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(unknown [9.177.29.5]) (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 9D176600EE; Wed, 21 Sep 2022 16:57:18 +1000 (AEST) From: Rohan McLure To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH v6 02/25] powerpc: Save caller r3 prior to system_call_exception Date: Wed, 21 Sep 2022 16:55:42 +1000 Message-Id: <20220921065605.1051927-3-rmclure@linux.ibm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220921065605.1051927-1-rmclure@linux.ibm.com> References: <20220921065605.1051927-1-rmclure@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: VffvtMhsUmNrOUbFkWrg4szTGN9qjUcX X-Proofpoint-ORIG-GUID: GyyZVfKf5JsiNhUkcOu_s-WbUWLbbBOb 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=2022-09-21_03,2022-09-20_02,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 mlxlogscore=957 priorityscore=1501 lowpriorityscore=0 spamscore=0 clxscore=1015 adultscore=0 phishscore=0 malwarescore=0 bulkscore=0 impostorscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2209130000 definitions=main-2209210043 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 , Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" This reverts commit 8875f47b7681 ("powerpc/syscall: Save r3 in regs->orig_r3 "). Save caller's original r3 state to the kernel stackframe before entering system_call_exception. This allows for user registers to be cleared by the time system_call_exception is entered, reducing the influence of user registers on speculation within the kernel. Prior to this commit, orig_r3 was saved at the beginning of system_call_exception. Instead, save orig_r3 while the user value is still live in r3. Also replicate this early save in 32-bit. A similar save was removed in commit 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32") when 32-bit adopted system_call_exception. Revert its removal of orig_r3 saves. Signed-off-by: Rohan McLure Reviewed-by: Nicholas Piggin --- V3: New commit. V5: New commit message, as we do more than just revert 8875f47b7681. --- arch/powerpc/kernel/entry_32.S | 1 + arch/powerpc/kernel/interrupt_64.S | 2 ++ arch/powerpc/kernel/syscall.c | 1 - 3 files changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S index 1d599df6f169..44dfce9a60c5 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -101,6 +101,7 @@ __kuep_unlock: .globl transfer_to_syscall transfer_to_syscall: + stw r3, ORIG_GPR3(r1) stw r11, GPR1(r1) stw r11, 0(r1) mflr r12 diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S index ce25b28cf418..71d2d9497283 100644 --- a/arch/powerpc/kernel/interrupt_64.S +++ b/arch/powerpc/kernel/interrupt_64.S @@ -91,6 +91,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name) li r11,\trapnr std r11,_TRAP(r1) std r12,_CCR(r1) + std r3,ORIG_GPR3(r1) addi r10,r1,STACK_FRAME_OVERHEAD ld r11,exception_marker@toc(r2) std r11,-16(r10) /* "regshere" marker */ @@ -275,6 +276,7 @@ END_BTB_FLUSH_SECTION std r10,_LINK(r1) std r11,_TRAP(r1) std r12,_CCR(r1) + std r3,ORIG_GPR3(r1) addi r10,r1,STACK_FRAME_OVERHEAD ld r11,exception_marker@toc(r2) std r11,-16(r10) /* "regshere" marker */ diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c index 81ace9e8b72b..64102a64fd84 100644 --- a/arch/powerpc/kernel/syscall.c +++ b/arch/powerpc/kernel/syscall.c @@ -25,7 +25,6 @@ notrace long system_call_exception(long r3, long r4, long r5, kuap_lock(); add_random_kstack_offset(); - regs->orig_gpr3 = r3; if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG)) BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED); -- 2.34.1