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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 14344D29FB2 for ; Thu, 4 Dec 2025 20:04:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E6A726B00CD; Thu, 4 Dec 2025 15:04:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E1C7D6B00CF; Thu, 4 Dec 2025 15:04:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C6E216B00D0; Thu, 4 Dec 2025 15:04:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id B29416B00CD for ; Thu, 4 Dec 2025 15:04:26 -0500 (EST) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 662851A0382 for ; Thu, 4 Dec 2025 20:04:26 +0000 (UTC) X-FDA: 84182865732.25.C019543 Received: from mail-pf1-f173.google.com (mail-pf1-f173.google.com [209.85.210.173]) by imf19.hostedemail.com (Postfix) with ESMTP id 3D58C1A0016 for ; Thu, 4 Dec 2025 20:04:24 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=rivosinc.com header.s=google header.b=UpVIw3nX; spf=pass (imf19.hostedemail.com: domain of debug@rivosinc.com designates 209.85.210.173 as permitted sender) smtp.mailfrom=debug@rivosinc.com; dmarc=pass (policy=none) header.from=rivosinc.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1764878664; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=sAn4eyifcNxkK4OJtkwndj7H0VvpEsY65F3VIiHjxfM=; b=YWJbI+HHHUwiJiMZSQ6jovUdF0eE9Bn1Cn7ikqU/pQ3NpaUinkE1X0y6JTrjsxcPwjex+P QsWyGSAtnIPQWigv6RSRFKcEhpEPbKKTvK0mGSFQ83ZnTSEs6MSCQbvuWS8QhU359mDTrt bFlbIKUfPHVwR1JlVfIEPifdlPeVEQM= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1764878664; a=rsa-sha256; cv=none; b=YV6AJrtXuIz5/jVPL/rL/Q3Cfk2ZQOu6HadBF+6JMvU0GNlLSIY2ebkCTkL2Bu4yzjtKVa qBWJt45D9cuEqhC8jlNVlelZsI3OsyjrBuSknrQN+5rMfUPZaS9a6SnIGvelWzrEruRRS+ qC5kZcQjFKsqdVylde85Yvkdhy+dZvk= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=rivosinc.com header.s=google header.b=UpVIw3nX; spf=pass (imf19.hostedemail.com: domain of debug@rivosinc.com designates 209.85.210.173 as permitted sender) smtp.mailfrom=debug@rivosinc.com; dmarc=pass (policy=none) header.from=rivosinc.com Received: by mail-pf1-f173.google.com with SMTP id d2e1a72fcca58-7aa2170adf9so1181133b3a.0 for ; Thu, 04 Dec 2025 12:04:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc.com; s=google; t=1764878663; x=1765483463; darn=kvack.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=sAn4eyifcNxkK4OJtkwndj7H0VvpEsY65F3VIiHjxfM=; b=UpVIw3nXWGJp+1RMroUH1+08x5rPte7idiEJQNN7/QNAakcUgCNAlQ1c/cBh65f30h Z9wWWV4OX1/BpRyp/JW8UNlmQ61o7PSZRLkAhwU72b4D79Va9zeBeQ/+3gBy8wM3tv/j RVyyKC2F/UOWJONVR+ENeqRtg/45n6Dv8FtkHgsNmb8swgJrq1WUUyClxIFI3wc4ZMFe qb/EwY2+v8HnjAD2R6NWjqNQSh0A2bff5RmkmXXNyeEksq/g7FDvHrXlcE+ZutmTLcXy 0YgoL6xx314RTEOpfypKU03jXY0jxKlv6bh17w0FijLYNZ57sYvF6M1CkkpHvH00+Mmu pp+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1764878663; x=1765483463; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-gg:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=sAn4eyifcNxkK4OJtkwndj7H0VvpEsY65F3VIiHjxfM=; b=ATomib9WW/Jrxw+WnMenhJMxPBcAqc6dm+JTr4RWNZ1mm+AGwXUFRIOU04dVaHR2+D E6pCOXOrR/ycgB/IXTMM7FTsammYDk+SaM6q0IGxpGKJzr3x3H8oAb+/FRlHmyvBLTC6 bIcrz5JFzO/b0pA8jTt5aa1mOy/aQPEvBOU3QjwTJrjJPaxYMeGyEJX/p9FTvYoLM+4L yrol5V10dcHTg8mJYNmxnOzxFdworq7KIHd+qvgbc0mChVlVGVQPzSRCY5opFmjak9Aw FyeITaHXRGEXewICUE6NcnpXrOV2y2sagMIHYy2TTTT0rx95hln4kU6vhDCwXe/OPTEV mCeQ== X-Forwarded-Encrypted: i=1; AJvYcCXW7da2p65Gxcgf7YfVPWDxXm4CaFbVvhYaF1vjAmGgJTGPPci3rKDGUutM/ZttrryZ5KkNNIzv+w==@kvack.org X-Gm-Message-State: AOJu0Yy5qHZT1VF1AH7zzZNvKbZ9zFWABrGBnTN2yqpCTQlQXmJXTAm5 hYqUFUcyK+SwRV0LohWObYcZZ0d+gu8MI3Mv/1fg5vNZkGlfwagy1WG0kSVAjiBnhfg= X-Gm-Gg: ASbGncv0YZ8dEQBvmeK4K17XIr0bPJAaqZCkZpKToGXUjKO32OBBsAMmKLbfuyOyeWL 9bbPDojtBgairxbsImu/SBfKe9+I4hk3SWNbwQcPoe+AdQhX5rGjpcifSVwQy1rE6IEOuKyj9wl +1XO7/1N18MmrddyeCWwAW2JZFtUZw/cLvYE96mWr1TL5cZszRte0koskzpAh1Fj4EqY0uQY9qG uVg2Z+5G/slMTNQVd6kXSAN0FTJDueIKP8/1UDLb5wPFjcWmjO3U5XPHotWEHmLAdMvA/msoRke mVZPRA2Lzou4pYis1K8BxPBeoTkDpmYD0r4UYbab5N7VzyKLK4WdVDPkaVJPSzX9/RoDLaI5BWO ZDPtwc6+rPedziHZZGGvWKRCk7wnY59A/MxFOSy8t/u4IXwt3B2VIERKtlLFlbQ0LiwZMFP2HqO bLVPp6n6Vq6U1mAxACG/kJ X-Google-Smtp-Source: AGHT+IHZviKfh6rSZnrsc9H+dFkwapEmofO4StEYkFD85GschOZnYY6gkRvLJyPxgwRJZCF8j610PQ== X-Received: by 2002:a05:7022:6389:b0:119:e55a:9c04 with SMTP id a92af1059eb24-11df649d534mr3010415c88.32.1764878662786; Thu, 04 Dec 2025 12:04:22 -0800 (PST) Received: from debug.ba.rivosinc.com ([64.71.180.162]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-11df76e2eefsm10417454c88.6.2025.12.04.12.04.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Dec 2025 12:04:22 -0800 (PST) From: Deepak Gupta Date: Thu, 04 Dec 2025 12:04:01 -0800 Subject: [PATCH v24 12/28] riscv: Implements arch agnostic shadow stack prctls MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251204-v5_user_cfi_series-v24-12-ada7a3ba14dc@rivosinc.com> References: <20251204-v5_user_cfi_series-v24-0-ada7a3ba14dc@rivosinc.com> In-Reply-To: <20251204-v5_user_cfi_series-v24-0-ada7a3ba14dc@rivosinc.com> To: 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 , Jann Horn , Conor Dooley , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , Alice Ryhl , Trevor Gross , Benno Lossin Cc: 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, rust-for-linux@vger.kernel.org, Zong Li , Andreas Korb , Valentin Haudiquet , Deepak Gupta X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1764878635; l=7555; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=UB7DB8iQ68E73LowKHzcTBS0aUXVgW818RL3xhZs1m8=; b=EztNLj7IiLpxHRmvhuGHyQdgvmiXSvDSgvCh1a0ilHstgSwNC7TEp3aPWzusJY9Mm/LJ5PoKB VmqC3fQlY+TAzIlTzrOdVtAVubIkz/oNzQGqjRabLW3mDRXYa+VDMJt X-Developer-Key: i=debug@rivosinc.com; a=ed25519; pk=O37GQv1thBhZToXyQKdecPDhtWVbEDRQ0RIndijvpjk= X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 3D58C1A0016 X-Stat-Signature: 9egicbjuf7m4yjqcrberju6cqxqy9hor X-Rspam-User: X-HE-Tag: 1764878664-968549 X-HE-Meta: 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 P+/TDm6F 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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: Implement architecture agnostic prctls() interface for setting and getting shadow stack status. prctls implemented are PR_GET_SHADOW_STACK_STATUS, PR_SET_SHADOW_STACK_STATUS and PR_LOCK_SHADOW_STACK_STATUS. As part of PR_SET_SHADOW_STACK_STATUS/PR_GET_SHADOW_STACK_STATUS, only PR_SHADOW_STACK_ENABLE is implemented because RISCV allows each mode to write to their own shadow stack using `sspush` or `ssamoswap`. PR_LOCK_SHADOW_STACK_STATUS locks current configuration of shadow stack enabling. Reviewed-by: Zong Li Tested-by: Andreas Korb Tested-by: Valentin Haudiquet Signed-off-by: Deepak Gupta --- arch/riscv/include/asm/usercfi.h | 16 ++++++ arch/riscv/kernel/process.c | 8 +++ arch/riscv/kernel/usercfi.c | 110 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 134 insertions(+) diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/usercfi.h index a16a5dff8b0e..d71093f414df 100644 --- a/arch/riscv/include/asm/usercfi.h +++ b/arch/riscv/include/asm/usercfi.h @@ -7,6 +7,7 @@ #ifndef __ASSEMBLER__ #include +#include struct task_struct; struct kernel_clone_args; @@ -14,6 +15,7 @@ struct kernel_clone_args; #ifdef CONFIG_RISCV_USER_CFI struct cfi_state { unsigned long ubcfi_en : 1; /* Enable for backward cfi. */ + unsigned long ubcfi_locked : 1; unsigned long user_shdw_stk; /* Current user shadow stack pointer */ unsigned long shdw_stk_base; /* Base address of shadow stack */ unsigned long shdw_stk_size; /* size of shadow stack */ @@ -26,6 +28,12 @@ void set_shstk_base(struct task_struct *task, unsigned long shstk_addr, unsigned unsigned long get_shstk_base(struct task_struct *task, unsigned long *size); void set_active_shstk(struct task_struct *task, unsigned long shstk_addr); bool is_shstk_enabled(struct task_struct *task); +bool is_shstk_locked(struct task_struct *task); +bool is_shstk_allocated(struct task_struct *task); +void set_shstk_lock(struct task_struct *task); +void set_shstk_status(struct task_struct *task, bool enable); + +#define PR_SHADOW_STACK_SUPPORTED_STATUS_MASK (PR_SHADOW_STACK_ENABLE) #else @@ -41,6 +49,14 @@ bool is_shstk_enabled(struct task_struct *task); #define is_shstk_enabled(task) false +#define is_shstk_locked(task) false + +#define is_shstk_allocated(task) false + +#define set_shstk_lock(task) do {} while (0) + +#define set_shstk_status(task, enable) do {} while (0) + #endif /* CONFIG_RISCV_USER_CFI */ #endif /* __ASSEMBLER__ */ diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 72d35adc6e0e..a137d3483646 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -156,6 +156,14 @@ void start_thread(struct pt_regs *regs, unsigned long pc, regs->epc = pc; regs->sp = sp; + /* + * clear shadow stack state on exec. + * libc will set it later via prctl. + */ + set_shstk_status(current, false); + set_shstk_base(current, 0, 0); + set_active_shstk(current, 0); + #ifdef CONFIG_64BIT regs->status &= ~SR_UXL; diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c index 872e0c52e034..0b77b812e4d7 100644 --- a/arch/riscv/kernel/usercfi.c +++ b/arch/riscv/kernel/usercfi.c @@ -24,6 +24,16 @@ bool is_shstk_enabled(struct task_struct *task) return task->thread_info.user_cfi_state.ubcfi_en; } +bool is_shstk_allocated(struct task_struct *task) +{ + return task->thread_info.user_cfi_state.shdw_stk_base; +} + +bool is_shstk_locked(struct task_struct *task) +{ + return task->thread_info.user_cfi_state.ubcfi_locked; +} + void set_shstk_base(struct task_struct *task, unsigned long shstk_addr, unsigned long size) { task->thread_info.user_cfi_state.shdw_stk_base = shstk_addr; @@ -42,6 +52,26 @@ void set_active_shstk(struct task_struct *task, unsigned long shstk_addr) task->thread_info.user_cfi_state.user_shdw_stk = shstk_addr; } +void set_shstk_status(struct task_struct *task, bool enable) +{ + if (!cpu_supports_shadow_stack()) + return; + + task->thread_info.user_cfi_state.ubcfi_en = enable ? 1 : 0; + + if (enable) + task->thread.envcfg |= ENVCFG_SSE; + else + task->thread.envcfg &= ~ENVCFG_SSE; + + csr_write(CSR_ENVCFG, task->thread.envcfg); +} + +void set_shstk_lock(struct task_struct *task) +{ + task->thread_info.user_cfi_state.ubcfi_locked = 1; +} + /* * If size is 0, then to be compatible with regular stack we want it to be as big as * regular stack. Else PAGE_ALIGN it and return back @@ -260,3 +290,83 @@ void shstk_release(struct task_struct *tsk) vm_munmap(base, size); set_shstk_base(tsk, 0, 0); } + +int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *status) +{ + unsigned long bcfi_status = 0; + + if (!cpu_supports_shadow_stack()) + return -EINVAL; + + /* this means shadow stack is enabled on the task */ + bcfi_status |= (is_shstk_enabled(t) ? PR_SHADOW_STACK_ENABLE : 0); + + return copy_to_user(status, &bcfi_status, sizeof(bcfi_status)) ? -EFAULT : 0; +} + +int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status) +{ + unsigned long size = 0, addr = 0; + bool enable_shstk = false; + + if (!cpu_supports_shadow_stack()) + return -EINVAL; + + /* Reject unknown flags */ + if (status & ~PR_SHADOW_STACK_SUPPORTED_STATUS_MASK) + return -EINVAL; + + /* bcfi status is locked and further can't be modified by user */ + if (is_shstk_locked(t)) + return -EINVAL; + + enable_shstk = status & PR_SHADOW_STACK_ENABLE; + /* Request is to enable shadow stack and shadow stack is not enabled already */ + if (enable_shstk && !is_shstk_enabled(t)) { + /* shadow stack was allocated and enable request again + * no need to support such usecase and return EINVAL. + */ + if (is_shstk_allocated(t)) + return -EINVAL; + + size = calc_shstk_size(0); + addr = allocate_shadow_stack(0, size, 0, false); + if (IS_ERR_VALUE(addr)) + return -ENOMEM; + set_shstk_base(t, addr, size); + set_active_shstk(t, addr + size); + } + + /* + * If a request to disable shadow stack happens, let's go ahead and release it + * Although, if CLONE_VFORKed child did this, then in that case we will end up + * not releasing the shadow stack (because it might be needed in parent). Although + * we will disable it for VFORKed child. And if VFORKed child tries to enable again + * then in that case, it'll get entirely new shadow stack because following condition + * are true + * - shadow stack was not enabled for vforked child + * - shadow stack base was anyways pointing to 0 + * This shouldn't be a big issue because we want parent to have availability of shadow + * stack whenever VFORKed child releases resources via exit or exec but at the same + * time we want VFORKed child to break away and establish new shadow stack if it desires + * + */ + if (!enable_shstk) + shstk_release(t); + + set_shstk_status(t, enable_shstk); + return 0; +} + +int arch_lock_shadow_stack_status(struct task_struct *task, + unsigned long arg) +{ + /* If shtstk not supported or not enabled on task, nothing to lock here */ + if (!cpu_supports_shadow_stack() || + !is_shstk_enabled(task) || arg != 0) + return -EINVAL; + + set_shstk_lock(task); + + return 0; +} -- 2.45.0