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Support six-argument syscalls from C for 32-bit x86, use generic lowl…
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…evellock-futex.h (bug 18138).

This patch follows the approach outlined in
<https://sourceware.org/ml/libc-alpha/2015-03/msg00656.html> to
support six-argument syscalls from INTERNAL_SYSCALL for 32-bit x86,
making them call a function __libc_do_syscall that takes the syscall
number and three syscall arguments in the registers in which the
kernel expects them, along with a pointer to a structure containing
the other three arguments.

In turn, this allows the generic lowlevellock-futex.h to be used on
32-bit x86, so supporting lll_futex_timed_wait_bitset (and so allowing
FUTEX_CLOCK_REALTIME to be used in various cases, so fixing bug 18138
for 32-bit x86 and leaving hppa as the only architecture missing
lll_futex_timed_wait_bitset).  The change to lowlevellock.h's
definition of SYS_futex is because the generic lowlevelloc-futex.h
ends up bringing in bits/syscall.h which defines SYS_futex to
__NR_futex, so resulting in redefinition errors.  The revised
definition in lowlevellock.h is in line with what the x86_64 version
does.

__libc_do_syscall is only needed in libpthread at present (meaning
nothing special needs to be done to make it shared-only in most
libraries containing it, static in libc only, as on ARM).

Tested for 32-bit x86, with the glibc testsuite and with the test in
bug 18138.  The failures seen

FAIL: nptl/tst-cleanupx4
FAIL: rt/tst-cpuclock2

are pre-existing.

	[BZ #18138]
	* sysdeps/unix/sysv/linux/i386/sysdep.h (struct
	libc_do_syscall_args): New structure.
	(INTERNAL_SYSCALL_MAIN_0): New macro.
	(INTERNAL_SYSCALL_MAIN_1): Likewise.
	(INTERNAL_SYSCALL_MAIN_2): Likewise.
	(INTERNAL_SYSCALL_MAIN_3): Likewise.
	(INTERNAL_SYSCALL_MAIN_4): Likewise.
	(INTERNAL_SYSCALL_MAIN_5): Likewise.
	(INTERNAL_SYSCALL_MAIN_6): Likewise.  Call __libc_do_syscall.
	(INTERNAL_SYSCALL): Define to use INTERNAL_SYSCALL_MAIN_##nr.
	Replace conditional definitions by conditional definitions of ....
	(INTERNAL_SYSCALL_MAIN_INLINE): ... this.  New macro.
	* sysdeps/unix/sysv/linux/i386/libc-do-syscall.S: New file.
	* sysdeps/unix/sysv/linux/i386/Makefile [$(subdir) = nptl]
	(libpthread-sysdep_routines): Add libc-do-syscall.
	* sysdeps/unix/sysv/linux/i386/lowlevellock-futex.h: Remove file.
	* sysdeps/unix/sysv/linux/i386/lowlevellock.h (SYS_futex): Define
	to __NR_futex not 240.
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Joseph Myers committed Mar 25, 2015
1 parent afcd948 commit a9fe4c5
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22 changes: 22 additions & 0 deletions ChangeLog
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Original file line number Diff line number Diff line change
@@ -1,3 +1,25 @@
2015-03-25 Joseph Myers <joseph@codesourcery.com>

[BZ #18138]
* sysdeps/unix/sysv/linux/i386/sysdep.h (struct
libc_do_syscall_args): New structure.
(INTERNAL_SYSCALL_MAIN_0): New macro.
(INTERNAL_SYSCALL_MAIN_1): Likewise.
(INTERNAL_SYSCALL_MAIN_2): Likewise.
(INTERNAL_SYSCALL_MAIN_3): Likewise.
(INTERNAL_SYSCALL_MAIN_4): Likewise.
(INTERNAL_SYSCALL_MAIN_5): Likewise.
(INTERNAL_SYSCALL_MAIN_6): Likewise. Call __libc_do_syscall.
(INTERNAL_SYSCALL): Define to use INTERNAL_SYSCALL_MAIN_##nr.
Replace conditional definitions by conditional definitions of ....
(INTERNAL_SYSCALL_MAIN_INLINE): ... this. New macro.
* sysdeps/unix/sysv/linux/i386/libc-do-syscall.S: New file.
* sysdeps/unix/sysv/linux/i386/Makefile [$(subdir) = nptl]
(libpthread-sysdep_routines): Add libc-do-syscall.
* sysdeps/unix/sysv/linux/i386/lowlevellock-futex.h: Remove file.
* sysdeps/unix/sysv/linux/i386/lowlevellock.h (SYS_futex): Define
to __NR_futex not 240.

2015-03-25 Alan Modra <amodra@gmail.com>

* NEWS: Advertise TLS optimization.
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5 changes: 5 additions & 0 deletions sysdeps/unix/sysv/linux/i386/Makefile
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Expand Up @@ -14,6 +14,11 @@ ifeq ($(subdir),io)
sysdep_routines += call_sync_file_range
endif

# libpthread uses six-argument inline syscalls.
ifeq ($(subdir),nptl)
libpthread-sysdep_routines += libc-do-syscall
endif

ifeq ($(subdir),resource)
sysdep_routines += oldgetrlimit64
endif
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50 changes: 50 additions & 0 deletions sysdeps/unix/sysv/linux/i386/libc-do-syscall.S
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@@ -0,0 +1,50 @@
/* Out-of-line syscall stub for six-argument syscalls from C.
Copyright (C) 2015 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */

#include <sysdep.h>

/* %eax, %ecx, %edx and %esi contain the values expected by the kernel.
%edi points to a structure with the values of %ebx, %edi and %ebp. */

.hidden __libc_do_syscall

ENTRY (__libc_do_syscall)
pushl %ebx
cfi_adjust_cfa_offset (4)
cfi_rel_offset (ebx, 0)
pushl %edi
cfi_adjust_cfa_offset (4)
cfi_rel_offset (edi, 0)
pushl %ebp
cfi_adjust_cfa_offset (4)
cfi_rel_offset (ebp, 0)
movl 0(%edi), %ebx
movl 8(%edi), %ebp
movl 4(%edi), %edi
ENTER_KERNEL
popl %ebp
cfi_adjust_cfa_offset (-4)
cfi_restore (ebp)
popl %edi
cfi_adjust_cfa_offset (-4)
cfi_restore (edi)
popl %ebx
cfi_adjust_cfa_offset (-4)
cfi_restore (ebx)
ret
END (__libc_do_syscall)
137 changes: 0 additions & 137 deletions sysdeps/unix/sysv/linux/i386/lowlevellock-futex.h
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This file was deleted.

2 changes: 1 addition & 1 deletion sysdeps/unix/sysv/linux/i386/lowlevellock.h
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Expand Up @@ -48,7 +48,7 @@
#include <lowlevellock-futex.h>

/* XXX Remove when no assembler code uses futexes anymore. */
#define SYS_futex 240
#define SYS_futex __NR_futex

#ifndef __ASSEMBLER__

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65 changes: 50 additions & 15 deletions sysdeps/unix/sysv/linux/i386/sysdep.h
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Expand Up @@ -304,6 +304,17 @@ asm (".L__X'%ebx = 1\n\t"
".endif\n\t"
".endm\n\t");

/* Six-argument syscalls use an out-of-line helper, because an inline
asm using all registers apart from %esp cannot work reliably and
the assembler does not support describing an asm that saves and
restores %ebp itself as a separate stack frame. This structure
stores the arguments not passed in registers; %edi is passed with a
pointer to this structure. */
struct libc_do_syscall_args
{
int ebx, edi, ebp;
};

/* Define a macro which expands inline into the wrapper code for a system
call. */
#undef INLINE_SYSCALL
Expand All @@ -325,11 +336,42 @@ asm (".L__X'%ebx = 1\n\t"
The _NCS variant allows non-constant syscall numbers but it is not
possible to use more than four parameters. */
#undef INTERNAL_SYSCALL
#ifdef I386_USE_SYSENTER
# ifdef SHARED
# define INTERNAL_SYSCALL(name, err, nr, args...) \
#define INTERNAL_SYSCALL_MAIN_0(name, err, args...) \
INTERNAL_SYSCALL_MAIN_INLINE(name, err, 0, args)
#define INTERNAL_SYSCALL_MAIN_1(name, err, args...) \
INTERNAL_SYSCALL_MAIN_INLINE(name, err, 1, args)
#define INTERNAL_SYSCALL_MAIN_2(name, err, args...) \
INTERNAL_SYSCALL_MAIN_INLINE(name, err, 2, args)
#define INTERNAL_SYSCALL_MAIN_3(name, err, args...) \
INTERNAL_SYSCALL_MAIN_INLINE(name, err, 3, args)
#define INTERNAL_SYSCALL_MAIN_4(name, err, args...) \
INTERNAL_SYSCALL_MAIN_INLINE(name, err, 4, args)
#define INTERNAL_SYSCALL_MAIN_5(name, err, args...) \
INTERNAL_SYSCALL_MAIN_INLINE(name, err, 5, args)
/* Each object using 6-argument inline syscalls must include a
definition of __libc_do_syscall. */
#define INTERNAL_SYSCALL_MAIN_6(name, err, arg1, arg2, arg3, \
arg4, arg5, arg6) \
struct libc_do_syscall_args _xv = \
{ \
(int) (arg1), \
(int) (arg5), \
(int) (arg6) \
}; \
asm volatile ( \
"movl %1, %%eax\n\t" \
"call __libc_do_syscall" \
: "=a" (resultvar) \
: "i" (__NR_##name), "c" (arg2), "d" (arg3), "S" (arg4), "D" (&_xv) \
: "memory", "cc")
#define INTERNAL_SYSCALL(name, err, nr, args...) \
({ \
register unsigned int resultvar; \
INTERNAL_SYSCALL_MAIN_##nr (name, err, args); \
(int) resultvar; })
#ifdef I386_USE_SYSENTER
# ifdef SHARED
# define INTERNAL_SYSCALL_MAIN_INLINE(name, err, nr, args...) \
EXTRAVAR_##nr \
asm volatile ( \
LOADARGS_##nr \
Expand All @@ -338,8 +380,7 @@ asm (".L__X'%ebx = 1\n\t"
RESTOREARGS_##nr \
: "=a" (resultvar) \
: "i" (__NR_##name), "i" (offsetof (tcbhead_t, sysinfo)) \
ASMFMT_##nr(args) : "memory", "cc"); \
(int) resultvar; })
ASMFMT_##nr(args) : "memory", "cc")
# define INTERNAL_SYSCALL_NCS(name, err, nr, args...) \
({ \
register unsigned int resultvar; \
Expand All @@ -353,18 +394,15 @@ asm (".L__X'%ebx = 1\n\t"
ASMFMT_##nr(args) : "memory", "cc"); \
(int) resultvar; })
# else
# define INTERNAL_SYSCALL(name, err, nr, args...) \
({ \
register unsigned int resultvar; \
# define INTERNAL_SYSCALL_MAIN_INLINE(name, err, nr, args...) \
EXTRAVAR_##nr \
asm volatile ( \
LOADARGS_##nr \
"movl %1, %%eax\n\t" \
"call *_dl_sysinfo\n\t" \
RESTOREARGS_##nr \
: "=a" (resultvar) \
: "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc"); \
(int) resultvar; })
: "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc")
# define INTERNAL_SYSCALL_NCS(name, err, nr, args...) \
({ \
register unsigned int resultvar; \
Expand All @@ -378,18 +416,15 @@ asm (".L__X'%ebx = 1\n\t"
(int) resultvar; })
# endif
#else
# define INTERNAL_SYSCALL(name, err, nr, args...) \
({ \
register unsigned int resultvar; \
# define INTERNAL_SYSCALL_MAIN_INLINE(name, err, nr, args...) \
EXTRAVAR_##nr \
asm volatile ( \
LOADARGS_##nr \
"movl %1, %%eax\n\t" \
"int $0x80\n\t" \
RESTOREARGS_##nr \
: "=a" (resultvar) \
: "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc"); \
(int) resultvar; })
: "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc")
# define INTERNAL_SYSCALL_NCS(name, err, nr, args...) \
({ \
register unsigned int resultvar; \
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