From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EDF17C433E0 for ; Tue, 4 Aug 2020 19:34:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B24F622BED for ; Tue, 4 Aug 2020 19:34:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B24F622BED Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EF30C8D0184; Tue, 4 Aug 2020 15:34:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E9F5E8D0081; Tue, 4 Aug 2020 15:34:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D8D6D8D0184; Tue, 4 Aug 2020 15:34:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0136.hostedemail.com [216.40.44.136]) by kanga.kvack.org (Postfix) with ESMTP id C1F5D8D0081 for ; Tue, 4 Aug 2020 15:34:48 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 83EEA180AD802 for ; Tue, 4 Aug 2020 19:34:48 +0000 (UTC) X-FDA: 77113888656.16.twig55_5615c8626fa8 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin16.hostedemail.com (Postfix) with ESMTP id 3645E100E690C for ; Tue, 4 Aug 2020 19:34:48 +0000 (UTC) X-HE-Tag: twig55_5615c8626fa8 X-Filterd-Recvd-Size: 10143 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Tue, 4 Aug 2020 19:34:47 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 840C230E; Tue, 4 Aug 2020 12:34:46 -0700 (PDT) Received: from [192.168.178.44] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CF8FA3F71F; Tue, 4 Aug 2020 12:34:44 -0700 (PDT) Subject: Re: [PATCH v7 18/29] arm64: mte: Allow user control of the tag check mode via prctl() To: Catalin Marinas , linux-arm-kernel@lists.infradead.org Cc: linux-mm@kvack.org, linux-arch@vger.kernel.org, Will Deacon , Dave P Martin , Vincenzo Frascino , Szabolcs Nagy , Andrey Konovalov , Peter Collingbourne , Andrew Morton References: <20200715170844.30064-1-catalin.marinas@arm.com> <20200715170844.30064-19-catalin.marinas@arm.com> From: Kevin Brodsky Message-ID: <9342a080-9450-c01a-54a0-9ddebfe45613@arm.com> Date: Tue, 4 Aug 2020 20:34:42 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20200715170844.30064-19-catalin.marinas@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-GB X-Rspamd-Queue-Id: 3645E100E690C X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 15/07/2020 18:08, Catalin Marinas wrote: > By default, even if PROT_MTE is set on a memory range, there is no tag > check fault reporting (SIGSEGV). Introduce a set of option to the > exiting prctl(PR_SET_TAGGED_ADDR_CTRL) to allow user control of the tag > check fault mode: > > PR_MTE_TCF_NONE - no reporting (default) > PR_MTE_TCF_SYNC - synchronous tag check fault reporting > PR_MTE_TCF_ASYNC - asynchronous tag check fault reporting > > These options translate into the corresponding SCTLR_EL1.TCF0 bitfield, > context-switched by the kernel. Note that uaccess done by the kernel is > not checked and cannot be configured by the user. The last sentence is outdated, it should probably say that uaccess is only checked in in synchronous mode. Kevin > Signed-off-by: Catalin Marinas > Cc: Will Deacon > --- > > Notes: > v3: > - Use SCTLR_EL1_TCF0_NONE instead of 0 for consistency. > - Move mte_thread_switch() in this patch from an earlier one. In > addition, it is called after the dsb() in __switch_to() so that any > asynchronous tag check faults have been registered in the TFSR_EL1 > registers (to be added with the in-kernel MTE support. > > v2: > - Handle SCTLR_EL1_TCF0_NONE explicitly for consistency with PR_MTE_TCF_NONE. > - Fix SCTLR_EL1 register setting in flush_mte_state() (thanks to Peter > Collingbourne). > - Added ISB to update_sctlr_el1_tcf0() since, with the latest > architecture update/fix, the TCF0 field is used by the uaccess > routines. > > arch/arm64/include/asm/mte.h | 14 ++++++ > arch/arm64/include/asm/processor.h | 3 ++ > arch/arm64/kernel/mte.c | 77 ++++++++++++++++++++++++++++++ > arch/arm64/kernel/process.c | 26 ++++++++-- > include/uapi/linux/prctl.h | 6 +++ > 5 files changed, 123 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h > index b2577eee62c2..df2efbc9f8f1 100644 > --- a/arch/arm64/include/asm/mte.h > +++ b/arch/arm64/include/asm/mte.h > @@ -21,6 +21,9 @@ void mte_clear_page_tags(void *addr); > void mte_sync_tags(pte_t *ptep, pte_t pte); > void mte_copy_page_tags(void *kto, const void *kfrom); > void flush_mte_state(void); > +void mte_thread_switch(struct task_struct *next); > +long set_mte_ctrl(unsigned long arg); > +long get_mte_ctrl(void); > > #else > > @@ -36,6 +39,17 @@ static inline void mte_copy_page_tags(void *kto, const void *kfrom) > static inline void flush_mte_state(void) > { > } > +static inline void mte_thread_switch(struct task_struct *next) > +{ > +} > +static inline long set_mte_ctrl(unsigned long arg) > +{ > + return 0; > +} > +static inline long get_mte_ctrl(void) > +{ > + return 0; > +} > > #endif > > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index 240fe5e5b720..80e7f0573309 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -151,6 +151,9 @@ struct thread_struct { > struct ptrauth_keys_user keys_user; > struct ptrauth_keys_kernel keys_kernel; > #endif > +#ifdef CONFIG_ARM64_MTE > + u64 sctlr_tcf0; > +#endif > }; > > static inline void arch_thread_struct_whitelist(unsigned long *offset, > diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c > index 5f54fd140610..375483a1f573 100644 > --- a/arch/arm64/kernel/mte.c > +++ b/arch/arm64/kernel/mte.c > @@ -5,6 +5,8 @@ > > #include > #include > +#include > +#include > #include > #include > > @@ -49,6 +51,26 @@ int memcmp_pages(struct page *page1, struct page *page2) > return ret; > } > > +static void update_sctlr_el1_tcf0(u64 tcf0) > +{ > + /* ISB required for the kernel uaccess routines */ > + sysreg_clear_set(sctlr_el1, SCTLR_EL1_TCF0_MASK, tcf0); > + isb(); > +} > + > +static void set_sctlr_el1_tcf0(u64 tcf0) > +{ > + /* > + * mte_thread_switch() checks current->thread.sctlr_tcf0 as an > + * optimisation. Disable preemption so that it does not see > + * the variable update before the SCTLR_EL1.TCF0 one. > + */ > + preempt_disable(); > + current->thread.sctlr_tcf0 = tcf0; > + update_sctlr_el1_tcf0(tcf0); > + preempt_enable(); > +} > + > void flush_mte_state(void) > { > if (!system_supports_mte()) > @@ -58,4 +80,59 @@ void flush_mte_state(void) > dsb(ish); > write_sysreg_s(0, SYS_TFSRE0_EL1); > clear_thread_flag(TIF_MTE_ASYNC_FAULT); > + /* disable tag checking */ > + set_sctlr_el1_tcf0(SCTLR_EL1_TCF0_NONE); > +} > + > +void mte_thread_switch(struct task_struct *next) > +{ > + if (!system_supports_mte()) > + return; > + > + /* avoid expensive SCTLR_EL1 accesses if no change */ > + if (current->thread.sctlr_tcf0 != next->thread.sctlr_tcf0) > + update_sctlr_el1_tcf0(next->thread.sctlr_tcf0); > +} > + > +long set_mte_ctrl(unsigned long arg) > +{ > + u64 tcf0; > + > + if (!system_supports_mte()) > + return 0; > + > + switch (arg & PR_MTE_TCF_MASK) { > + case PR_MTE_TCF_NONE: > + tcf0 = SCTLR_EL1_TCF0_NONE; > + break; > + case PR_MTE_TCF_SYNC: > + tcf0 = SCTLR_EL1_TCF0_SYNC; > + break; > + case PR_MTE_TCF_ASYNC: > + tcf0 = SCTLR_EL1_TCF0_ASYNC; > + break; > + default: > + return -EINVAL; > + } > + > + set_sctlr_el1_tcf0(tcf0); > + > + return 0; > +} > + > +long get_mte_ctrl(void) > +{ > + if (!system_supports_mte()) > + return 0; > + > + switch (current->thread.sctlr_tcf0) { > + case SCTLR_EL1_TCF0_NONE: > + return PR_MTE_TCF_NONE; > + case SCTLR_EL1_TCF0_SYNC: > + return PR_MTE_TCF_SYNC; > + case SCTLR_EL1_TCF0_ASYNC: > + return PR_MTE_TCF_ASYNC; > + } > + > + return 0; > } > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 695705d1f8e5..d19ce8053a03 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -544,6 +544,13 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, > */ > dsb(ish); > > + /* > + * MTE thread switching must happen after the DSB above to ensure that > + * any asynchronous tag check faults have been logged in the TFSR*_EL1 > + * registers. > + */ > + mte_thread_switch(next); > + > /* the actual thread switch */ > last = cpu_switch_to(prev, next); > > @@ -603,9 +610,15 @@ static unsigned int tagged_addr_disabled; > > long set_tagged_addr_ctrl(unsigned long arg) > { > + unsigned long valid_mask = PR_TAGGED_ADDR_ENABLE; > + > if (is_compat_task()) > return -EINVAL; > - if (arg & ~PR_TAGGED_ADDR_ENABLE) > + > + if (system_supports_mte()) > + valid_mask |= PR_MTE_TCF_MASK; > + > + if (arg & ~valid_mask) > return -EINVAL; > > /* > @@ -615,6 +628,9 @@ long set_tagged_addr_ctrl(unsigned long arg) > if (arg & PR_TAGGED_ADDR_ENABLE && tagged_addr_disabled) > return -EINVAL; > > + if (set_mte_ctrl(arg) != 0) > + return -EINVAL; > + > update_thread_flag(TIF_TAGGED_ADDR, arg & PR_TAGGED_ADDR_ENABLE); > > return 0; > @@ -622,13 +638,17 @@ long set_tagged_addr_ctrl(unsigned long arg) > > long get_tagged_addr_ctrl(void) > { > + long ret = 0; > + > if (is_compat_task()) > return -EINVAL; > > if (test_thread_flag(TIF_TAGGED_ADDR)) > - return PR_TAGGED_ADDR_ENABLE; > + ret = PR_TAGGED_ADDR_ENABLE; > > - return 0; > + ret |= get_mte_ctrl(); > + > + return ret; > } > > /* > diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h > index 07b4f8131e36..2390ab324afa 100644 > --- a/include/uapi/linux/prctl.h > +++ b/include/uapi/linux/prctl.h > @@ -233,6 +233,12 @@ struct prctl_mm_map { > #define PR_SET_TAGGED_ADDR_CTRL 55 > #define PR_GET_TAGGED_ADDR_CTRL 56 > # define PR_TAGGED_ADDR_ENABLE (1UL << 0) > +/* MTE tag check fault modes */ > +# define PR_MTE_TCF_SHIFT 1 > +# define PR_MTE_TCF_NONE (0UL << PR_MTE_TCF_SHIFT) > +# define PR_MTE_TCF_SYNC (1UL << PR_MTE_TCF_SHIFT) > +# define PR_MTE_TCF_ASYNC (2UL << PR_MTE_TCF_SHIFT) > +# define PR_MTE_TCF_MASK (3UL << PR_MTE_TCF_SHIFT) > > /* Control reclaim behavior when allocating memory */ > #define PR_SET_IO_FLUSHER 57