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df76ff3a44
X32 has 32-bit long and pointer with 64-bit off_t. Since x32 psABI
requires that pointers passed in registers must be zero-extended to
64bit, x32 can share many syscall interfaces with LP64. When a LP64
syscall with long and unsigned long arguments is used for x32, these
arguments must be properly extended to 64-bit. Otherwise if the upper
32 bits of the register have undefined value, such a syscall will be
rejected by kernel.
Enforce zero-extension for pointers and array system call arguments.
For integer types, extend to int64_t (the full register) using a
regular cast, resulting in zero or sign extension based on the
signedness of the original type.
For
void *mmap(void *addr, size_t length, int prot, int flags,
int fd, off_t offset);
we now generate
0: 41 f7 c1 ff 0f 00 00 test $0xfff,%r9d
7: 75 1f jne 28 <__mmap64+0x28>
9: 48 63 d2 movslq %edx,%rdx
c: 89 f6 mov %esi,%esi
e: 4d 63 c0 movslq %r8d,%r8
11: 4c 63 d1 movslq %ecx,%r10
14: b8 09 00 00 40 mov $0x40000009,%eax
19: 0f 05 syscall
That is
1. addr is unchanged.
2. length is zero-extend to 64 bits.
3. prot is sign-extend to 64 bits.
4. flags is sign-extend to 64 bits.
5. fd is sign-extend to 64 bits.
6. offset is unchanged.
For int arguments, since kernel uses only the lower 32 bits and ignores
the upper 32 bits in 64-bit registers, these work correctly.
Tested on x86-64 and x32. There are no code changes on x86-64.
46 lines
1.7 KiB
C
46 lines
1.7 KiB
C
/* Copyright (C) 2012-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _LINUX_X32_SYSDEP_H
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#define _LINUX_X32_SYSDEP_H 1
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/* There is some commonality. */
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#include <sysdeps/unix/sysv/linux/x86_64/sysdep.h>
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#include <sysdeps/x86_64/x32/sysdep.h>
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/* How to pass the off{64}_t argument on p{readv,writev}{64}. */
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#undef LO_HI_LONG
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#define LO_HI_LONG(val) (val)
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#ifndef __ASSEMBLER__
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# undef ARGIFY
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/* Enforce zero-extension for pointers and array system call arguments.
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For integer types, extend to int64_t (the full register) using a
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regular cast, resulting in zero or sign extension based on the
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signedness of the original type. */
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# define ARGIFY(X) \
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({ \
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_Pragma ("GCC diagnostic push"); \
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_Pragma ("GCC diagnostic ignored \"-Wpointer-to-int-cast\""); \
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(__builtin_classify_type (X) == 5 \
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? (uintptr_t) (X) : (int64_t) (X)); \
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_Pragma ("GCC diagnostic pop"); \
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})
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#endif /* __ASSEMBLER__ */
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#endif /* linux/x86_64/x32/sysdep.h */
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