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08d0ce30e0
Commitf0bddf5058("riscv: entry: Convert to generic entry") moved syscall handling to C code, which exposed function pointer type mismatches that trip fine-grained forward-edge Control-Flow Integrity (CFI) checks as syscall handlers are all called through the same syscall_t pointer type. To fix the type mismatches, implement pt_regs based syscall wrappers similarly to x86 and arm64. This patch is based on arm64 syscall wrappers added in commit4378a7d4be("arm64: implement syscall wrappers"), where the main goal was to minimize the risk of userspace-controlled values being used under speculation. This may be a concern for riscv in future as well. Following other architectures, the syscall wrappers generate three functions for each syscall; __riscv_<compat_>sys_<name> takes a pt_regs pointer and extracts arguments from registers, __se_<compat_>sys_<name> is a sign-extension wrapper that casts the long arguments to the correct types for the real syscall implementation, which is named __do_<compat_>sys_<name>. Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Link: https://lore.kernel.org/r/20230710183544.999540-9-samitolvanen@google.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
103 lines
2.4 KiB
C
103 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved.
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* Copyright 2010 Tilera Corporation. All Rights Reserved.
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* Copyright 2015 Regents of the University of California, Berkeley
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*
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* See asm-generic/syscall.h for descriptions of what we must do here.
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*/
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#ifndef _ASM_RISCV_SYSCALL_H
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#define _ASM_RISCV_SYSCALL_H
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#include <asm/hwprobe.h>
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#include <uapi/linux/audit.h>
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#include <linux/sched.h>
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#include <linux/err.h>
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/* The array of function pointers for syscalls. */
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extern void * const sys_call_table[];
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extern void * const compat_sys_call_table[];
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/*
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* Only the low 32 bits of orig_r0 are meaningful, so we return int.
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* This importantly ignores the high bits on 64-bit, so comparisons
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* sign-extend the low 32 bits.
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*/
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static inline int syscall_get_nr(struct task_struct *task,
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struct pt_regs *regs)
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{
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return regs->a7;
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}
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static inline void syscall_rollback(struct task_struct *task,
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struct pt_regs *regs)
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{
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regs->a0 = regs->orig_a0;
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}
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static inline long syscall_get_error(struct task_struct *task,
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struct pt_regs *regs)
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{
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unsigned long error = regs->a0;
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return IS_ERR_VALUE(error) ? error : 0;
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}
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static inline long syscall_get_return_value(struct task_struct *task,
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struct pt_regs *regs)
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{
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return regs->a0;
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}
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static inline void syscall_set_return_value(struct task_struct *task,
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struct pt_regs *regs,
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int error, long val)
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{
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regs->a0 = (long) error ?: val;
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}
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static inline void syscall_get_arguments(struct task_struct *task,
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struct pt_regs *regs,
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unsigned long *args)
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{
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args[0] = regs->orig_a0;
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args++;
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memcpy(args, ®s->a1, 5 * sizeof(args[0]));
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}
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static inline int syscall_get_arch(struct task_struct *task)
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{
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#ifdef CONFIG_64BIT
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return AUDIT_ARCH_RISCV64;
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#else
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return AUDIT_ARCH_RISCV32;
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#endif
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}
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typedef long (*syscall_t)(const struct pt_regs *);
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static inline void syscall_handler(struct pt_regs *regs, ulong syscall)
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{
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syscall_t fn;
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#ifdef CONFIG_COMPAT
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if ((regs->status & SR_UXL) == SR_UXL_32)
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fn = compat_sys_call_table[syscall];
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else
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#endif
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fn = sys_call_table[syscall];
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regs->a0 = fn(regs);
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}
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static inline bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
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{
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return false;
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}
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asmlinkage long sys_riscv_flush_icache(uintptr_t, uintptr_t, uintptr_t);
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asmlinkage long sys_riscv_hwprobe(struct riscv_hwprobe *, size_t, size_t,
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unsigned long *, unsigned int);
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#endif /* _ASM_RISCV_SYSCALL_H */
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