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AJvYcCVF/6Fki/wJXZsRV5mMMYhSHh5hSlPIarZ8KS9OxKGpjHonvtnJMTVIPVrlW8TvqjiQ06ziK09nUA==@kvack.org X-Gm-Message-State: AOJu0YwMNKW7VNsbY2MBC76XeCiK061eZpnEjwYH6VC7ArR1qbUmZo3I 7u5Hz8/yvq4y9Kv8LUt7EL5OuKLFdM6MFwlVFYlfycXiwCz3jLg4ziJ2B4H+ooY= X-Google-Smtp-Source: AGHT+IHTSbLYPW9H6IMMv3J9GeiSG052ik1ZNbE+SJ7zga3eJUIE3+gCfX95oRz+I+/KI8Ko3d5rzw== X-Received: by 2002:a17:902:cec7:b0:20c:7d4c:64db with SMTP id d9443c01a7336-211b5d542aemr85459765ad.49.1731599449294; Thu, 14 Nov 2024 07:50:49 -0800 (PST) Received: from debug.ba.rivosinc.com ([64.71.180.162]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-211c7d377ecsm12256145ad.265.2024.11.14.07.50.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Nov 2024 07:50:48 -0800 (PST) Date: Thu, 14 Nov 2024 07:50:45 -0800 From: Deepak Gupta To: Nick Hu Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , Paul Walmsley , Palmer Dabbelt , Albert Ou , Conor Dooley , Rob Herring , Krzysztof Kozlowski , Arnd Bergmann , Christian Brauner , Peter Zijlstra , Oleg Nesterov , Eric Biederman , Kees Cook , Jonathan Corbet , Shuah Khan , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, alistair.francis@wdc.com, richard.henderson@linaro.org, jim.shu@sifive.com, andybnac@gmail.com, kito.cheng@sifive.com, charlie@rivosinc.com, atishp@rivosinc.com, evan@rivosinc.com, cleger@rivosinc.com, alexghiti@rivosinc.com, samitolvanen@google.com, broonie@kernel.org, rick.p.edgecombe@intel.com Subject: Re: [PATCH v8 24/29] riscv: enable kernel access to shadow stack memory via FWFT sbi call Message-ID: References: <20241111-v5_user_cfi_series-v8-0-dce14aa30207@rivosinc.com> <20241111-v5_user_cfi_series-v8-24-dce14aa30207@rivosinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: 9eqi5j99ge8o4wnsmpdcexpmus8uirdn X-Rspamd-Queue-Id: 46ABF80021 X-Rspamd-Server: rspam08 X-Rspam-User: X-HE-Tag: 1731599367-880637 X-HE-Meta: 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 VUdNc090 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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: Hi Nick, Thanks for reviewing and helping. On Thu, Nov 14, 2024 at 02:17:30PM +0800, Nick Hu wrote: >Hi Deepak > >On Thu, Nov 14, 2024 at 9:25 AM Deepak Gupta wrote: >> >> On Thu, Nov 14, 2024 at 09:20:14AM +0800, Nick Hu wrote: >> >Hi Deepak >> > >> >On Thu, Nov 14, 2024 at 9:06 AM Deepak Gupta wrote: >> >> >> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S >> >> >> index 356d5397b2a2..6244408ca917 100644 >> >> >> --- a/arch/riscv/kernel/head.S >> >> >> +++ b/arch/riscv/kernel/head.S >> >> >> @@ -164,6 +164,12 @@ secondary_start_sbi: >> >> >> call relocate_enable_mmu >> >> >> #endif >> >> >> call .Lsetup_trap_vector >> >> >> + li a7, SBI_EXT_FWFT >> >> >> + li a6, SBI_EXT_FWFT_SET >> >> >> + li a0, SBI_FWFT_SHADOW_STACK >> >> >> + li a1, 1 /* enable supervisor to access shadow stack access */ >> >> >> + li a2, SBI_FWFT_SET_FLAG_LOCK >> >> >> + ecall >> >> >> scs_load_current >> >> >> call smp_callin >> >> >> #endif /* CONFIG_SMP */ >> >> >> @@ -320,6 +326,12 @@ SYM_CODE_START(_start_kernel) >> >> >> la tp, init_task >> >> >> la sp, init_thread_union + THREAD_SIZE >> >> >> addi sp, sp, -PT_SIZE_ON_STACK >> >> >> + li a7, SBI_EXT_FWFT >> >> >> + li a6, SBI_EXT_FWFT_SET >> >> >> + li a0, SBI_FWFT_SHADOW_STACK >> >> >> + li a1, 1 /* enable supervisor to access shadow stack access */ >> >> >> + li a2, SBI_FWFT_SET_FLAG_LOCK >> >> >> + ecall >> >> >> scs_load_current >> >> >> >> >> >> #ifdef CONFIG_KASAN >> >> >> >> >> >> -- >> >> >> 2.45.0 >> >> >> >> >> >Should we clear the SBI_FWFT_SET_FLAG_LOCK before the cpu hotplug >> >> >otherwise the menvcfg.sse won't be set by the fwft set sbi call when >> >> >the hotplug cpu back to kernel? >> >> >> >> Hmm... >> >> >> >> An incoming hotplug CPU has no features setup on it. >> >> I see that `sbi_cpu_start` will supply `secondary_start_sbi` as start >> >> up code for incoming CPU. `secondary_start_sbi` is in head.S which converges >> >> in `.Lsecondary_start_common`. And thus hotplugged CPU should be >> >> issuing shadow stack set FWFT sbi as well. >> >> >> >> Am I missing something ? >> >> >> >This is the correct flow. However the opensbi will deny it due to the >> >SBI_FWFT_SET_FLAG_LOCK already being set. >> >So the menvcfg.sse will not set by this flow. >> > >> >if (conf->flags & SBI_FWFT_SET_FLAG_LOCK) >> > return SBI_EDENIED; >> > >> >> hmm... Why? >> >> `conf` is pointing to per-hart state in firmware. >> >> On this incoming cpu, opensbi (or equivalent) firmware must have >> ensured that this per-hart state doesn't have lock set. >> >> Am I missing something? >> >Current OpenSBI doesn't clear the lock in the warm init of the hotplug path. >It seems like we need a patch to address it. Got it thanks. Since you already know what's the problem, can you send a patch to opensbi. If you want rather have me do it, let me know. Thanks. > >Regards, >Nick >> >Regards, >> >Nick >> >> > >> >> >Regards, >> >> >Nick >> >> >> >> >> >> _______________________________________________ >> >> >> linux-riscv mailing list >> >> >> linux-riscv@lists.infradead.org >> >> >> http://lists.infradead.org/mailman/listinfo/linux-riscv