status);
}
- hdr = &((struct boot_params *)efi_table_attr(image, image_base))->hdr;
+ image_base = efi_table_attr(image, image_base);
+ image_offset = (void *)startup_32 - image_base;
+
+ hdr = &((struct boot_params *)image_base)->hdr;
above4g = hdr->xloadflags & XLF_CAN_BE_LOADED_ABOVE_4G;
status = efi_allocate_pages(0x4000, (unsigned long *)&boot_params,
@@ -400,7 +405,7 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
hdr = &boot_params->hdr;
/* Copy the second sector to boot_params */
- memcpy(&hdr->jump, efi_table_attr(image, image_base) + 512, 512);
+ memcpy(&hdr->jump, image_base + 512, 512);
/*
* Fill out some of the header fields ourselves because the
@@ -727,7 +732,7 @@ unsigned long efi_main(efi_handle_t handle,
* If the kernel isn't already loaded at the preferred load
* address, relocate it.
*/
- if (bzimage_addr != hdr->pref_address) {
+ if (bzimage_addr - image_offset != hdr->pref_address) {
status = efi_relocate_kernel(&bzimage_addr,
hdr->init_size, hdr->init_size,
hdr->pref_address,
@@ -737,6 +742,12 @@ unsigned long efi_main(efi_handle_t handle,
efi_printk("efi_relocate_kernel() failed!\n");
goto fail;
}
+ /*
+ * Now that we've copied the kernel elsewhere, we no longer
+ * have a set up block before startup_32(), so reset image_offset
+ * to zero in case it was set earlier.
+ */
+ image_offset = 0;
}
/*