[PATCH v8 20/23] x86/decompressor: Factor out kernel decompression and relocation

Ard Biesheuvel
2023-08-02T15:51:38Z

Factor out the decompressor sequence that invokes the decompressor,
parses the ELF and applies the relocations so that it can be called
directly from the EFI stub.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/boot/compressed/misc.c | 28 ++++++++++++++++----
arch/x86/include/asm/boot.h | 8 ++++++
2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 2d91d56b59e1af93..f711f2a85862e9ef 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -330,11 +330,33 @@ static size_t parse_elf(void *output)
return ehdr.e_entry - LOAD_PHYSICAL_ADDR;
}

+const unsigned long kernel_total_size = VO__end - VO__text;
+
static u8 boot_heap[BOOT_HEAP_SIZE] __aligned(4);

extern unsigned char input_data[];
extern unsigned int input_len, output_len;

+unsigned long decompress_kernel(unsigned char *outbuf, unsigned long virt_addr,
+ void (*error)(char *x))
+{
+ unsigned long entry;
+
+ if (!free_mem_ptr) {
+ free_mem_ptr = (unsigned long)boot_heap;
+ free_mem_end_ptr = (unsigned long)boot_heap + sizeof(boot_heap);
+ }
+
+ if (__decompress(input_data, input_len, NULL, NULL, outbuf, output_len,
+ NULL, error) < 0)
+ return ULONG_MAX;
+
+ entry = parse_elf(outbuf);
+ handle_relocations(outbuf, output_len, virt_addr);
+
+ return entry;
+}
+
/*
* The compressed kernel image (ZO), has been moved so that its position
* is against the end of the buffer used to hold the uncompressed kernel
@@ -354,7 +376,6 @@ extern unsigned int input_len, output_len;
*/
asmlinkage __visible void *extract_kernel(void *rmode, unsigned char *output)
{
- const unsigned long kernel_total_size = VO__end - VO__text;
unsigned long virt_addr = LOAD_PHYSICAL_ADDR;
memptr heap = (memptr)boot_heap;
unsigned long needed_size;
@@ -463,10 +484,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, unsigned char *output)
accept_memory(__pa(output), __pa(output) + needed_size);
}

- __decompress(input_data, input_len, NULL, NULL, output, output_len,
- NULL, error);
- entry_offset = parse_elf(output);
- handle_relocations(output, output_len, virt_addr);
+ entry_offset = decompress_kernel(output, virt_addr, error);

debug_putstr("done.\nBooting the kernel (entry_offset: 0x");
debug_puthex(entry_offset);
diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h
index 9191280d9ea3160d..4ae14339cb8cc72d 100644
--- a/arch/x86/include/asm/boot.h
+++ b/arch/x86/include/asm/boot.h
@@ -62,4 +62,12 @@
# define BOOT_STACK_SIZE 0x1000
#endif

+#ifndef __ASSEMBLY__
+extern unsigned int output_len;
+extern const unsigned long kernel_total_size;
+
+unsigned long decompress_kernel(unsigned char *outbuf, unsigned long virt_addr,
+ void (*error)(char *x));
+#endif
+
#endif /* _ASM_X86_BOOT_H */
--
2.39.2