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>
Without CET, a jump into a newly loaded object through an overwritten
link map often does not crash, it just executes some random code.
CET detects this in some cases because the function pointer does not
point to the start of a function in the replacement shared object,
so there is no ENDBR instruction.
The new test uses a small shared object and the existing dangling
link map to trigger the bug.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
We should clear GL(dl_initfirst) when freeing its link_map memory.
Tested on Fedora 31/x86-64 with CET.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
This new test was introduced with recent commit
591236f1a3.
If run on 32bit, it fails while renaming tst-ldconfig-ld-mod.so as there is no
/usr/lib64 directory. This patch is constructing the file name with help of
support_libdir_prefix.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Test ldconfig after /etc/ld.so.conf update and verify a running process
observes changes to /etc/ld.so.cache.
The test uses the test-in-container framework.
Reviewed-by: Arjun Shankar <arjun@redhat.com>
This patch moves the vDSO setup from libc to loader code, just after
the vDSO link_map setup. For static case the initialization
is moved to _dl_non_dynamic_init instead.
Instead of using the mangled pointer, the vDSO data is set as
attribute_relro (on _rtld_global_ro for shared or _dl_vdso_* for
static). It is read-only even with partial relro.
It fixes BZ#24967 now that the vDSO pointer is setup earlier than
malloc interposition is called.
Also, vDSO calls should not be a problem for static dlopen as
indicated by BZ#20802. The vDSO pointer would be zero-initialized
and the syscall will be issued instead.
Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu,
arm-linux-gnueabihf, powerpc64le-linux-gnu, powerpc64-linux-gnu,
powerpc-linux-gnu, s390x-linux-gnu, sparc64-linux-gnu, and
sparcv9-linux-gnu. I also run some tests on mips.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
The code is similar to the one at elf/dl-reloc.c, where it checks for
the l_relro_size from the link_map (obtained from PT_GNU_RELRO header
from program headers) and calls_dl_protected_relro.
For testing I will use the ones proposed by Florian's patch
'elf: Add tests for working RELRO protection' [1].
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
aarch64-linux-gnu, s390x-linux-gnu, and sparc64-linux-gnu. I also
check with --enable-static pie on x86_64-linux-gnu, i686-linux-gnu,
and aarch64-linux-gnu which seems the only architectures where
static PIE is actually working (as per 9d7a3741c9, on
arm-linux-gnueabihf, powerpc64{le}-linux-gnu, and s390x-linux-gnu
I am seeing runtime issues not related to my patch).
[1] https://sourceware.org/ml/libc-alpha/2019-10/msg00059.html
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
I've updated copyright dates in glibc for 2020. This is the patch for
the changes not generated by scripts/update-copyrights and subsequent
build / regeneration of generated files. As well as the usual annual
updates, mainly dates in --version output (minus libc.texinfo which
previously had to be handled manually but is now successfully updated
by update-copyrights), there is a fix to
sysdeps/unix/sysv/linux/powerpc/bits/termios-c_lflag.h where a typo in
the copyright notice meant it failed to be updated automatically.
Please remember to include 2020 in the dates for any new files added
in future (which means updating any existing uncommitted patches you
have that add new files to use the new copyright dates in them).
Previously, ld.so was invoked only with the elf subdirectory on the
library search path. Since the soname link for libc.so only exists in
the top-level build directory, this leaked the system libc into the
test.
Blocking signals causes issues with certain anti-malware solutions
which rely on an unblocked SIGSYS signal for system calls they
intercept.
This reverts commit a2e8aa0d9e
("Block signals during the initial part of dlopen") and adds
comments related to async signal safety to active_nodelete and
its caller.
Note that this does not make lazy binding async-signal-safe with regards
to dlopen. It merely avoids introducing new async-signal-safety hazards
as part of the NODELETE changes.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Commit a2e8aa0d9e ("Block signals during
the initial part of dlopen") was deemed necessary because of
read-modify-write operations like the one in add_dependency in
elf/dl-lookup.c. In the old code, we check for any kind of NODELETE
status and bail out:
/* Redo the NODELETE check, as when dl_load_lock wasn't held
yet this could have changed. */
if (map->l_nodelete != link_map_nodelete_inactive)
goto out;
And then set pending status (during relocation):
if (flags & DL_LOOKUP_FOR_RELOCATE)
map->l_nodelete = link_map_nodelete_pending;
else
map->l_nodelete = link_map_nodelete_active;
If a signal arrives during relocation and the signal handler, through
lazy binding, adds a global scope dependency on the same map, it will
set map->l_nodelete to link_map_nodelete_active. This will be
overwritten with link_map_nodelete_pending by the dlopen relocation
code.
To avoid such problems in relation to the l_nodelete member, this
commit introduces two flags for active NODELETE status (irrevocable)
and pending NODELETE status (revocable until activate_nodelete is
invoked). As a result, NODELETE processing in dlopen does not
introduce further reasons why lazy binding from signal handlers
is unsafe during dlopen, and a subsequent commit can remove signal
blocking from dlopen.
This does not address pre-existing issues (unrelated to the NODELETE
changes) which make lazy binding in a signal handler during dlopen
unsafe, such as the use of malloc in both cases.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The assumption behind the assert in activate_nodelete was wrong:
Inconsistency detected by ld.so: dl-open.c: 459: activate_nodelete:
Assertion `!imap->l_init_called || imap->l_type != lt_loaded' failed! (edit)
It can happen that an already-loaded object that is in the local
scope is promoted to NODELETE status, via binding to a unique
symbol.
Similarly, it is possible that such NODELETE promotion occurs to
an already-loaded object from the global scope. This is why the
loop in activate_nodelete has to cover all objects in the namespace
of the new object.
In do_lookup_unique, it could happen that the NODELETE status of
an already-loaded object was overwritten with a pending NODELETE
status. As a result, if dlopen fails, this could cause a loss of
the NODELETE status of the affected object, eventually resulting
in an incorrect unload.
Fixes commit f63b73814f ("Remove all
loaded objects if dlopen fails, ignoring NODELETE [BZ #20839]").
Since commit a3cc4f48e9 ("Remove
--as-needed configure test."), --as-needed support is no longer
optional.
The macros are not much shorter and do not provide documentary
value, either, so this commit removes them.
This commit adds missing skip_ifunc checks to aarch64, arm, i386,
sparc, and x86_64. A new test case ensures that IRELATIVE IFUNC
resolvers do not run in various diagnostic modes of the dynamic
loader.
Reviewed-By: Szabolcs Nagy <szabolcs.nagy@arm.com>
This reverts the non-test change from commit d0093c5cef
("Call _dl_open_check after relocation [BZ #24259]"), given that
the underlying bug has been fixed properly in commit 61b74477fa7f63
("Remove all loaded objects if dlopen fails, ignoring NODELETE
[BZ #20839]").
Tested on x86-64-linux-gnu, with and without --enable-cet.
Change-Id: I995a6cfb89f25d2b0cf5e606428c2a93eb48fc33
Lazy binding in a signal handler that interrupts a dlopen sees
intermediate dynamic linker state. This has likely been always
unsafe, but with the new pending NODELETE state, this is clearly
incorrect. Other threads are excluded via the loader lock, but the
current thread is not. Blocking signals until right before ELF
constructors run is the safe thing to do.
Change-Id: Iad079080ebe7442c13313ba11dc2797953faef35
This introduces a “pending NODELETE” state in the link map, which is
flipped to the persistent NODELETE state late in dlopen, via
activate_nodelete. During initial relocation, symbol binding
records pending NODELETE state only. dlclose ignores pending NODELETE
state. Taken together, this results that a partially completed dlopen
is rolled back completely because new NODELETE mappings are unloaded.
Tested on x86_64-linux-gnu and i386-linux-gnu.
Change-Id: Ib2a3d86af6f92d75baca65431d74783ee0dbc292
This change splits the scope and TLS slotinfo updates in dlopen into
two parts: one to resize the data structures, and one to actually apply
the update. The call to add_to_global_resize in dl_open_worker is moved
before the demarcation point at which no further memory allocations are
allowed.
_dl_add_to_slotinfo is adjusted to make the list update optional. There
is some optimization possibility here because we could grow the slotinfo
list of arrays in a single call, one the largest TLS modid is known.
This commit does not fix the fatal meory allocation failure in
_dl_update_slotinfo. Ideally, this error during dlopen should be
recoverable.
The update order of scopes and TLS data structures is retained, although
it appears to be more correct to fully initialize TLS first, and then
expose symbols in the newly loaded objects via the scope update.
Tested on x86_64-linux-gnu.
Change-Id: I240c58387dabda3ca1bcab48b02115175fa83d6c
The call to add_to_global in dl_open_worker happens after running ELF
constructors for new objects. At this point, proper recovery from
malloc failure would be quite complicated: We would have to run the
ELF destructors and close all opened objects, something that we
currently do not do.
Instead, this change splits add_to_global into two phases,
add_to_global_resize (which can raise an exception, called before ELF
constructors run), and add_to_global_update (which cannot, called
after ELF constructors). A complication arises due to recursive
dlopen: After the inner dlopen consumes some space, the pre-allocation
in the outer dlopen may no longer be sufficient. A new member in the
namespace structure, _ns_global_scope_pending_adds keeps track of the
maximum number of objects that need to be added to the global scope.
This enables the inner add_to_global_resize call to take into account
the needs of an outer dlopen.
Most code in the dynamic linker assumes that the number of global
scope entries fits into an unsigned int (matching the r_nlist member
of struct r_scop_elem). Therefore, change the type of
_ns_global_scope_alloc to unsigned int (from size_t), and add overflow
checks.
Change-Id: Ie08e2f318510d5a6a4bcb1c315f46791b5b77524
If a lazy binding failure happens during the execution of an ELF
constructor or destructor, the dynamic loader catches the error
and reports it using the dlerror mechanism. This is undesirable
because there could be other constructors and destructors that
need processing (which are skipped), and the process is in an
inconsistent state at this point. Therefore, we have to issue
a fatal dynamic loader error error and terminate the process.
Note that the _dl_catch_exception in _dl_open is just an inner catch,
to roll back some state locally. If called from dlopen, there is
still an outer catch, which is why calling _dl_init via call_dl_init
and a no-exception is required and cannot be avoiding by moving the
_dl_init call directly into _dl_open.
_dl_fini does not need changes because it does not install an error
handler, so errors are already fatal there.
Change-Id: I6b1addfe2e30f50a1781595f046f44173db9491a
Obtaining the link map is potentially very slow because it requires
iterating over all loaded objects in the current implementation. If
the caller supplied an explicit handle (i.e., not one of the RTLD_*
constants), the dlsym implementation does not need the identity of the
caller (except in the special case of auditing), so this change
avoids computing it in that case.
Even in the minimal case (dlsym called from a main program linked with
-dl), this shows a small speedup, perhaps around five percent. The
performance improvement can be arbitrarily large in principle (if
_dl_find_dso_for_object has to iterate over many link maps).
Change-Id: Ide5d9e2cc7ac25a0ffae8fb4c26def0c898efa29
In GCC 10, the default at -O2 is now -ftree-loop-distribute-patterns.
This optimization causes GCC to "helpfully" convert the hand-written
loop in _dl_start into a call to memset, which is not available that
early in program startup. Similar problems in other places in GLIBC
have been addressed by explicitly building with
-fno-tree-loop-distribute-patterns, but this one may have been
overlooked previously because it only affects targets where
HAVE_BUILTIN_MEMSET is not defined.
This patch fixes a bug observed on nios2-linux-gnu target that caused
all programs to segv on startup.
This will allow changes in dependency processing during non-lazy
binding, for more precise processing of NODELETE objects: During
initial relocation in dlopen, the fate of NODELETE objects is still
unclear, so objects which are depended upon by NODELETE objects
cannot immediately be marked as NODELETE.
Change-Id: Ic7b94a3f7c4719a00ca8e6018088567824da0658
In some cases, it is necessary to introduce noexcept regions
where raised dynamic loader exceptions (e.g., from lazy binding)
are fatal, despite being nested in a code region with an active
exception handler. This change enhances _dl_catch_exception with
to provide such a capability. The existing function is reused,
so that it is not necessary to introduce yet another function with
a similar purpose.
Change-Id: Iec1bf642ff95a349fdde8040e9baf851ac7b8904
To improve GCC 10 compatibility, it is necessary to remove the l_audit
zero-length array from the end of struct link_map. In preparation of
that, this commit introduces an accessor function for the audit state,
so that it is possible to change the representation of the audit state
without adjusting the code that accesses it.
Tested on x86_64-linux-gnu. Built on i686-gnu.
Change-Id: Id815673c29950fc011ae5301d7cde12624f658df
Only one of the currently defined flags is incompatible with versioned
symbol lookups, so it makes sense to check for that flag and not its
complement.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>
Change-Id: I3384349cef90cfd91862ebc34a4053f0c0a99404
From the beginning, elf/tst-dlopen-aout has exercised two different
bugs: (a) failure to report errors for a dlopen of the executable
itself in some cases (bug 24900) and (b) incorrect rollback of the
TLS modid allocation in case of a dlopen failure (bug 16634).
This commit replaces the test with elf/tst-dlopen-self for (a) and
elf/tst-dlopen-tlsmodid for (b). The latter tests use the
elf/tst-dlopen-self binaries (or iconv) with dlopen, so they are
no longer self-dlopen tests.
Tested on x86_64-linux-gnu and i686-linux-gnu, with a toolchain that
does not default to PIE.
Commit a42faf59d6 ("Fix BZ #16634.")
attempted to fix a TLS modid consistency issue by adding additional
checks to the open_verify function. However, this is fragile
because open_verify cannot reliably predict whether
_dl_map_object_from_fd will later fail in the more complex cases
(such as memory allocation failures). Therefore, this commit
assigns the TLS modid as late as possible. At that point, the link
map pointer will eventually be passed to _dl_close, which will undo
the TLS modid assignment.
Reviewed-by: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>
If the loader is invoked explicitly and loads the main executable,
it stores the file ID of the main executable in l_file_id. This
information is not available if the main excutable is loaded by the
kernel, so this is another case where the two cases differ.
This enhances commit 23d2e5faf0
("elf: Self-dlopen failure with explict loader invocation
[BZ #24900]").
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com>
The testcase forks a child process and runs pldd with PID of
this child. On systems where /proc/sys/kernel/yama/ptrace_scope
differs from zero, pldd will fail with
/usr/bin/pldd: cannot attach to process 3: Operation not permitted
This patch checks if ptrace_scope exists, is zero "classic ptrace permissions"
or one "restricted ptrace". If ptrace_scope exists and has a higher
restriction, then the test is marked as UNSUPPORTED.
The case "restricted ptrace" is handled by rearranging the processes involved
during the test. Now we have the following process tree:
-parent: do_test (performs output checks)
--subprocess 1: pldd_process (becomes pldd via execve)
---subprocess 2: target_process (ptraced via pldd)
ChangeLog:
* elf/tst-pldd.c (do_test): Add UNSUPPORTED check.
Rearrange subprocesses.
(pldd_process): New function.
* support/Makefile (libsupport-routines): Add support_ptrace.
* support/xptrace.h: New file.
* support/support_ptrace.c: Likewise.
This patch is a reimplementation of [1], which was submitted back in
2015. Copyright issue has been sorted [2] last year. It proposed a new
section (.gnu.xhash) and related dynamic tag (GT_GNU_XHASH). The new
section would be virtually identical to the existing .gnu.hash except
for the translation table (xlat) which would contain correct MIPS
.dynsym indexes corresponding to the hashvals in chains. This is because
MIPS ABI imposes a different ordering of the dynsyms than the one
expected by the .gnu.hash section. Another addition would be a leading
word at the beggining of the section, which would contain the number of
entries in the translation table.
In this patch, the new section name and dynamic tag are changed to
reflect the fact that the section should be treated as MIPS specific
(.MIPS.xhash and DT_MIPS_XHASH).
This patch addresses the alignment issue reported in [3] which is caused
by the leading word of the .MIPS.xhash section. Leading word is now
removed in the corresponding binutils patch, and the number of entries
in the translation table is computed using DT_MIPS_SYMTABNO dynamic tag.
Since the MIPS specific dl-lookup.c file was removed following the
initial patch submission, I opted for the definition of three new macros
in the generic ldsodefs.h. ELF_MACHINE_GNU_HASH_ADDRIDX defines the
index of the dynamic tag in the l_info array. ELF_MACHINE_HASH_SYMIDX is
used to calculate the index of a symbol in GNU hash. On MIPS, it is
defined to look up the symbol index in the translation table.
ELF_MACHINE_XHASH_SETUP is defined for MIPS only. It initializes the
.MIPS.xhash pointer in the link_map_machine struct.
The other major change is bumping the highest EI_ABIVERSION value for
MIPS to suggest that the dynamic linker now supports GNU hash.
The patch was tested by running the glibc testsuite for the three MIPS
ABIs (o32, n32 and n64) and for x86_64-linux-gnu.
[1] https://sourceware.org/ml/binutils/2015-10/msg00057.html
[2] https://sourceware.org/ml/binutils/2018-03/msg00025.html
[3] https://sourceware.org/ml/binutils/2016-01/msg00006.html
* elf/dl-addr.c (determine_info): Calculate the symbol index
using the newly defined ELF_MACHINE_HASH_SYMIDX macro.
* elf/dl-lookup.c (do_lookup_x): Ditto.
(_dl_setup_hash): Initialize MIPS xhash translation table.
* elf/elf.h (SHT_MIPS_XHASH): New define.
(DT_MIPS_XHASH): New define.
* sysdeps/generic/ldsodefs.h (ELF_MACHINE_GNU_HASH_ADDRIDX): New
define.
(ELF_MACHINE_HASH_SYMIDX): Ditto.
(ELF_MACHINE_XHASH_SETUP): Ditto.
* sysdeps/mips/ldsodefs.h (ELF_MACHINE_GNU_HASH_ADDRIDX): New
define.
(ELF_MACHINE_HASH_SYMIDX): Ditto.
(ELF_MACHINE_XHASH_SETUP): Ditto.
* sysdeps/mips/linkmap.h (struct link_map_machine): New member.
* sysdeps/unix/sysv/linux/mips/ldsodefs.h: Increment valid ABI
version.
* sysdeps/unix/sysv/linux/mips/libc-abis: New ABI version.
