linux-kernel - [PATCH 4/6] x86, boot: Clarify purpose of functions in misc.c

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Date:	Mon, 18 Apr 2016 09:42:13 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Kees Cook <keescook@...omium.org>, Yinghai Lu <yinghai@...nel.org>,
	Baoquan He <bhe@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	"H.J. Lu" <hjl.tools@...il.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Borislav Petkov <bp@...e.de>,
	Andy Lutomirski <luto@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 4/6] x86, boot: Clarify purpose of functions in misc.c

The function "decompress_kernel" now performs many more duties, so this
patch renames it to "extract_kernel" and updates callers and comments.
Additionally the file header comment for misc.c is improved to actually
describe what is contained.

Suggested-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/boot/compressed/head_32.S |  8 ++++----
 arch/x86/boot/compressed/head_64.S |  4 ++--
 arch/x86/boot/compressed/misc.c    | 10 ++++++----
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 0256064da8da..26dd9df19a69 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -233,9 +233,9 @@ relocated:
 2:
 
 /*
- * Do the decompression, and jump to the new kernel..
+ * Do the extraction, and jump to the new kernel..
  */
-				/* push arguments for decompress_kernel: */
+				/* push arguments for extract_kernel: */
 	pushl	$z_run_size	/* size of kernel with .bss and .brk */
 	pushl	$z_output_len	/* decompressed length, end of relocs */
 	leal	z_extract_offset_negative(%ebx), %ebp
@@ -246,11 +246,11 @@ relocated:
 	leal	boot_heap(%ebx), %eax
 	pushl	%eax		/* heap area */
 	pushl	%esi		/* real mode pointer */
-	call	decompress_kernel /* returns kernel location in %eax */
+	call	extract_kernel	/* returns kernel location in %eax */
 	addl	$28, %esp
 
 /*
- * Jump to the decompressed kernel.
+ * Jump to the extracted kernel.
  */
 	xorl	%ebx, %ebx
 	jmp	*%eax
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 86558a199139..d43c30ed89ed 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -408,7 +408,7 @@ relocated:
 2:
 	
 /*
- * Do the decompression, and jump to the new kernel..
+ * Do the extraction, and jump to the new kernel..
  */
 	pushq	%rsi			/* Save the real mode argument */
 	movq	$z_run_size, %r9	/* size of kernel with .bss and .brk */
@@ -419,7 +419,7 @@ relocated:
 	movl	$z_input_len, %ecx	/* input_len */
 	movq	%rbp, %r8		/* output target address */
 	movq	$z_output_len, %r9	/* decompressed length, end of relocs */
-	call	decompress_kernel	/* returns kernel location in %rax */
+	call	extract_kernel		/* returns kernel location in %rax */
 	popq	%r9
 	popq	%rsi
 
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 462dfbf7467b..0d69e809673a 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -1,8 +1,10 @@
 /*
  * misc.c
  *
- * This is a collection of several routines from gzip-1.0.3
- * adapted for Linux.
+ * This is a collection of several routines used to extract the kernel
+ * which includes KASLR relocation, decompression, ELF parsing, and
+ * relocation processing. Additionally included are the screen and serial
+ * output functions and related debugging support functions.
  *
  * malloc by Hannu Savolainen 1993 and Matthias Urlichs 1994
  * puts by Nick Holloway 1993, better puts by Martin Mares 1995
@@ -383,7 +385,7 @@ static void parse_elf(void *output)
 	free(phdrs);
 }
 
-asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
+asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 				  unsigned char *input_data,
 				  unsigned long input_len,
 				  unsigned char *output,
@@ -412,7 +414,7 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
 	cols = boot_params->screen_info.orig_video_cols;
 
 	console_init();
-	debug_putstr("early console in decompress_kernel\n");
+	debug_putstr("early console in extract_kernel\n");
 
 	free_mem_ptr     = heap;	/* Heap */
 	free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
-- 
2.6.3