In r326576 ("use @@@ instead of @@ in __sym_default"), an earlier version of
the phabricator-discussed patch was inadvertently committed. The commit
message claims that @@@ means that weak is not needed, but that was due to a
misunderstanding of the use of weak symbols in this context by the submitted
in the first draft of the patch; the description text was not updated to
match the discussion. As discussed in phabricator, weak is needed for
symbol interposing because of the behavior of our rtld, and is widely used
elsewhere in libc.
This partial revert restores the approved version of the patch and permits
symbol interposing for openat.
Reported by: Raymond Ramsden <rramsden AT isilon.com>
Reviewed by: dim, emaste, kib (2017)
Discussed with: kib (2020)
Differential Revision: https://reviews.freebsd.org/D11653
Using
.symver foo,foo@@VER
causes foo and foo@@VER to be output to the .o file. This requires foo
to be weak since the linker handles foo@@VER as foo.
Using
.symver foo,foo@@@VER
causes just foo@@ver to be output and avoid the need for making foo
weak. It also reduces the constraint on how exactly a linker has to
handle foo and foo@@VER being present.
Submitted by: Rafael Espíndola
Reviewed by: dim, kib
Differential Revision: https://reviews.freebsd.org/D11653
(or loading a dso linked to libthr.so into process which was not
linked against threading library).
- Remove libthr interposers of the libc functions, including
__error(). Instead, functions calls are indirected through the
interposing table, similar to how pthread stubs in libc are already
done. Libc by default points either to syscall trampolines or to
existing libc implementations. On libthr load, libthr rewrites the
pointers to the cancellable implementations already in libthr. The
interposition table is separate from pthreads stubs indirection
table to not pull pthreads stubs into static binaries.
- Postpone the malloc(3) internal mutexes initialization until libthr
is loaded. This avoids recursion between calloc(3) and static
pthread_mutex_t initialization.
- Reinstall signal handlers with wrapper on libthr load. The
_rtld_is_dlopened(3) is used to avoid useless calls to sigaction(2)
when libthr is statically referenced from the main binary.
In the process, fix openat(2), swapcontext(2) and setcontext(2)
interposing. The libc symbols were exported at different versions
than libthr interposers. Export both libc and libthr versions from
libc now, with default set to the higher version from libthr.
Remove unused and disconnected swapcontext(3) userspace implementation
from libc/gen.
No objections from: deischen
Tested by: pho, antoine (exp-run) (previous versions)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
