From nobody Thu Dec 11 19:18:40 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DA78B359FAD; Fri, 5 Dec 2025 18:41:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764960111; cv=none; b=NN0DrHyHj4EcnzNJMij9PZgRj1DLjGAdhFdx+PnLqmh3B41ilNabhXDhxEWk5MILzxYDQaQo34mI2rkLrwMvrgUCcDLWjNaJSGlmXdAgbb0twPi5UcTs0O/HuvjSXfhX/eQErFJlA0T6OSP268fjmMNfQGruZ/jt9p8FGQEPUXY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764960111; c=relaxed/simple; bh=lJBxGtUxX1ML+GQ5mbkI60bpfUo2bpfFzmOpADbeTJI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=tfoLPpBjs+c8FscxKMP+APwwhCaVOsIpqRX7JB+7WrKSRZj5x43+2qpdU0FYSPnF8v+Q9k3RsWG6t2q8KbNmTNk1pWroJ54yVjTVf3EEsRc+QYjhG4CMb1H1onZ4z+qhV1B/kcEFn1LDzny6n9aQ6XWHGcIDDbNmVyQXdiKYkn0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eFfszPMq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="eFfszPMq" Received: by smtp.kernel.org (Postfix) with ESMTPS id 6AF79C2BCB8; Fri, 5 Dec 2025 18:41:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764960110; bh=lJBxGtUxX1ML+GQ5mbkI60bpfUo2bpfFzmOpADbeTJI=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=eFfszPMqogm3poECa6l5ZBewpXUVt2N6P/zkLgDcUO06wQzbGQRcKve/EHquUgN3r mbw+wV68+POkLtfXAwmoZMIGDFVQ+sVg6irgqlunaAxwW/mfh5SCE5D2yZMsmYSUg5 FB0OQymmjS5qmyntv3UUAseYgkgq1n1woesROJUKqRQo9Xt0KQa+Mv1Jx1q5s/y36n 3zo6tvDkTQNHVil+j6oQnR5hXH27PRpynCeU7J/XH9B0iAbu7jZhNl4+Iuql1UYph2 /m5SqhuQCBD8QWXrIU63it5MZBjluXw7JBQIFicubyt5FG4b3zLjARMbaSp/ofs8uS xsj1ey80/Q4gQ== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58AD4D339AE; Fri, 5 Dec 2025 18:41:50 +0000 (UTC) From: Deepak Gupta via B4 Relay Date: Fri, 05 Dec 2025 10:41:44 -0800 Subject: [PATCH v25 06/28] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251205-v5_user_cfi_series-v25-6-1a07c0127361@rivosinc.com> References: <20251205-v5_user_cfi_series-v25-0-1a07c0127361@rivosinc.com> In-Reply-To: <20251205-v5_user_cfi_series-v25-0-1a07c0127361@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=1764960107; l=4345; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=S6iS9MzpSn4NM/2oev7SNcHK5+9hek6gf9jlYKR3Pow=; b=kQiEjA+LjJtIWm+kVaGpIuG4bRWyodQTXnps3YB4gSBRWO6TSLPPTluKf24r9u97jagShSGal RVo+f/hXzR2BjSwHRqEPLWJduK68WVNyi/q7QyADFw6qh8Yh9gKArNY X-Developer-Key: i=debug@rivosinc.com; a=ed25519; pk=O37GQv1thBhZToXyQKdecPDhtWVbEDRQ0RIndijvpjk= X-Endpoint-Received: by B4 Relay for debug@rivosinc.com/20251023 with auth_id=553 X-Original-From: Deepak Gupta Reply-To: debug@rivosinc.com From: Deepak Gupta `arch_calc_vm_prot_bits` is implemented on risc-v to return VM_READ | VM_WRITE if PROT_WRITE is specified. Similarly `riscv_sys_mmap` is updated to convert all incoming PROT_WRITE to (PROT_WRITE | PROT_READ). This is to make sure that any existing apps using PROT_WRITE still work. Earlier `protection_map[VM_WRITE]` used to pick read-write PTE encodings. Now `protection_map[VM_WRITE]` will always pick PAGE_SHADOWSTACK PTE encodings for shadow stack. Above changes ensure that existing apps continue to work because underneath kernel will be picking `protection_map[VM_WRITE|VM_READ]` PTE encodings. Reviewed-by: Zong Li Reviewed-by: Alexandre Ghiti Signed-off-by: Arnd Bergmann Tested-by: Andreas Korb Tested-by: Valentin Haudiquet Signed-off-by: Deepak Gupta --- arch/riscv/include/asm/mman.h | 26 ++++++++++++++++++++++++++ arch/riscv/include/asm/pgtable.h | 1 + arch/riscv/kernel/sys_riscv.c | 10 ++++++++++ arch/riscv/mm/init.c | 2 +- 4 files changed, 38 insertions(+), 1 deletion(-) diff --git a/arch/riscv/include/asm/mman.h b/arch/riscv/include/asm/mman.h new file mode 100644 index 000000000000..0ad1d19832eb --- /dev/null +++ b/arch/riscv/include/asm/mman.h @@ -0,0 +1,26 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_MMAN_H__ +#define __ASM_MMAN_H__ + +#include +#include +#include +#include + +static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot, + unsigned long pkey __always_unused) +{ + unsigned long ret =3D 0; + + /* + * If PROT_WRITE was specified, force it to VM_READ | VM_WRITE. + * Only VM_WRITE means shadow stack. + */ + if (prot & PROT_WRITE) + ret =3D (VM_READ | VM_WRITE); + return ret; +} + +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pk= ey) + +#endif /* ! __ASM_MMAN_H__ */ diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgta= ble.h index 29e994a9afb6..4c4057a2550e 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -182,6 +182,7 @@ extern struct pt_alloc_ops pt_ops __meminitdata; #define PAGE_READ_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | _PAGE_EXEC) #define PAGE_WRITE_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | \ _PAGE_EXEC | _PAGE_WRITE) +#define PAGE_SHADOWSTACK __pgprot(_PAGE_BASE | _PAGE_WRITE) =20 #define PAGE_COPY PAGE_READ #define PAGE_COPY_EXEC PAGE_READ_EXEC diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c index 795b2e815ac9..22fc9b3268be 100644 --- a/arch/riscv/kernel/sys_riscv.c +++ b/arch/riscv/kernel/sys_riscv.c @@ -7,6 +7,7 @@ =20 #include #include +#include =20 static long riscv_sys_mmap(unsigned long addr, unsigned long len, unsigned long prot, unsigned long flags, @@ -16,6 +17,15 @@ static long riscv_sys_mmap(unsigned long addr, unsigned = long len, if (unlikely(offset & (~PAGE_MASK >> page_shift_offset))) return -EINVAL; =20 + /* + * If PROT_WRITE is specified then extend that to PROT_READ + * protection_map[VM_WRITE] is now going to select shadow stack encodings. + * So specifying PROT_WRITE actually should select protection_map [VM_WRI= TE | VM_READ] + * If user wants to create shadow stack then they should use `map_shadow_= stack` syscall. + */ + if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ))) + prot |=3D PROT_READ; + return ksys_mmap_pgoff(addr, len, prot, flags, fd, offset >> (PAGE_SHIFT - page_shift_offset)); } diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index d85efe74a4b6..62ab2c7de7c8 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -376,7 +376,7 @@ pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(P= AGE_SIZE); static const pgprot_t protection_map[16] =3D { [VM_NONE] =3D PAGE_NONE, [VM_READ] =3D PAGE_READ, - [VM_WRITE] =3D PAGE_COPY, + [VM_WRITE] =3D PAGE_SHADOWSTACK, [VM_WRITE | VM_READ] =3D PAGE_COPY, [VM_EXEC] =3D PAGE_EXEC, [VM_EXEC | VM_READ] =3D PAGE_READ_EXEC, --=20 2.43.0