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Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:45074) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mPk2v-0003MW-P0; Mon, 13 Sep 2021 12:22:44 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1mPk2t-0001zV-61; Mon, 13 Sep 2021 12:22:43 +0100 Date: Mon, 13 Sep 2021 12:22:43 +0100 From: "Russell King (Oracle)" To: Ard Biesheuvel Cc: linux-arm-kernel@lists.infradead.org, Keith Packard , Kees Cook , Arnd Bergmann , Linus Walleij Subject: Re: [PATCH v4 4/5] ARM: smp: Store current pointer in TPIDRURO register if available Message-ID: References: <20210913104001.3043132-1-ardb@kernel.org> <20210913104001.3043132-5-ardb@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210913104001.3043132-5-ardb@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210913_042451_193048_7BCC81BD X-CRM114-Status: GOOD ( 12.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 13, 2021 at 12:40:00PM +0200, Ard Biesheuvel wrote: > @@ -767,13 +769,18 @@ ENTRY(__switch_to) > mcr p15, 0, r6, c3, c0, 0 @ Set domain register > #endif > mov r5, r0 > - add r4, r2, #TI_CPU_SAVE > + mov r4, r2 > ldr r0, =thread_notify_head > mov r1, #THREAD_NOTIFY_SWITCH > bl atomic_notifier_call_chain > #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP) > str r7, [r8] > #endif > +#ifdef CONFIG_CURRENT_POINTER_IN_TPIDRURO > + ldr ip, [r4, #TI_TASK] > + set_current ip > +#endif > + add r4, r4, #TI_CPU_SAVE > THUMB( mov ip, r4 ) > mov r0, r5 > ARM( ldmia r4, {r4 - sl, fp, sp, pc} ) @ Load all regs saved previously I would like to keep this as optimal as possible, and the setting of TPIDRURO to be as close to the stack pointer change too, so I'd suggest a slightly different approach: switch_tls r1, r4, r5, r3, r7 +#if (defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP)) || \ + defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) + ldr r9, [r2, #TI_TASK] +#endif #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP) - ldr r7, [r2, #TI_TASK] ldr r8, =__stack_chk_guard .if (TSK_STACK_CANARY > IMM12_MASK) - add r7, r7, #TSK_STACK_CANARY & ~IMM12_MASK - .endif + add r7, r9, #TSK_STACK_CANARY & ~IMM12_MASK ldr r7, [r7, #TSK_STACK_CANARY & IMM12_MASK] + .else + ldr r7, [r9, #TSK_STACK_CANARY & IMM12_MASK] + .endif #endif ... mov r0, r5 +#ifdef CONFIG_CURRENT_POINTER_IN_TPIDRURO + set_current r9 +#endif ARM( ldmia r4, {r4 - sl, fp, sp, pc} ) @ Load all regs saved previously It's a slightly more complex change, but one I think we should do. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel