Marshall Dawson has uploaded this change for review. ( https://review.coreboot.org/20537
Change subject: x86/lapic/secondary.S: Align stack for _secondary_start ......................................................................
x86/lapic/secondary.S: Align stack for _secondary_start
At a process _start, the stack is expected to be aligned to a 16-byte boundary. Upon entry to any function the stack frame must have the end of any arguments also aligned. In other words the value of %esp+4 or %rsp+8 is always a multiple of 16 (1).
Align the stack down inside _secondary_start and preserve proper alignment for the call to secondary_cpu_init.
Although 4-byte alignment is the minimum requirement for i386, some AMD platforms use SSE instructions which expect 16-byte.
1) http://wiki.osdev.org/System_V_ABI See "Initial Stack and Register State" and "The Stack Frame" in the supplements.
BUG=chrome-os-partner:62841664
Change-Id: I72b7a474013e5caf67aedfabeb8d8d2553499b73 Signed-off-by: Marshall Dawson marshalldawson3rd@gmail.com --- M src/cpu/x86/lapic/secondary.S 1 file changed, 4 insertions(+), 1 deletion(-)
git pull ssh://review.coreboot.org:29418/coreboot refs/changes/37/20537/1
diff --git a/src/cpu/x86/lapic/secondary.S b/src/cpu/x86/lapic/secondary.S index 0c4c0d0..1bb957d 100644 --- a/src/cpu/x86/lapic/secondary.S +++ b/src/cpu/x86/lapic/secondary.S @@ -55,7 +55,6 @@ ljmpl $0x10, $__ap_protected_start
__ap_protected_start: - movw $0x18, %ax movw %ax, %ds movw %ax, %es @@ -69,6 +68,10 @@ /* Set the stack pointer, and flag that we are done */ xorl %eax, %eax movl secondary_stack, %esp + andl $0xfffffff0, %esp + pushl $0x0 /* maintain 16-byte alignment for the call below */ + pushl $0x0 + pushl $0x0 movl secondary_cpu_index, %edi pushl %edi movl %eax, secondary_stack