2017-01-01 00:14:16 +00:00
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/* Copyright (C) 2015-2017 Free Software Foundation, Inc.
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i386: Remove syscall assembly codes with 6 arguments
This patch removes i386 assembly implementation for mmap, mmap64,
semtimeop now that i386 have 6 argument syscall support from C code
and GCC 5 can inline syscalls with 6 arguments. We also compile mmap.c,
mmap64.c and semtimedop.c with -fomit-frame-pointer since %ebp may be
used to pass the 6th argument to syscall.
Fo sysdeps/unix/sysv/linux/i386/mmap.c, with -O2 -march=i686
-mtune=generic, GCC 5.2 now generates:
<__mmap>:
0: sub $0x10,%esp
3: mov 0x28(%esp),%eax
7: mov %ebx,(%esp)
a: mov 0x18(%esp),%ecx
e: mov %esi,0x4(%esp)
12: mov 0x14(%esp),%ebx
16: mov %edi,0x8(%esp)
1a: mov 0x1c(%esp),%edx
1e: test $0xfff,%eax
23: mov 0x20(%esp),%esi
27: mov %ebp,0xc(%esp)
2b: mov 0x24(%esp),%edi
2f: jne 60 <__mmap+0x60>
31: shr $0xc,%eax
34: mov %eax,%ebp
36: mov $0xc0,%eax
3b: call *%gs:0x10
42: cmp $0xfffff000,%eax
47: ja 65 <__mmap+0x65>
49: mov (%esp),%ebx
4c: mov 0x4(%esp),%esi
50: mov 0x8(%esp),%edi
54: mov 0xc(%esp),%ebp
58: add $0x10,%esp
5b: ret
5c: lea 0x0(%esi,%eiz,1),%esi
60: mov $0xffffffea,%eax
65: mov (%esp),%ebx
68: mov 0x4(%esp),%esi
6c: mov 0x8(%esp),%edi
70: mov 0xc(%esp),%ebp
74: add $0x10,%esp
77: jmp 78 <__mmap+0x78>
vs sysdeps/unix/sysv/linux/i386/mmap.S:
<__mmap>:
0: push %ebp
1: push %ebx
2: push %esi
3: push %edi
4: mov 0x14(%esp),%ebx
8: mov 0x18(%esp),%ecx
c: mov 0x1c(%esp),%edx
10: mov 0x20(%esp),%esi
14: mov 0x24(%esp),%edi
18: mov 0x28(%esp),%ebp
1c: test $0xfff,%ebp
22: mov $0xffffffea,%eax
27: jne 38 <__mmap+0x38>
29: shr $0xc,%ebp
2c: mov $0xc0,%eax
31: call *%gs:0x10
38: pop %edi
39: pop %esi
3a: pop %ebx
3b: pop %ebp
3c: cmp $0xfffff000,%eax
41: ja 44 <__mmap+0x44>
43: ret
44: call 45 <__mmap+0x45> 45: R_386_PC32 __x86.get_pc_thunk.cx
49: add $0x2,%ecx 4b: R_386_GOTPC _GLOBAL_OFFSET_TABLE_
4f: mov 0x0(%ecx),%ecx 51: R_386_TLS_GOTIE __libc_errno
55: neg %eax
57: mov %eax,%gs:(%ecx)
5a: or $0xffffffff,%eax
5d: ret
The C version has:
3: mov 0x28(%esp),%eax
...
1e: test $0xfff,%eax
...
31: sar $0xc,%eax
34: mov %eax,%ebp
is due to missing $ebx register constraint for inline asm. We have
to use "r" constraint with
register unsigned int _a6 asm ("ebp") = (unsigned int) (arg6);
and compiler chose %eax for offset (arg6) in
if (offset & (MMAP_PAGE_UNIT - 1))
* sysdeps/unix/sysv/linux/i386/Makefile (CFLAGS-epoll_pwait.c):
Add -fomit-frame-pointer.
(CFLAGS-mmap.c): Likewise.
(CFLAGS-mmap64.c): Likewise.
(CFLAGS-semtimedop.c): Likewise.
* sysdeps/unix/sysv/linux/i386/mmap.c: New file.
* sysdeps/unix/sysv/linux/i386/mmap.S: Remove file.
* sysdeps/unix/sysv/linux/i386/mmap64.S: Likewise.
* sysdeps/unix/sysv/linux/i386/semtimedop.S: Likewise.
2015-10-15 11:33:15 +00:00
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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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<http://www.gnu.org/licenses/>. */
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <errno.h>
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#include <sysdep.h>
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#ifndef MMAP_PAGE_UNIT
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# define MMAP_PAGE_UNIT 4096UL
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#endif
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__ptr_t
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__mmap (__ptr_t addr, size_t len, int prot, int flags, int fd, off_t offset)
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{
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if (offset & (MMAP_PAGE_UNIT - 1))
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return (__ptr_t) INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
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return (__ptr_t) INLINE_SYSCALL (mmap2, 6, addr, len, prot, flags, fd,
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offset / MMAP_PAGE_UNIT);
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}
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weak_alias (__mmap, mmap)
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