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Thu, 25 Jan 2024 09:54:29 -0800 (PST) Received: from debug.ba.rivosinc.com ([64.71.180.162]) by smtp.gmail.com with ESMTPSA id u24-20020a170902a61800b001d74343a53dsm7538299plq.81.2024.01.25.09.54.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Jan 2024 09:54:28 -0800 (PST) Date: Thu, 25 Jan 2024 09:54:24 -0800 From: Deepak Gupta To: Stefan O'Rear Cc: rick.p.edgecombe@intel.com, broonie@kernel.org, Szabolcs.Nagy@arm.com, "kito.cheng@sifive.com" , Kees Cook , Andrew Jones , paul.walmsley@sifive.com, Palmer Dabbelt , Conor Dooley , cleger@rivosinc.com, Atish Patra , Alexandre Ghiti , =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , Alexandre Ghiti , Jonathan Corbet , Albert Ou , oleg@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, "Eric W. Biederman" , shuah@kernel.org, Christian Brauner , guoren , samitolvanen@google.com, Evan Green , xiao.w.wang@intel.com, Anup Patel , mchitale@ventanamicro.com, waylingii@gmail.com, greentime.hu@sifive.com, Heiko Stuebner , Jisheng Zhang , shikemeng@huaweicloud.com, david@redhat.com, Charlie Jenkins , panqinglin2020@iscas.ac.cn, willy@infradead.org, Vincent Chen , Andy Chiu , Greg Ungerer , jeeheng.sia@starfivetech.com, mason.huo@starfivetech.com, ancientmodern4@gmail.com, mathis.salmen@matsal.de, cuiyunhui@bytedance.com, bhe@redhat.com, ruscur@russell.cc, bgray@linux.ibm.com, alx@kernel.org, baruch@tkos.co.il, zhangqing@loongson.cn, Catalin Marinas , revest@chromium.org, josh@joshtriplett.org, joey.gouly@arm.com, shr@devkernel.io, omosnace@redhat.com, ojeda@kernel.org, jhubbard@nvidia.com, linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [RFC PATCH v1 02/28] riscv: envcfg save and restore on trap entry/exit Message-ID: References: <20240125062739.1339782-1-debug@rivosinc.com> <20240125062739.1339782-3-debug@rivosinc.com> <23d023c0-27cf-44fa-be0a-000d1534ef86@app.fastmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 6A78C18001C X-Rspam-User: X-Stat-Signature: 8ji5d5r7i1t3sub7scimy3zbj7h4wi9b X-Rspamd-Server: rspam01 X-HE-Tag: 1706205270-434446 X-HE-Meta: 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 Dl7oZi6J 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 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: List-Subscribe: List-Unsubscribe: On Thu, Jan 25, 2024 at 09:09:14AM -0800, Deepak Gupta wrote: >On Thu, Jan 25, 2024 at 02:19:29AM -0500, Stefan O'Rear wrote: >>On Thu, Jan 25, 2024, at 1:21 AM, debug@rivosinc.com wrote: >>>From: Deepak Gupta >>> >>>envcfg CSR defines enabling bits for cache management instructions and soon >>>will control enabling for control flow integrity and pointer masking features. >>> >>>Control flow integrity enabling for forward cfi and backward cfi is controlled >>>via envcfg and thus need to be enabled on per thread basis. >>> >>>This patch creates a place holder for envcfg CSR in `thread_info` and adds >>>logic to save and restore on trap entry and exits. >> >>Should only be "restore"? I don't see saving. > >It's always saved in `thread_info` and user mode can't change it. >So no point saving it. Also I'll fix the commit message. I think that's what you were pointing out. > >> >>> >>>Signed-off-by: Deepak Gupta >>>--- >>> arch/riscv/include/asm/thread_info.h | 1 + >>> arch/riscv/kernel/asm-offsets.c | 1 + >>> arch/riscv/kernel/entry.S | 4 ++++ >>> 3 files changed, 6 insertions(+) >>> >>>diff --git a/arch/riscv/include/asm/thread_info.h >>>b/arch/riscv/include/asm/thread_info.h >>>index 574779900bfb..320bc899a63b 100644 >>>--- a/arch/riscv/include/asm/thread_info.h >>>+++ b/arch/riscv/include/asm/thread_info.h >>>@@ -57,6 +57,7 @@ struct thread_info { >>> long user_sp; /* User stack pointer */ >>> int cpu; >>> unsigned long syscall_work; /* SYSCALL_WORK_ flags */ >>>+ unsigned long envcfg; >>> #ifdef CONFIG_SHADOW_CALL_STACK >>> void *scs_base; >>> void *scs_sp; >>>diff --git a/arch/riscv/kernel/asm-offsets.c >>>b/arch/riscv/kernel/asm-offsets.c >>>index a03129f40c46..cdd8f095c30c 100644 >>>--- a/arch/riscv/kernel/asm-offsets.c >>>+++ b/arch/riscv/kernel/asm-offsets.c >>>@@ -39,6 +39,7 @@ void asm_offsets(void) >>> OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count); >>> OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp); >>> OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp); >>>+ OFFSET(TASK_TI_ENVCFG, task_struct, thread_info.envcfg); >>> #ifdef CONFIG_SHADOW_CALL_STACK >>> OFFSET(TASK_TI_SCS_SP, task_struct, thread_info.scs_sp); >>> #endif >>>diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S >>>index 54ca4564a926..63c3855ba80d 100644 >>>--- a/arch/riscv/kernel/entry.S >>>+++ b/arch/riscv/kernel/entry.S >>>@@ -129,6 +129,10 @@ SYM_CODE_START_NOALIGN(ret_from_exception) >>> addi s0, sp, PT_SIZE_ON_STACK >>> REG_S s0, TASK_TI_KERNEL_SP(tp) >>> >>>+ /* restore envcfg bits for current thread */ >>>+ REG_L s0, TASK_TI_ENVCFG(tp) >>>+ csrw CSR_ENVCFG, s0 >>>+ >> >>This is redundant if we're repeatedly processing interrupts or exceptions >>within a single task. We should only be writing envcfg when switching >>between tasks or as part of the prctl. >> >>We need to use an ALTERNATIVE for this since the oldest supported hardware >>does not have envcfg csrs. > >Yeah fixing that in next series. Thanks > >> >>-s >> >>> /* Save the kernel shadow call stack pointer */ >>> scs_save_current >>> >>>-- >>>2.43.0 >>> >>> >>>_______________________________________________ >>>linux-riscv mailing list >>>linux-riscv@lists.infradead.org >>>http://lists.infradead.org/mailman/listinfo/linux-riscv