glibc/sysdeps/unix/sysv/linux/openat64.c

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Avoid cancellable I/O primitives in ld.so. Neither the <dlfcn.h> entry points, nor lazy symbol resolution, nor initial shared library load-up, are cancellation points, so ld.so should exclusively use I/O primitives that are not cancellable. We currently achieve this by having the cancellation hooks compile as no-ops when IS_IN(rtld); this patch changes to using exclusively _nocancel primitives in the source code instead, which makes the intent clearer and significantly reduces the amount of code compiled under IS_IN(rtld) as well as IS_IN(libc) -- in particular, elf/Makefile no longer thinks we require a copy of unwind.c in rtld-libc.a. (The older mechanism is preserved as a backstop.) The bulk of the change is splitting up the files that define the _nocancel I/O functions, so they don't also define the variants that *are* cancellation points; after which, the existing logic for picking out the bits of libc that need to be recompiled as part of ld.so Just Works. I did this for all of the _nocancel functions, not just the ones used by ld.so, for consistency. fcntl was a little tricky because it's only a cancellation point for certain opcodes (F_SETLKW(64), which can block), and the existing __fcntl_nocancel wasn't applying the FCNTL_ADJUST_CMD hook, which strikes me as asking for trouble, especially as the only nontrivial definition of FCNTL_ADJUST_CMD (for powerpc64) changes F_*LK* opcodes. To fix this, fcntl_common moves to fcntl_nocancel.c along with __fcntl_nocancel, and changes its name to the extern (but hidden) symbol __fcntl_nocancel_adjusted, so that regular fcntl can continue calling it. __fcntl_nocancel now applies FCNTL_ADJUST_CMD; so that both both fcntl.c and fcntl_nocancel.c can see it, the only nontrivial definition moves from sysdeps/u/s/l/powerpc/powerpc64/fcntl.c to .../powerpc64/sysdep.h and becomes entirely a macro, instead of a macro that calls an inline function. The nptl version of libpthread also changes a little, because its "compat-routines" formerly included files that defined all the _nocancel functions it uses; instead of continuing to duplicate them, I exported the relevant ones from libc.so as GLIBC_PRIVATE. Since the Linux fcntl.c calls a function defined by fcntl_nocancel.c, it can no longer be used from libpthread.so; instead, introduce a custom forwarder, pt-fcntl.c, and export __libc_fcntl from libc.so as GLIBC_PRIVATE. The nios2-linux ABI doesn't include a copy of vfork() in libpthread, and it was handling that by manipulating libpthread-routines in .../linux/nios2/Makefile; it is cleaner to do what other such ports do, and have a pt-vfork.S that defines no symbols. Right now, it appears that Hurd does not implement _nocancel I/O, so sysdeps/generic/not-cancel.h will forward everything back to the regular functions. This changed the names of some of the functions that sysdeps/mach/hurd/dl-sysdep.c needs to interpose. * elf/dl-load.c, elf/dl-misc.c, elf/dl-profile.c, elf/rtld.c * sysdeps/unix/sysv/linux/dl-sysdep.c Include not-cancel.h. Use __close_nocancel instead of __close, __open64_nocancel instead of __open, __read_nocancel instead of __libc_read, and __write_nocancel instead of __libc_write. * csu/check_fds.c (check_one_fd) * sysdeps/posix/fdopendir.c (__fdopendir) * sysdeps/posix/opendir.c (__alloc_dir): Use __fcntl_nocancel instead of __fcntl and/or __libc_fcntl. * sysdeps/unix/sysv/linux/pthread_setname.c (pthread_setname_np) * sysdeps/unix/sysv/linux/pthread_getname.c (pthread_getname_np) * sysdeps/unix/sysv/linux/i386/smp.h (is_smp_system): Use __open64_nocancel instead of __open_nocancel. * sysdeps/unix/sysv/linux/not-cancel.h: Move all of the hidden_proto declarations to the end and issue them if either IS_IN(libc) or IS_IN(rtld). * sysdeps/unix/sysv/linux/Makefile [subdir=io] (sysdep_routines): Add close_nocancel, fcntl_nocancel, nanosleep_nocancel, open_nocancel, open64_nocancel, openat_nocancel, pause_nocancel, read_nocancel, waitpid_nocancel, write_nocancel. * io/Versions [GLIBC_PRIVATE]: Add __libc_fcntl, __fcntl_nocancel, __open64_nocancel, __write_nocancel. * posix/Versions: Add __nanosleep_nocancel, __pause_nocancel. * nptl/pt-fcntl.c: New file. * nptl/Makefile (pthread-compat-wrappers): Remove fcntl. (libpthread-routines): Add pt-fcntl. * include/fcntl.h (__fcntl_nocancel_adjusted): New function. (__libc_fcntl): Remove attribute_hidden. * sysdeps/unix/sysv/linux/fcntl.c (__libc_fcntl): Call __fcntl_nocancel_adjusted, not fcntl_common. (__fcntl_nocancel): Move to new file fcntl_nocancel.c. (fcntl_common): Rename to __fcntl_nocancel_adjusted; also move to fcntl_nocancel.c. * sysdeps/unix/sysv/linux/fcntl_nocancel.c: New file. * sysdeps/unix/sysv/linux/powerpc/powerpc64/fcntl.c: Remove file. * sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h: Define FCNTL_ADJUST_CMD here, as a self-contained macro. * sysdeps/unix/sysv/linux/close.c: Move __close_nocancel to... * sysdeps/unix/sysv/linux/close_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/nanosleep.c: Move __nanosleep_nocancel to... * sysdeps/unix/sysv/linux/nanosleep_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/open.c: Move __open_nocancel to... * sysdeps/unix/sysv/linux/open_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/open64.c: Move __open64_nocancel to... * sysdeps/unix/sysv/linux/open64_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/openat.c: Move __openat_nocancel to... * sysdeps/unix/sysv/linux/openat_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/openat64.c: Move __openat64_nocancel to... * sysdeps/unix/sysv/linux/openat64_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/pause.c: Move __pause_nocancel to... * sysdeps/unix/sysv/linux/pause_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/read.c: Move __read_nocancel to... * sysdeps/unix/sysv/linux/read_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/waitpid.c: Move __waitpid_nocancel to... * sysdeps/unix/sysv/linux/waitpid_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/write.c: Move __write_nocancel to... * sysdeps/unix/sysv/linux/write_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/nios2/Makefile: Don't override libpthread-routines. * sysdeps/unix/sysv/linux/nios2/pt-vfork.S: New file which defines nothing. * sysdeps/mach/hurd/dl-sysdep.c: Define __read instead of __libc_read, and __write instead of __libc_write. Define __open64 in addition to __open.
2018-04-03 22:26:44 +00:00
/* Linux openat syscall implementation, LFS.
Copyright (C) 2007-2019 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 <fcntl.h>
#include <stdarg.h>
#include <sysdep-cancel.h>
#ifdef __OFF_T_MATCHES_OFF64_T
# define EXTRA_OPEN_FLAGS 0
#else
# define EXTRA_OPEN_FLAGS O_LARGEFILE
#endif
/* Open FILE with access OFLAG. Interpret relative paths relative to
the directory associated with FD. If OFLAG includes O_CREAT or
O_TMPFILE, a fourth argument is the file protection. */
int
__libc_openat64 (int fd, const char *file, int oflag, ...)
{
mode_t mode = 0;
if (__OPEN_NEEDS_MODE (oflag))
{
va_list arg;
va_start (arg, oflag);
mode = va_arg (arg, mode_t);
va_end (arg);
}
return SYSCALL_CANCEL (openat, fd, file, oflag | EXTRA_OPEN_FLAGS, mode);
}
strong_alias (__libc_openat64, __openat64)
libc_hidden_weak (__openat64)
weak_alias (__libc_openat64, openat64)
#ifdef __OFF_T_MATCHES_OFF64_T
strong_alias (__libc_openat64, __openat)
libc_hidden_weak (__openat)
weak_alias (__libc_openat64, openat)
#endif