Exporting functions and relying on symbol interposition from libc.so
makes the choice of implementation dependent on DT_NEEDED order, which
is not what some compiler drivers expect.
This commit replaces one magic mechanism (symbol interposition) with
another one (preprocessor-/compiler-based redirection). This makes
the hand-over from the minimal malloc to the full malloc more
explicit.
Removing the ABI symbols is backwards-compatible because libc.so is
always in scope, and the dynamic loader will find the malloc-related
symbols there since commit f0b2132b35
("ld.so: Support moving versioned symbols between sonames
[BZ #24741]").
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
With commit f0b2132b35 ("ld.so:
Support moving versioned symbols between sonames [BZ #24741]"), the
dynamic linker will find the definition of vfork in libc and binds
a vfork reference to that symbol, even if the soname in the version
reference says that the symbol should be located in libpthread.
As a result, the forwarder (whether it's IFUNC-based or a duplicate
of the libc implementation) is no longer necessary.
On older architectures, a placeholder symbol is required, to make sure
that the GLIBC_2.1.2 symbol version does not go away, or is turned in
to a weak symbol definition by the link editor. (The symbol version
needs to preserved so that the symbol coverage check in
elf/dl-version.c does not fail for old binaries.)
mips32 is an outlier: It defined __vfork@@GLIBC_2.2, but the
baseline is GLIBC_2.0. Since there are other @@GLIBC_2.2 symbols,
the placeholder symbol is not needed there.
When adding/updating localplt.data for various architectures to get
the compilation tests passing everywhere, I generally made it reflect
the existing state of what local PLT entries were actually seen,
rather than an ideal state with as few as possible such entries,
mainly for functions that are intended to be interposable.
This patch eliminates some local PLT entries for hppa by using
__sigprocmask instead of sigprocmask in getcontext and setcontext.
The specific case of sigprocmask called by setcontext is the third of
four items in bug 18124 (the other three have already been fixed for
2.26 or earlier releases). Note that hppa-specific localplt.data
entries for __sigsetjmp, _IO_funlockfile and __errno_location remain,
but the causes / fixes are less immediately obvious from source
inspection.
Tested (compilation tests only) with build-many-glibcs.py for
hppa-linux-gnu.
[BZ #18124]
* sysdeps/hppa/bsd-setjmp.S: Include <sysdep.h>.
(setjmp): Use HIDDEN_JUMPTARGET with __sigsetjmp.
* sysdeps/unix/sysv/linux/hppa/getcontext.S (__getcontext): Call
__sigprocmask instead of sigprocmask.
* sysdeps/unix/sysv/linux/hppa/setcontext.S (__setcontext):
Likewise.
* sysdeps/unix/sysv/linux/hppa/localplt.data: Remove entries for
__sigsetjmp and sigprocmask.
This commit separates allocating and raising exceptions. This
simplifies catching and re-raising them because it is no longer
necessary to make a temporary, on-stack copy of the exception message.
It is no longer needed since commit 6c444ad6e9
(elf: Do not use memalign for TCB/TLS blocks allocation [BZ #17730]).
Applications do not link against ld.so and will use the definition in
libc.so, so there is no ABI impact.
This change moves the main implementation of _dl_catch_error,
_dl_signal_error to libc.so, where TLS variables can be used
directly. This removes a writable function pointer from the
rtld_global variable.
For use during initial relocation, minimal implementations of these
functions are provided in ld.so. These are eventually interposed
by the libc.so implementations. This is implemented by compiling
elf/dl-error-skeleton.c twice, via elf/dl-error.c and
elf/dl-error-minimal.c.
As a side effect of this change, the static version of dl-error.c
no longer includes support for the
_dl_signal_cerror/_dl_receive_error mechanism because it is only
used in ld.so.
This patch adds a localplt.data file for hppa so that test passes.
Architecture maintainers should feel free to clean up the sysdeps code
so that some or all of the system-specific entries
libc.so: _exit
libc.so: __sigsetjmp
libc.so: _IO_funlockfile
libc.so: sigprocmask
libc.so: __errno_location
libpthread.so: __errno_location
are no longer needed.
Tested for hppa. Note: check-execstack and check-textrel still fail;
you may wish to look at those to get to a clean baseline there (they
are less obvious for people not familiar with the architecture).
* sysdeps/unix/sysv/linux/hppa/localplt.data: New file.
