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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_RETURN and INLINE_SYSCALL_ERROR_RETURN so that i386
can optimize setting errno by branching to the internal __syscall_error
without PLT.
INLINE_SYSCALL_ERROR_RETURN is designed to take the negative error
number returned from the majority of Linux kernels for which negating
is a no-op with INTERNAL_SYSCALL_ERRNO.
With i386 INLINE_SYSCALL_RETURN, INLINE_SYSCALL_ERROR_RETURN 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/sysdep.h (INLINE_SYSCALL_RETURN): New.
(INLINE_SYSCALL_ERROR_RETURN): Likewise.
* sysdeps/unix/sysv/linux/adjtime.c (ADJTIME): Use
INLINE_SYSCALL_RETURN and INLINE_SYSCALL_ERROR_RETURN.
* sysdeps/unix/sysv/linux/aio_sigqueue.c (__aio_sigqueue):
Likewise.
* sysdeps/unix/sysv/linux/dl-openat64.c (openat64): Likewise.
* sysdeps/unix/sysv/linux/eventfd.c (eventfd): Likewise.
* sysdeps/unix/sysv/linux/faccessat.c (faccessat): Likewise.
* sysdeps/unix/sysv/linux/fchmodat.c (fchmodat): Likewise.
* sysdeps/unix/sysv/linux/fcntl.c (do_fcntl): Likewise.
* sysdeps/unix/sysv/linux/fstatfs64.c (__fstatfs64): Likewise.
* sysdeps/unix/sysv/linux/ftruncate64.c (__ftruncate64): Likewise.
* sysdeps/unix/sysv/linux/futimens.c (futimens): Likewise.
* sysdeps/unix/sysv/linux/futimes.c (__futimes): Likewise.
* sysdeps/unix/sysv/linux/futimesat.c (futimesat): Likewise.
* sysdeps/unix/sysv/linux/fxstat.c (__fxstat): Likewise.
* sysdeps/unix/sysv/linux/fxstat64.c (___fxstat64): Likewise.
* sysdeps/unix/sysv/linux/fxstatat.c (__fxstatat): Likewise.
* sysdeps/unix/sysv/linux/fxstatat64.c (__fxstatat64): Likewise.
* sysdeps/unix/sysv/linux/gai_sigqueue.c (__gai_sigqueue):
Likewise.
* sysdeps/unix/sysv/linux/getpriority.c (__getpriority): Likewise.
* sysdeps/unix/sysv/linux/getrlimit64.c (__getrlimit64): Likewise.
* sysdeps/unix/sysv/linux/llseek.c (__llseek): Likewise.
* sysdeps/unix/sysv/linux/lutimes.c (lutimes): Likewise.
* sysdeps/unix/sysv/linux/lxstat.c (__lxstat): Likewise.
* sysdeps/unix/sysv/linux/lxstat64.c (___lxstat64): Likewise.
* sysdeps/unix/sysv/linux/mmap64.c (__mmap64): Likewise.
* sysdeps/unix/sysv/linux/mq_close.c (mq_close): Likewise.
* sysdeps/unix/sysv/linux/mq_open.c (__mq_open): Likewise.
* sysdeps/unix/sysv/linux/mq_unlink.c (mq_unlink): Likewise.
* sysdeps/unix/sysv/linux/msgget.c (msgget): Likewise.
* sysdeps/unix/sysv/linux/prlimit.c (prlimit): Likewise.
* sysdeps/unix/sysv/linux/pt-raise.c (raise): Likewise.
* sysdeps/unix/sysv/linux/raise.c (raise): Likewise.
* sysdeps/unix/sysv/linux/readahead.c (__readahead): Likewise.
* sysdeps/unix/sysv/linux/reboot.c (reboot): Likewise.
* sysdeps/unix/sysv/linux/semget.c (semget): Likewise.
* sysdeps/unix/sysv/linux/semop.c (semop): Likewise.
* sysdeps/unix/sysv/linux/semtimedop.c (semtimedop): Likewise.
* sysdeps/unix/sysv/linux/setrlimit64.c (setrlimit64): Likewise.
* sysdeps/unix/sysv/linux/shmat.c (shmat): Likewise.
* sysdeps/unix/sysv/linux/shmdt.c (shmdt): Likewise.
* sysdeps/unix/sysv/linux/shmget.c (shmget): Likewise.
* sysdeps/unix/sysv/linux/signalfd.c (signalfd): Likewise.
* sysdeps/unix/sysv/linux/sigpending.c (sigpending): Likewise.
* sysdeps/unix/sysv/linux/sigprocmask.c ( __sigprocmask): Likewise.
* sysdeps/unix/sysv/linux/sigqueue.c (__sigqueue): Likewise.
* sysdeps/unix/sysv/linux/speed.c (cfsetospeed): Likewise.
* sysdeps/unix/sysv/linux/statfs64.c (__statfs64): Likewise.
* sysdeps/unix/sysv/linux/sysctl.c (__sysctl): Likewise.
* sysdeps/unix/sysv/linux/tcsendbrk.c (tcsendbreak): Likewise.
* sysdeps/unix/sysv/linux/tcsetattr.c (tcsetattr): Likewise.
* sysdeps/unix/sysv/linux/timer_getoverr.c (timer_getoverrun):
Likewise.
* sysdeps/unix/sysv/linux/timer_gettime.c (timer_gettime):
Likewise.
* sysdeps/unix/sysv/linux/timer_settime.c (timer_settime):
Likewise.
* sysdeps/unix/sysv/linux/truncate64.c (truncate64): Likewise.
* sysdeps/unix/sysv/linux/ustat.c (ustat): Likewise.
* sysdeps/unix/sysv/linux/utimensat.c (utimensat): Likewise.
* sysdeps/unix/sysv/linux/utimes.c (__utimes): Likewise.
* sysdeps/unix/sysv/linux/xmknod.c (__xmknod): Likewise.
* sysdeps/unix/sysv/linux/xmknodat.c (__xmknodat): Likewise.
* sysdeps/unix/sysv/linux/xstat.c (__xstat): Likewise.
* sysdeps/unix/sysv/linux/xstat64.c (___xstat64): Likewise.
* sysdeps/unix/sysv/linux/xstatconv.c (__xstat_conv): Likewise.
(__xstat64_conv): Likewise.
(__xstat32_conv): Likewise.
* sysdeps/unix/sysv/linux/sched_getaffinity.c
(__sched_getaffinity_new): Add libc_hidden_proto and
libc_hidden_def. Use INLINE_SYSCALL_ERROR_RETURN.
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This patch cleans up for __ASSUME_ATFCTS now always being true for the
supported Linux kernel versions by removing conditional code in
sysdeps/unix/sysv/linux. Several fchownat.c files that were only
present because of differences in the fallback syscalls used
(depending on the architecture-specific names of chown-related
syscalls for 32-bit uids) are removed. Files that looks like they
could be replaced by syscalls.list entries have the standard "Consider
moving to syscalls.list." comment (see bug 14138) added. Conditionals
on the relevant __NR_* syscall numbers being defined are also removed,
since my analysis indicated that the relevant syscalls are always
defined for all relevant kernel versions using any affected file.
Much of the removed fallback code had unbounded stack allocations, so
this reduces the number of cases to consider for anyone reviewing uses
of alloca and VLAs in glibc.
There remain tests of __ASSUME_ATFCTS in io/openat.c (to determine
whether to define __have_atfcts) and sysdeps/posix/getcwd.c (which
also uses __have_atfcts); thus, the definition of __ASSUME_ATFCTS
remains in kernel-features.h. The logical condition relevant there is
whether openat64_not_cancel_3 is known to work. Hurd doesn't use this
version of getcwd at all, so the conditionals in getcwd.c are always
true in glibc. However, this code is also used in gnulib. So the
best way to deal with the conditionals there may be for gnulib people
to deal with merging all relevant changes in both directions between
the glibc and gnulib versions of this file, at the end of which the
openat conditionals should be in whatever form is best for gnulib, and
hardcoded in the _LIBC case to having openat supported.
Tested by comparing before-and-after disassembly of installed
(stripped) shared libraries, on x86_64 and x86. On x86 the patch made
no change to the disassembly; on x86_64, the only changes were in
readlinkat, where formerly the return value from the readlinkat
syscall was stored in an int variable before being converted to
ssize_t for the return, and now the return value is returned directly
without truncation to int. I think it's clearly correct not to
truncate the return value (although I also think the truncation would
not have been a user-visible bug because the kernel would never have
returned a value it could have affected).
* include/fcntl.h (__atfct_seterrno): Remove prototype.
(__atfct_seterrno_2): Likewise.
* sysdeps/unix/sysv/linux/alpha/dl-fxstatat64.c: Do not include
<kernel-features.h>.
(__ASSUME_ATFCTS): Do not undefine and redefine.
* sysdeps/unix/sysv/linux/alpha/fxstatat.c [__ASSUME_ATFCTS]
(__have_atfcts): Remove conditional definition.
(__fxstatat([__NR_fstatat64]: Make code unconditional.
(__fxstatat) [!__ASSUME_ATFCTS]: Remove conditional code and code
unreachable if [__ASSUME_ATFCTS].
* sysdeps/unix/sysv/linux/dl-fxstatat64.c (__ASSUME_ATFCTS): Do
not undefine and redefine.
* sysdeps/unix/sysv/linux/faccessat.c: Do not include
<kernel-features.h>.
(faccessat) [__NR_faccessat]: Make code unconditional.
(faccessat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/fchmodat.c: Do not include
<kernel-features.h>.
(fchmodat) [__NR_fchmodat]: Make code unconditional.
(fchmodat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/fchownat.c: Do not include
<kernel-features.h>.
(fchownat) [__NR_fchownat]: Make code unconditional.
(fchownat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/futimesat.c: Do not include
<kernel-features.h>.
(futimesat) [__NR_futimesat]: Make code unconditional.
(futimesat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/fxstatat.c: Do not include
<kernel-features.h>.
(__fxstatat) [__NR_newfstatat]: Make code unconditional.
(__fxstatat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/fxstatat64.c: Do not include
<kernel-features.h>.
(__fxstatat64) [__NR_fstatat64]: Make code unconditional.
(__fxstatat64) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/i386/fchownat.c: Remove file.
* sysdeps/unix/sysv/linux/i386/fxstatat.c: Do not include
<kernel-features.h>.
(__fxstatat) [__NR_fstatat64]: Make code unconditional.
(__fxstatat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/linkat.c: Do not include
<kernel-features.h>.
(linkat) [__NR_linkat]: Make code unconditional.
(linkat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/m68k/fchownat.c: Remove file.
* sysdeps/unix/sysv/linux/mips/mips64/fxstatat64.c: Do not include
<kernel-features.h>.
(__fxstatat64) [__NR_newfstatat]: Make code unconditional.
(__fxstatat64) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/mkdirat.c: Do not include
<kernel-features.h>.
(mkdirat) [__NR_mkdirat]: Make code unconditional.
(mkdirat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/openat.c: Do not include
<kernel-features.h>.
[!__ASSUME_ATFCTS] (__atfct_seterrno): Remove function.
[!__ASSUME_ATFCTS] (__have_atfcts): Remove variable.
(OPENAT_NOT_CANCEL) [__NR_openat]: Make code unconditional.
(OPENAT_NOT_CANCEL) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/powerpc/fchownat.c: Remove file.
* sysdeps/unix/sysv/linux/readlinkat.c: Do not include
<kernel-features.h>.
(readlinkat) [__NR_readlinkat]: Make code unconditional.
(readlinkat) [!__ASSUME_ATFCTS]: Remove conditional code. Return
result of INLINE_SYSCALL directly, not via int variable.
* sysdeps/unix/sysv/linux/renameat.c: Do not include
<kernel-features.h>.
[!__ASSUME_ATFCTS] (__atfct_seterrno_2): Remove function.
(renameat) [__NR_renameat]: Make code unconditional.
(renameat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/s390/s390-32/fchownat.c: Remove file.
* sysdeps/unix/sysv/linux/sh/fchownat.c: Remove file.
* sysdeps/unix/sysv/linux/sparc/sparc32/fchownat.c: Remove file.
* sysdeps/unix/sysv/linux/sparc/sparc64/dl-fxstatat64.c
(__ASSUME_ATFCTS): Do not undefine and redefine.
* sysdeps/unix/sysv/linux/symlinkat.c: Do not include
<kernel-features.h>.
(symlinkat) [__NR_symlinkat]: Make code unconditional.
(symlinkat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/unlinkat.c: Do not include
<kernel-features.h>.
(unlinkat) [__NR_unlinkat]: Make code unconditional.
(unlinkat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/wordsize-64/dl-fxstatat64.c
(__ASSUME_ATFCTS): Do not undefine and redefine.
* sysdeps/unix/sysv/linux/wordsize-64/fxstatat.c: Do not include
<kernel-features.h>.
(__fxstatat) [__NR_newfstatat]: Make code unconditional.
(__fxstatat) [!__ASSUME_ATFCTS]: Remove conditional code.
* sysdeps/unix/sysv/linux/xmknodat.c: Do not include
<kernel-features.h>.
(__xmknodat) [__NR_mknodat]: Make code unconditional.
(__xmknodat) [!__ASSUME_ATFCTS]: Remove conditional code.
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