Change in coreboot[master]: x86/lapic/secondary.S: Align stack for _secondary_start

[Marshall Dawson (Code Review)]

Marshall Dawson has uploaded a new patch set (#2). ( https://review.coreboot.org/20537 )

Change subject: x86/lapic/secondary.S: Align stack for _secondary_start
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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 
---
M src/cpu/x86/lapic/secondary.S
1 file changed, 4 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/37/20537/2