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.crac...@nxp.com>
---
v1-->v2
- fixed warnings reported by the automated build system
arch/powerpc/kernel/head_booke.h | 11 +++++++++++
arch/powerpc/kernel/head_fsl_booke.S | 15 +++++++++++++++
2 files changed, 26 insertions(+)
diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index d0862a1..27f5249 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -32,6 +32,15 @@
*/
#define THREAD_NORMSAVE(offset) (THREAD_NORMSAVES + (offset * 4))
+#ifdef CONFIG_PPC_FSL_BOOK3E
+#define BOOKE_CLEAR_BTB(reg)
\
+START_BTB_FLUSH_SECTION
\
+ BTB_FLUSH(reg)
\
+END_BTB_FLUSH_SECTION
+#else
+#define BOOKE_CLEAR_BTB(reg)
+#endif
+
#define NORMAL_EXCEPTION_PROLOG(intno)
\
mtspr SPRN_SPRG_WSCRATCH0, r10; /* save one register */ \
mfspr r10, SPRN_SPRG_THREAD; \
@@ -43,6 +52,7 @@
andi. r11, r11, MSR_PR; /* check whether user or kernel */\
mr r11, r1; \
beq 1f; \
+ BOOKE_CLEAR_BTB(r11) \
/* 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 +138,7 @@
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; \
+ BOOKE_CLEAR_BTB(r10) \
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 */\
diff --git a/arch/powerpc/kernel/head_fsl_booke.S
b/arch/powerpc/kernel/head_fsl_booke.S
index e2750b8..2386ce2 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -453,6 +453,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
mfcr r13
stw r13, THREAD_NORMSAVE(3)(r10)
DO_KVM BOOKE_INTERRUPT_DTLB_MISS SPRN_SRR1
+START_BTB_FLUSH_SECTION
+ mfspr r11, SPRN_SRR1
+ andi. r10,r11,MSR_PR
+ beq 1f
+ BTB_FLUSH(r10)
+1:
+END_BTB_FLUSH_SECTION
mfspr r10, SPRN_DEAR /* Get faulting address */
/* If we are faulting a kernel address, we have to use the
@@ -547,6 +554,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
mfcr r13
stw r13, THREAD_NORMSAVE(3)(r10)
DO_KVM BOOKE_INTERRUPT_ITLB_MISS SPRN_SRR1
+START_BTB_FLUSH_SECTION
+ mfspr r11, SPRN_SRR1
+ andi. r10,r11,MSR_PR
+ beq 1f
+ BTB_FLUSH(r10)
+1:
+END_BTB_FLUSH_SECTION
+
mfspr r10, SPRN_SRR0 /* Get faulting address */
/* If we are faulting a kernel address, we have to use the
--
2.5.5
