Commit 688eb282 authored Oct 11, 2020 by Arvind Sankar Committed by Ard Biesheuvel Oct 26, 2020

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



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>

parent bc13809f

drivers/firmware/efi/libstub/x86-stub.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -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);

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