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Thu, 12 Sep 2024 16:17:53 -0700 (PDT) From: Deepak Gupta To: paul.walmsley@sifive.com, palmer@sifive.com, conor@kernel.org, linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: corbet@lwn.net, palmer@dabbelt.com, aou@eecs.berkeley.edu, robh@kernel.org, krzk+dt@kernel.org, oleg@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, peterz@infradead.org, akpm@linux-foundation.org, arnd@arndb.de, ebiederm@xmission.com, kees@kernel.org, Liam.Howlett@oracle.com, vbabka@suse.cz, lorenzo.stoakes@oracle.com, shuah@kernel.org, brauner@kernel.org, samuel.holland@sifive.com, debug@rivosinc.com, andy.chiu@sifive.com, jerry.shih@sifive.com, greentime.hu@sifive.com, charlie@rivosinc.com, evan@rivosinc.com, cleger@rivosinc.com, xiao.w.wang@intel.com, ajones@ventanamicro.com, anup@brainfault.org, mchitale@ventanamicro.com, atishp@rivosinc.com, sameo@rivosinc.com, bjorn@rivosinc.com, alexghiti@rivosinc.com, david@redhat.com, libang.li@antgroup.com, jszhang@kernel.org, leobras@redhat.com, guoren@kernel.org, samitolvanen@google.com, songshuaishuai@tinylab.org, costa.shul@redhat.com, bhe@redhat.com, zong.li@sifive.com, puranjay@kernel.org, namcaov@gmail.com, antonb@tenstorrent.com, sorear@fastmail.com, quic_bjorande@quicinc.com, ancientmodern4@gmail.com, ben.dooks@codethink.co.uk, quic_zhonhan@quicinc.com, cuiyunhui@bytedance.com, yang.lee@linux.alibaba.com, ke.zhao@shingroup.cn, sunilvl@ventanamicro.com, tanzhasanwork@gmail.com, schwab@suse.de, dawei.li@shingroup.cn, rppt@kernel.org, willy@infradead.org, usama.anjum@collabora.com, osalvador@suse.de, ryan.roberts@arm.com, andrii@kernel.org, alx@kernel.org, catalin.marinas@arm.com, broonie@kernel.org, revest@chromium.org, bgray@linux.ibm.com, deller@gmx.de, zev@bewilderbeest.net Subject: [PATCH v4 11/30] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE Date: Thu, 12 Sep 2024 16:16:30 -0700 Message-ID: <20240912231650.3740732-12-debug@rivosinc.com> X-Mailer: git-send-email 2.45.0 In-Reply-To: <20240912231650.3740732-1-debug@rivosinc.com> References: <20240912231650.3740732-1-debug@rivosinc.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 `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. Signed-off-by: Deepak Gupta --- arch/riscv/include/asm/mman.h | 24 ++++++++++++++++++++++++ arch/riscv/include/asm/pgtable.h | 1 + arch/riscv/kernel/sys_riscv.c | 10 ++++++++++ arch/riscv/mm/init.c | 2 +- mm/mmap.c | 1 + 5 files changed, 37 insertions(+), 1 deletion(-) create mode 100644 arch/riscv/include/asm/mman.h diff --git a/arch/riscv/include/asm/mman.h b/arch/riscv/include/asm/mman.h new file mode 100644 index 000000000000..ef9fedf32546 --- /dev/null +++ b/arch/riscv/include/asm/mman.h @@ -0,0 +1,24 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_MMAN_H__ +#define __ASM_MMAN_H__ + +#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 089f3c9f56a3..af4337774fe5 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -181,6 +181,7 @@ 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 d77afe05578f..43a448bf254b 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 eb0649a61b4c..000b51c26943 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -324,7 +324,7 @@ 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, diff --git a/mm/mmap.c b/mm/mmap.c index d0dfc85b209b..04023a464fac 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -47,6 +47,7 @@ #include #include #include +#include #include #include