[v3,11/12] arm64: BTI: Reset BTYPE when skipping emulated instructions
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Message ID 1571419545-20401-12-git-send-email-Dave.Martin@arm.com
State New
Headers show
Series
  • arm64: ARMv8.5-A: Branch Target Identification support
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Commit Message

Dave Martin Oct. 18, 2019, 5:25 p.m. UTC
Since normal execution of any non-branch instruction resets the
PSTATE BTYPE field to 0, so do the same thing when emulating a
trapped instruction.

Branches don't trap directly, so we should never need to assign a
non-zero value to BTYPE here.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>

---

Changes since v2:

 * Drop (u64) case when masking out PSR_BTYPE_MASK in
   arm64_skip_faulting_instruction().

   PSTATE may grow, but we should address this more generally rather
   than with point hacks in this series.
---
 arch/arm64/kernel/traps.c | 2 ++
 1 file changed, 2 insertions(+)

Patch
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diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 3af2768..5c46a7b 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -331,6 +331,8 @@  void arm64_skip_faulting_instruction(struct pt_regs *regs, unsigned long size)
 
 	if (regs->pstate & PSR_MODE32_BIT)
 		advance_itstate(regs);
+	else
+		regs->pstate &= ~PSR_BTYPE_MASK;
 }
 
 static LIST_HEAD(undef_hook);