linux-kernel - [PATCH v2 13/20] x86: decompressor: Factor out kernel decompression and relocation

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Message-Id: <20230508070330.582131-14-ardb@kernel.org>
Date:   Mon,  8 May 2023 09:03:23 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-efi@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Evgeniy Baskov <baskov@...ras.ru>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Peter Jones <pjones@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Dave Young <dyoung@...hat.com>,
        Mario Limonciello <mario.limonciello@....com>,
        Kees Cook <keescook@...omium.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH v2 13/20] 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 we will be able to
call it directly from the EFI stub.

Signed-off-by: Ard Biesheuvel <ardb@...nel.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 1cd40cb9fb4e5027..3635cbeaca1c03cf 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;
@@ -457,10 +478,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, unsigned char *output)
 #endif
 
 	debug_putstr("\nDecompressing Linux... ");
-	__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