x86/decompressor: Factor out kernel decompression and relocation

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>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-21-ardb@kernel.org

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 2d91d56b59e1af93034e8755a0b1798ad3913809..f711f2a85862e9ef017d3e0d0d63e63728201399 100644 (file)
--- 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 9191280d9ea3160d8d92db5e688fc34712b90bf8..4ae14339cb8cc72da4df2442a363ca2f728573c6 100644 (file)
--- 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 */