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x86/entry/32: Fix FS and GS restore in opportunistic SYSEXIT 

We either need to restore them before popping and thus changing
ESP, or we need to adjust the offsets.  The former is simpler.

Reported-and-tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 5f310f739b x86/entry/32: ("Re-implement SYSENTER using the new C path")
Link: http://lkml.kernel.org/r/461e5c7d8fa3821529893a4893ac9c4bc37f9e17.1445035014.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-10-16 15:42:55 -07:00 committed by Ingo Molnar
parent 657c1eea00
commit 3bd29515d1
1 changed files with 2 additions and 2 deletions
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4
arch/x86/entry/entry_32.S
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@ -315,14 +315,14 @@ sysenter_past_esp:
TRACE_IRQS_ON /* User mode traces as IRQs on. */
movl PT_EIP(%esp), %edx /* pt_regs->ip */
movl PT_OLDESP(%esp), %ecx /* pt_regs->sp */
1: mov PT_FS(%esp), %fs
PTGS_TO_GS
popl %ebx /* pt_regs->bx */
addl $2*4, %esp /* skip pt_regs->cx and pt_regs->dx */
popl %esi /* pt_regs->si */
popl %edi /* pt_regs->di */
popl %ebp /* pt_regs->bp */
popl %eax /* pt_regs->ax */
1: mov PT_FS(%esp), %fs
PTGS_TO_GS
/*
* Return back to the vDSO, which will pop ecx and edx.