To help detect common kinds of memory (and other resource) management
bugs, GCC 11 adds support for the detection of mismatched calls to
allocation and deallocation functions. At each call site to a known
deallocation function GCC checks the set of allocation functions
the former can be paired with and, if the two don't match, issues
a -Wmismatched-dealloc warning (something similar happens in C++
for mismatched calls to new and delete). GCC also uses the same
mechanism to detect attempts to deallocate objects not allocated
by any allocation function (or pointers past the first byte into
allocated objects) by -Wfree-nonheap-object.
This support is enabled for built-in functions like malloc and free.
To extend it beyond those, GCC extends attribute malloc to designate
a deallocation function to which pointers returned from the allocation
function may be passed to deallocate the allocated objects. Another,
optional argument designates the positional argument to which
the pointer must be passed.
This change is the first step in enabling this extended support for
Glibc.
Big win in binary size and avoids duplicating the logic in multiple
places.
On x86_64, dropped from 1883206 to 1881790, a 1416 byte decrease.
Also changed logic to track if ttyname_buf has been allocated by
checking if it's NULL instead of tracking buflen as an additional
variable.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Both the sysfs and procfs parsing (through GET_NPROCS_PARSER) are
removed in favor the syscall. The initial scratch buffer should
fit to most of the common usage (1024 bytes with maps to 8192 CPUs).
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
The symbols were moved using move-symbol-to-libc.py.
Both functions are moved at the same time because they depend
on internal functions in sysdeps/pthread/sem_routines.c, which
are moved in this commit as well. Additional hidden prototypes
are required to avoid check-localplt failures.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Calling free directly may end up freeing a pointer allocated by the
dynamic loader using malloc from libc.so in the base namespace using
the allocator from libc.so in a secondary namespace, which results in
crashes.
This commit redirects the free call through GLRO and the dynamic
linker, to reach the correct namespace. It also cleans up the dlerror
handling along the way, so that pthread_setspecific is no longer
needed (which avoids triggering bug 24774).
It's necessary to stub out __libc_disable_asynccancel and
__libc_enable_asynccancel via rtld-stubbed-symbols because the new
direct references to the unwinder result in symbol conflicts when the
rtld exception handling from libc is linked in during the construction
of librtld.map.
unwind-forcedunwind.c is merged into unwind-resume.c. libc now needs
the functions that were previously only used in libpthread.
The GLIBC_PRIVATE exports of __libc_longjmp and __libc_siglongjmp are
no longer needed, so switch them to hidden symbols.
The symbol __pthread_unwind_next has been moved using
scripts/move-symbol-to-libc.py.
Reviewed-by: Adhemerva Zanella <adhemerval.zanella@linaro.org>
So that text_set_element/data_set_element/bss_set_element defined
variables will be retained by the linker.
Note: 'used' and 'retain' are orthogonal: 'used' makes sure the variable
will not be optimized out; 'retain' prevents section garbage collection
if the linker support SHF_GNU_RETAIN.
GNU ld 2.37 and LLD 13 will support -z start-stop-gc which allow C
identifier name sections to be GCed even if there are live
__start_/__stop_ references.
Without the change, there are some static linking problems, e.g.
_IO_cleanup (libio/genops.c) may be discarded by ld --gc-sections, so
stdout is not flushed on exit.
Note: GCC may warning 'retain' attribute ignored while __has_attribute(retain)
is 1 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99587).
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
The commit 2433d39b69, which added time64 support to select, changed
the function to use __NR_pselect6 (or __NR_pelect6_time64) on all
architectures. However, on architectures where the symbol was
implemented with __NR_select the kernel normalizes the passed timeout
instead of return EINVAL. For instance, the input timeval
{ 0, 5000000 } is interpreted as { 5, 0 }.
And as indicated by BZ #27651, this semantic seems to be expected
and changing it results in some performance issues (most likely
the program does not check the return code and keeps issuing
select with unormalized tv_usec argument).
To avoid a different semantic depending whether which syscall the
architecture used to issue, select now always normalize the timeout
input. This is a slight change for some ABIs (for instance aarch64).
Checked on x86_64-linux-gnu and i686-linux-gnu.
The libc version is identical and built with same flags. The libc
version is set as the default version.
The libpthread compat symbol requires to mask it when building the
loader object otherwise ld might complain about a missing
versioned symbol (as for alpha).
Checked on x86_64-linux-gnu.
This is only used internally in malloc.c, the extern declaration
was wrong, __mtag_mmap_flags has internal linkage.
Reviewed-by: DJ Delorie <dj@redhat.com>
This essentially folds compat_symbol_unique functionality into
compat_symbol.
This change eliminates the need for intermediate aliases for defining
multiple symbol versions, for both compat_symbol and versioned_symbol.
Some binutils versions do not suport multiple versions per symbol on
some targets, so aliases are automatically introduced, similar to what
compat_symbol_unique did. To reduce symbol table sizes, a configure
check is added to avoid these aliases if they are not needed.
The new mechanism works with data symbols as well as function symbols,
due to the way an assembler-level redirect is used. It is not
compatible with weak symbols for old binutils versions, which is why
the definition of __malloc_initialize_hook had to be changed. This
is not a loss of functionality because weak symbols do not matter
to dynamic linking.
The placeholder symbol needs repeating in nptl/libpthread-compat.c
now that compat_symbol is used, but that seems more obvious than
introducing yet another macro.
A subtle difference was that compat_symbol_unique made the symbol
global automatically. compat_symbol does not do this, so static
had to be removed from the definition of
__libpthread_version_placeholder.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
A subsequent change will require including <config.h> for defining
symbol_version_reference. <libc-symbol.h> should not include
<config.h> for _ISOMAC, so it cannot define symbol_version_reference
anymore, but symbol_version_reference is needed <shlib-compat.h> even
for _ISOMAC. Moving the definition of symbol_version_reference to a
separate file <libc-symver.h> makes it possible to use a single
definition for both cases.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Both htl and nptl uses a different data structure to implement atfork
handlers. The nptl one was refactored by 27761a1042 to use a dynarray
which simplifies the code.
This patch moves the nptl one to be the generic implementation and
replace Hurd linked one. Different than previous NPTL, Hurd also uses
a global lock, so performance should be similar.
Checked on x86_64-linux-gnu, i686-linux-gnu, and with a build for
i686-gnu.
This is helpful for testing compat symbols in cases where _ISOMAC
is activated implicitly due to -DMODULE_NAME=testsuite and cannot
be disabled easily.
There is no need to handle ENOSYS on fstatfs64 call, required only
for alpha (where is already fallbacks to fstatfs).
Checked on x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The __NR_fstatfs64 syscall is supported on all architectures but
aarch64, mips64, riscv64, and x86_64. And newer ABIs also uses
the new fstatfs64 interface (where the struct size is used as
first argument).
So the default implementation now uses:
1. __NR_fstatfs64 for non-LFS call and handle overflow directly
There is no need to handle __NR_fstatfs since all architectures
that only support are LFS only.
2. __NR_fstatfs if defined or __NR_fstatfs64 otherwise for LFS
call.
Alpha is the only outlier, it is a 64-bit architecture which
provides non-LFS interface and only provides __NR_fstatfs64 on
newer kernels (5.1+).
Checked on x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Add __nonnull((2)) to the setrlimit()/getrlimit() function declaration
to avoid null pointer access.
-----
v2
According to the suggestions of the Adhemerval Zanella and Zack Weinberg:
use __nonnull() to check null pointers in the compilation phase.
do not add pointer check code to setrlimit()/getrlimit().
The validity of the "resource" parameter is checked in the syscall.
v1
https://public-inbox.org/libc-alpha/20201230114131.47589-1-nixiaoming@huawei.com/
-----
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Previously, glibc would pick an arbitrary tmpfs file system from
/proc/mounts if /dev/shm was not available. This could lead to
an unsuitable file system being picked for the backing storage for
shm_open, sem_open, and related functions.
This patch introduces a new function, __shm_get_name, which builds
the file name under the appropriate (now hard-coded) directory. It is
called from the various shm_* and sem_* function. Unlike the
SHM_GET_NAME macro it replaces, the callers handle the return values
and errno updates. shm-directory.c is moved directly into the posix
subdirectory because it can be implemented directly using POSIX
functionality. It resides in libc because it is needed by both
librt and nptl/htl.
In the sem_open implementation, tmpfname is initialized directly
from a string constant. This happens to remove one alloca call.
Checked on x86_64-linux-gnu.
Add _SC_MINSIGSTKSZ for the minimum signal stack size derived from
AT_MINSIGSTKSZ, which is the minimum number of bytes of free stack
space required in order to gurantee successful, non-nested handling
of a single signal whose handler is an empty function, and _SC_SIGSTKSZ
which is the suggested minimum number of bytes of stack space required
for a signal stack.
If AT_MINSIGSTKSZ isn't available, sysconf (_SC_MINSIGSTKSZ) returns
MINSIGSTKSZ. On Linux/x86 with XSAVE, the signal frame used by kernel
is composed of the following areas and laid out as:
------------------------------
| alignment padding |
------------------------------
| xsave buffer |
------------------------------
| fsave header (32-bit only) |
------------------------------
| siginfo + ucontext |
------------------------------
Compute AT_MINSIGSTKSZ value as size of xsave buffer + size of fsave
header (32-bit only) + size of siginfo and ucontext + alignment padding.
If _SC_SIGSTKSZ_SOURCE or _GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ
are redefined as
/* Default stack size for a signal handler: sysconf (SC_SIGSTKSZ). */
# undef SIGSTKSZ
# define SIGSTKSZ sysconf (_SC_SIGSTKSZ)
/* Minimum stack size for a signal handler: SIGSTKSZ. */
# undef MINSIGSTKSZ
# define MINSIGSTKSZ SIGSTKSZ
Compilation will fail if the source assumes constant MINSIGSTKSZ or
SIGSTKSZ.
The reason for not simply increasing the kernel's MINSIGSTKSZ #define
(apart from the fact that it is rarely used, due to glibc's shadowing
definitions) was that userspace binaries will have baked in the old
value of the constant and may be making assumptions about it.
For example, the type (char [MINSIGSTKSZ]) changes if this #define
changes. This could be a problem if an newly built library tries to
memcpy() or dump such an object defined by and old binary.
Bounds-checking and the stack sizes passed to things like sigaltstack()
and makecontext() could similarly go wrong.
This reverts commit 2682695e5c.
Fixes bug 27237.
That commit turned out to be too intrusive affecting crt files, test
system and benchmark files. They should not be affected, but the
build system does not set the MODULE_NAME and LIBC_NONSHARED reliably.
This reverts commit 20b39d5946 for static
library. This avoids the need to rebuild the world for the case where
libstdc++ (and potentially other libraries) are linked to a old glibc.
To avoid requering to provide xstat symbols for newer ABIs (such as
riscv32) a new LIB_COMPAT macro is added. It is similar to SHLIB_COMPAT
but also works for static case (thus evaluating similar to SHLIB_COMPAT
for both shared and static case).
Checked with a check-abi on all affected ABIs. I also check if the
static library does contains the xstat symbols.
Hidden visibility can avoid indirections and RELATIVE relocs in
static PIE libc.
The check should use IS_IN_LIB instead of IS_IN(libc) since all
symbols are defined locally in static PIE and the optimization is
useful in all libraries not just libc. However the test system
links objects from libcrypt.a into dynamic linked test binaries
where hidden visibility does not work. I think mixing static and
shared libc components in the same binary should not be supported
usage, but to be safe only use hidden in libc.a.
On some targets (i386) this optimization cannot be applied because
hidden visibility PIE ifunc functions don't work, so it is gated by
NO_HIDDEN_EXTERN_FUNC_IN_PIE.
From -static-pie linked 'int main(){}' this shaves off 71 relative
relocs on aarch64 and reduces code size by about 2k.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
Introduce a new _FORTIFY_SOURCE level of 3 to enable additional
fortifications that may have a noticeable performance impact, allowing
more fortification coverage at the cost of some performance.
With llvm 9.0 or later, this will replace the use of
__builtin_object_size with __builtin_dynamic_object_size.
__builtin_dynamic_object_size
-----------------------------
__builtin_dynamic_object_size is an LLVM builtin that is similar to
__builtin_object_size. In addition to what __builtin_object_size
does, i.e. replace the builtin call with a constant object size,
__builtin_dynamic_object_size will replace the call site with an
expression that evaluates to the object size, thus expanding its
applicability. In practice, __builtin_dynamic_object_size evaluates
these expressions through malloc/calloc calls that it can associate
with the object being evaluated.
A simple motivating example is below; -D_FORTIFY_SOURCE=2 would miss
this and emit memcpy, but -D_FORTIFY_SOURCE=3 with the help of
__builtin_dynamic_object_size is able to emit __memcpy_chk with the
allocation size expression passed into the function:
void *copy_obj (const void *src, size_t alloc, size_t copysize)
{
void *obj = malloc (alloc);
memcpy (obj, src, copysize);
return obj;
}
Limitations
-----------
If the object was allocated elsewhere that the compiler cannot see, or
if it was allocated in the function with a function that the compiler
does not recognize as an allocator then __builtin_dynamic_object_size
also returns -1.
Further, the expression used to compute object size may be non-trivial
and may potentially incur a noticeable performance impact. These
fortifications are hence enabled at a new _FORTIFY_SOURCE level to
allow developers to make a choice on the tradeoff according to their
environment.
Make the _FORTIFY_SOURCE macro soup in features.h warn about
unsupported fortification levels. For example, it will warn about
_FORTIFY_SOURCE=3 and over with an indication of which level has been
selected.
Co-authored-by: Paul Eggert <eggert@cs.ucla.edu>
This patch adds the basic support for memory tagging.
Various flavours are supported, particularly being able to turn on
tagged memory at run-time: this allows the same code to be used on
systems where memory tagging support is not present without neededing
a separate build of glibc. Also, depending on whether the kernel
supports it, the code will use mmap for the default arena if morecore
does not, or cannot support tagged memory (on AArch64 it is not
available).
All the hooks use function pointers to allow this to work without
needing ifuncs.
Reviewed-by: DJ Delorie <dj@redhat.com>
Change sbrk to fail for !__libc_initial (in the generic
implementation). As a result, sbrk is (relatively) safe to use
for the __libc_initial case (from the main libc). It is therefore
no longer necessary to avoid using it in that case (or updating the
brk cache), and the __libc_initial flag does not need to be updated
as part of dlmopen or static dlopen.
As before, direct brk system calls on Linux may lead to memory
corruption.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
GCC 11 with
commit 6fbec038f7a7ddf29f074943611b53210d17c40c
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Mon Feb 3 11:55:43 2020 -0800
Use SHF_GNU_RETAIN to preserve symbol definitions
places used symbols in SECTION_RETAIN sections if assembler supports it.
Mark __libc_freeres_fn as used to avoid
gconv_dl.c: In function 'free_mem':
gconv_dl.c:191:1: error: 'do_release_all' without 'used' attribute and 'free_mem' with 'used' attribute are placed in a section with the same name [-Werror=attributes]
191 | do_release_all (void *nodep)
| ^~~~~~~~~~~~~~
In file included from <command-line>:
gconv_dl.c:202:18: note: 'free_mem' was declared here
202 | libc_freeres_fn (free_mem)
| ^~~~~~~~
./../include/libc-symbols.h:316:15: note: in definition of macro 'libc_freeres_fn'
316 | static void name (void)
| ^~~~
cc1: all warnings being treated as errors
If glibc is build with -O3 on at least 390 (-m31) or x86 (-m32),
gcc 11 dumps this warning:
svc_tcp.c: In function 'rendezvous_request':
svc_tcp.c:274:3: error: 'memcpy' offset [0, 15] is out of the bounds [0, 0] [-Werror=array-bounds]
274 | memcpy (&xprt->xp_raddr, &addr, sizeof (addr));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
In out-of-memory case, if one of the mallocs in makefd_xprt function
returns NULL, a message is dumped, makefd_xprt returns NULL
and the subsequent memcpy would copy to NULL.
Instead of a segfaulting, we delay a bit (see also __svc_accept_failed
and Bug 14889 (CVE-2011-4609) - svc_run() produces high cpu usage when
accept() fails with EMFILE (CVE-2011-4609).
The same applies to svc_unix.c.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The functions strtoimax, strtoumax, wcstoimax, wcstoumax currently
have three implementations each (wordsize-32, wordsize-64 and dummy
implementation in stdlib/ using #error), defining the functions as
thin wrappers round corresponding *_internal functions. Simplify the
code by changing them into aliases of functions such as strtol and
wcstoull. This is more consistent with how e.g. imaxdiv is handled.
Tested for x86_64 and x86.
This change uses (in gai_misc.h):
- __futex_abstimed_wait64 (instead of futex_reltimed_wait)
- __futex_abstimed_wait_cancellable64
(instead of futex_reltimed_wait_cancellable)
from ./sysdeps/nptl/futex-helpers.h
The gai_suspend() accepts relative timeout, which then is converted to
absolute one.
The i686-gnu port (HURD) do not define DONT_NEED_GAI_MISC_COND and as it
doesn't (yet) support 64 bit time it uses not converted
pthread_cond_timedwait().
The __gai_suspend() is supposed to be run on ports with __TIMESIZE !=64 and
__WORDSIZE==32. It internally utilizes __gai_suspend_time64() and hence the
conversion from 32 bit struct timespec to 64 bit one is required.
For ports supporting 64 bit time the __gai_suspend_time64() will be used
either via alias (to __gai_suspend when __TIMESIZE==64) or redirection
(when -D_TIME_BITS=64 is passed).
Build tests:
./src/scripts/build-many-glibcs.py glibcs
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
The __gai_suspend_time64, which supports 64 bit time on ports with
__WORDSIZE == 32 && __TIMESIZE != 64, shall be exported from libanl
(the same library from which original gai_suspend is exported).
Up till now there were no defines for this library. This commit adds
them.
The aio_suspend function has been converted to support 64 bit time.
This change uses (in aio_misc.h):
- __futex_abstimed_wait64 (instead of futex_reltimed_wait)
- __futex_abstimed_wait_cancellable64
(instead of futex_reltimed_wait_cancellable)
from ./sysdeps/nptl/futex-helpers.h
The aio_suspend() accepts relative timeout, which then is converted to
absolute one.
The i686-gnu port (HURD) do not define DONT_NEED_AIO_MISC_COND and as it
doesn't (yet) support 64 bit time it uses not converted
pthread_cond_timedwait().
The __aio_suspend() is supposed to be run on ports with __TIMESIZE !=64 and
__WORDSIZE==32. It internally utilizes __aio_suspend_time64() and hence the
conversion from 32 bit struct timespec to 64 bit one is required.
For ports supporting 64 bit time the __aio_suspend_time64() will be used
either via alias (to __aio_suspend when __TIMESIZE==64) or redirection
(when -D_TIME_BITS=64 is passed).
Build tests:
./src/scripts/build-many-glibcs.py glibcs
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The tls.h inclusion is not really required and limits possible
definition on more arch specific headers.
This is a cleanup to allow inline functions on sysdep.h, more
specifically on i386 and ia64 which requires to access some tls
definitions its own.
No semantic changes expected, checked with a build against all
affected ABIs.
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.
The explicit error return value (without in-band signaling) avoids
complicated steps to detect errors based on whether errno has been
updated.
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
It basically calls the 64-bit __clock_gettime64 and adds the overflow
check.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Lukasz Majewski <lukma@denx.de>
I couldn't pinpoint which standard has added it, but no other POSIX
system supports it and/or no longer provide it. The 'struct vtimes'
also has a lot of drawbacks due its limited internal type size.
I couldn't also see find any project that actually uses this symbol,
either in some dignostic way (such as sanitizer). So I think it should
be safer to just move to compat symbol, instead of deprecated. The
idea it to avoid new ports to export such broken interface (riscv32
for instance).
Checked on x86_64-linux-gnu and i686-linux-gnu.
