From 633f11274fcbc9442be0be0d0bc531f43a74981b Mon Sep 17 00:00:00 2001
From: Aaron Durbin <adurbin@chromium.org>
Date: Wed, 6 Feb 2013 15:28:40 -0600
Subject: x86: remove stack definition in linker script

In order to prepare the ramstage to be linked by the rmodule linker the
stack needs to be self-contained within the ramstage objects. The
reasoning is that the rmodule linker provides a way to define a heap,
but it doesn't currently have a region for the stack.

The downside to this is that memory footprint of the ramstage can change
when compared before this change. The size difference stems from the
link ordering of the objects as the stack is now defined within
c_start.S. The size fluctuation ranges from 0 to CONFIG_STACK_SIZE - 1
because of the previous behavior or aligning to CONFIG_STACK_SIZE. It
should be noted that such an alignment is unnecessary for 32-bit x86 as
the alignment requirement for the stacks are 4 byte alignment. Also the
memory footprint is still dominated by CONFIG_RAMTOP and CONFIG_RAMBASE.

Change-Id: I63a4ddd249104bc27aff2ab6b39fc6db12b54028
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2785
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marc.jones@se-eng.com>
---
 src/arch/x86/coreboot_ram.ld | 14 --------------
 src/arch/x86/lib/c_start.S   | 36 ++++++++++++++++++++++++------------
 2 files changed, 24 insertions(+), 26 deletions(-)

(limited to 'src/arch/x86')

diff --git a/src/arch/x86/coreboot_ram.ld b/src/arch/x86/coreboot_ram.ld
index 7ce0367cf1..d9f09090d9 100644
--- a/src/arch/x86/coreboot_ram.ld
+++ b/src/arch/x86/coreboot_ram.ld
@@ -92,20 +92,6 @@ SECTIONS
 		*(COMMON)
 	}
 	_ebss = .;
-	_end = .;
-
-	/* coreboot really "ends" here. Only heap and stack are placed after
-	 * this line.
-	 */
-
-	. = ALIGN(CONFIG_STACK_SIZE);
-
-	_stack = .;
-	.stack . : {
-		/* Reserve a stack for each possible cpu */
-		. += CONFIG_MAX_CPUS*CONFIG_STACK_SIZE;
-	}
-	_estack = .;
 
         _heap = .;
         .heap . : {
diff --git a/src/arch/x86/lib/c_start.S b/src/arch/x86/lib/c_start.S
index 9a8b4ac3c2..295283b24a 100644
--- a/src/arch/x86/lib/c_start.S
+++ b/src/arch/x86/lib/c_start.S
@@ -1,5 +1,16 @@
 #include <cpu/x86/post_code.h>
 
+/* Place the stack in the bss section. It's not necessary to define it in the
+ * the linker script. */
+	.section .bss, "aw", @nobits
+.global _stack
+.global _estack
+
+.align CONFIG_STACK_SIZE
+_stack:
+.space CONFIG_MAX_CPUS*CONFIG_STACK_SIZE
+_estack:
+
 	.section ".textfirst"
 	.code32
 	.globl _start
@@ -16,19 +27,7 @@ _start:
 
 	post_code(POST_ENTRY_C_START)		/* post 13 */
 
-	/** poison the stack. Code should not count on the
-	 * stack being full of zeros. This stack poisoning
-	 * recently uncovered a bug in the broadcast SIPI
-	 * code.
-	 */
 	cld
-	leal	_stack, %edi
-	movl	$_estack, %ecx
-	subl	%edi, %ecx
-	shrl	$2, %ecx   /* it is 32 bit aligned, right? */
-	movl	$0xDEADBEEF, %eax
-	rep
-	stosl
 
 	/** clear bss, which unlike the stack is zero by definition */
 	leal	_bss, %edi
@@ -41,6 +40,19 @@ _start:
 	stosl
 .Lnobss:
 
+	/** poison the stack. Code should not count on the
+	 * stack being full of zeros. This stack poisoning
+	 * recently uncovered a bug in the broadcast SIPI
+	 * code.
+	 */
+	leal	_stack, %edi
+	movl	$_estack, %ecx
+	subl	%edi, %ecx
+	shrl	$2, %ecx   /* it is 32 bit aligned, right? */
+	movl	$0xDEADBEEF, %eax
+	rep
+	stosl
+
 	/* set new stack */
 	movl	$_estack, %esp
 
-- 
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