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Fri, 05 Dec 2025 10:37:01 -0800 (PST) From: Deepak Gupta Date: Fri, 05 Dec 2025 10:36:52 -0800 Subject: [PATCH v25 06/28] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251205-v5_user_cfi_series-v25-6-8a3570c3e145@rivosinc.com> References: <20251205-v5_user_cfi_series-v25-0-8a3570c3e145@rivosinc.com> In-Reply-To: <20251205-v5_user_cfi_series-v25-0-8a3570c3e145@rivosinc.com> To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. 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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=1764959808; l=4345; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=7yLe9hWq2WlkWVyw5cBB8KO8waygymuFRUw/WyJutrk=; b=brRg4Sn8vtoSLKpcwx4+loNsIV5h3ZB1DTXP5anyC0qWKOWE2LiMPjioo+IiPxRaUxf/54FOC aXStfisB/ojBRwd6CwGucPTtiKuZH9f6XIZV3TLOlrJBIxk+6atHMhk X-Developer-Key: i=debug@rivosinc.com; a=ed25519; pk=O37GQv1thBhZToXyQKdecPDhtWVbEDRQ0RIndijvpjk= X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: BAC7518000D X-Stat-Signature: 1c8jh99pmckt883opfxpe1otguxbxwtj X-Rspam-User: X-HE-Tag: 1764959823-383813 X-HE-Meta: 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 lkYM0uNx xWgJMo9mv11Ul9Mc+aXDHb2AhrXvWgOHc7FUPQ7yQ5dtrDhUTvT/x5tjH/oublXt3MteQMpPvXlpnlM/jqUtnpYPPt1eYQAReQdC8h5G1JTNXRHD7dPTkwnCU2Waj+/tODtzpeDgpkcswcg5y164ntPQaBjF+HFvd0KC5imvWzmly//hfqBribkqiDnz4IFxFEbJfHNgZja5TLpdqXQZuMGLEa3bvV//QMjvXfYf5ndd5DL3KEWpq5W5zCQtBxnkmusx9OlB4+6n/v7xnWa4Nry4NtXQttdrHWAKIEeijNoZlgePQ9FL8/LsK2SOdl003QFO/39ePYd4bd57qE0cbVBdl2RhdCCam+trCGgZIS2v5P6MVKnbTOug21YBy4F+Itzf3aReBaXrWqoU6xXedWN9zy04Kt6wIGg84ANreTSp1/ed436WVewOxph3W3IKSCoZTsFmysQnZ2oEOKYhW6cXF7zF1wLB6xFlCat2yrqK0NiYy1/xplcL+7PChMyxwGefwfnayPr0Bjce8VC0Nq+DLSZuyILzpW6le6mQKJeM/u7+xtFsNuf8lVaT32fatbNZ2Ef9r6urTBXA1IU1u5STJcroc4xH9mTooIFVKh2xjO7aokDdD3SYdTSEi5ggHvLM/+NXFFJqsb64U8ujmJNz5V6PDcYxyisoC 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: `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 = 0; + + /* + * If PROT_WRITE was specified, force it to VM_READ | VM_WRITE. + * Only VM_WRITE means shadow stack. + */ + if (prot & PROT_WRITE) + ret = (VM_READ | VM_WRITE); + return ret; +} + +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey) + +#endif /* ! __ASM_MMAN_H__ */ diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.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) #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 @@ #include #include +#include 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; + /* + * 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_WRITE | 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 |= 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(PAGE_SIZE); static const pgprot_t protection_map[16] = { [VM_NONE] = PAGE_NONE, [VM_READ] = PAGE_READ, - [VM_WRITE] = PAGE_COPY, + [VM_WRITE] = PAGE_SHADOWSTACK, [VM_WRITE | VM_READ] = PAGE_COPY, [VM_EXEC] = PAGE_EXEC, [VM_EXEC | VM_READ] = PAGE_READ_EXEC, -- 2.45.0