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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 , Deepak Gupta X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1762994618; l=4219; i=debug@rivosinc.com; s=20251023; h=from:subject:message-id; bh=lpSh/4YF4b6DV2vqO7uhXaAxm8ZQQfhDo9tNU1Zgc2g=; b=He5Ojlz6cjGM/VJRt23CyG7jXvrwDEs5E2Wo+I1dwe36mE0DfaK3v9msi0F2FBLNzYQgnAzJ0 JkIknttpojPATvNAgIhKBl9T2uMGuISM1b3cMPXkVi0RP8B2W2E2qCX 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-Rspamd-Queue-Id: 7327940003 X-Stat-Signature: jy83cm9aaicsmh5d5xcwg3dk9149qf8h X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1762994626-286225 X-HE-Meta: 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 O/rTxJFJ 41fBKksRrSSueUY4FHlpuXkcPRlP3YG6diuvwCihEh6T6zp3SlOszmjoD1lpdzRirNwOtCiyT6dVoGXN3FtZ/KUwmLNsSXqeyzHdpPZNLEm/VQQohsEgVrgs88q8oUywaW6ehJI8Fh6SNfEPtA/S/CI6Ly2MDDvAN5MA/bUnJujo/XtoQjgHGM83Ae6QHS4tKty2jMMPFdi6PCVqGZ3aP2Hq5OtRyZR9yZHN29QhVBOHRNX2gBYTJn7sOebGi/KmldChMEQspfLI1b4R2XXMy06782oLWy/K6zqW93X5YPLz3+K8OK5HpXYx8RZfS0TAtOhc0unvPZZjlEpmpNduYdTa1Sln3PJsKj2VmTg8oFjA2BhAEdnUPWhr/11+f37hAy4TGFWcrzewY3GI1v4cSsHsBfm93yi3sAugT/WtW0uQmObJr8xKEw8XmkV+zCTwDm4DMIgliJGp+9Kry09gD5F8Ss4Oiyvt8fvUQOgWAjqY/SMWkrwTwdBUSGKSminRgTMdk/bprbugQasTGPlM2sjC7W4hyjS+cMpU2EF1PNA4beCk= 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 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, -- 2.43.0