linux-kernel - [PATCH 1/4] x86 boot: Jump to the entry point address in the elf header.

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Date:	Sun, 08 Jul 2012 23:52:15 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Tejun Heo <tj@...nel.org>, hacklu <embedway.linux@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] x86 boot: Jump to the entry point address in the elf header.


Since we have the kernel's entry point stored in the ELF header use it,
and stop hardcoding the value.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 arch/x86/boot/compressed/head_32.S |    2 +-
 arch/x86/boot/compressed/head_64.S |    2 +-
 arch/x86/boot/compressed/misc.c    |   16 +++++++++-------
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index c85e3ac..1b15e2c 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -211,7 +211,7 @@ relocated:
  * Jump to the decompressed kernel.
  */
 	xorl	%ebx, %ebx
-	jmp	*%ebp
+	jmp	*%eax
 
 /*
  * Stack and heap for uncompression
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 87e03a1..9b8d782 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -337,7 +337,7 @@ relocated:
 /*
  * Jump to the decompressed kernel.
  */
-	jmp	*%rbp
+	jmp	*%rax
 
 	.data
 gdt:
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 7116dcb..fc96c3e 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -273,7 +273,7 @@ static void error(char *x)
 		asm("hlt");
 }
 
-static void parse_elf(void *output)
+static void *parse_elf(void *output)
 {
 #ifdef CONFIG_X86_64
 	Elf64_Ehdr ehdr;
@@ -323,13 +323,15 @@ static void parse_elf(void *output)
 	}
 
 	free(phdrs);
+	return output + (ehdr.e_entry - LOAD_PHYSICAL_ADDR);
 }
 
-asmlinkage void decompress_kernel(void *rmode, memptr heap,
-				  unsigned char *input_data,
-				  unsigned long input_len,
-				  unsigned char *output)
+asmlinkage void *decompress_kernel(void *rmode, memptr heap,
+				   unsigned char *input_data,
+				   unsigned long input_len,
+				   unsigned char *output)
 {
+	void *entry;
 	real_mode = rmode;
 
 	if (cmdline_find_option_bool("quiet"))
@@ -372,8 +374,8 @@ asmlinkage void decompress_kernel(void *rmode, memptr heap,
 	if (!quiet)
 		putstr("\nDecompressing Linux... ");
 	decompress(input_data, input_len, NULL, NULL, output, NULL, error);
-	parse_elf(output);
+	entry = parse_elf(output);
 	if (!quiet)
 		putstr("done.\nBooting the kernel.\n");
-	return;
+	return entry;
 }
-- 
1.7.5.4

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