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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=1765473664; l=4299; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=iZqvtimsKyFTZgyCGpJkQVX4KJa2k7Dv0ibvxxfASY4=; b=fbmM7rKCfooYVJOStB5zvDavYdaaOFGp8RJ6XmYnNG7zZjRrFzkzkTr1EgyL0Ftor/Dq+7hQD x2vp0/TG1bJBUdNzL5gzD7ONx9g/KrfAuC2/TeLpCsLzvhtfBqNr/dJ 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 X-Stat-Signature: m7boueuy9hqfkuiy4wdn68sk96q4t5xm X-Rspam-User: X-Rspamd-Queue-Id: 1181616001F X-Rspamd-Server: rspam07 X-HE-Tag: 1765473670-131468 X-HE-Meta: U2FsdGVkX19BGVVpemnR0FWJW0xUP5B5ZjKXCRHL4zDOEhG4tyhNeDsvZIM+1f234lugUwx4oxRyGNSWeCJDjNn54Y0FNG/FM/zSy8D5tJHc12zgIFaFi2SNPBIOepnZapUJCa6B5OcEaTj44PILRyfdwy8+VQ5nm9Fhn9bo7DNqHIQjND4CwpMDuxuHlub1nSYYcWsej5hhyr/GqWA6Ta40BN3iE9RcuZtTvDPfJbTWCyN7c5Fs3nzQo7i0v24XCkA6ZnH7DF1num3G9eVyVJmvV/IbTTJDidezZVm6X7BuH39NzMawzM+W55+Xm0/SQBTBRHE00YCxxSrCZb2se2wYD8YMWwZQf37s+PCyxYbmKMn1RKg/YG3kSsqctHU6QZfJTN/SxDCvu6k3742WBsJF0iE4eLxYM4RVHIJA2+F6huyQlwTXGdMlWDqxh1HWJPfE8MgDQNU2Zc7oawFS6WyUQU/SQAnDY1UKcjtiBgHf9eQzvNSSqDrMvqOjq5z6Zeoq/gQpthmPu9FVhYZLYnJrYSTIoIhYUFuKOukpWpxpjfqVVoziu4OtDH2Nsj+rAtSdGp0F+5GvfYqVxb328i3kyJkjh1xdfn37lfmoSVFonP7JDaBvomcgnbJ1ae2VEQ5c2Y6Vdc6/baOBgpzBeWoQVg6Ib14ilOoVVpdYqei/a8DgieCs5K4cFjnWx9UCbPEEN0qSRpzMFpVWIjD0z+duyeanDAuDQB8O034+ml1CTW8MYPYp6V6Lk0cAi6mJTYeqWz7GInJXcRdLA8Nzmub7+l6Xlt3aqm95bg0GK49PigMS/QWDtGB3WAUrMB6TcWKX2Y9b9o8MDiG58Dct4Yi5BiV6qa6z/Kzdi57YpYS4nEwn06kwE9OdR3jFtgtN111HJUGM7H7FafvgbT+DlWwZxngvwpJpRsrkHhQzKvmlBuqf+tF4sW+wEKhH0XIkcLjpk9exV6nMzMguoSy HT+ScVkc Nr/zLvi/PiLAN9SeggQTZREAQp3gqzgMx2TwkHBIFTqb2KG0dTHtjtCyHCoOIIRPSGL5B3tm0eI/zjXcJC8q6wdOIldUvLwX4lXSn/v+D0fPKGt2OzgJDX/atHR50Q5fQQCxg2Grb9oQshrGiFlvpfknbbG7B/MA6bSmhgOIi0epzfag10zX9fjh57DJK/rAOz2fYHHN72sH6Zqqiy5FUI2MwTwVWVrSmoccxe0GPRgzX+jJoHa8R+cub4wWE5YuIc5OeaHU/RSX2UXYqYON0G1Aq4ItwpoLdXBpTRt+Bgdsgl07AaGp6TVjXBXHOLtvbV3i26UIBlrkm9UXMBpyFt160RBkre3/UqSK98ZowqbQ2htHzE7tgGCPEmvhCsCeslBXZn5VnW6ULg91ZerjgW84+nw8vLNub5HfJ6RJJMRIMKASE7BxvtedGFztRV13hNjBF2UbZPDLDkQvLKYPnahGsvNABRzX1LALnh9XiGOE/pkZrQIVUv9qQYNDfttcZiyga4QAYLv2BEdRmo+vMoQjCw3JOj2t1cUluDvyDWWqxFk1eaQdY8pxR2EnGRvCKd0ZiNdAsSmV5hiMpnGMhqrMOdXPoTS3B/68a 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: 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 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, -- 2.43.0