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xen/x86: Zero out .bss for PV guests 

ELF spec is unclear about whether .bss must me cleared by the loader.
Currently the domain builder does it when loading the guest but because
it is not (or rather may not be) guaranteed we should zero it out
explicitly.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This commit is contained in:
Boris Ostrovsky 2016-02-26 14:02:36 -05:00 committed by David Vrabel
parent a4d7b75be0
commit 04b6b4a568
1 changed files with 9 additions and 0 deletions
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9
arch/x86/xen/xen-head.S
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@ -38,6 +38,15 @@
__INIT
ENTRY(startup_xen)
cld
/* Clear .bss */
xor %eax,%eax
mov $__bss_start, %_ASM_DI
mov $__bss_stop, %_ASM_CX
sub %_ASM_DI, %_ASM_CX
shr $__ASM_SEL(2, 3), %_ASM_CX
rep __ASM_SIZE(stos)
#ifdef CONFIG_X86_32
mov %esi,xen_start_info
mov $init_thread_union+THREAD_SIZE,%esp