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Mon, 20 Oct 2025 13:22:50 -0700 (PDT) From: Deepak Gupta Date: Mon, 20 Oct 2025 13:22:35 -0700 Subject: [PATCH v22 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: <20251020-v5_user_cfi_series-v22-6-66732256ad8f@rivosinc.com> References: <20251020-v5_user_cfi_series-v22-0-66732256ad8f@rivosinc.com> In-Reply-To: <20251020-v5_user_cfi_series-v22-0-66732256ad8f@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 , Deepak Gupta X-Mailer: b4 0.13.0 X-Stat-Signature: wqce5ukw5ronw3bm5hiw8arx66aa8owf X-Rspamd-Queue-Id: 360B8180006 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1760991771-142167 X-HE-Meta: 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 gyvezBEO c09pY/TwfrJeaJ3DdywS1fcRcP3Q1LjIyPoSRUCMCQ85th42foDUQxDvR09QzhR+1F5oMwQOlic1Vr2SlJS2EZdH4SWdvyUsnxk46FT2u3FEJ1+icty4mGu5jHVKvnZ2huJFpiuUGby9mkd8= 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 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