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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>
This commit is contained in:
Aaron Durbin 2013-02-06 15:28:40 -06:00 committed by Stefan Reinauer
parent 81108b9059
commit 633f11274f
2 changed files with 24 additions and 26 deletions
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14
src/arch/x86/coreboot_ram.ld
View File

@ -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 . : {

36
src/arch/x86/lib/c_start.S
View File

@ -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