Add a new glibc tunable: mem.tagging. This is a decimal constant in
the range 0-255 but used as a bit-field.
Bit 0 enables use of tagged memory in the malloc family of functions.
Bit 1 enables precise faulting of tag failure on platforms where this
can be controlled.
Other bits are currently unused, but if set will cause memory tag
checking for the current process to be enabled in the kernel.
Change sbrk to fail for !__libc_initial (in the generic
implementation). As a result, sbrk is (relatively) safe to use
for the __libc_initial case (from the main libc). It is therefore
no longer necessary to avoid using it in that case (or updating the
brk cache), and the __libc_initial flag does not need to be updated
as part of dlmopen or static dlopen.
As before, direct brk system calls on Linux may lead to memory
corruption.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Otherwise, it will not participate in the dependency sorting.
Fixes commit 9ffa50b26b
("elf: Include libc.so.6 as main program in dependency sort
(bug 20972)").
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The failure paths in _dl_map_object_from_fd did not clean every
potentially allocated resource up.
Handle l_phdr, l_libname and mapped segments in the common failure
handling code.
There are various bits that may not be cleaned properly on failure
(e.g. executable stack, incomplete dl_map_segments) fixing those
need further changes.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
_dl_map_object_from_fd has complex error handling with cleanups.
It was managed by a separate function to avoid code bloat at
every failure case, but since the code was changed to use gotos
there is no longer such code bloat from inlining.
Maintaining a separate error handling function is harder as it
needs to access local state which has to be passed down. And the
same lose function was used in open_verify which is error prone.
The goto labels are changed since there is no longer a call.
The new code generates slightly smaller binary.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Since elf.h is a public header file copied to other projects,
try to make it free from spelling typos.
This change fixes the following spelling typos in comments of elf.h:
Auxialiary -> Auxiliary
tenatively -> tentatively
compatability -> compatibility
_dl_map_object_deps always sorts the initially loaded object first
during dependency sorting. This means it is relocated last in
dl_open_worker. This results in crashes in IFUNC resolvers without
lazy bindings if libraries are preloaded that refer to IFUNCs in
libc.so.6: the resolvers are called when libc.so.6 has not been
relocated yet, so references to _rtld_global_ro etc. crash.
The fix is to check against the libc.so.6 link map recorded by the
__libc_early_init framework, and let it participate in the dependency
sort.
This fixes bug 20972.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
To handle GNU property notes on aarch64 some segments need to
be mmaped again, so the fd of the loaded ELF module is needed.
When the fd is not available (kernel loaded modules), then -1
is passed.
The fd is passed to both _dl_process_pt_gnu_property and
_dl_process_pt_note for consistency. Target specific note
processing functions are updated accordingly.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Program headers are processed in two pass: after the first pass
load segments are mmapped so in the second pass target specific
note processing logic can access the notes.
The second pass is moved later so various link_map fields are
set up that may be useful for note processing such as l_phdr.
The second pass should be before the fd is closed so that is
available.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Subdirectories z13, z14, z15 can be selected, mostly based on the
level of support for vector instructions.
Co-Authored-By: Stefan Liebler <stli@linux.ibm.com>
The misattributed dependencies can cause failures in parallel testing
if the dependencies have not been built yet.
Fixes commit a332bd1518
("elf: Add elf/tst-dlopenfail-2 [BZ #25396]").
This recognizes the DL_CACHE_HWCAP_EXTENSION flag in cache entries,
and picks the supported cache entry with the highest priority.
The elf/tst-glibc-hwcaps-prepend-cache test documents a non-desired
aspect of the current cache implementation: If the cache selects a DSO
that does not exist on disk, _dl_map_object falls back to open_path,
which may or may not find an alternative implementation. This is an
existing limitation that also applies to the legacy hwcaps processing
for ld.so.cache.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Libraries from these subdirectories are added to the cache
with a special hwcap bit DL_CACHE_HWCAP_EXTENSION, so that
they are ignored by older dynamic loaders.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This simplifies the string table construction in elf/cache.c
because there is no more need to keep track of offsets explicitly;
the string table implementation does this internally.
This change slightly reduces the size of the cache on disk. The
file format does not change as a result. The strings are
null-terminated, without explicit length, so tail merging is
transparent to readers.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This will be used in ldconfig to reduce the ld.so.cache size slightly.
Tail merging is an optimization where a pointer points into another
string if the first string is a suffix of the second string.
The hash function FNV-1a was chosen because it is simple and achieves
good dispersion even for short strings (so that the hash table bucket
count can be a power of two). It is clearly superior to the hsearch
hash and the ELF hash in this regard.
The hash table uses chaining for collision resolution.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
A previously unused new-format header field is used to record
the address of an extension directory.
This change adds a demo extension which records the version of
ldconfig which builds a file.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Use a reserved byte in the new format cache header to indicate whether
the file is in little endian or big endian format. Eventually, this
information could be used to provide a unified cache for qemu-user
and similiar scenarios.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This hacks non-power-set processing into _dl_important_hwcaps.
Once the legacy hwcaps handling goes away, the subdirectory
handling needs to be reworked, but it is premature to do this
while both approaches are still supported.
ld.so supports two new arguments, --glibc-hwcaps-prepend and
--glibc-hwcaps-mask. Each accepts a colon-separated list of
glibc-hwcaps subdirectory names. The prepend option adds additional
subdirectories that are searched first, in the specified order. The
mask option restricts the automatically selected subdirectories to
those listed in the option argument. For example, on systems where
/usr/lib64 is on the library search path,
--glibc-hwcaps-prepend=valgrind:debug causes the dynamic loader to
search the directories /usr/lib64/glibc-hwcaps/valgrind and
/usr/lib64/glibc-hwcaps/debug just before /usr/lib64 is searched.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
On GNU/Hurd we not only need $(common-objpfx) in LD_LIBRARY_PATH when loading
dynamic objects, but also $(common-objpfx)/mach and $(common-objpfx)/hurd. This
adds an ld-library-path variable to be used as LD_LIBRARY_PATH basis in
Makefiles, and a sysdep-ld-library-path variable for sysdeps to add some
more paths, here mach/ and hurd/.
Now __thread_gscope_wait (the function behind THREAD_GSCOPE_WAIT,
formerly __wait_lookup_done) can be implemented directly in ld.so,
eliminating the unprotected GL (dl_wait_lookup_done) function
pointer.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
We need NO_RTLD_HIDDEN because of the need for PLT calls in ld.so.
See Roland's comment in
https://sourceware.org/bugzilla/show_bug.cgi?id=15605
"in the Hurd it's crucial that calls like __mmap be the libc ones
instead of the rtld-local ones after the bootstrap phase, when the
dynamic linker is being used for dlopen and the like."
We used to just avoid all hidden use in the rtld ; this commit switches to
keeping only those that should use PLT calls, i.e. essentially those defined in
sysdeps/mach/hurd/dl-sysdep.c:
__assert_fail
__assert_perror_fail
__*stat64
_exit
This fixes a few startup issues, notably the call to __tunable_get_val that is
made before PLTs are set up.
struct file_entry_new starts with the fields of struct file_entry,
so the code can be shared if the size computation is made dynamic.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The elf/elf.h header is shared, verbatim, by the elfutils project.
However, elfutils can be used on systems with libcs other than glibc,
making the presence of __BEGIN_DECLS, __END_DECLS and <features.h> in
the file something that downstream distros may have to add patches for.
Furthermore, this file doesn't declare anything with language linkage,
so `extern "C" {}` blocks aren't necessary; it also doesn't have any
conditional definitions based on feature test macros, making inclusion
of features.h unnecessary.
The SXID_* tunable properties only influence processes that are
AT_SECURE, so make that a bit more explicit in the documentation and
comment.
Revisiting the code after a few years I managed to confuse myself, so
I imagine there could be others who may have incorrectly assumed like
I did that the SXID_ERASE tunables are not inherited by children of
non-AT_SECURE processes.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
They have been renamed from env_path_list and rtld_search_dirs to
avoid linknamespace issues.
This change will allow future use these variables in diagnostics.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This requires defining a macro for the full path, matching the
-Wl,--dynamic-link= arguments used for linking glibc programs,
and ldd script.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This prints out version information for the dynamic loader and
exits immediately, without further command line processing
(which seems to match what some GNU tools do).
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
--help processing is deferred to the point where the executable has
been loaded, so that it is possible to eventually include information
from the main executable in the help output.
As suggested in the GNU command-line interface guidelines, the help
message is printed to standard output, and the exit status is
successful.
Handle usage errors closer to the GNU command-line interface
guidelines.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Also add a comment to elf/Makefile, explaining why we cannot use
config.status for autoconf template processing.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
