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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 520E4605A6; Mon, 8 May 2023 12:01:35 +1000 (AEST) From: Rohan McLure To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH 05/12] powerpc: Mark [h]ssr_valid accesses in check_return_regs_valid Date: Mon, 8 May 2023 12:01:13 +1000 Message-Id: <20230508020120.218494-6-rmclure@linux.ibm.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20230508020120.218494-1-rmclure@linux.ibm.com> References: <20230508020120.218494-1-rmclure@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: MEhZNDYR4mIDkZVkucmJShfqEAAlOKBo X-Proofpoint-ORIG-GUID: Wj5voPRuBAwvQdzy4uVSf8IoLEsbjwTk X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-05-07_10,2023-05-05_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 suspectscore=0 mlxlogscore=492 mlxscore=0 spamscore=0 clxscore=1015 phishscore=0 priorityscore=1501 bulkscore=0 lowpriorityscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2303200000 definitions=main-2305080009 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, arnd@arndb.de Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Checks to see if the [H]SRR registers have been clobbered by (soft) NMI interrupts imply the possibility for a data race on the [h]srr_valid entries in the PACA. Annotate accesses to these fields with READ_ONCE, removing the need for the barrier. The diagnostic can use plain-access reads and writes, but annotate with data_race. Signed-off-by: Rohan McLure Reported-by: Michael Ellerman Reviewed-by: Nicholas Piggin --- arch/powerpc/include/asm/ptrace.h | 4 ++-- arch/powerpc/kernel/interrupt.c | 14 ++++++-------- 2 files changed, 8 insertions(+), 10 deletions(-) diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h index 0eb90a013346..9db8b16567e2 100644 --- a/arch/powerpc/include/asm/ptrace.h +++ b/arch/powerpc/include/asm/ptrace.h @@ -180,8 +180,8 @@ void do_syscall_trace_leave(struct pt_regs *regs); static inline void set_return_regs_changed(void) { #ifdef CONFIG_PPC_BOOK3S_64 - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + WRITE_ONCE(local_paca->hsrr_valid, 0); + WRITE_ONCE(local_paca->srr_valid, 0); #endif } diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c index e34c72285b4e..1f033f11b871 100644 --- a/arch/powerpc/kernel/interrupt.c +++ b/arch/powerpc/kernel/interrupt.c @@ -125,7 +125,7 @@ static notrace void check_return_regs_valid(struct pt_regs *regs) case 0x1600: case 0x1800: validp = &local_paca->hsrr_valid; - if (!*validp) + if (!READ_ONCE(*validp)) return; srr0 = mfspr(SPRN_HSRR0); @@ -135,7 +135,7 @@ static notrace void check_return_regs_valid(struct pt_regs *regs) break; default: validp = &local_paca->srr_valid; - if (!*validp) + if (!READ_ONCE(*validp)) return; srr0 = mfspr(SPRN_SRR0); @@ -161,19 +161,17 @@ static notrace void check_return_regs_valid(struct pt_regs *regs) * such things will get caught most of the time, statistically * enough to be able to get a warning out. */ - barrier(); - - if (!*validp) + if (!READ_ONCE(*validp)) return; - if (!warned) { - warned = true; + if (!data_race(warned)) { + data_race(warned = true); printk("%sSRR0 was: %lx should be: %lx\n", h, srr0, regs->nip); printk("%sSRR1 was: %lx should be: %lx\n", h, srr1, regs->msr); show_regs(regs); } - *validp = 0; /* fixup */ + WRITE_ONCE(*validp, 0); /* fixup */ #endif }