glibc/io/Versions
Zack Weinberg 329ea513b4 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.
2018-06-12 09:53:04 -04:00

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libc {
GLIBC_2.0 {
# functions used in inline functions or macros
__xstat; __fxstat; __lxstat; __xmknod; __write; __close; __fcntl;
__lseek; __open; __read;
# functions used by libstdc++ 2.7.2
__dup2; __pipe;
# a*
access;
# c*
chdir; chmod; chown; close; creat;
# d*
dup; dup2;
# e*
euidaccess;
# f*
fchdir; fchmod; fchown; fcntl; flock; fstatfs; fts_children; fts_close;
fts_open; fts_read; fts_set; ftw;
# g*
get_current_dir_name; getcwd; getwd;
# i*
isatty;
# l*
lchown; link; lockf; lseek;
# m*
mkdir; mkfifo;
# o*
open;
# p*
pipe; poll;
# r*
read; readlink; rmdir;
# s*
statfs; symlink;
# t*
ttyname; ttyname_r;
# u*
umask; unlink; utime;
# w*
write;
}
GLIBC_2.1 {
# functions used in other libraries
__xstat64; __fxstat64; __lxstat64; __poll;
# c*
creat64;
# f*
fstatfs64; fstatvfs; fstatvfs64; ftw64;
# l*
lockf64; lseek64;
# n*
nftw; nftw64;
# o*
open64;
# s*
sendfile;
statfs64; statvfs; statvfs64;
}
GLIBC_2.2 {
# p*
posix_fadvise; posix_fadvise64; posix_fallocate; posix_fallocate64;
__open64;
}
GLIBC_2.3 {
# s*
sendfile64;
}
GLIBC_2.3.2 {
# l*
lchmod;
}
GLIBC_2.3.3 {
# n*
nftw; nftw64;
}
GLIBC_2.4 {
eaccess;
faccessat;
fchmodat;
fchownat;
__fxstatat; __fxstatat64;
linkat;
mkdirat; mkfifoat; __xmknodat;
openat; openat64;
readlinkat;
symlinkat;
unlinkat;
ppoll;
}
GLIBC_2.6 {
utimensat; futimens;
}
GLIBC_2.7 {
__open_2; __open64_2; __openat_2; __openat64_2;
}
GLIBC_2.9 {
dup3; pipe2;
}
GLIBC_2.23 {
fts64_children; fts64_close; fts64_open; fts64_read; fts64_set;
}
GLIBC_2.27 {
copy_file_range;
}
GLIBC_PRIVATE {
__libc_fcntl;
__fcntl_nocancel;
__open64_nocancel;
__write_nocancel;
}
}