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efi/x86: Only copy the compressed kernel image in efi_relocate_kernel()

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The image_size argument to efi_relocate_kernel() is currently specified
as init_size, but this is unnecessarily large. The compressed kernel is
much smaller, in fact, its image only extends up to the start of _bss,
since at this point, the .bss section is still uninitialized.

Depending on compression level, this can reduce the amount of data
copied by 4-5x.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20201011142012.96493-1-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Arvind Sankar 2020-10-11 10:20:12 -04:00 committed by Ard Biesheuvel
parent bc13809f1c
commit 688eb28211
1 changed files with 4 additions and 1 deletions
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5
drivers/firmware/efi/libstub/x86-stub.c
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@ -715,8 +715,11 @@ unsigned long efi_main(efi_handle_t handle,
(IS_ENABLED(CONFIG_X86_32) && buffer_end > KERNEL_IMAGE_SIZE) ||
(IS_ENABLED(CONFIG_X86_64) && buffer_end > MAXMEM_X86_64_4LEVEL) ||
(image_offset == 0)) {
extern char _bss[];
status = efi_relocate_kernel(&bzimage_addr,
hdr->init_size, hdr->init_size,
(unsigned long)_bss - bzimage_addr,
hdr->init_size,
hdr->pref_address,
hdr->kernel_alignment,
LOAD_PHYSICAL_ADDR);