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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>
150 lines
4.3 KiB
C
150 lines
4.3 KiB
C
/*
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* arch/arm64/kernel/sys32.c
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*
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* Copyright (C) 2015 ARM Ltd.
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*
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* This program is free software(void); 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(void);//www.gnu.org/licenses/>.
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*/
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/*
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* Needed to avoid conflicting __NR_* macros between uapi/asm/unistd.h and
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* asm/unistd32.h.
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*/
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#define __COMPAT_SYSCALL_NR
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#include <linux/compat.h>
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#include <linux/compiler.h>
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#include <linux/syscalls.h>
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#include <asm/syscall.h>
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asmlinkage long compat_sys_sigreturn(void);
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asmlinkage long compat_sys_rt_sigreturn(void);
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COMPAT_SYSCALL_DEFINE3(aarch32_statfs64, const char __user *, pathname,
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compat_size_t, sz, struct compat_statfs64 __user *, buf)
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{
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/*
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* 32-bit ARM applies an OABI compatibility fixup to statfs64 and
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* fstatfs64 regardless of whether OABI is in use, and therefore
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* arbitrary binaries may rely upon it, so we must do the same.
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* For more details, see commit:
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*
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* 713c481519f19df9 ("[ARM] 3108/2: old ABI compat: statfs64 and
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* fstatfs64")
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*/
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if (sz == 88)
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sz = 84;
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return kcompat_sys_statfs64(pathname, sz, buf);
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}
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COMPAT_SYSCALL_DEFINE3(aarch32_fstatfs64, unsigned int, fd, compat_size_t, sz,
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struct compat_statfs64 __user *, buf)
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{
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/* see aarch32_statfs64 */
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if (sz == 88)
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sz = 84;
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return kcompat_sys_fstatfs64(fd, sz, buf);
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}
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/*
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* Note: off_4k is always in units of 4K. If we can't do the
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* requested offset because it is not page-aligned, we return -EINVAL.
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*/
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COMPAT_SYSCALL_DEFINE6(aarch32_mmap2, unsigned long, addr, unsigned long, len,
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unsigned long, prot, unsigned long, flags,
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unsigned long, fd, unsigned long, off_4k)
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{
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if (off_4k & (~PAGE_MASK >> 12))
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return -EINVAL;
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off_4k >>= (PAGE_SHIFT - 12);
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return ksys_mmap_pgoff(addr, len, prot, flags, fd, off_4k);
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}
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#ifdef CONFIG_CPU_BIG_ENDIAN
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#define arg_u32p(name) u32, name##_hi, u32, name##_lo
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#else
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#define arg_u32p(name) u32, name##_lo, u32, name##_hi
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#endif
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#define arg_u64(name) (((u64)name##_hi << 32) | name##_lo)
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COMPAT_SYSCALL_DEFINE6(aarch32_pread64, unsigned int, fd, char __user *, buf,
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size_t, count, u32, __pad, arg_u32p(pos))
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{
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return ksys_pread64(fd, buf, count, arg_u64(pos));
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}
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COMPAT_SYSCALL_DEFINE6(aarch32_pwrite64, unsigned int, fd,
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const char __user *, buf, size_t, count, u32, __pad,
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arg_u32p(pos))
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{
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return ksys_pwrite64(fd, buf, count, arg_u64(pos));
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}
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COMPAT_SYSCALL_DEFINE4(aarch32_truncate64, const char __user *, pathname,
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u32, __pad, arg_u32p(length))
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{
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return ksys_truncate(pathname, arg_u64(length));
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}
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COMPAT_SYSCALL_DEFINE4(aarch32_ftruncate64, unsigned int, fd, u32, __pad,
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arg_u32p(length))
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{
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return ksys_ftruncate(fd, arg_u64(length));
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}
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COMPAT_SYSCALL_DEFINE5(aarch32_readahead, int, fd, u32, __pad,
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arg_u32p(offset), size_t, count)
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{
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return ksys_readahead(fd, arg_u64(offset), count);
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}
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COMPAT_SYSCALL_DEFINE6(aarch32_fadvise64_64, int, fd, int, advice,
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arg_u32p(offset), arg_u32p(len))
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{
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return ksys_fadvise64_64(fd, arg_u64(offset), arg_u64(len), advice);
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}
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COMPAT_SYSCALL_DEFINE6(aarch32_sync_file_range2, int, fd, unsigned int, flags,
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arg_u32p(offset), arg_u32p(nbytes))
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{
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return ksys_sync_file_range(fd, arg_u64(offset), arg_u64(nbytes),
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flags);
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}
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COMPAT_SYSCALL_DEFINE6(aarch32_fallocate, int, fd, int, mode,
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arg_u32p(offset), arg_u32p(len))
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{
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return ksys_fallocate(fd, mode, arg_u64(offset), arg_u64(len));
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}
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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/unistd32.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 compat_sys_call_table[__NR_compat_syscalls] = {
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[0 ... __NR_compat_syscalls - 1] = (syscall_fn_t)sys_ni_syscall,
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#include <asm/unistd32.h>
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};
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