linux_dsm_epyc7002/arch/arm64/kernel/sys32.c
Mark Rutland 4378a7d4be arm64: implement syscall wrappers
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>
2018-07-12 14:49:48 +01:00

150 lines
4.3 KiB
C

/*
* arch/arm64/kernel/sys32.c
*
* Copyright (C) 2015 ARM Ltd.
*
* This program is free software(void); you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http(void);//www.gnu.org/licenses/>.
*/
/*
* Needed to avoid conflicting __NR_* macros between uapi/asm/unistd.h and
* asm/unistd32.h.
*/
#define __COMPAT_SYSCALL_NR
#include <linux/compat.h>
#include <linux/compiler.h>
#include <linux/syscalls.h>
#include <asm/syscall.h>
asmlinkage long compat_sys_sigreturn(void);
asmlinkage long compat_sys_rt_sigreturn(void);
COMPAT_SYSCALL_DEFINE3(aarch32_statfs64, const char __user *, pathname,
compat_size_t, sz, struct compat_statfs64 __user *, buf)
{
/*
* 32-bit ARM applies an OABI compatibility fixup to statfs64 and
* fstatfs64 regardless of whether OABI is in use, and therefore
* arbitrary binaries may rely upon it, so we must do the same.
* For more details, see commit:
*
* 713c481519f19df9 ("[ARM] 3108/2: old ABI compat: statfs64 and
* fstatfs64")
*/
if (sz == 88)
sz = 84;
return kcompat_sys_statfs64(pathname, sz, buf);
}
COMPAT_SYSCALL_DEFINE3(aarch32_fstatfs64, unsigned int, fd, compat_size_t, sz,
struct compat_statfs64 __user *, buf)
{
/* see aarch32_statfs64 */
if (sz == 88)
sz = 84;
return kcompat_sys_fstatfs64(fd, sz, buf);
}
/*
* Note: off_4k is always in units of 4K. If we can't do the
* requested offset because it is not page-aligned, we return -EINVAL.
*/
COMPAT_SYSCALL_DEFINE6(aarch32_mmap2, unsigned long, addr, unsigned long, len,
unsigned long, prot, unsigned long, flags,
unsigned long, fd, unsigned long, off_4k)
{
if (off_4k & (~PAGE_MASK >> 12))
return -EINVAL;
off_4k >>= (PAGE_SHIFT - 12);
return ksys_mmap_pgoff(addr, len, prot, flags, fd, off_4k);
}
#ifdef CONFIG_CPU_BIG_ENDIAN
#define arg_u32p(name) u32, name##_hi, u32, name##_lo
#else
#define arg_u32p(name) u32, name##_lo, u32, name##_hi
#endif
#define arg_u64(name) (((u64)name##_hi << 32) | name##_lo)
COMPAT_SYSCALL_DEFINE6(aarch32_pread64, unsigned int, fd, char __user *, buf,
size_t, count, u32, __pad, arg_u32p(pos))
{
return ksys_pread64(fd, buf, count, arg_u64(pos));
}
COMPAT_SYSCALL_DEFINE6(aarch32_pwrite64, unsigned int, fd,
const char __user *, buf, size_t, count, u32, __pad,
arg_u32p(pos))
{
return ksys_pwrite64(fd, buf, count, arg_u64(pos));
}
COMPAT_SYSCALL_DEFINE4(aarch32_truncate64, const char __user *, pathname,
u32, __pad, arg_u32p(length))
{
return ksys_truncate(pathname, arg_u64(length));
}
COMPAT_SYSCALL_DEFINE4(aarch32_ftruncate64, unsigned int, fd, u32, __pad,
arg_u32p(length))
{
return ksys_ftruncate(fd, arg_u64(length));
}
COMPAT_SYSCALL_DEFINE5(aarch32_readahead, int, fd, u32, __pad,
arg_u32p(offset), size_t, count)
{
return ksys_readahead(fd, arg_u64(offset), count);
}
COMPAT_SYSCALL_DEFINE6(aarch32_fadvise64_64, int, fd, int, advice,
arg_u32p(offset), arg_u32p(len))
{
return ksys_fadvise64_64(fd, arg_u64(offset), arg_u64(len), advice);
}
COMPAT_SYSCALL_DEFINE6(aarch32_sync_file_range2, int, fd, unsigned int, flags,
arg_u32p(offset), arg_u32p(nbytes))
{
return ksys_sync_file_range(fd, arg_u64(offset), arg_u64(nbytes),
flags);
}
COMPAT_SYSCALL_DEFINE6(aarch32_fallocate, int, fd, int, mode,
arg_u32p(offset), arg_u32p(len))
{
return ksys_fallocate(fd, mode, arg_u64(offset), arg_u64(len));
}
asmlinkage long sys_ni_syscall(const struct pt_regs *);
#define __arm64_sys_ni_syscall sys_ni_syscall
#undef __SYSCALL
#define __SYSCALL(nr, sym) asmlinkage long __arm64_##sym(const struct pt_regs *);
#include <asm/unistd32.h>
#undef __SYSCALL
#define __SYSCALL(nr, sym) [nr] = (syscall_fn_t)__arm64_##sym,
const syscall_fn_t compat_sys_call_table[__NR_compat_syscalls] = {
[0 ... __NR_compat_syscalls - 1] = (syscall_fn_t)sys_ni_syscall,
#include <asm/unistd32.h>
};