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(unknown [9.192.255.53]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 25 Jul 2022 06:32:20 +0000 (GMT) From: Rohan McLure To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH v2 14/14] powerpc/64s: Clear gprs on interrupt routine entry Date: Mon, 25 Jul 2022 16:32:17 +1000 Message-Id: <20220725063217.121476-1-rmclure@linux.ibm.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: ulyN9nVR1KbppNdvrCY_98qRJmJAdmm4 X-Proofpoint-ORIG-GUID: ybHBGXL-qhEJwiGnZQI2c-TjO99-0Mtm X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-07-23_02,2022-07-21_02,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 phishscore=0 lowpriorityscore=0 suspectscore=0 clxscore=1015 mlxscore=0 adultscore=0 bulkscore=0 malwarescore=0 impostorscore=0 spamscore=0 mlxlogscore=950 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2206140000 definitions=main-2207250028 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rohan McLure , npiggin@gmail.com Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Zero GPRS r0, r2-r11, r14-r31, on entry into the kernel for all other interrupt sources to limit influence of user-space values in potential speculation gadgets. The remaining gprs are overwritten by entry macros to interrupt handlers, irrespective of whether or not a given handler consumes these register values. Prior to this commit, r14-r31 are restored on a per-interrupt basis at exit, but now they are always restored. Remove explicit REST_NVGPRS invocations on interrupt entry and simplify exit logic. 32-bit systems will still conditionally need to restore NVGPRS so keep return value for interrupt_exit_user_prepare. The mmap_bench benchmark in selftests should rapidly invoke pagefaults. See ~0.8% performance regression with this mitigation, but this indicates the worst-case performance due to heavier-weight interrupt handlers. Signed-off-by: Rohan McLure --- V1 -> V2: Add benchmark data --- arch/powerpc/kernel/exceptions-64s.S | 21 ++++++++------------- arch/powerpc/kernel/interrupt_64.S | 9 ++------- 2 files changed, 10 insertions(+), 20 deletions(-) diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 102896fc6a86..62dd6270852e 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -502,6 +502,7 @@ DEFINE_FIXED_SYMBOL(\name\()_common_real, text) std r10,0(r1) /* make stack chain pointer */ std r0,GPR0(r1) /* save r0 in stackframe */ std r10,GPR1(r1) /* save r1 in stackframe */ + NULLIFY_GPR(0) /* Mark our [H]SRRs valid for return */ li r10,1 @@ -538,14 +539,18 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) ld r10,IAREA+EX_R10(r13) std r9,GPR9(r1) std r10,GPR10(r1) + NULLIFY_GPRS(9, 10) ld r9,IAREA+EX_R11(r13) /* move r11 - r13 to stackframe */ ld r10,IAREA+EX_R12(r13) ld r11,IAREA+EX_R13(r13) std r9,GPR11(r1) std r10,GPR12(r1) std r11,GPR13(r1) + /* keep r12 ([H]SRR1/MSR), r13 (PACA) for interrupt routine */ + NULLIFY_GPR(11) SAVE_NVGPRS(r1) + NULLIFY_NVGPRS() .if IDAR .if IISIDE @@ -577,8 +582,8 @@ BEGIN_FTR_SECTION END_FTR_SECTION_IFSET(CPU_FTR_CFAR) ld r10,IAREA+EX_CTR(r13) std r10,_CTR(r1) - std r2,GPR2(r1) /* save r2 in stackframe */ - SAVE_GPRS(3, 8, r1) /* save r3 - r8 in stackframe */ + SAVE_GPRS(2, 8, r1) /* save r2 - r8 in stackframe */ + NULLIFY_GPRS(2, 8) mflr r9 /* Get LR, later save to stack */ ld r2,PACATOC(r13) /* get kernel TOC into r2 */ std r9,_LINK(r1) @@ -696,6 +701,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR) mtlr r9 ld r9,_CCR(r1) mtcr r9 + REST_NVGPRS(r1) REST_GPRS(2, 13, r1) REST_GPR(0, r1) /* restore original r1. */ @@ -1368,11 +1374,6 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX) b interrupt_return_srr 1: bl do_break - /* - * do_break() may have changed the NV GPRS while handling a breakpoint. - * If so, we need to restore them with their updated values. - */ - REST_NVGPRS(r1) b interrupt_return_srr @@ -1598,7 +1599,6 @@ EXC_COMMON_BEGIN(alignment_common) GEN_COMMON alignment addi r3,r1,STACK_FRAME_OVERHEAD bl alignment_exception - REST_NVGPRS(r1) /* instruction emulation may change GPRs */ b interrupt_return_srr @@ -1708,7 +1708,6 @@ EXC_COMMON_BEGIN(program_check_common) .Ldo_program_check: addi r3,r1,STACK_FRAME_OVERHEAD bl program_check_exception - REST_NVGPRS(r1) /* instruction emulation may change GPRs */ b interrupt_return_srr @@ -2139,7 +2138,6 @@ EXC_COMMON_BEGIN(emulation_assist_common) GEN_COMMON emulation_assist addi r3,r1,STACK_FRAME_OVERHEAD bl emulation_assist_interrupt - REST_NVGPRS(r1) /* instruction emulation may change GPRs */ b interrupt_return_hsrr @@ -2457,7 +2455,6 @@ EXC_COMMON_BEGIN(facility_unavailable_common) GEN_COMMON facility_unavailable addi r3,r1,STACK_FRAME_OVERHEAD bl facility_unavailable_exception - REST_NVGPRS(r1) /* instruction emulation may change GPRs */ b interrupt_return_srr @@ -2485,7 +2482,6 @@ EXC_COMMON_BEGIN(h_facility_unavailable_common) GEN_COMMON h_facility_unavailable addi r3,r1,STACK_FRAME_OVERHEAD bl facility_unavailable_exception - REST_NVGPRS(r1) /* XXX Shouldn't be necessary in practice */ b interrupt_return_hsrr @@ -2711,7 +2707,6 @@ EXC_COMMON_BEGIN(altivec_assist_common) addi r3,r1,STACK_FRAME_OVERHEAD #ifdef CONFIG_ALTIVEC bl altivec_assist_exception - REST_NVGPRS(r1) /* instruction emulation may change GPRs */ #else bl unknown_exception #endif diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S index efaf162fa772..083a94604072 100644 --- a/arch/powerpc/kernel/interrupt_64.S +++ b/arch/powerpc/kernel/interrupt_64.S @@ -430,9 +430,6 @@ interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user) addi r3,r1,STACK_FRAME_OVERHEAD bl interrupt_exit_user_prepare - cmpdi r3,0 - bne- .Lrestore_nvgprs_\srr -.Lrestore_nvgprs_\srr\()_cont: std r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */ #ifdef CONFIG_PPC_BOOK3S .Linterrupt_return_\srr\()_user_rst_start: @@ -446,6 +443,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user) stb r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS .Lfast_user_interrupt_return_\srr\(): + REST_NVGPRS(r1) #ifdef CONFIG_PPC_BOOK3S .ifc \srr,srr lbz r4,PACASRR_VALID(r13) @@ -515,10 +513,6 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS) b . /* prevent speculative execution */ .Linterrupt_return_\srr\()_user_rst_end: -.Lrestore_nvgprs_\srr\(): - REST_NVGPRS(r1) - b .Lrestore_nvgprs_\srr\()_cont - #ifdef CONFIG_PPC_BOOK3S interrupt_return_\srr\()_user_restart: _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user_restart) @@ -559,6 +553,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_kernel) 1: .Lfast_kernel_interrupt_return_\srr\(): + REST_NVGPRS(r1) cmpdi cr1,r3,0 #ifdef CONFIG_PPC_BOOK3S .ifc \srr,srr