powerpc/fsl: Flush the branch predictor at each kernel entry (32 bit)

commit 7fef436295bf6c05effe682c8797dfcb0deb112a upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index d0862a1..15ac510 100644 (file)
--- 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 */\

diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index e2750b8..2386ce2 100644 (file)
--- 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