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powerpc/64: Use barrier_nospec in syscall entry

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Our syscall entry is done in assembly so patch in an explicit
barrier_nospec.

Based on a patch by Michal Suchanek.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Michael Ellerman 2018-04-24 14:15:59 +10:00
parent ddf35cf376
commit 51973a815c
1 changed files with 10 additions and 0 deletions
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10
arch/powerpc/kernel/entry_64.S
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@ -36,6 +36,7 @@
#include <asm/context_tracking.h>
#include <asm/tm.h>
#include <asm/ppc-opcode.h>
#include <asm/barrier.h>
#include <asm/export.h>
#ifdef CONFIG_PPC_BOOK3S
#include <asm/exception-64s.h>
@ -178,6 +179,15 @@ system_call: /* label this so stack traces look sane */
clrldi r8,r8,32
15:
slwi r0,r0,4
barrier_nospec_asm
/*
* Prevent the load of the handler below (based on the user-passed
* system call number) being speculatively executed until the test
* against NR_syscalls and branch to .Lsyscall_enosys above has
* committed.
*/
ldx r12,r11,r0 /* Fetch system call handler [ptr] */
mtctr r12
bctrl /* Call handler */