It's not necessary to introduce temporaries because the compiler
is able to evaluate l_soname just once in constracts like:
l_soname (l) != NULL && strcmp (l_soname (l), LIBC_SO) != 0
This reduces code size and dependencies on ld.so internals from
libc.so.
Fixes commit f4c142bb9f
("arm: Use _dl_find_object on __gnu_Unwind_Find_exidx (BZ 31405)").
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Decorate BSS mappings with [anon: glibc: .bss <file>], for example
[anon: glibc: .bss /lib/libc.so.6]. The string ".bss" is already used
by bionic so use the same, but add the filename as well. If the name
would be longer than what the kernel allows, drop the directory part
of the path.
Refactor glibc.mem.decorate_maps check to a separate function and use
it to avoid assembling a name, which would not be used later.
Signed-off-by: Petr Malat <oss@malat.biz>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Older versions such as binutils 2.35.2 do not recognize
PT_GNU_PROPERTY.
Fixes commit d3f2b71ef1
("aarch64: Fix tests not compatible with targets supporting GCS").
- Add GCS marking to some of the tests when target supports GCS
- Fix tst-ro-dynamic-mod.map linker script to avoid removing
GNU properties
- Add header with macros for GNU properties
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Use the same code to compute the TLS block size and its alignment.
The code in elf/dl-tls.c is linked in anyway for all binaries
due to the reference to _dl_tls_static_surplus_init.
It is not possible to call _dl_allocate_tls_storage directly
because malloc is not available in the static case. (The
dynamic linker uses the minimal malloc at this stage.) Therefore,
split _dl_tls_block_size_with_pre and _dl_tls_block_align from
_dl_allocate_tls_storage, and call those new functions from
__libc_setup_tls.
This fixes extra TLS allocation for the static case, and apparently
some pre-existing bugs as well (the independent recomputation of
TLS block sizes in init_static_tls looks rather suspect).
Fixes commit 0e411c5d30 ("Add generic
'extra TLS'").
The old code used the slotinfo array as a scratch area to pass the
list of TLS-using objects to _dl_determine_tlsoffset. All array
entries are subsequently overwritten by _dl_add_to_slotinfo,
except the first one. The link maps are usually not at their
right position for their module ID in the slotinfo array, so
the initial use of the slotinfo array would be incorrect if not
for scratch purposes only.
In _dl_tls_initial_modid_limit_setup, the old code relied that
some link map was written to the first slotinfo entry. After the
change, this no longer happens because TLS module ID zero is unused.
It's also necessary to move the call after the real initialization
of the slotinfo array.
The __ifunc_resolver macro expands to:
extern __typeof (__redirect_name) name __attribute__ ((ifunc ("iname_ifunc")));
static __typeof (__redirect_name) *name_ifunc (void) { [...] };
And although NAME_IFUNC is and alias for NAME, clang-18 still emits
an 'unused function 'name_ifunc' [-Werror,-Wunused-function]'
warning.
Add the logic to append an 'extra TLS' block in the TLS block allocator
with a generic stub implementation. The duplicated code in
'csu/libc-tls.c' and 'elf/dl-tls.c' is to handle both statically linked
applications and the ELF dynamic loader.
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
On 32-bit Arm, -fasynchronous-unwind-tables creates a reference
to the symbol __aeabi_unwind_cpp_pr0. Compile the tests without
this flag even if it is passed as part of CC, to avoid linker
failures.
Commit 8f8dd904c4 (“elf:
rtld_multiple_ref is always true”) removed some code that happened
to enable compatibility with programs that do not link against
libc.so. Such programs cannot call dlopen or any dynamic linker
functions (except __tls_get_addr), so this is not really useful.
Still ld.so should not crash with a null-pointer dereference
or undefined symbol reference in these cases.
In the main relocation loop, call _dl_relocate_object unconditionally
because it already checks if the object has been relocated.
If libc.so was loaded, self-relocate ld.so against it and call
__rtld_mutex_init and __rtld_malloc_init_real to activate the full
implementations. Those are available only if libc.so is there,
so skip these initialization steps if libc.so is absent. Without
libc.so, the global scope can be completely empty. This can cause
ld.so self-relocation to fail because if it uses symbol-based
relocations, which is why the second ld.so self-relocation is not
performed if libc.so is missing.
The previous concern regarding GOT updates through self-relocation
no longer applies because function pointers are updated
explicitly through __rtld_mutex_init and __rtld_malloc_init_real,
and not through relocation. However, the second ld.so self-relocation
is still delayed, in case there are other symbols being used.
Fixes commit 8f8dd904c4 (“elf:
rtld_multiple_ref is always true”).
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Since have-mtls-descriptor is only used for glibc testing, rename it to
have-test-mtls-descriptor. Also enable tst-gnu2-tls2-amx only if
$(have-test-mtls-descriptor) == gnu2.
Tested with GCC 14 and Clang 19/18/17 on x86-64.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
Use explicit instantiation declaration and definition to silence Clang
error:
tst-unique3.cc:6:18: error: instantiation of variable 'S<char>::i' required here, but no definition is available [-Werror,-Wundefined-var-template]
6 | int t = S<char>::i;
| ^
./tst-unique3.h:5:14: note: forward declaration of template entity is here
5 | static int i;
| ^
tst-unique3.cc:6:18: note: add an explicit instantiation declaration to suppress this warning if 'S<char>::i' is explicitly instantiated in another translation unit
6 | int t = S<char>::i;
| ^
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
This fixes commit 5e249192ca ("elf:
Remove the GET_ADDR_ARGS and related macros from the TLS code"):
GET_ADDR_ARGS was indeed unused, but GET_ADDR_OFFSET was used
on several targets, those that define TLS_DTV_OFFSET. Instead
of reintroducing GET_ADDR_OFFSET, use TLS_DTV_OFFSET directly,
now that it is defined on all targets.
In the new tls_get_addr_adjust helper function, add a cast to
uintptr_t to help the s390 case, where the offset can be positive or
negative, depending on the addresses malloc returns. The cast avoids
pointer wraparound/overflow. The outer uintptr_t cast is needed
to suppress a warning on x86-64 x32 about mismatched integer/pointer
sizes.
Eventually this offset should be folded into the DTV addresses
themselves, to eliminate the subtraction on the TLS fast path.
This will require an adjustment to libthread_db because the
debugger interface currently returns unadjusted pointers.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This is needed for the next patch which updates copyright dates.
* assert/test-assert-2.c: Remove trailing white space.
* elf/tst-startup-errno.c: Remove trailing empty lines.
The new tunable can be used to control whether executable stacks are
allowed from either the main program or dependencies. The default is
to allow executable stacks.
The executable stacks default permission is checked agains the one
provided by the PT_GNU_STACK from program headers (if present). The
tunable also disables the stack permission change if any dependency
requires an executable stack at loading time.
Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
If some shared library loaded with dlopen/dlmopen requires an executable
stack, either implicitly because of a missing GNU_STACK ELF header
(where the ABI default flags implies in the executable bit) or explicitly
because of the executable bit from GNU_STACK; the loader will try to set
the both the main thread and all thread stacks (from the pthread cache)
as executable.
Besides the issue where any __nptl_change_stack_perm failure does not
undo the previous executable transition (meaning that if the library
fails to load, there can be thread stacks with executable stacks), this
behavior was used on a CVE [1] as a vector for RCE.
This patch changes that if a shared library requires an executable
stack, and the current stack is not executable, dlopen fails. The
change is done only for dynamically loaded modules, if the program
or any dependency requires an executable stack, the loader will still
change the main thread before program execution and any thread created
with default stack configuration.
[1] https://www.qualys.com/2023/07/19/cve-2023-38408/rce-openssh-forwarded-ssh-agent.txt
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
This was used to manage an IA-64 ABI divergence is no longere needed
after the IA-64 removal.
(It should be possible to encode all the required information in
one machine word, so the pointer indirection is really unnecessary.
Technically, none of this is part of the ABI, so perhaps it's
possible to do this retroactively. See bug 27404.)
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Since Clang doesn't properly handle
/* FALLTHROUGH */
in elf/tst-align2.c nor
/* fall through */
in misc/tst-tsearch.c
tst-align2.c💯9: error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough]
100 | case 'A':
| ^
tst-align2.c💯9: note: insert '__attribute__((fallthrough));' to silence this warning
100 | case 'A':
| ^
| __attribute__((fallthrough));
tst-align2.c💯9: note: insert 'break;' to avoid fall-through
100 | case 'A':
| ^
| break;
suppress them when compiled with Clang.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
Add __attribute_optimization_barrier__ to disable inlining and cloning on a
function. For Clang, expand it to
__attribute__ ((optnone))
Otherwise, expand it to
__attribute__ ((noinline, clone))
Co-Authored-By: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
clang warns that the instantiation of the variable is required,
but no definition is available. They are implemented on
tst-unique4lib.so.
Checked on x86_64-linux-gnu.
Reviewed-by: Sam James <sam@gentoo.org>
tst-dlopen-nodelete-reloc requires STB_GNU_UNIQUE support so that NODELETE
is propagated by do_lookup_unique. Enable it only if TEST_CXX supports
STB_GNU_UNIQUE,
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
Compiler may default to -fno-semantic-interposition. But some elf test
modules must be compiled with -fsemantic-interposition to function properly.
Add a TEST_CC check for -fsemantic-interposition and use it on elf test
modules. This fixed
FAIL: elf/tst-dlclose-lazy
FAIL: elf/tst-pie1
FAIL: elf/tst-plt-rewrite1
FAIL: elf/unload4
when Clang 19 is used to test glibc.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
Since trampoline is required to test execstack, enable execstack tests
only if compiler supports trampoline.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
This was discovered after extending elf/tst-audit23 to cover
dlclose of the dlmopen namespace.
Auditors already experience the new order during process
shutdown (_dl_fini), so no LAV_CURRENT bump or backwards
compatibility code seems necessary.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Previously, the ld.so link map was silently added to the namespace.
This change produces an auditing event for it.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
After commit 1d5024f4f0
("support: Build with exceptions and asynchronous unwind tables
[BZ #30587]"), libgcc_s is expected to show up in the DSO
list on 32-bit Arm. Do not update max_objs because vdso is not
tracked (and which is the reason why the test currently passes
even with libgcc_s present).
Also write the log output from the auditor to standard output,
for easier test debugging.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This avoids immediate GLIBC_PRIVATE ABI issues if the size of
struct link_map or struct auditstate changes.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Unconditionally define it to false for static builds.
This avoids the awkward use of weak_extern for _dl_rtld_map
in checks that cannot be possibly true on static builds.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The current DSO dependency sorting tests are for a limited number of
specific cases, including some from particular bug reports.
Add tests that systematically cover all possible DAGs for an
executable and the shared libraries it depends on, directly or
indirectly, up to four objects (an executable and three shared
libraries). (For this kind of DAG - ones with a single source vertex
from which all others are reachable, and an ordering on the edges from
each vertex - there are 57 DAGs on four vertices, 3399 on five
vertices and 1026944 on six vertices; see
https://arxiv.org/pdf/2303.14710 for more details on this enumeration.
I've tested that the 3399 cases with five vertices do all pass if
enabled.)
These tests are replicating the sorting logic from the dynamic linker
(thereby, for example, asserting that it doesn't accidentally change);
I'm not claiming that the logic in the dynamic linker is in some
abstract sense optimal. Note that these tests do illustrate how in
some cases the two sorting algorithms produce different results for a
DAG (I think all the existing tests for such differences are ones
involving cycles, and the motivation for the new algorithm was also to
improve the handling of cycles):
tst-dso-ordering-all4-44: a->[bc];{}->[cba]
output(glibc.rtld.dynamic_sort=1): c>b>a>{}<a<b<c
output(glibc.rtld.dynamic_sort=2): b>c>a>{}<a<c<b
They also illustrate that sometimes the sorting algorithms do not
follow the order in which dependencies are listed in DT_NEEDED even
though there is a valid topological sort that does follow that, which
might be counterintuitive considering that the DT_NEEDED ordering is
followed in the simplest cases:
tst-dso-ordering-all4-56: {}->[abc]
output: c>b>a>{}<a<b<c
shows such a simple case following DT_NEEDED order for destructor
execution (the reverse of it for constructor execution), but
tst-dso-ordering-all4-41: a->[cb];{}->[cba]
output: c>b>a>{}<a<b<c
shows that c and b are in the opposite order to what might be expected
from the simplest case, though there is no dependency requiring such
an opposite order to be used.
(I'm not asserting that either of those things is a problem, simply
observing them as less obvious properties of the sorting algorithms
shown up by these tests.)
Tested for x86_64.
Add explicit instantiation declaration of S<char>::i to silence Clang
error:
tst-unique3.cc:6:18: error: instantiation of variable 'S<char>::i' required here, but no definition is available [-Werror,-Wundefined-var-template]
6 | int t = S<char>::i;
| ^
./tst-unique3.h:5:14: note: forward declaration of template entity is here
5 | static int i;
| ^
tst-unique3.cc:6:18: note: add an explicit instantiation declaration to suppress this warning if 'S<char>::i' is explicitly instantiated in another translation unit
6 | int t = S<char>::i;
| ^
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Since GCC 4.9 doesn't have __builtin_add_overflow:
In file included from tst-stringtable.c:180:0:
stringtable.c: In function ‘stringtable_finalize’:
stringtable.c:185:7: error: implicit declaration of function ‘__builtin_add_overflow’ [-Werror=implicit-function-declaration]
else if (__builtin_add_overflow (previous->offset,
^
return EXIT_UNSUPPORTED for GCC 4.9 or older.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
Since elf/ifuncmain9.c fails at run-time when compiled with GCC 5.4 or
older (PR ipa/81128), return EXIT_UNSUPPORTED for GCC 5.4 or older.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
The postclean-generated setting in elf/Makefile lists
$(objpfx)/dso-sort-tests-2.generated-makefile twice and
$(objpfx)/dso-sort-tests-1.generated-makefile not at all, which looks
like a typo; fix it to list each once.
Tested for x86_64.
Add an additional test of TLS variables, with different alignment,
accessed from different modules. The idea of the alignment test is
similar to tst-tlsalign and the same code is shared for setting up
test variables, but unlike the tst-tlsalign code, there are multiple
threads and variables are accessed from multiple objects to verify
that they get a consistent notion of the address of an object within a
thread. Threads are repeatedly created and shut down to verify proper
initialization in each new thread. The test is also repeated with TLS
descriptors when supported. (However, only initial-exec TLS is
covered in this test.)
Tested for x86_64.
Add tests that the dynamic linker works correctly with symbol names
involving hash collisions, for both choices of hash style (and
--hash-style=both as well). I note that there weren't actually any
previous tests using --hash-style (so tests would only cover the
default linker configuration in that regard). Also test symbol
versions involving hash collisions.
Tested for x86_64.
For a static PIE with non-zero load address, its PT_DYNAMIC segment
entries contain the relocated values for the load address in static PIE.
Since static PIE usually doesn't have PT_PHDR segment, use p_vaddr of
the PT_LOAD segment with offset == 0 as the load address in static PIE
and adjust the entries of PT_DYNAMIC segment in static PIE by properly
setting the l_addr field for static PIE. This fixes BZ #31799.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
The remaining_to_add variable can be 0 if (current_used + count) wraps,
This is caught by GCC 14+ on hppa, which determines from there that
target_seg could be be NULL when remaining_to_add is zero, which in
turns causes a -Wstringop-overflow warning:
In file included from ../include/atomic.h:49,
from dl-find_object.c:20:
In function '_dlfo_update_init_seg',
inlined from '_dl_find_object_update_1' at dl-find_object.c:689:30,
inlined from '_dl_find_object_update' at dl-find_object.c:805:13:
../sysdeps/unix/sysv/linux/hppa/atomic-machine.h:44:4: error: '__atomic_store_4' writing 4 bytes into a region of size 0 overflows the destination [-Werror=stringop-overflow=]
44 | __atomic_store_n ((mem), (val), __ATOMIC_RELAXED); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
dl-find_object.c:644:3: note: in expansion of macro 'atomic_store_relaxed'
644 | atomic_store_relaxed (&seg->size, new_seg_size);
| ^~~~~~~~~~~~~~~~~~~~
In function '_dl_find_object_update':
cc1: note: destination object is likely at address zero
In practice, this is not possible as it represent counts of link maps.
Link maps have sizes larger than 1 byte, so the sum of any two link map
counts will always fit within a size_t without wrapping around.
This patch therefore adds a check on remaining_to_add == 0 and tell GCC
that this can not happen using __builtin_unreachable.
Thanks to Andreas Schwab for the investigation.
Closes: BZ #32245
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Tested-by: John David Anglin <dave.anglin@bell.net>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Linux 6.11 has getrandom() in vDSO. It operates on a thread-local opaque
state allocated with mmap using flags specified by the vDSO.
Multiple states are allocated at once, as many as fit into a page, and
these are held in an array of available states to be doled out to each
thread upon first use, and recycled when a thread terminates. As these
states run low, more are allocated.
To make this procedure async-signal-safe, a simple guard is used in the
LSB of the opaque state address, falling back to the syscall if there's
reentrancy contention.
Also, _Fork() is handled by blocking signals on opaque state allocation
(so _Fork() always sees a consistent state even if it interrupts a
getrandom() call) and by iterating over the thread stack cache on
reclaim_stack. Each opaque state will be in the free states list
(grnd_alloc.states) or allocated to a running thread.
The cancellation is handled by always using GRND_NONBLOCK flags while
calling the vDSO, and falling back to the cancellable syscall if the
kernel returns EAGAIN (would block). Since getrandom is not defined by
POSIX and cancellation is supported as an extension, the cancellation is
handled as 'may occur' instead of 'shall occur' [1], meaning that if
vDSO does not block (the expected behavior) getrandom will not act as a
cancellation entrypoint. It avoids a pthread_testcancel call on the fast
path (different than 'shall occur' functions, like sem_wait()).
It is currently enabled for x86_64, which is available in Linux 6.11,
and aarch64, powerpc32, powerpc64, loongarch64, and s390x, which are
available in Linux 6.12.
Link: https://pubs.opengroup.org/onlinepubs/9799919799/nframe.html [1]
Co-developed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Tested-by: Jason A. Donenfeld <Jason@zx2c4.com> # x86_64
Tested-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> # x86_64, aarch64
Tested-by: Xi Ruoyao <xry111@xry111.site> # x86_64, aarch64, loongarch64
Tested-by: Stefan Liebler <stli@linux.ibm.com> # s390x
The declaration of found_other_class could be jumped
over via the goto just above it, but the code jumped
to uses found_other_class. Move the declaration
up a bit to ensure it's properly declared and initialized.
Before commit ee1ada1bdb
("elf: Rework exception handling in the dynamic loader
[BZ #25486]"), the previous order called the main calloc
to allocate a shadow GOT/PLT array for auditing support.
This happened before libc.so.6 ELF constructors were run, so
a user malloc could run without libc.so.6 having been
initialized fully. One observable effect was that
environ was NULL at this point.
It does not seem to be possible at present to trigger such
an allocation, but it seems more robust to delay switching
to main malloc after ld.so self-relocation is complete.
The elf/tst-rtld-no-malloc-audit test case fails with a
2.34-era glibc that does not have this fix.
Reviewed-by: DJ Delorie <dj@redhat.com>
For a long time, libc.so.6 has dependend on ld.so, which
means that there is a reference to ld.so in all processes,
and rtld_multiple_ref is always true. In fact, if
rtld_multiple_ref were false, some of the ld.so setup code
would not run.
Reviewed-by: DJ Delorie <dj@redhat.com>
In commit c628c22963 (elf: Remove
ldconfig kernel version check), the layout of auxcache entries
changed because the osversion field was removed from
struct aux_cache_file_entry. However, AUX_CACHEMAGIC was not
changed, so existing files are still used, potentially leading
to unintended ldconfig behavior. This commit changes AUX_CACHEMAGIC,
so that the file is regenerated.
Reported-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The refactoring did not take the change of variable into account.
Fixes commit 43db5e2c06
("elf: Signal RT_CONSISTENT after relocation processing in dlopen
(bug 31986)").
Previously, a la_activity audit event was generated before
relocation processing completed. This does did not match what
happened during initial startup in elf/rtld.c (towards the end
of dl_main). It also caused various problems if an auditor
tried to open the same shared object again using dlmopen:
If it was the directly loaded object, it had a search scope
associated with it, so the early exit in dl_open_worker_begin
was taken even though the object was unrelocated. This caused
the r_state == RT_CONSISTENT assert to fail. Avoidance of the
assert also depends on reversing the order of r_state update
and auditor event (already implemented in a previous commit).
At the later point, args->map can be NULL due to failure,
so use the assigned namespace ID instead if that is available.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Auditors can call into the dynamic loader again if
LA_ACT_CONSISTENT, and those recursive calls could observe
r_state != RT_CONSISTENT.
We should consider failing dlopen/dlmopen/dlclose if
r_state != RT_CONSISTENT. The dynamic linker is probably not
in a state in which it can handle reentrant calls. This
needs further investigation.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This is conceptually similar to the reported bug, but does not
depend on auditing. The fix is simple: just complete execution
of the constructors. This exposed the fact that the link map
for statically linked executables does not have l_init_called
set, even though constructors have run.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Calling an extern function in a different translation unit before
self-relocation is brittle. The compiler may load the address
at an earlier point in _dl_start, before self-relocation. In
_dl_start_final, the call is behind a compiler barrier, so this
cannot happen.
This case is detected early in the elf/dl-version.c consistency
checks. (These checks could be disabled in the future to allow
the removal of symbol versioning from objects.)
Commit f0b2132b35 ("ld.so: Support moving versioned symbols between
sonames [BZ #24741]) removed another call to _dl_name_match_p. The
_dl_check_caller function no longer exists, and the remaining calls
to _dl_name_match_p happen under the loader lock. This means that
atomic accesses are no longer required for the l_libname list. This
supersedes commit 395be7c218 ("elf: Fix data race in _dl_name_match_p
[BZ #21349]").
Add new testcase elf/tst-startup-errno.c which tests that errno is set
to 0 at first ELF constructor execution and at the start of the
program's main function.
Tested for x86_64
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The current racy approach is to enable asynchronous cancellation
before making the syscall and restore the previous cancellation
type once the syscall returns, and check if cancellation has happen
during the cancellation entrypoint.
As described in BZ#12683, this approach shows 2 problems:
1. Cancellation can act after the syscall has returned from the
kernel, but before userspace saves the return value. It might
result in a resource leak if the syscall allocated a resource or a
side effect (partial read/write), and there is no way to program
handle it with cancellation handlers.
2. If a signal is handled while the thread is blocked at a cancellable
syscall, the entire signal handler runs with asynchronous
cancellation enabled. This can lead to issues if the signal
handler call functions which are async-signal-safe but not
async-cancel-safe.
For the cancellation to work correctly, there are 5 points at which the
cancellation signal could arrive:
[ ... )[ ... )[ syscall ]( ...
1 2 3 4 5
1. Before initial testcancel, e.g. [*... testcancel)
2. Between testcancel and syscall start, e.g. [testcancel...syscall start)
3. While syscall is blocked and no side effects have yet taken
place, e.g. [ syscall ]
4. Same as 3 but with side-effects having occurred (e.g. a partial
read or write).
5. After syscall end e.g. (syscall end...*]
And libc wants to act on cancellation in cases 1, 2, and 3 but not
in cases 4 or 5. For the 4 and 5 cases, the cancellation will eventually
happen in the next cancellable entrypoint without any further external
event.
The proposed solution for each case is:
1. Do a conditional branch based on whether the thread has received
a cancellation request;
2. It can be caught by the signal handler determining that the saved
program counter (from the ucontext_t) is in some address range
beginning just before the "testcancel" and ending with the
syscall instruction.
3. SIGCANCEL can be caught by the signal handler and determine that
the saved program counter (from the ucontext_t) is in the address
range beginning just before "testcancel" and ending with the first
uninterruptable (via a signal) syscall instruction that enters the
kernel.
4. In this case, except for certain syscalls that ALWAYS fail with
EINTR even for non-interrupting signals, the kernel will reset
the program counter to point at the syscall instruction during
signal handling, so that the syscall is restarted when the signal
handler returns. So, from the signal handler's standpoint, this
looks the same as case 2, and thus it's taken care of.
5. For syscalls with side-effects, the kernel cannot restart the
syscall; when it's interrupted by a signal, the kernel must cause
the syscall to return with whatever partial result is obtained
(e.g. partial read or write).
6. The saved program counter points just after the syscall
instruction, so the signal handler won't act on cancellation.
This is similar to 4. since the program counter is past the syscall
instruction.
So The proposed fixes are:
1. Remove the enable_asynccancel/disable_asynccancel function usage in
cancellable syscall definition and instead make them call a common
symbol that will check if cancellation is enabled (__syscall_cancel
at nptl/cancellation.c), call the arch-specific cancellable
entry-point (__syscall_cancel_arch), and cancel the thread when
required.
2. Provide an arch-specific generic system call wrapper function
that contains global markers. These markers will be used in
SIGCANCEL signal handler to check if the interruption has been
called in a valid syscall and if the syscalls has side-effects.
A reference implementation sysdeps/unix/sysv/linux/syscall_cancel.c
is provided. However, the markers may not be set on correct
expected places depending on how INTERNAL_SYSCALL_NCS is
implemented by the architecture. It is expected that all
architectures add an arch-specific implementation.
3. Rewrite SIGCANCEL asynchronous handler to check for both canceling
type and if current IP from signal handler falls between the global
markers and act accordingly.
4. Adjust libc code to replace LIBC_CANCEL_ASYNC/LIBC_CANCEL_RESET to
use the appropriate cancelable syscalls.
5. Adjust 'lowlevellock-futex.h' arch-specific implementations to
provide cancelable futex calls.
Some architectures require specific support on syscall handling:
* On i386 the syscall cancel bridge needs to use the old int80
instruction because the optimized vDSO symbol the resulting PC value
for an interrupted syscall points to an address outside the expected
markers in __syscall_cancel_arch. It has been discussed in LKML [1]
on how kernel could help userland to accomplish it, but afaik
discussion has stalled.
Also, sysenter should not be used directly by libc since its calling
convention is set by the kernel depending of the underlying x86 chip
(check kernel commit 30bfa7b3488bfb1bb75c9f50a5fcac1832970c60).
* mips o32 is the only kABI that requires 7 argument syscall, and to
avoid add a requirement on all architectures to support it, mips
support is added with extra internal defines.
Checked on aarch64-linux-gnu, arm-linux-gnueabihf, powerpc-linux-gnu,
powerpc64-linux-gnu, powerpc64le-linux-gnu, i686-linux-gnu, and
x86_64-linux-gnu.
[1] https://lkml.org/lkml/2016/3/8/1105
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
With ia64 removal, the function descriptor supports is only used
by HPPA and new architectures do not seem leaning towards this
design.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Macros will automatically use the correct types, without
having to fiddle with internal glibc macros. It's also
impossible to get the types wrong due to aliasing because
support_check_stat_fd and support_check_stat_path do not
depend on the struct stat* types.
The changes reveal some inconsistencies in tests.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The old code used l_init_called as an indicator for whether TLS
initialization was complete. However, it is possible that
TLS for an object is initialized, written to, and then dlopen
for this object is called again, and l_init_called is not true at
this point. Previously, this resulted in TLS being initialized
twice, discarding any interim writes (technically introducing a
use-after-free bug even).
This commit introduces an explicit per-object flag, l_tls_in_slotinfo.
It indicates whether _dl_add_to_slotinfo has been called for this
object. This flag is used to avoid double-initialization of TLS.
In update_tls_slotinfo, the first_static_tls micro-optimization
is removed because preserving the initalization flag for subsequent
use by the second loop for static TLS is a bit complicated, and
another per-object flag does not seem to be worth it. Furthermore,
the l_init_called flag is dropped from the second loop (for static
TLS initialization) because l_need_tls_init on its own prevents
double-initialization.
The remaining l_init_called usage in resize_scopes and update_scopes
is just an optimization due to the use of scope_has_map, so it is
not changed in this commit.
The isupper check ensures that libc.so.6 is TLS is not reverted.
Such a revert happens if l_need_tls_init is not cleared in
_dl_allocate_tls_init for the main_thread case, now that
l_init_called is not checked anymore in update_tls_slotinfo
in elf/dl-open.c.
Reported-by: Jonathon Anderson <janderson@rice.edu>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
AT_HWCAP on some architecture can indeed use all bits.
Checked on x86_64-linux-gnu and powerpc-linux-gnu.
Reviewed-By: Andreas K. Hüttel <dilfridge@gentoo.org>
This avoids a test failure when the system has no /etc/ld.so.cache.
Tested on x86_64-linux-gnu.
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
ldconfig already ignores files with the -gdb.py suffix, but GDB also
looks for -gdb.gdb and -gdb.scm files. These aren't as widely used, but
libguile at least comes with a -gdb.scm file.
Rename is_gdb_python_file to is_gdb_extension_file, and make it
recognise all three types of GDB extension.
Signed-off-by: Adam Sampson <ats@offog.org>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
is_gdb_python_file is doing a similar test, so it can use this helper
function as well.
Signed-off-by: Adam Sampson <ats@offog.org>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
While working on a patch to add support for the extensible rseq ABI, we
came across an issue where a new 'const' variable would be merged with
the existing '__rseq_size' variable. We tracked this to the use of
'-fmerge-all-constants' which allows the compiler to merge identical
constant variables. This means that all 'const' variables in a compile
unit that are of the same size and are initialized to the same value can
be merged.
In this specific case, on 32 bit systems 'unsigned int' and 'ptrdiff_t'
are both 4 bytes and initialized to 0 which should trigger the merge.
However for reasons we haven't delved into when the attribute 'section
(".data.rel.ro")' is added to the mix, only variables of the same exact
types are merged. As far as we know this behavior is not specified
anywhere and could change with a new compiler version, hence this patch.
Move the definitions of these variables into an assembler file and add
hidden writable aliases for internal use. This has the added bonus of
removing the asm workaround to set the values on rseq registration.
Tested on Debian 12 with GCC 12.2.
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Starting with commit
59974938fe
elf/rtld: Count skipped environment variables for enable_secure
The new testcase elf/tst-tunables-enable_secure-env segfaults on s390 (31bit).
There _start parses the auxiliary vector for some additional checks.
Therefore it skips over the zeros after the environment variables ...
0x7fffac20: 0x7fffbd17 0x7fffbd32 0x7fffbd69 0x00000000
------------------------------------------------^^^last environment variable
... and then it parses the auxiliary vector and stops at AT_NULL.
0x7fffac30: 0x00000000 0x00000021 0x00000000 0x00000000
--------------------------------^^^AT_SYSINFO_EHDR--------------^^^AT_NULL
----------------^^^newp-----------------------------------------^^^oldp
Afterwards it tries to access AT_PHDR which points to somewhere and segfaults.
Due to not incorporating the skip_env variable in the computation of oldp
when shuffling down the auxv in rtld.c, it just copies one entry with AT_NULL
and value 0x00000021 and stops the loop. In reality we have skipped
GLIBC_TUNABLES environment variable (=> skip_env=1). Thus we should copy from
here:
0x7fffac40: 0x00000021 0x7ffff000 0x00000010 0x007fffff
----------------^^^fixed-oldp
This patch fixes the computation of oldp when shuffling down auxiliary vector.
It also adds some checks in the testcase. Those checks also fail on
s390x (64bit) and x86_64 without the fix.
Co-authored-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
It turns out that quite a few applications use bundled mallocs that
have been built to use global-dynamic TLS (instead of the recommended
initial-exec TLS). The previous workaround from
commit afe42e935b ("elf: Avoid some
free (NULL) calls in _dl_update_slotinfo") does not fix all
encountered cases unfortunatelly.
This change avoids the TLS generation update for recursive use
of TLS from a malloc that was called during a TLS update. This
is possible because an interposed malloc has a fixed module ID and
TLS slot. (It cannot be unloaded.) If an initially-loaded module ID
is encountered in __tls_get_addr and the dynamic linker is already
in the middle of a TLS update, use the outdated DTV, thus avoiding
another call into malloc. It's still necessary to update the
DTV to the most recent generation, to get out of the slow path,
which is why the check for recursion is needed.
The bookkeeping is done using a global counter instead of per-thread
flag because TLS access in the dynamic linker is tricky.
All this will go away once the dynamic linker stops using malloc
for TLS, likely as part of a change that pre-allocates all TLS
during pthread_create/dlopen.
Fixes commit d2123d6827 ("elf: Fix slow
tls access after dlopen [BZ #19924]").
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
The conditionals for several mtrace-based tests in catgets, elf, libio,
malloc, misc, nptl, posix, and stdio-common were incorrect leading to
test failures when bootstrapping glibc without perl.
The correct conditional for mtrace-based tests requires three checks:
first checking for run-built-tests, then build-shared, and lastly that
PERL is not equal to "no" (missing perl).
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Remove the definitions of HWCAP_IMPORTANT after removal of
LD_HWCAP_MASK / tunable glibc.cpu.hwcap_mask. There HWCAP_IMPORTANT
was used as default value.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Remove the environment variable LD_HWCAP_MASK and the tunable
glibc.cpu.hwcap_mask as those are not used anymore in common-code
after removal in elf/dl-cache.c:search_cache().
The only remaining user is sparc32 where it is used in
elf_machine_matches_host(). If sparc32 does not need it anymore,
we can get rid of it at all. Otherwise we could also move
LD_HWCAP_MASK / tunable glibc.cpu.hwcap_mask to be sparc32 specific.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Despite of powerpc where the returned integer is stored in tcb,
and the diagnostics output, there is no user anymore.
Thus this patch removes the diagnostics output and
_dl_string_platform for all other platforms.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The legacy hwcaps mechanism was removed with glibc 2.37:
See this commit series:
- d178c67535
x86_64: Remove platform directory library loading test
- 6099908fb8
elf: Remove legacy hwcaps support from the dynamic loader
- b78ff5a25d
elf: Remove legacy hwcaps support from ldconfig
- 4a7094119c
elf: Remove hwcap parameter from add_to_cache signature
- cfbf883db3
elf: Remove hwcap and bits_hwcap fields from struct cache_entry
- 78d9a1620b
Add NEWS entry for legacy hwcaps removal
- ab40f20364
elf: Remove _dl_string_hwcap
- e76369ed63
elf: Simplify output of hwcap subdirectories in ld.so help
According to Florian Weimer, this was an oversight and should also
have been removed.
As ldconfig does not generate ld.so.cache entries with hwcap/platform
bits in the hwcap-field anymore, this patch now skips those entries.
Thus currently only named-hwcap-entries and the default entries are
allowed.
For named-hwcap entries bit 62 is set and also the isa-level bits can
be set.
For the default entries the hwcap-field is 0.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The __stack_prot is used by Linux to make the stack executable if
a modules requires it. It is also marked as RELRO, which requires
to change the segment permission to RW to update it.
Also, there is no need to keep track of the flags: either the stack
will have the default permission of the ABI or should be change to
PROT_READ | PROT_WRITE | PROT_EXEC. The only additional flag,
PROT_GROWSDOWN or PROT_GROWSUP, is Linux only and can be deducted
from _STACK_GROWS_DOWN/_STACK_GROWS_UP.
Also, the check_consistency function was already removed some time
ago.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Linux 6.9 adds the ELF note type NT_ARM_FPMR. Add this to glibc's
elf.h, along with the previously missed NT_ARM_SSVE, NT_ARM_ZA and
NT_ARM_ZT (added in older kernel versions).
Tested for x86_64.
This has been confirmed to work around some interposed mallocs. Here
is a discussion of the impact test ust/libc-wrapper/test_libc-wrapper
in lttng-tools:
New TLS usage in libgcc_s.so.1, compatibility impact
<https://inbox.sourceware.org/libc-alpha/8734v1ieke.fsf@oldenburg.str.redhat.com/>
Reportedly, this patch also papers over a similar issue when tcmalloc
2.9.1 is not compiled with -ftls-model=initial-exec. Of course the
goal really should be to compile mallocs with the initial-exec TLS
model, but this commit appears to be a useful interim workaround.
Fixes commit d2123d6827 ("elf: Fix slow
tls access after dlopen [BZ #19924]").
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This new note type is defined at https://systemd.io/ELF_DLOPEN_METADATA/
and is used to list shared library dependencies loaded via dlopen().
Distro packagers can use this, via tools like those available at
https://github.com/systemd/package-notes to automatically generate
dependencies when building projects that make use of this
specification.
By defining the note id here we can use it in other projects as a
stable identifier, for example in 'readelf' to pretty-print its
content.
Signed-off-by: Luca Boccassi <bluca@debian.org>
Reviewed-by: Arjun Shankar <arjun@redhat.com>
Page was renamed some time ago, there's a redirect but better
to point to the right one
Signed-off-by: Luca Boccassi <bluca@debian.org>
Reviewed-by: Arjun Shankar <arjun@redhat.com>
There is no _dl_mcount_wrapper prototype in any installed header files.
Fix BZ #31765 by changing _dl_mcount_wrapper to a compat symbol and
obsolete it in glibc 2.40.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sunil K Pandey <skpgkp2@gmail.com>
This is mostly based on AArch64 and RISC-V implementation.
Add R_LARCH_TLS_DESC32 and R_LARCH_TLS_DESC64 relocations.
For _dl_tlsdesc_dynamic function slow path, temporarily save and restore
all vector registers.
Tunable with environment variables aliases are also ignored if
glibc.rtld.enable_secure is enabled. The tunable parsing is also
optimized a bit, where the loop that checks each environment variable
only checks for the tunables with aliases instead of all tables.
Checked on aarch64-linux-gnu and x86_64-linux-gnu.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Florian Weimer
Petr Malat
Sam James
Yury Khrustalev
Szabolcs Nagy
Adhemerval Zanella
Samuel Thibault
Michael Jeanson
H.J. Lu
Paul Eggert
Joseph Myers
Alejandro Colomar
Aurelien Jarno
DJ Delorie
Aaron Merey
Henrik Lindström
Xi Ruoyao
Adam Sampson
Stefan Liebler
Carlos O'Donell
Luca Boccassi
mengqinggang