From efe1691ac814e4cf3653538b701662cbd905bddc Mon Sep 17 00:00:00 2001 From: Rohan McLure Date: Thu, 1 Dec 2022 18:10:18 +1100 Subject: [PATCH] powerpc/64e: Clear gprs on interrupt routine entry on Book3E Zero GPRS r14-r31 on entry into the kernel for interrupt sources to limit influence of user-space values in potential speculation gadgets. Prior to this commit, all other GPRS are reassigned during the common prologue to interrupt handlers and so need not be zeroised explicitly. This may be done safely, without loss of register state prior to the interrupt, as the common prologue saves the initial values of non-volatiles, which are unconditionally restored in interrupt_64.S. Mitigation defaults to enabled by INTERRUPT_SANITIZE_REGISTERS. Reviewed-by: Nicholas Piggin Signed-off-by: Rohan McLure Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221201071019.1953023-6-rmclure@linux.ibm.com --- arch/powerpc/kernel/exceptions-64e.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S index b9cec22..3f86091 100644 --- a/arch/powerpc/kernel/exceptions-64e.S +++ b/arch/powerpc/kernel/exceptions-64e.S @@ -358,7 +358,6 @@ ret_from_mc_except: std r14,PACA_EXMC+EX_R14(r13); \ std r15,PACA_EXMC+EX_R15(r13) - /* Core exception code for all exceptions except TLB misses. */ #define EXCEPTION_COMMON_LVL(n, scratch, excf) \ exc_##n##_common: \ @@ -394,7 +393,8 @@ exc_##n##_common: \ std r12,STACK_INT_FRAME_MARKER(r1); /* mark the frame */ \ std r3,_TRAP(r1); /* set trap number */ \ std r0,RESULT(r1); /* clear regs->result */ \ - SAVE_NVGPRS(r1); + SAVE_NVGPRS(r1); \ + SANITIZE_NVGPRS(); /* minimise speculation influence */ #define EXCEPTION_COMMON(n) \ EXCEPTION_COMMON_LVL(n, SPRN_SPRG_GEN_SCRATCH, PACA_EXGEN) -- 2.7.4