powerpc/fsl: Flush the branch predictor at each kernel entry (32 bit)
In order to protect against speculation attacks on
indirect branches, the branch predictor is flushed at
kernel entry to protect for the following situations:
- userspace process attacking another userspace process
- userspace process attacking the kernel
Basically when the privillege level change (i.e.the kernel
is entered), the branch predictor state is flushed.
Signed-off-by: Diana Craciun <diana.craciun@nxp.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index d0862a1..15ac510 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -43,6 +43,9 @@
andi. r11, r11, MSR_PR; /* check whether user or kernel */\
mr r11, r1; \
beq 1f; \
+START_BTB_FLUSH_SECTION \
+ BTB_FLUSH(r11) \
+END_BTB_FLUSH_SECTION \
/* if from user, start at top of this thread's kernel stack */ \
lwz r11, THREAD_INFO-THREAD(r10); \
ALLOC_STACK_FRAME(r11, THREAD_SIZE); \
@@ -128,6 +131,9 @@
stw r9,_CCR(r8); /* save CR on stack */\
mfspr r11,exc_level_srr1; /* check whether user or kernel */\
DO_KVM BOOKE_INTERRUPT_##intno exc_level_srr1; \
+START_BTB_FLUSH_SECTION \
+ BTB_FLUSH(r10) \
+END_BTB_FLUSH_SECTION \
andi. r11,r11,MSR_PR; \
mfspr r11,SPRN_SPRG_THREAD; /* if from user, start at top of */\
lwz r11,THREAD_INFO-THREAD(r11); /* this thread's kernel stack */\