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Current GLIBC has two ways to implement the single thread optimization
on syscalls to avoid calling the cancellation path: either by using
global variables (__{libc,pthread}_multiple_thread) or by accessing
the TCB field (defined by TLS_MULTIPLE_THREADS_IN_TCB). Both the
variables and the macros to acces its value are defined in the
architecture sysdep-cancel.h header.
This patch consolidates its definition on only one header,
sysdeps/unix/sysv/linux/sysdep-cancel.h, and adds a new define
(SINGLE_THREAD_BY_GLOBAL) which the architecture defines if it prefer
to use the global variables instead of the TCB field. This is an
optimization, so if the architecture does not define it, the TCB
method will be used as default.
Checked on x86_64-linux-gnu and on a build with major touched
ABIs (aarch64-linux-gnu, alpha-linux-gnu, arm-linux-gnueabihf,
hppa-linux-gnu, i686-linux-gnu, m68k-linux-gnu, microblaze-linux-gnu,
mips-linux-gnu, mips64-linux-gnu, powerpc-linux-gnu,
powerpc64le-linux-gnu, s390-linux-gnu, s390x-linux-gnu, sh4-linux-gnu,
sparcv9-linux-gnu, sparc64-linux-gnu, tilegx-linux-gnu).
* sysdeps/unix/sysv/linux/aarch64/sysdep-cancel.h: Remove file.
* sysdeps/unix/sysv/linux/alpha/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/arm/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/hppa/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/mips/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/nios2/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/powerpc/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/sh/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/sparc/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/tile/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/x86_64/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
(SINGLE_THREAD_BY_GLOBAL): Define.
* sysdeps/unix/sysv/linux/aarch64/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
* sysdeps/unix/sysv/linux/alpha/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
* sysdeps/unix/sysv/linux/arm/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
* sysdeps/unix/sysv/linux/hppa/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
* sysdeps/unix/sysv/linux/microblaze/sysdep.h
(SINGLE_THREAD_BY_GLOBAL): Likewise.
* sysdeps/unix/sysv/linux/x86_64/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
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For ia32 PIC, the first thing of many syscalls does is to call
__x86.get_pc_thunk.reg to load PC into reg in case there is an error,
which is required for setting errno. In most cases, there are no
errors. But we still call __x86.get_pc_thunk.reg. This patch adds
INLINE_SYSCALL_ERROR_RETURN_VALUE so that i386 can optimize setting
errno by branching to the internal __syscall_error without PLT.
With i386 INLINE_SYSCALL_ERROR_RETURN_VALUE and i386 syscall inlining
optimization for GCC 5, for sysdeps/unix/sysv/linux/fchmodat.c with
-O2 -march=i686 -mtune=generic, GCC 5.2 now generates:
<fchmodat>:
0: push %ebx
1: mov 0x14(%esp),%eax
5: mov 0x8(%esp),%ebx
9: mov 0xc(%esp),%ecx
d: mov 0x10(%esp),%edx
11: test $0xfffffeff,%eax
16: jne 38 <fchmodat+0x38>
18: test $0x1,%ah
1b: jne 48 <fchmodat+0x48>
1d: mov $0x132,%eax
22: call *%gs:0x10
29: cmp $0xfffff000,%eax
2e: ja 58 <fchmodat+0x58>
30: pop %ebx
31: ret
32: lea 0x0(%esi),%esi
38: pop %ebx
39: mov $0xffffffea,%eax
3e: jmp 3f <fchmodat+0x3f> 3f: R_386_PC32 __syscall_error
43: nop
44: lea 0x0(%esi,%eiz,1),%esi
48: pop %ebx
49: mov $0xffffffa1,%eax
4e: jmp 4f <fchmodat+0x4f> 4f: R_386_PC32 __syscall_error
53: nop
54: lea 0x0(%esi,%eiz,1),%esi
58: pop %ebx
59: jmp 5a <fchmodat+0x5a> 5a: R_386_PC32 __syscall_error
instead of
<fchmodat>:
0: sub $0x8,%esp
3: mov 0x18(%esp),%eax
7: mov %ebx,(%esp)
a: call b <fchmodat+0xb> b: R_386_PC32 __x86.get_pc_thunk.bx
f: add $0x2,%ebx 11: R_386_GOTPC _GLOBAL_OFFSET_TABLE_
15: mov %edi,0x4(%esp)
19: test $0xfffffeff,%eax
1e: jne 70 <fchmodat+0x70>
20: test $0x1,%ah
23: jne 88 <fchmodat+0x88>
25: mov 0x14(%esp),%edx
29: mov 0x10(%esp),%ecx
2d: mov 0xc(%esp),%edi
31: xchg %ebx,%edi
33: mov $0x132,%eax
38: call *%gs:0x10
3f: xchg %edi,%ebx
41: cmp $0xfffff000,%eax
46: ja 58 <fchmodat+0x58>
48: mov (%esp),%ebx
4b: mov 0x4(%esp),%edi
4f: add $0x8,%esp
52: ret
53: nop
54: lea 0x0(%esi,%eiz,1),%esi
58: mov 0x0(%ebx),%edx 5a: R_386_TLS_GOTIE __libc_errno
5e: neg %eax
60: mov %eax,%gs:(%edx)
63: mov $0xffffffff,%eax
68: jmp 48 <fchmodat+0x48>
6a: lea 0x0(%esi),%esi
70: mov 0x0(%ebx),%eax 72: R_386_TLS_GOTIE __libc_errno
76: movl $0x16,%gs:(%eax)
7d: mov $0xffffffff,%eax
82: jmp 48 <fchmodat+0x48>
84: lea 0x0(%esi,%eiz,1),%esi
88: mov 0x0(%ebx),%eax 8a: R_386_TLS_GOTIE __libc_errno
8e: movl $0x5f,%gs:(%eax)
95: mov $0xffffffff,%eax
9a: jmp 48 <fchmodat+0x48>
* sysdeps/unix/sysv/linux/sysdep.h: New file.
* sysdeps/unix/sysv/linux/i386/sysdep.c: Likewise.
* sysdeps/unix/sysv/linux/alpha/sysdep.h: Include
<sysdeps/unix/sysv/linux/sysdep.h>.
* sysdeps/unix/sysv/linux/arm/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/generic/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/hppa/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/ia64/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/m68k/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/microblaze/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/mips/mips32/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/sh/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/sparc/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/x86_64/sysdep.h: Likewise.
* sysdeps/unix/sysv/linux/i386/Makefile [$(subdir) == csu]
(sysdep-dl-routines): Add sysdep.
[$(subdir) == nptl] (libpthread-routines): Likewise.
[$(subdir) == rt] (librt-routines): Likewise.
* sysdeps/unix/sysv/linux/i386/clone.S (__clone): Don't check
PIC when branching to SYSCALL_ERROR_LABEL.
* sysdeps/unix/sysv/linux/i386/sysdep.S: Removed.
* sysdeps/unix/sysv/linux/i386/sysdep.h: Include
<sysdeps/unix/sysv/linux/sysdep.h>.
(SYSCALL_ERROR_LABEL): Changed to __syscall_error.
(SYSCALL_ERROR_ERRNO): Removed.
(SYSCALL_ERROR_HANDLER): Changed to empty.
(SYSCALL_ERROR_HANDLER_TLS_STORE): Likewise.
(__syscall_error): New prototype.
[IS_IN (libc)] (INLINE_SYSCALL): New macro.
(INLINE_SYSCALL_ERROR_RETURN_VALUE): Likewise.
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