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(haven.au.ibm.com [9.192.254.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.au.ibm.com (Postfix) with ESMTPSA id A669460593; Fri, 16 Sep 2022 15:33:13 +1000 (AEST) From: Rohan McLure To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH 20/23] powerpc/64s: Clear/restore caller gprs in syscall interrupt/return Date: Fri, 16 Sep 2022 15:32:57 +1000 Message-Id: <20220916053300.786330-21-rmclure@linux.ibm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220916053300.786330-1-rmclure@linux.ibm.com> References: <20220916053300.786330-1-rmclure@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Y4bA_gyCP7g-5xstbVX9y2675ANIZ6tI X-Proofpoint-GUID: Y4bA_gyCP7g-5xstbVX9y2675ANIZ6tI X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.528,FMLib:17.11.122.1 definitions=2022-09-16_02,2022-09-14_04,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 priorityscore=1501 phishscore=0 impostorscore=0 mlxlogscore=501 suspectscore=0 clxscore=1015 adultscore=0 spamscore=0 bulkscore=0 malwarescore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2209130000 definitions=main-2209160041 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 Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Clear user state in gprs (assign to zero) to reduce the influence of user registers on speculation within kernel syscall handlers. Clears occur at the very beginning of the sc and scv 0 interrupt handlers, with restores occurring following the execution of the syscall handler. Signed-off-by: Rohan McLure --- V1 -> V2: Update summary V2 -> V3: Remove erroneous summary paragraph on syscall_exit_prepare V3 -> V4: Use ZEROIZE instead of NULLIFY. Clear r0 also. V4 -> V5: Move to end of patch series. --- arch/powerpc/kernel/interrupt_64.S | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S index 16a1b44088e7..40147558e1a6 100644 --- a/arch/powerpc/kernel/interrupt_64.S +++ b/arch/powerpc/kernel/interrupt_64.S @@ -70,7 +70,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name) ld r2,PACATOC(r13) mfcr r12 li r11,0 - /* Can we avoid saving r3-r8 in common case? */ + /* Save syscall parameters in r3-r8 */ SAVE_GPRS(3, 8, r1) /* Zero r9-r12, this should only be required when restoring all GPRs */ std r11,GPR9(r1) @@ -110,6 +110,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) * Zero user registers to prevent influencing speculative execution * state of kernel code. */ + ZEROIZE_GPR(0) ZEROIZE_GPRS(5, 12) ZEROIZE_NVGPRS() bl system_call_exception @@ -140,6 +141,7 @@ BEGIN_FTR_SECTION HMT_MEDIUM_LOW END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) + REST_NVGPRS(r1) cmpdi r3,0 bne .Lsyscall_vectored_\name\()_restore_regs @@ -243,7 +245,7 @@ END_BTB_FLUSH_SECTION ld r2,PACATOC(r13) mfcr r12 li r11,0 - /* Can we avoid saving r3-r8 in common case? */ + /* Save syscall parameters in r3-r8 */ SAVE_GPRS(3, 8, r1) /* Zero r9-r12, this should only be required when restoring all GPRs */ std r11,GPR9(r1) @@ -295,6 +297,7 @@ END_BTB_FLUSH_SECTION * Zero user registers to prevent influencing speculative execution * state of kernel code. */ + ZEROIZE_GPR(0) ZEROIZE_GPRS(5, 12) ZEROIZE_NVGPRS() bl system_call_exception @@ -337,6 +340,7 @@ BEGIN_FTR_SECTION stdcx. r0,0,r1 /* to clear the reservation */ END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS) + REST_NVGPRS(r1) cmpdi r3,0 bne .Lsyscall_restore_regs /* Zero volatile regs that may contain sensitive kernel data */ @@ -364,7 +368,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) .Lsyscall_restore_regs: ld r3,_CTR(r1) ld r4,_XER(r1) - REST_NVGPRS(r1) mtctr r3 mtspr SPRN_XER,r4 REST_GPR(0, r1)