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

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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>
This commit is contained in:
Diana Craciun
2018-12-12 16:03:06 +02:00
committed by Michael Ellerman
parent 10c5e83afd
commit 7fef436295
2 changed files with 21 additions and 0 deletions
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15
arch/powerpc/kernel/head_fsl_booke.S
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@@ -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