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>
Introduce struct dl_main_state and move it to <dl-main.h>. Rename
enum mode to enum rtld_mode and add the rtld_mode_ prefix to the enum
constants.
This avoids the need for putting state that is only needed during
startup into the ld.so data segment.
In some cases, it is difficult to determine the kind of malloc
based on the execution context, so a function to determine that
is helpful.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The generic version is parallel to _dl_writev. It cannot use
_dl_writev directly because the errno value needs to be obtained
under a lock.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This functionality does not seem to be useful since static dlopen
is mostly used for iconv/character set conversion and NSS support.
gconv modules are loaded with full paths anyway, so that the
HWCAP subdirectory logic does not apply.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Some tunable values and their minimum/maximum values must be determinted
at run-time. Add TUNABLE_SET_WITH_BOUNDS and TUNABLE_SET_WITH_BOUNDS_FULL
to update tunable value together with minimum and maximum values.
__tunable_set_val is updated to set tunable value as well as min/max
values.
It replaces the internal usage of __{f,l}xstat{at}{64} with the
__{f,l}stat{at}{64}. It should not change the generate code since
sys/stat.h explicit defines redirections to internal calls back to
xstat* symbols.
Checked with a build for all affected ABIs. I also check on
x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Constants double checked against binutils and the ELF for the Arm 64-bit
Architecture (AArch64) Release 2020Q2 document.
Only BTI PLT is used in glibc, there's no PAC PLT with glibc, and people
are expected to use BIND_NOW.
The _sys_errlist and _sys_siglist symbols are deprecated since 2.32.
This patch adds a TEST_COMPAT check around the tests. This fixes test
failures on new architectures (such as RV32) that don't have this
symbol defined.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Make the computation in elf/dl-tls.c more transparent, and add
an explicit test for the historic value.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The kernel ABI is not finalized, and there are now various proposals
to change the size of struct rseq, which would make the glibc ABI
dependent on the version of the kernels used for building glibc.
This is of course not acceptable.
This reverts commit 48699da1c4 ("elf:
Support at least 32-byte alignment in static dlopen"), commit
8f4632deb3 ("Linux: rseq registration
tests"), commit 6e29cb3f61 ("Linux: Use
rseq in sched_getcpu if available"), and commit
0c76fc3c2b ("Linux: Perform rseq
registration at C startup and thread creation"), resolving the conflicts
introduced by the ARC port and the TLS static surplus changes.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
On some targets static TLS surplus area can be used opportunistically
for dynamically loaded modules such that the TLS access then becomes
faster (TLSDESC and powerpc TLS optimization). However we don't want
all surplus TLS to be used for this optimization because dynamically
loaded modules with initial-exec model TLS can only use surplus TLS.
The new contract for surplus static TLS use is:
- libc.so can have up to 192 bytes of IE TLS,
- other system libraries together can have up to 144 bytes of IE TLS.
- Some "optional" static TLS is available for opportunistic use.
The optional TLS is now tunable: rtld.optional_static_tls, so users
can directly affect the allocated static TLS size. (Note that module
unloading with dlclose does not reclaim static TLS. After the optional
TLS runs out, TLS access is no longer optimized to use static TLS.)
The default setting of rtld.optional_static_tls is 512 so the surplus
TLS is 3*192 + 4*144 + 512 = 1664 by default, the same as before.
Fixes BZ #25051.
Tested on aarch64-linux-gnu and x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The new static TLS surplus size computation is
surplus_tls = 192 * (nns-1) + 144 * nns + 512
where nns is controlled via the rtld.nns tunable. This commit
accounts audit modules too so nns = rtld.nns + audit modules.
rtld.nns should only include the namespaces required by the
application, namespaces for audit modules are accounted on top
of that so audit modules don't use up the static TLS that is
reserved for the application. This allows loading many audit
modules without tuning rtld.nns or using up static TLS, and it
fixes
FAIL: elf/tst-auditmany
Note that DL_NNS is currently a hard upper limit for nns, and
if rtld.nns + audit modules go over the limit that's a fatal
error. By default rtld.nns is 4 which allows 12 audit modules.
Counting the audit modules is based on existing audit string
parsing code, we cannot use GLRO(dl_naudit) before the modules
are actually loaded.
TLS_STATIC_SURPLUS is 1664 bytes currently which is not enough to
support DL_NNS (== 16) number of dynamic link namespaces, if we
assume 192 bytes of TLS are reserved for libc use and 144 bytes
are reserved for other system libraries that use IE TLS.
A new tunable is introduced to control the number of supported
namespaces and to adjust the surplus static TLS size as follows:
surplus_tls = 192 * (rtld.nns-1) + 144 * rtld.nns + 512
The default is rtld.nns == 4 and then the surplus TLS size is the
same as before, so the behaviour is unchanged by default. If an
application creates more namespaces than the rtld.nns setting
allows, then it is not guaranteed to work, but the limit is not
checked. So existing usage will continue to work, but in the
future if an application creates more than 4 dynamic link
namespaces then the tunable will need to be set.
In this patch DL_NNS is a fixed value and provides a maximum to
the rtld.nns setting.
Static linking used fixed 2048 bytes surplus TLS, this is changed
so the same contract is used as for dynamic linking. With static
linking DL_NNS == 1 so rtld.nns tunable is forced to 1, so by
default the surplus TLS is reduced to 144 + 512 = 656 bytes. This
change is not expected to cause problems.
Tested on aarch64-linux-gnu and x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Add generic code to handle PT_GNU_PROPERTY notes. Invalid
content is ignored, _dl_process_pt_gnu_property is always called
after PT_LOAD segments are mapped and it has no failure modes.
Currently only one NT_GNU_PROPERTY_TYPE_0 note is handled, which
contains target specific properties: the _dl_process_gnu_property
hook is called for each property.
The old _dl_process_pt_note and _rtld_process_pt_note differ in how
the program header is read. The old _dl_process_pt_note is called
before PT_LOAD segments are mapped and _rtld_process_pt_note is called
after PT_LOAD segments are mapped. The old _rtld_process_pt_note is
removed and _dl_process_pt_note is always called after PT_LOAD
segments are mapped and now it has no failure modes.
The program headers are scanned backwards so that PT_NOTE can be
skipped if PT_GNU_PROPERTY exists.
Co-Authored-By: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The auditing interface identifies namespaces by their first loaded
module. Once the namespace is empty, it is no longer possible to signal
LA_ACT_CONSISTENT for it because the first loaded module is already gone
at that point.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The variable is placed in libc.so, and it can be true only in
an outer libc, not libcs loaded via dlmopen or static dlopen.
Since thread creation from inner namespaces does not work,
pthread_create can update __libc_single_threaded directly.
Using __libc_early_init and its initial flag, implementation of this
variable is very straightforward. A future version may reset the flag
during fork (but not in an inner namespace), or after joining all
threads except one.
Reviewed-by: DJ Delorie <dj@redhat.com>
Register rseq TLS for each thread (including main), and unregister for
each thread (excluding main). "rseq" stands for Restartable Sequences.
See the rseq(2) man page proposed here:
https://lkml.org/lkml/2018/9/19/647
Those are based on glibc master branch commit 3ee1e0ec5c.
The rseq system call was merged into Linux 4.18.
The TLS_STATIC_SURPLUS define is increased to leave additional room for
dlopen'd initial-exec TLS, which keeps elf/tst-auditmany working.
The increase (76 bytes) is larger than 32 bytes because it has not been
increased in quite a while. The cost in terms of additional TLS storage
is quite significant, but it will also obscure some initial-exec-related
dlopen failures.
Now that ldconfig defaults to the new format (only), check for it
first. Also apply the corruption check added in commit 2954daf00b
("Add more checks for valid ld.so.cache file (bug 18093)") to the
new-format-only case.
Suggested-by: Josh Triplett <josh@joshtriplett.org>
The existing macros are fragile and expect local variables with a
certain name. Fix this by defining them as functions with default
implementation in a new header dl-runtime.h which arches can override
if need be.
This came up during ARC port review, hence the need for argument pltgot
in reloc_index() which is not needed by existing ports.
This patch potentially only affects hppa/x86 ports,
build tested for both those configs and a few more.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
There are:
#define TUNABLE_SET_VAL_IF_VALID_RANGE(__cur, __val, __type) \
({ \
__type min = (__cur)->type.min; \
__type max = (__cur)->type.max; \
\
if ((__type) (__val) >= min && (__type) (val) <= max) \
^^^ Should be __val
{ \
(__cur)->val.numval = val; \
^^^ Should be __val
(__cur)->initialized = true; \
} \
})
Luckily since all TUNABLE_SET_VAL_IF_VALID_RANGE usages are
TUNABLE_SET_VAL_IF_VALID_RANGE (cur, val, int64_t);
this didn't cause any issues.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Historically, this mechanism was used to process "nosegneg"
subdirectories, and it is still used to include the "tls"
subdirectories. With nosegneg support gone from ld.so, this is part
no longer useful.
The entire mechanism is not well-designed because it causes the
meaning of hwcap bits in ld.so.cache to depend on the kernel version
that was used to generate the cache, which makes it difficult to use
this mechanism for anything else in the future.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This was only ever used for the "nosegneg" flag. This approach for
passing hardware capability information creates a subtle dependency
between the kernel and userspace, and ld.so.cache contents. It seems
inappropriate for toady, where people expect to be able to run
system images which very different kernel versions.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This change makes it easier to set a breakpoint on these calls.
This also addresses the issue that including <ldsodefs.h> without
<unistd.h> does not result usable _dl_*printf macros because of the
use of the STD*_FILENO macros there.
(The private symbol for _dl_fatal_printf will go away again
once the exception handling implementation is unified between
libc and ld.so.)
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
These property values are specified by the AArch64 ELF ABI and
binutils can create binaries marked with them.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This was originally added to support binutils older than version
2.22:
<https://sourceware.org/ml/libc-alpha/2010-12/msg00051.html>
Since 2.22 is older than the minimum required binutils version
for building glibc, we no longer need this. (The changes do
not impact the statically linked startup code.)
If we try to run constructors before relocation, this is always
a dynamic linker bug. An assert is easier to notice than a call
via an invalid function pointer (which may not even produce a valid
call stack).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
1. Include <dl-procruntime.c> to get architecture specific initializer in
rtld_global.
2. Change _dl_x86_feature_1[2] to _dl_x86_feature_1.
3. Add _dl_x86_feature_control after _dl_x86_feature_1, which is a
struct of 2 bitfields for IBT and SHSTK control
This fixes [BZ #25887].
The second call does not do anything because the data structures have
already been resized by the call that comes before the demarcation
point. Fixes commit a509eb117f
("Avoid late dlopen failure due to scope, TLS slotinfo updates
[BZ #25112]").
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Improve the commentary to aid future developers who will stumble
upon this novel, yet not always perfect, mechanism to support
alternative formats for long double.
Likewise, rename __LONG_DOUBLE_USES_FLOAT128 to
__LDOUBLE_REDIRECTS_TO_FLOAT128_ABI now that development work
has settled down. The command used was
git grep -l __LONG_DOUBLE_USES_FLOAT128 ':!./ChangeLog*' | \
xargs sed -i 's/__LONG_DOUBLE_USES_FLOAT128/__LDOUBLE_REDIRECTS_TO_FLOAT128_ABI/g'
Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
The rseq initialization should happen only for the libc in the base
namespace (in the dynamic case) or the statically linked libc. The
__libc_multiple_libcs flag does not quite cover this case at present,
so this commit introduces a flag argument to __libc_early_init,
indicating whether the libc being libc is the primary one (of the main
program).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This function is defined in libc.so, and the dynamic loader calls
right after relocation has been finished, before any ELF constructors
or the preinit function is invoked. It is also used in the static
build for initializing parts of the static libc.
To locate __libc_early_init, a direct symbol lookup function is used,
_dl_lookup_direct. It does not search the entire symbol scope and
consults merely a single link map. This function could also be used
to implement lookups in the vDSO (as an optimization).
A per-namespace variable (libc_map) is added for locating libc.so,
to avoid repeated traversals of the search scope. It is similar to
GL(dl_initfirst). An alternative would have been to thread a context
argument from _dl_open down to _dl_map_object_from_fd (where libc.so
is identified). This could have avoided the global variable, but
the change would be larger as a result. It would not have been
possible to use this to replace GL(dl_initfirst) because that global
variable is used to pass the function pointer past the stack switch
from dl_main to the main program. Replacing that requires adding
a new argument to _dl_init, which in turn needs changes to the
architecture-specific libc.so startup code written in assembler.
__libc_early_init should not be used to replace _dl_var_init (as
it exists today on some architectures). Instead, _dl_lookup_direct
should be used to look up a new variable symbol in libc.so, and
that should then be initialized from the dynamic loader, immediately
after the object has been loaded in _dl_map_object_from_fd (before
relocation is run). This way, more IFUNC resolvers which depend on
these variables will work.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
MIPS needs to ignore certain existing symbols during symbol lookup.
The old scheme uses the ELF_MACHINE_SYM_NO_MATCH macro, with an
inline function, within its own header, with a sysdeps override for
MIPS. This allows re-use of the function from another file (without
having to include <dl-machine.h> or providing the default definition
for ELF_MACHINE_SYM_NO_MATCH).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
GNU ld and gold's -Map include a line like:
path/to/build/libc_pic.a(check_fds.os)
lld -Map does not have the archive member list, but we can still derive the
members from the following output
VMA LMA Size Align Out In Symbol
...
1a1c0 1a1c0 e2 16 path/to/build/libc_pic.a(check_fds.os):(.text)
binutils ld has supported --audit, --depaudit for a long time,
only support in glibc has been missing.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
All list elements are colon-separated strings, and there is a hard
upper limit for the number of audit modules, so it is possible to
pre-allocate a fixed-size array of strings to which the LD_AUDIT
environment variable and --audit arguments are added.
Also eliminate the global variables for the audit list because
the list is only needed briefly during startup.
There is a slight behavior change: All duplicate LD_AUDIT environment
variables are now processed, not just the last one as before. However,
such environment vectors are invalid anyway.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The ldbl redirects for ieee128 have some jagged edges when
inspecting and manipulating symbols directly.
e.g asprintf is unconditionally redirected to __asprintfieee128
thus any tests relying on GCC's redirect behavior will encounter
problems if they inspect the symbol names too closely.
I've mitigated tests which expose the limitations of the
ldbl -> f128 redirects by giving them knowledge about the
redirected symbol names.
Hopefully there isn't much user code which depends on this
implementation specific behavior.
Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
With this patch, -v turns on a "from" trace for each directory
searched, that tells you WHY that directory is being searched -
is it a builtin, from the command line, or from some config file?
Writable, executable segments defeat security hardening. The
existing check for DT_TEXTREL does not catch this.
hppa and SPARC currently keep the PLT in an RWX load segment.
The present code leaves the function pointers unprotected, but moves
some of the static functions into .data.rel.ro instead. This causes
the linker to produce an allocatable, executable, writable section
and eventually an RWX load segment. Not only do we really do not
want that, it also breaks valgrind because valgrind does not load
debuginfo from the mmap interceptor if all it sees are RX and RWX
mappings.
Fixes commit 3a0ecccb59 ("ld.so: Do not
export free/calloc/malloc/realloc functions [BZ #25486]").
On !ELF_INITFINI architectures, _init is no longer called by the
dynamic linker. We can use an ELF constructor instead because the
constructor order does not matter. (The other constructors are used
to set up libio vtable bypasses and do not depend on this
initialization routine.)
This supersedes the init_array sysdeps directory. It allows us to
check for ELF_INITFINI in both C and assembler code, and skip DT_INIT
and DT_FINI processing completely on newer architectures.
A new header file is needed because <dl-machine.h> is incompatible
with assembler code. <sysdep.h> is compatible with assembler code,
but it cannot be included in all assembler files because on some
architectures, it redefines register names, and some assembler files
conflict with that.
<elf-initfini.h> is replicated for legacy architectures which need
DT_INIT/DT_FINI support. New architectures follow the generic default
and disable it.
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 definitions are moved into a new file, elf/dl-sym-post.h, so that
this code can be used by the dynamic loader as well.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This generalizes a mechanism used for stack-protector support, so
that it can be applied to other symbols if required.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
As the sort was removed, there's no need to keep a separate map of
links. Instead, when relocating objects iterate over l_initfini
directly.
This allows us to remove the loop copying l_initfini elements into
map. We still need a loop to identify the first and last elements that
need relocation.
Tested by running the testsuite on x86_64.
l_initfini is already sorted by dependency in _dl_map_object_deps(),
so avoid sorting again in dl_open_worker().
Tested by running the testsuite on x86_64.
There are two fixes that are needed to be able to dlopen filter
objects. First _dl_map_object_deps cannot assume that map will be at
the beginning of l_searchlist.r_list[], as filtees are inserted before
map. Secondly dl_open_worker needs to ensure that filtees get
relocated.
In _dl_map_object_deps:
* avoiding removing relocation dependencies of map by setting
l_reserved to 0 and otherwise processing the rest of the search
list.
* ensure that map remains at the beginning of l_initfini - the list
of things that need initialisation (and destruction). Do this by
splitting the copy up. This may not be required, but matches the
initialization order without dlopen.
Modify dl_open_worker to relocate the objects in new->l_inifini.
new->l_initfini is constructed in _dl_map_object_deps, and lists the
objects that need initialization and destruction. Originally the list
of objects in new->l_next are relocated. All of these objects should
also be included in new->l_initfini (both lists are populated with
dependencies in _dl_map_object_deps). We can't use new->l_prev to pick
up filtees, as during a recursive dlopen from an interposed malloc
call, l->prev can contain objects that are not ready for relocation.
Add tests to verify that symbols resolve to the filtee implementation
when auxiliary and filter objects are used, both as a normal link and
when dlopen'd.
Tested by running the testsuite on x86_64.
As noted in
<https://sourceware.org/ml/libc-alpha/2019-06/msg00824.html>,
elf/tst-rtld-preload fails when cross-testing because it attempts to
run the test wrapper with itself. Unfortunately, that thread never
resulted in a complete and correct patch for that test.
This patch addresses the issues with that test more thoroughly. The
test is changed not to use the wrapper twice, including updating the
message it prints about the command it runs to be more complete and
accurate after the change; the Makefile is changed not to pass the
redundant '$(test-wrapper)' argument.
Tested for Arm that this fixes the failure seen for that test in
cross-testing.
The tests elf/tst-ifunc-fault-bindnow and elf/tst-ifunc-fault-lazy
fail in cross-testing because they run the dynamic linker directly
without using the test wrapper. This patch fixes them to use the test
wrapper instead.
Tested that this fixes the failure of those two tests for powerpc
soft-float.
GCC 10.0 enabled -fno-common by default and this started to point that
__cache_line_size had been implemented in 2 different places: loader and
libc.
In order to avoid this duplication, the libc variable has been removed
and the loader variable is moved to rtld_global_ro.
File sysdeps/unix/sysv/linux/powerpc/dl-auxv.h has been added in order
to reuse code for both static and dynamic linking scenarios.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
