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>
The recent difftime changes introduced localplt test failures on nios2
and sparc32, two configurations where some soft-fp functions are
defined in / exported from libc.so, and where the difftime changes
affected the particular set of floating-point operations used in
libc.so. This patch adds those functions to localplt.data, alongside
other such functions already there. (In the sparc32 case, and more
generally on any platform where long double is a software
floating-point type, it would probably be more efficient to avoid
using long double at all in difftime, but that's a pre-existing
issue.)
Tested with build-many-glibcs.py for its nios2 and sparcv9
configurations.
[BZ #24023]
* sysdeps/unix/sysv/linux/nios2/localplt.data: Allow __floatundidf
PLT reference in libc.so.
* sysdeps/unix/sysv/linux/sparc/sparc32/localplt.data: Allow
_Q_lltoq and _Q_qtod PLT references in libc.so.
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.
A recent GCC change to expand floating-point classification built-in
functions inline using integer rather than floating-point arithmetic
in some cases resulted in localplt test failures for nios2 and sparc32
<https://sourceware.org/ml/libc-testresults/2017-q2/msg00320.html>.
This patch updates the localplt.data files in question to mark the
relevant symbols as optional / add a new optional symbol. (The GCC
patch has been reverted because of other problems it caused, but one
can assume it will be applied again, without changes that would affect
the PLT entries generated, once those issues have been resolved.)
Tested with build-many-glibcs.py.
* sysdeps/unix/sysv/linux/nios2/localplt.data (__gtdf2): Mark
libc.so PLT entry optional.
(__gtsf2): Likewise.
(__unorddf2): Likewise.
(__unordsf2): Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/localplt.data (_Q_fgt):
New optional libc.so PLT entry.
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.
For maximum paranoia we run ld.so through the normal set
of tests for all of the shared libraries. This includes
running ld.so through check-localplt, check-textrel, and
check-execstack. While none of these should trigger any
failures given the way ld.so is built, it might possibly
fail if a developer does something wrong. This paranoia
was triggered by a discussion over the use of __strcpy
vs. strcpy [1] and if the symbol could leak and use the
libc.so version.
The check-localplt test fails right away because localplt.data
needs updating for all arches. By default we add 6 new symbols:
__tls_get_addr, __libc_memalign, malloc, calloc, realloc and
free. Other machines like i386, power, and s390 require some
different symbol sets e.g. ___tls_get_addr vs. __tls_get_addr
for i386.
Verified for i386
Verified for x86_64
Verified for ppc32
Verified for ppc64
Verified for ppc64le
Verified for arm
Verified for aarch64
Verified for s390
Verified for s390x
Guessed for alpha
Guessed for ia64
Guessed for m68k
Guessed for microblaze
Guessed for sparc32
Guessed for sparc64
Defaults for sh
Defaults for mips
Defaults for hppa
Defaults for tile
Machine manintainers notified to double check the data
used in localplt.data.
[1] https://sourceware.org/ml/libc-alpha/2014-10/msg00548.html
