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To minimize the risk of userspace-controlled values being used under speculation, this patch adds pt_regs based syscall wrappers for arm64, which pass the minimum set of required userspace values to syscall implementations. For each syscall, a wrapper which takes a pt_regs argument is automatically generated, and this extracts the arguments before calling the "real" syscall implementation. Each syscall has three functions generated: * __do_<compat_>sys_<name> is the "real" syscall implementation, with the expected prototype. * __se_<compat_>sys_<name> is the sign-extension/narrowing wrapper, inherited from common code. This takes a series of long parameters, casting each to the requisite types required by the "real" syscall implementation in __do_<compat_>sys_<name>. This wrapper *may* not be necessary on arm64 given the AAPCS rules on unused register bits, but it seemed safer to keep the wrapper for now. * __arm64_<compat_>_sys_<name> takes a struct pt_regs pointer, and extracts *only* the relevant register values, passing these on to the __se_<compat_>sys_<name> wrapper. The syscall invocation code is updated to handle the calling convention required by __arm64_<compat_>_sys_<name>, and passes a single struct pt_regs pointer. The compiler can fold the syscall implementation and its wrappers, such that the overhead of this approach is minimized. Note that we play games with sys_ni_syscall(). It can't be defined with SYSCALL_DEFINE0() because we must avoid the possibility of error injection. Additionally, there are a couple of locations where we need to call it from C code, and we don't (currently) have a ksys_ni_syscall(). While it has no wrapper, passing in a redundant pt_regs pointer is benign per the AAPCS. When ARCH_HAS_SYSCALL_WRAPPER is selected, no prototype is defines for sys_ni_syscall(). Since we need to treat it differently for in-kernel calls and the syscall tables, the prototype is defined as-required. The wrappers are largely the same as their x86 counterparts, but simplified as we don't have a variety of compat calling conventions that require separate stubs. Unlike x86, we have some zero-argument compat syscalls, and must define COMPAT_SYSCALL_DEFINE0() to ensure that these are also given an __arm64_compat_sys_ prefix. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
69 lines
2.0 KiB
C
69 lines
2.0 KiB
C
/*
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* AArch64-specific system calls implementation
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*
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* Copyright (C) 2012 ARM Ltd.
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* Author: Catalin Marinas <catalin.marinas@arm.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/compiler.h>
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#include <linux/errno.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/export.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/syscalls.h>
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#include <asm/cpufeature.h>
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#include <asm/syscall.h>
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SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
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unsigned long, prot, unsigned long, flags,
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unsigned long, fd, off_t, off)
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{
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if (offset_in_page(off) != 0)
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return -EINVAL;
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return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
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}
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SYSCALL_DEFINE1(arm64_personality, unsigned int, personality)
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{
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if (personality(personality) == PER_LINUX32 &&
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!system_supports_32bit_el0())
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return -EINVAL;
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return ksys_personality(personality);
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}
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/*
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* Wrappers to pass the pt_regs argument.
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*/
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#define sys_personality sys_arm64_personality
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asmlinkage long sys_ni_syscall(const struct pt_regs *);
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#define __arm64_sys_ni_syscall sys_ni_syscall
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#undef __SYSCALL
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#define __SYSCALL(nr, sym) asmlinkage long __arm64_##sym(const struct pt_regs *);
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#include <asm/unistd.h>
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#undef __SYSCALL
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#define __SYSCALL(nr, sym) [nr] = (syscall_fn_t)__arm64_##sym,
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const syscall_fn_t sys_call_table[__NR_syscalls] = {
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[0 ... __NR_syscalls - 1] = (syscall_fn_t)sys_ni_syscall,
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#include <asm/unistd.h>
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};
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