Commit Graph

2654 Commits

Author SHA1 Message Date
H.J. Lu
a93d9e03a3 Extend struct r_debug to support multiple namespaces [BZ #15971]
Glibc does not provide an interface for debugger to access libraries
loaded in multiple namespaces via dlmopen.

The current rtld-debugger interface is described in the file:

elf/rtld-debugger-interface.txt

under the "Standard debugger interface" heading.  This interface only
provides access to the first link-map (LM_ID_BASE).

1. Bump r_version to 2 when multiple namespaces are used.  This triggers
the GDB bug:

https://sourceware.org/bugzilla/show_bug.cgi?id=28236

2. Add struct r_debug_extended to extend struct r_debug into a linked-list,
where each element correlates to an unique namespace.
3. Initialize the r_debug_extended structure.  Bump r_version to 2 for
the new namespace and add the new namespace to the namespace linked list.
4. Add _dl_debug_update to return the address of struct r_debug' of a
namespace.
5. Add a hidden symbol, _r_debug_extended, for struct r_debug_extended.
6. Provide the symbol, _r_debug, with size of struct r_debug, as an alias
of _r_debug_extended, for programs which reference _r_debug.

This fixes BZ #15971.

Reviewed-by: Florian Weimer <fweimer@redhat.com>
2021-09-19 13:51:35 -07:00
Sergey Bugaev
c484da9087 elf: Remove THREAD_GSCOPE_IN_TCB
All the ports now have THREAD_GSCOPE_IN_TCB set to 1. Remove all
support for !THREAD_GSCOPE_IN_TCB, along with the definition itself.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20210915171110.226187-4-bugaevc@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
2021-09-16 01:04:20 +02:00
Sergey Bugaev
520a588705 elf: Replace most uses of THREAD_GSCOPE_IN_TCB
While originally this definition was indeed used to distinguish between
the cases where the GSCOPE flag was stored in TCB or not, it has since
become used as a general way to distinguish between HTL and NPTL.

THREAD_GSCOPE_IN_TCB will be removed in the following commits, as HTL,
which currently is the only port that does not put the flag into TCB,
will get ported to put the GSCOPE flag into the TCB as well. To prepare
for that change, migrate all code that wants to distinguish between HTL
and NPTL to use PTHREAD_IN_LIBC instead, which is a better choice since
the distinction mostly has to do with whether libc has access to the
list of thread structures and therefore can initialize thread-local
storage.

The parts of code that actually depend on whether the GSCOPE flag is in
TCB are left unchanged.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20210907133325.255690-2-bugaevc@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
2021-09-15 01:29:23 +02:00
Siddhesh Poyarekar
30891f35fa Remove "Contributed by" lines
We stopped adding "Contributed by" or similar lines in sources in 2012
in favour of git logs and keeping the Contributors section of the
glibc manual up to date.  Removing these lines makes the license
header a bit more consistent across files and also removes the
possibility of error in attribution when license blocks or files are
copied across since the contributed-by lines don't actually reflect
reality in those cases.

Move all "Contributed by" and similar lines (Written by, Test by,
etc.) into a new file CONTRIBUTED-BY to retain record of these
contributions.  These contributors are also mentioned in
manual/contrib.texi, so we just maintain this additional record as a
courtesy to the earlier developers.

The following scripts were used to filter a list of files to edit in
place and to clean up the CONTRIBUTED-BY file respectively.  These
were not added to the glibc sources because they're not expected to be
of any use in future given that this is a one time task:

https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc
https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-09-03 22:06:44 +05:30
Fangrui Song
9926f6e2ee elf: Skip tst-auditlogmod-* if the linker doesn't support --depaudit [BZ #28151]
gold and ld.lld do not support --audit or --depaudit.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-08-24 09:35:32 -07:00
Andreas Schwab
a4f5a3103f rtld: copy terminating null in tunables_strdup (bug 28256)
Avoid triggering a false positive from valgrind by copying the terminating
null in tunables_strdup.  At this point the heap is still clean, but
valgrind is stricter here.
2021-08-23 15:31:09 +02:00
Arjun Shankar
82fbcd7118 elf: Fix missing colon in LD_SHOW_AUXV output [BZ #28253]
This commit adds a missing colon in the AT_MINSIGSTKSZ entry in
the _dl_show_auxv function.
2021-08-20 16:29:43 +02:00
Fangrui Song
33c50ef428 elf: Drop elf/tls-macros.h in favor of __thread and tls_model attributes [BZ #28152] [BZ #28205]
elf/tls-macros.h was added for TLS testing when GCC did not support
__thread. __thread and tls_model attributes are mature now and have been
used by many newer tests.

Also delete tst-tls2.c which tests .tls_common (unused by modern GCC and
unsupported by Clang/LLD). .tls_common and .tbss definition are almost
identical after linking, so the runtime test doesn't add additional
coverage.  Assembler and linker tests should be on the binutils side.

When LLD 13.0.0 is allowed in configure.ac
(https://sourceware.org/pipermail/libc-alpha/2021-August/129866.html),
`make check` result is on par with glibc built with GNU ld on aarch64
and x86_64.

As a future clean-up, TLS_GD/TLS_LD/TLS_IE/TLS_IE macros can be removed from
sysdeps/*/tls-macros.h. We can add optional -mtls-dialect={gnu2,trad}
tests to ensure coverage.

Tested on aarch64-linux-gnu, powerpc64le-linux-gnu, and x86_64-linux-gnu.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
2021-08-16 09:59:30 -07:00
Fangrui Song
302247c891 elf: Unconditionally use __ehdr_start
We can consider __ehdr_start (from binutils 2.23 onwards)
unconditionally supported, since configure.ac requires binutils>=2.25.

The configure.ac check is related to an ia64 bug fixed by binutils 2.24.
See https://sourceware.org/pipermail/libc-alpha/2014-August/053503.html

Tested on x86_64-linux-gnu. Tested build-many-glibcs.py with
aarch64-linux-gnu and s390x-linux-gnu.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
2021-08-10 11:04:56 -07:00
Siddhesh Poyarekar
b0234d79e7 ldconfig: avoid leak on empty paths in config file
Reviewed-by: Arjun Shankar <arjun@redhat.com>
2021-08-03 21:10:10 +05:30
Adhemerval Zanella
3908fa933a elf: Fix audit regression
Commit 03e187a41d added a regression when an audit module does not have
libc as DT_NEEDED (although unusual it is possible).

Checked on x86_64-linux-gnu.
2021-07-30 16:01:44 -03:00
Siddhesh Poyarekar
2d2d9f2b48 Move malloc hooks into a compat DSO
Remove all malloc hook uses from core malloc functions and move it
into a new library libc_malloc_debug.so.  With this, the hooks now no
longer have any effect on the core library.

libc_malloc_debug.so is a malloc interposer that needs to be preloaded
to get hooks functionality back so that the debugging features that
depend on the hooks, i.e. malloc-check, mcheck and mtrace work again.
Without the preloaded DSO these debugging features will be nops.
These features will be ported away from hooks in subsequent patches.

Similarly, legacy applications that need hooks functionality need to
preload libc_malloc_debug.so.

The symbols exported by libc_malloc_debug.so are maintained at exactly
the same version as libc.so.

Finally, static binaries will no longer be able to use malloc
debugging features since they cannot preload the debugging DSO.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
2021-07-22 18:37:59 +05:30
Adhemerval Zanella
881b68e45c elf: Fix a wrong array access on tst-tls20
Check on x86_64-linux-gnu with --enable-stack-protector=all.
2021-07-16 08:32:37 -03:00
Adhemerval Zanella
3a0253ac6f elf: Add -Wl,--no-as-needed for tst-tls-manydynamic*mod-dep-bad.so (BZ #28089)
The tests explicit requires the dependencies and it is required for
the case the toolchain defaults to -Wl,--as-needed.

Checked on x86_64-linux-gnu.
2021-07-15 08:18:21 -03:00
Adhemerval Zanella
ba33937be2 elf: Fix DTV gap reuse logic (BZ #27135)
This is updated version of the 572bd547d5 (reverted by 40ebfd016a)
that fixes the _dl_next_tls_modid issues.

This issue with 572bd547d5 patch is the DTV entry will be only
update on dl_open_worker() with the update_tls_slotinfo() call after
all dependencies are being processed by _dl_map_object_deps().  However
_dl_map_object_deps() itself might call _dl_next_tls_modid(), and since
the _dl_tls_dtv_slotinfo_list::map is not yet set the entry will be
wrongly reused.

This patch fixes by renaming the _dl_next_tls_modid() function to
_dl_assign_tls_modid() and by passing the link_map so it can set
the slotinfo value so a subsequente _dl_next_tls_modid() call will
see the entry as allocated.

The intermediary value is cleared up on remove_slotinfo() for the case
a library fails to load with RTLD_NOW.

This patch fixes BZ #27135.

Checked on x86_64-linux-gnu.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
2021-07-14 15:10:27 -03:00
Florian Weimer
7c241325d6 Force building with -fno-common
As a result, is not necessary to specify __attribute__ ((nocommon))
on individual definitions.

GCC 10 defaults to -fno-common on all architectures except ARC,
but this change is compatible with older GCC versions and ARC, too.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-07-09 20:09:14 +02:00
Joseph Myers
bba4383c6b Add NT_ARM_PAC_ENABLED_KEYS to elf.h
This patch adds the new NT_ARM_PAC_ENABLED_KEYS constant from Linux
5.13 to glibc's elf.h.

Tested for x86_64.
2021-07-08 17:36:27 +00:00
Siddhesh Poyarekar
5ceb1630bd elf/tests: Make thrlock and noload depend on libm
Both tests try to dlopen libm.so at runtime, so make them depend on it
so that they're executed if libm.so has been updated.

Reviewed-by: Florian Weimer <fweimer@redhat.com>
2021-07-08 13:39:19 +05:30
Florian Weimer
7a5db2e82f elf: Clean up GLIBC_PRIVATE exports of internal libdl symbols
They are no longer needed after everything has been moved into
libc.  The _dl_vsym test has to be removed because the symbol
cannot be used outside libc anymore.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-07-07 08:41:24 +02:00
Florian Weimer
832f50be6c elf: Call free from base namespace on error in dl-libc.c [BZ #27646]
In dlerror_run, free corresponds to the local malloc in the
namespace, but GLRO (dl_catch_error) uses the malloc from the base
namespace.  elf/tst-dlmopen-gethostbyname triggers this mismatch,
but it does not crash, presumably because of a fastbin deallocation.

Fixes commit c2059edce2 ("elf: Use
_dl_catch_error from base namespace in dl-libc.c [BZ #27646]") and
commit b2964eb1d9 ("dlfcn: Failures
after dlmopen should not terminate process [BZ #24772]").
2021-07-06 14:30:33 +02:00
Florian Weimer
30639e79d3 Linux: Cleanups after librt move
librt.so is no longer installed for PTHREAD_IN_LIBC, and tests
are not linked against it.  $(librt) is introduced globally for
shared tests that need to be linked for both PTHREAD_IN_LIBC
and !PTHREAD_IN_LIBC.

GLIBC_PRIVATE symbols that were needed during the transition are
removed again.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-06-28 09:51:01 +02:00
Florian Weimer
8208be389b Install shared objects under their ABI names
Previously, the installed objects were named like libc-2.33.so,
and the ABI soname libc.so.6 was just a symbolic link.

The Makefile targets to install these symbolic links are no longer
needed after this, so they are removed with this commit.  The more
general $(make-link) command (which invokes scripts/rellns-sh) is
retained because other symbolic links are still needed.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@rehdat.com>
2021-06-28 08:33:57 +02:00
Florian Weimer
6bf789d69e elf: Generalize name-based DSO recognition in ldconfig
This introduces <dl-is_dso.h> and the _dl_is_dso function.  A
test ensures that the official names of libc.so, ld.so, and their
versioned names are recognized.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
2021-06-28 08:33:57 +02:00
Florian Weimer
40ebfd016a elf: Disable most of TLS modid gaps processing [BZ #27135]
Revert "elf: Fix DTV gap reuse logic [BZ #27135]"

This reverts commit 572bd547d5.

It turns out that the _dl_next_tls_modid in _dl_map_object_from_fd keeps
returning the same modid over and over again if there is a gap and
more than TLS-using module is loaded in one dlopen call.  This corrupts
TLS data structures.  The bug is still present after a revert, but
empirically it is much more difficult to trigger (because it involves a
dlopen failure).
2021-06-25 08:09:08 +02:00
Florian Weimer
66db95b6e8 elf: Fix glibc-hwcaps priorities with cache flags mismatches [BZ #27046]
If lib->flags (in the cache) did not match GLRO (dl_correct_cache_id),
searching for further glibc-hwcaps entries did not happen, and it
was possible that the best glibc-hwcaps was not found.  By accident,
this causes a test failure for elf/tst-glibc-hwcaps-prepend-cache
on armv7l.

This commit changes the cache lookup logic to continue searching
if (a) no match has been found, (b) a named glibc-hwcaps match
has been found(), or (c) non-glibc-hwcaps match has been found
and the entry flags and cache default flags do not match.

_DL_CACHE_DEFAULT_ID is used instead of GLRO (dl_correct_cache_id)
because the latter is only written once on i386 if loading
of libc.so.5 libraries is selected, so GLRO (dl_correct_cache_id)
should probably removed in a future change.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
2021-06-25 08:02:33 +02:00
Adhemerval Zanella
52a5fe70a2 Use 64 bit time_t stat internally
For the legacy ABI with supports 32-bit time_t it calls the 64-bit
time directly, since the LFS symbols calls the 64-bit time_t ones
internally.

Checked on i686-linux-gnu and x86_64-linux-gnu.

Reviewed-by: Lukasz Majewski <lukma@denx.de>
2021-06-22 12:09:52 -03:00
Florian Weimer
c2059edce2 elf: Use _dl_catch_error from base namespace in dl-libc.c [BZ #27646]
dlerrror_run in elf/dl-libc.c needs to call GLRO (dl_catch_error)
from the base namespace, just like the exported dlerror
implementation.

Fixes commit b2964eb1d9 ("dlfcn:
Failures after dlmopen should not terminate process [BZ #24772]").

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
2021-06-17 15:06:46 +02:00
Florian Weimer
699361795f Remove stale references to libdl.a
Since commit 0c1c3a771e
("dlfcn: Move dlopen into libc") libdl.a is empty, so linking
against it is no longer necessary.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-06-09 19:14:02 +02:00
Stefan Liebler
51a3df5e35 Fix elf/tst-tls9-static after libdl cleanups.
The testcase elf/tst-tls9-static sometimes fails with:
cannot open 'tst-tlsmod5.so': tst-tlsmod5.so: cannot open shared object file: No such file or directory
cannot open 'tst-tlsmod6.so': tst-tlsmod6.so: cannot open shared object file: No such file or directory

After recent commit
6f1c701026
"dlfcn: Cleanups after -ldl is no longer required"
the libdl variable is not set anymore and thus the
dependencies were missing.
2021-06-09 13:38:41 +02:00
Florian Weimer
466c1ea15f dlfcn: Rework static dlopen hooks
Consolidate all hooks structures into a single one.  There are
no static dlopen ABI concerns because glibc 2.34 already comes
with substantial ABI-incompatible changes in this area.  (Static
dlopen requires the exact same dynamic glibc version that was used
for static linking.)

The new approach uses a pointer to the hooks structure into
_rtld_global_ro and initalizes it in __rtld_static_init.  This avoids
a back-and-forth with various callback functions.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-06-03 09:12:05 +02:00
Florian Weimer
6f1c701026 dlfcn: Cleanups after -ldl is no longer required
This commit removes the ELF constructor and internal variables from
dlfcn/dlfcn.c.  The file now serves the same purpose as
nptl/libpthread-compat.c, so it is renamed to dlfcn/libdl-compat.c.
The use of libdl-shared-only-routines ensures that libdl.a is empty.

This commit adjusts the test suite not to use $(libdl).  The libdl.so
symbolic link is no longer installed.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-06-03 09:11:45 +02:00
Florian Weimer
add8d7ea01 dlfcn: Move dlvsym into libc
The symbol was moved using scripts/move-symbol-to-libc.py.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-06-03 08:26:04 +02:00
Florian Weimer
77f876c0e3 dlfcn: Move dlsym into libc
The symbol was moved using scripts/move-symbol-to-libc.py.

In elf/Makefile, remove the $(libdl) dependency from testobj1.so
because it the unused libdl DSO now causes elf/tst-unused-deps to
fail.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-06-03 08:26:04 +02:00
Florian Weimer
7862ff8e69 elf: Use custom NODELETE DSO for tst-dlopenfail, tst-dlopenfail-2
Once libpthread is empty and no longer marked NODELETE, it no longer
can be used for testing.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-21 22:35:00 +02:00
Florian Weimer
d03511f48f nptl: Eliminate the __static_tls_size, __static_tls_align_m1 variables
Use the  __nptl_tls_static_size_for_stack inline function instead,
and the GLRO (dl_tls_static_align) value directly.

The computation of GLRO (dl_tls_static_align)  in
_dl_determine_tlsoffset ensures that the alignment is at least
TLS_TCB_ALIGN, which at least STACK_ALIGN (see allocate_stack).
Therefore, the additional rounding-up step is removed.

ALso move the initialization of the default stack size from
__pthread_initialize_minimal_internal to __pthread_early_init.
This introduces an extra system call during single-threaded startup,
but this simplifies the initialization sequence.  No locking is
needed around the writes to __default_pthread_attr because the
process is single-threaded at this point.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-21 22:35:00 +02:00
Florian Weimer
9ec7fff6cd elf: Initialize GLRO (dl_minsigstacksize) after static dlopen
This is another field of _rtld_global_ro that benefits from
initialization in __rtld_static_init.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
2021-05-20 18:56:42 +02:00
Florian Weimer
eb24865637 elf: Add hook for checking HWCAP bits after auxiliary vector parsing
Reviewed-by: Stefan Liebler <stli@linux.ibm.com>
2021-05-19 11:09:57 +02:00
Siddhesh Poyarekar
22866ed858 ldconfig: Avoid boolean coercion of opt_chroot
Generated code is unchanged.
2021-05-18 09:34:04 +05:30
Siddhesh Poyarekar
468d772e81 ldconfig: Fix memory leaks
Coverity discovered that paths allocated by chroot_canon are not freed
in a couple of routines in ldconfig.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-18 09:29:02 +05:30
Siddhesh Poyarekar
a85cdcdb35 elf/cache.c: Fix resource leaks identified by static analyzers
A coverity run identified a number of resource leaks in cache.c.
There are a couple of simple memory leaks where a local allocation is
not freed before function return.  Then there is a mmap leak and a
file descriptor leak where a map is not unmapped in the error case and
a file descriptor remains open respectively.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-18 09:08:41 +05:30
Florian Weimer
9dc21009a4 elf: Move static TLS size and alignment into _rtld_global_ro
This helps to clarify that the caching of these fields in libpthread
(in __static_tls_size, __static_tls_align_m1) is unnecessary.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-17 10:17:41 +02:00
Florian Weimer
0b3e92bdf3 elf: Remove DL_STATIC_INIT
All users have been converted to the __rtld_static_init mechanism.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-17 10:08:19 +02:00
Florian Weimer
78b31cc834 elf: Partially initialize ld.so after static dlopen (bug 20802)
After static dlopen, a copy of ld.so is loaded into the inner
namespace, but that copy is not initialized at all.  Some
architectures run into serious problems as result, which is why the
_dl_var_init mechanism was invented.  With libpthread moving into
libc and parts into ld.so, more architectures impacted, so it makes
sense to switch to a generic mechanism which performs the partial
initialization.

As a result, getauxval now works after static dlopen (bug 20802).

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-17 10:06:57 +02:00
Romain GEISSLER
5188a9d026 Remove all usage of @BASH@ or ${BASH} in installed files, and hardcode /bin/bash instead
(FYI, this is a repost of
https://sourceware.org/pipermail/libc-alpha/2019-July/105035.html now
that FSF papers have been signed and confirmed on FSF side).

This trivial patch attemps to fix BZ 24106. Basically the bash locally
used when building glibc on the host shall not leak on the installed
glibc, as the system where it is installed might be different and use
another bash location.

So I have looked for all occurences of @BASH@ or $(BASH) in installed
files, and replaced it by /bin/bash. This was suggested by Florian
Weimer in the bug report.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
2021-05-12 07:47:11 +05:30
Szabolcs Nagy
572bd547d5 elf: Fix DTV gap reuse logic [BZ #27135]
For some reason only dlopen failure caused dtv gaps to be reused.

It is possible that the intent was to never reuse modids for a
different module, but after dlopen failure all gaps are reused
not just the ones caused by the unfinished dlopened.

So the code has to handle reused modids already which seems to
work, however the data races at thread creation and tls access
(see bug 19329 and bug 27111) may be more severe if slots are
reused so this is scheduled after those fixes. I think fixing
the races are not simpler if reuse is disallowed and reuse has
other benefits, so set GL(dl_tls_dtv_gaps) whenever entries are
removed from the middle of the slotinfo list. The value does
not have to be correct: incorrect true value causes the next
modid query to do a slotinfo walk, incorrect false will leave
gaps and new entries are added at the end.

Fixes bug 27135.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-11 17:16:37 +01:00
Szabolcs Nagy
9d0e30329c elf: Add test case for [BZ #19329]
Test concurrent dlopen and pthread_create when the loaded modules have
TLS.  This triggers dl-tls assertion failures more reliably than the
nptl/tst-stack4 test.

The dlopened module has 100 DT_NEEDED dependencies with TLS, they were
reused from an existing TLS test. The number of created threads during
dlopen depends on filesystem speed and hardware, but at most 3 threads
are alive at a time to limit resource usage.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-11 17:16:37 +01:00
Szabolcs Nagy
f4f8f4d4e0 elf: Use relaxed atomics for racy accesses [BZ #19329]
This is a follow up patch to the fix for bug 19329.  This adds relaxed
MO atomics to accesses that were previously data races but are now
race conditions, and where relaxed MO is sufficient.

The race conditions all follow the pattern that the write is behind the
dlopen lock, but a read can happen concurrently (e.g. during tls access)
without holding the lock.  For slotinfo entries the read value only
matters if it reads from a synchronized write in dlopen or dlclose,
otherwise the related dtv entry is not valid to access so it is fine
to leave it in an inconsistent state.  The same applies for
GL(dl_tls_max_dtv_idx) and GL(dl_tls_generation), but there the
algorithm relies on the fact that the read of the last synchronized
write is an increasing value.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-11 17:16:37 +01:00
Szabolcs Nagy
1387ad6225 elf: Fix data races in pthread_create and TLS access [BZ #19329]
DTV setup at thread creation (_dl_allocate_tls_init) is changed
to take the dlopen lock, GL(dl_load_lock).  Avoiding data races
here without locks would require design changes: the map that is
accessed for static TLS initialization here may be concurrently
freed by dlclose.  That use after free may be solved by only
locking around static TLS setup or by ensuring dlclose does not
free modules with static TLS, however currently every link map
with TLS has to be accessed at least to see if it needs static
TLS.  And even if that's solved, still a lot of atomics would be
needed to synchronize DTV related globals without a lock. So fix
both bug 19329 and bug 27111 with a lock that prevents DTV setup
running concurrently with dlopen or dlclose.

_dl_update_slotinfo at TLS access still does not use any locks
so CONCURRENCY NOTES are added to explain the synchronization.
The early exit from the slotinfo walk when max_modid is reached
is not strictly necessary, but does not hurt either.

An incorrect acquire load was removed from _dl_resize_dtv: it
did not synchronize with any release store or fence and
synchronization is now handled separately at thread creation
and TLS access time.

There are still a number of racy read accesses to globals that
will be changed to relaxed MO atomics in a followup patch. This
should not introduce regressions compared to existing behaviour
and avoid cluttering the main part of the fix.

Not all TLS access related data races got fixed here: there are
additional races at lazy tlsdesc relocations see bug 27137.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-05-11 17:16:37 +01:00
Siddhesh Poyarekar
81046e2812 _dl_exception_create_format: Add missing va_end
Coverity discovered a missing va_end.
2021-05-11 09:07:56 +05:30
Florian Weimer
2dd87703d4 nptl: Move changing of stack permissions into ld.so
All the stack lists are now in _rtld_global, so it is possible
to change stack permissions directly from there, instead of
calling into libpthread to do the change.

Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-05-10 10:31:41 +02:00