Crossing 2GB boundaries with indirect calls and jumps can use more
branch prediction resources on Intel Golden Cove CPU (see the
"Misprediction for Branches >2GB" section in Intel 64 and IA-32
Architectures Optimization Reference Manual.) There is visible
performance improvement on workloads with many PLT calls when executable
and shared libraries are mmapped below 2GB. Add the Prefer_MAP_32BIT_EXEC
bit so that mmap will try to map executable or denywrite pages in shared
libraries with MAP_32BIT first.
NB: Prefer_MAP_32BIT_EXEC reduces bits available for address space
layout randomization (ASLR), which is always disabled for SUID programs
and can only be enabled by the tunable, glibc.cpu.prefer_map_32bit_exec,
or the environment variable, LD_PREFER_MAP_32BIT_EXEC. This works only
between shared libraries or between shared libraries and executables with
addresses below 2GB. PIEs are usually loaded at a random address above
4GB by the kernel.
V2 of this patch fixes an issue in V1, where the state was changed to ON not
OFF at end of _mcleanup. I hadn't noticed that (counterintuitively) ON=0 and
OFF=3, hence zeroing the buffer turned it back on. So set the state to OFF
after the memset.
1. Prevent double free, and reads from unallocated memory, when
_mcleanup is (incorrectly) called two or more times in a row,
without an intervening call to __monstartup; with this patch, the
second and subsequent calls effectively become no-ops instead.
While setting tos=NULL is minimal fix, safest action is to zero the
whole gmonparam buffer.
2. Prevent memory leak when __monstartup is (incorrectly) called two
or more times in a row, without an intervening call to _mcleanup;
with this patch, the second and subsequent calls effectively become
no-ops instead.
3. After _mcleanup, treat __moncontrol(1) as __moncontrol(0) instead.
With zeroing of gmonparam buffer in _mcleanup, this stops the
state incorrectly being changed to GMON_PROF_ON despite profiling
actually being off. If we'd just done the minimal fix to _mcleanup
of setting tos=NULL, there is risk of far worse memory corruption:
kcount would point to deallocated memory, and the __profil syscall
would make the kernel write profiling data into that memory,
which could have since been reallocated to something unrelated.
4. Ensure __moncontrol(0) still turns off profiling even in error
state. Otherwise, if mcount overflows and sets state to
GMON_PROF_ERROR, when _mcleanup calls __moncontrol(0), the __profil
syscall to disable profiling will not be invoked. _mcleanup will
free the buffer, but the kernel will still be writing profiling
data into it, potentially corrupted arbitrary memory.
Also adds a test case for (1). Issues (2)-(4) are not feasible to test.
Signed-off-by: Simon Kissane <skissane@gmail.com>
Reviewed-by: DJ Delorie <dj@redhat.com>
When mcount overflows, no gmon.out file is generated, but no message is printed
to the user, leaving the user with no idea why, and thinking maybe there is
some bug - which is how BZ 27576 ended up being logged. Print a message to
stderr in this case so the user knows what is going on.
As a comment in sys/gmon.h acknowledges, the hardcoded MAXARCS value is too
small for some large applications, including the test case in that BZ. Rather
than increase it, add tunables to enable MINARCS and MAXARCS to be overridden
at runtime (glibc.gmon.minarcs and glibc.gmon.maxarcs). So if a user gets the
mcount overflow error, they can try increasing maxarcs (they might need to
increase minarcs too if the heuristic is wrong in their case.)
Note setting minarcs/maxarcs too large can cause monstartup to fail with an
out of memory error. If you set them large enough, it can cause an integer
overflow in calculating the buffer size. I haven't done anything to defend
against that - it would not generally be a security vulnerability, since these
tunables will be ignored in suid/sgid programs (due to the SXID_ERASE default),
and if you can set GLIBC_TUNABLES in the environment of a process, you can take
it over anyway (LD_PRELOAD, LD_LIBRARY_PATH, etc). I thought about modifying
the code of monstartup to defend against integer overflows, but doing so is
complicated, and I realise the existing code is susceptible to them even prior
to this change (e.g. try passing a pathologically large highpc argument to
monstartup), so I decided just to leave that possibility in-place.
Add a test case which demonstrates mcount overflow and the tunables.
Document the new tunables in the manual.
Signed-off-by: Simon Kissane <skissane@gmail.com>
Reviewed-by: DJ Delorie <dj@redhat.com>
The `__monstartup()` allocates a buffer used to store all the data
accumulated by the monitor.
The size of this buffer depends on the size of the internal structures
used and the address range for which the monitor is activated, as well
as on the maximum density of call instructions and/or callable functions
that could be potentially on a segment of executable code.
In particular a hash table of arcs is placed at the end of this buffer.
The size of this hash table is calculated in bytes as
p->fromssize = p->textsize / HASHFRACTION;
but actually should be
p->fromssize = ROUNDUP(p->textsize / HASHFRACTION, sizeof(*p->froms));
This results in writing beyond the end of the allocated buffer when an
added arc corresponds to a call near from the end of the monitored
address range, since `_mcount()` check the incoming caller address for
monitored range but not the intermediate result hash-like index that
uses to write into the table.
It should be noted that when the results are output to `gmon.out`, the
table is read to the last element calculated from the allocated size in
bytes, so the arcs stored outside the buffer boundary did not fall into
`gprof` for analysis. Thus this "feature" help me to found this bug
during working with https://sourceware.org/bugzilla/show_bug.cgi?id=29438
Just in case, I will explicitly note that the problem breaks the
`make test t=gmon/tst-gmon-dso` added for Bug 29438.
There, the arc of the `f3()` call disappears from the output, since in
the DSO case, the call to `f3` is located close to the end of the
monitored range.
Signed-off-by: Леонид Юрьев (Leonid Yuriev) <leo@yuriev.ru>
Another minor error seems a related typo in the calculation of
`kcountsize`, but since kcounts are smaller than froms, this is
actually to align the p->froms data.
Co-authored-by: DJ Delorie <dj@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
* malloc/malloc.c (_int_malloc): remove redundant check of
unsorted bin corruption
With commit "b90ddd08f6dd688e651df9ee89ca3a69ff88cd0c"
(malloc: Additional checks for unsorted bin integrity),
same check of (bck->fd != victim) is added before checking of unsorted
chunk corruption, which was added in "bdc3009b8ff0effdbbfb05eb6b10966753cbf9b8"
(Added check before removing from unsorted list).
..
3773 if (__glibc_unlikely (bck->fd != victim)
3774 || __glibc_unlikely (victim->fd != unsorted_chunks (av)))
3775 malloc_printerr ("malloc(): unsorted double linked list corrupted");
..
..
3815 /* remove from unsorted list */
3816 if (__glibc_unlikely (bck->fd != victim))
3817 malloc_printerr ("malloc(): corrupted unsorted chunks 3");
3818 unsorted_chunks (av)->bk = bck;
..
So this extra check can be removed.
Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
Signed-off-by: Ayush Mittal <ayush.m@samsung.com>
Reviewed-by: DJ Delorie <dj@redhat.com>
Linux 6.2 removed the hppa compatibility MAP_VARIABLE define. That
means that, whether or not we remove it in glibc, it needs to be
ignored in tst-mman-consts.py (since this macro comparison
infrastructure expects that new kernel header versions only add new
macros, not remove old ones).
Tested with build-many-glibcs.py for hppa-linux-gnu (Linux 6.2
headers).
Fix the computation to allow for cntfrq_el0 being larger than 1GHz.
Assume cntfrq_el0 is a multiple of 1MHz to increase the maximum
interval (1024 seconds at 1GHz).
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
It fixes the build after 7ea510127e and 22999b2f0f.
Checked with build for s390x-linux-gnu with -march=z13.
Reviewed-by: Arjun Shankar <arjun@redhat.com>
__builtin_arm_uqsub8 is only available on gcc newer or equal than 10.
Checked on arm-linux-gnueabihf built with gcc 9.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
The default Linux implementation already handled the Linux generic
ABIs interface used on newer architectures, so there is no need to
Imply the generic any longer.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And disable if kernel does not support it.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And disable if kernel does not support it.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
And remove redundant entries on other architectures Version. The
version for fallocate64 was supposed to be 2.10, but it was then
added to 32-bit platforms in 2.11 because it mistakenly wasn't
exported for them in 2.10 (see the commit message for
1f3615a1c9).
The linux/generic did not exist before 2.15, i.e. when the tile
ports were added (and microblaze did not exist before 2.18), which
explains those differences but also illustrates that "2.11 for 32-bit,
2.10 for 64-bit" should be sufficient since versions older than the
minimum for the architecture are automatically adjusted.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
While cleaning up old libc version support, the deprecated libc4 code was
accidentally kept in `implicit_soname`, instead of the libc6 code.
This causes additional symlinks to be created by `ldconfig` for libraries
without a soname, e.g. a library `libsomething.123.456.789` without a soname
will create a `libsomething.123` -> `libsomething.123.456.789` symlink.
As the libc6 version of the `implicit_soname` code is a trivial `xstrdup`,
just inline it and remove `implicit_soname` altogether.
Some further simplification looks possible (e.g. the call to `create_links`
looks like a no-op if `soname == NULL`, other than the verbose printfs), but
logic is kept as-is for now.
Fixes: BZ #30125
Fixes: 8ee878592c ("Assume only FLAG_ELF_LIBC6 suport")
Signed-off-by: Joan Bruguera <joanbrugueram@gmail.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Post review removal of "goto restart" from
https://sourceware.org/pipermail/libc-alpha/2021-April/125470.html
introduced a bug when some atexit handers skipped.
Signed-off-by: Vitaly Buka <vitalybuka@google.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The PAGE_SIZE from the Mach headers statically defines the machine's
page size. There's no need to query it dynamically; furthermore, the
implementation of the vm_statistics () RPC unconditionally fills in
pagesize = PAGE_SIZE;
Not doing the extra RPC shaves off 2 RPCs from the start-up of every
process!
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230218203717.373211-7-bugaevc@gmail.com>
And make it a bit more 64-bit ready. This is in preparation to moving this
file into x86/
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230218203717.373211-6-bugaevc@gmail.com>
This ensures that a timer_t value can be cast to struct timer_node *
and back.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230218203717.373211-5-bugaevc@gmail.com>
Fix a few more cases of build errors caused by mismatched types. This is a
continuation of f4315054b4.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230218203717.373211-3-bugaevc@gmail.com>
This is going to be done differently on x86_64.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230218203717.373211-2-bugaevc@gmail.com>
Add extra check for compiler definitions to ensure that compiler provides
sqrt and fma hw fpu instructions else use software implementation.
As divide/sqrt and FMA hw support from CPU side is optional,
the compiler can be configured by options to generate hw FPU instructions,
but without use of FDDIV, FDSQRT, FSDIV, FSSQRT, FDMADD and FSMADD
instructions. In this case __builtin_sqrt and __builtin_sqrtf provided by
compiler can't be used inside the glibc code, as these builtins are used
in implementations of sqrt() and sqrtf() functions but at the same time
these builtins unfold to sqrt() and sqrtf(). So it is possible to receive
code like that:
0001c4b4 <__ieee754_sqrtf>:
1c4b4: 0001 0000 b 0 ;1c4b4 <__ieee754_sqrtf>
The same is also true for __builtin_fma and __builtin_fmaf.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The ARCv2 ABI requires 4 byte stack pointer alignment. Don't allow to
use unaligned child stack in clone. As the stack grows down,
align it down.
This was pointed by misc/tst-misalign-clone-internal and
misc/tst-misalign-clone tests. Stack alignmet fixes these tests
fails.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Use put/get macros __builtin_bswap32 instead. It allows to remove
the unaligned routines, the compiler will generate unaligned access
if the ABI allows it.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
And use a packed structure instead. The compiler generates optimized
unaligned code if the architecture supports it.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
It only adds a small overhead for unaligned inputs (which should not
be common) and unify the code.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Assume unaligned inputs on all cases. The code is built and used only
in compat mode.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Builds for s390 recently started failing with:
../sysdeps/s390/multiarch/ifunc-impl-list.c: In function '__libc_ifunc_impl_list':
../sysdeps/s390/multiarch/ifunc-impl-list.c:83:21: error: unused variable 'dl_hwcap' [-Werror=unused-variable]
83 | unsigned long int dl_hwcap = features->hwcap;
| ^~~~~~~~
https://sourceware.org/pipermail/libc-testresults/2023q1/010855.html
Add __attribute__ ((unused)) as already done for another variable
there.
Tested with build-many-glibcs.py (compilers and glibcs) for
s390x-linux-gnu and s390-linux-gnu.
Note: s390x-linux-gnu-O3 started failing with a different error
earlier; that problem may still need to be fixed after this fix is in.
https://sourceware.org/pipermail/libc-testresults/2023q1/010829.html
C2x adds binary integer constants starting with 0b or 0B, and supports
those constants in strtol-family functions when the base passed is 0
or 2. Implement that strtol support for glibc.
As discussed at
<https://sourceware.org/pipermail/libc-alpha/2020-December/120414.html>,
this is incompatible with previous C standard versions, in that such
an input string starting with 0b or 0B was previously required to be
parsed as 0 (with the rest of the string unprocessed). Thus, as
proposed there, this patch adds 20 new __isoc23_* functions with
appropriate header redirection support. This patch does *not* do
anything about scanf %i (which will need 12 new functions per long
double variant, so 12, 24 or 36 depending on the glibc configuration),
instead leaving that for a future patch. The function names would
remain as __isoc23_* even if C2x ends up published in 2024 rather than
2023.
Making this change leads to the question of what should happen to
internal uses of these functions in glibc and its tests. The header
redirection (which applies for _GNU_SOURCE or any other feature test
macros enabling C2x features) has the effect of redirecting internal
uses but without those uses then ending up at a hidden alias (see the
comment in include/stdio.h about interaction with libc_hidden_proto).
It seems desirable for the default for internal uses to be the same
versions used by normal code using _GNU_SOURCE, so rather than doing
anything to disable that redirection, similar macro definitions to
those in include/stdio.h are added to the include/ headers for the new
functions.
Given that the default for uses in glibc is for the redirections to
apply, the next question is whether the C2x semantics are correct for
all those uses. Uses with the base fixed to 10, 16 or any other value
other than 0 or 2 can be ignored. I think this leaves the following
internal uses to consider (an important consideration for review of
this patch will be both whether this list is complete and whether my
conclusions on all entries in it are correct):
benchtests/bench-malloc-simple.c
benchtests/bench-string.h
elf/sotruss-lib.c
math/libm-test-support.c
nptl/perf.c
nscd/nscd_conf.c
nss/nss_files/files-parse.c
posix/tst-fnmatch.c
posix/wordexp.c
resolv/inet_addr.c
rt/tst-mqueue7.c
soft-fp/testit.c
stdlib/fmtmsg.c
support/support_test_main.c
support/test-container.c
sysdeps/pthread/tst-mutex10.c
I think all of these places are OK with the new semantics, except for
resolv/inet_addr.c, where the POSIX semantics of inet_addr do not
allow for binary constants; thus, I changed that file (to use
__strtoul_internal, whose semantics are unchanged) and added a test
for this case. In the case of posix/wordexp.c I think accepting
binary constants is OK since POSIX explicitly allows additional forms
of shell arithmetic expressions, and in stdlib/fmtmsg.c SEV_LEVEL is
not in POSIX so again I think accepting binary constants is OK.
Functions such as __strtol_internal, which are only exported for
compatibility with old binaries from when those were used in inline
functions in headers, have unchanged semantics; the __*_l_internal
versions (purely internal to libc and not exported) have a new
argument to specify whether to accept binary constants.
As well as for the standard functions, the header redirection also
applies to the *_l versions (GNU extensions), and to legacy functions
such as strtoq, to avoid confusing inconsistency (the *q functions
redirect to __isoc23_*ll rather than needing their own __isoc23_*
entry points). For the functions that are only declared with
_GNU_SOURCE, this means the old versions are no longer available for
normal user programs at all. An internal __GLIBC_USE_C2X_STRTOL macro
is used to control the redirections in the headers, and cases in glibc
that wish to avoid the redirections - the function implementations
themselves and the tests of the old versions of the GNU functions -
then undefine and redefine that macro to allow the old versions to be
accessed. (There would of course be greater complexity should we wish
to make any of the old versions into compat symbols / avoid them being
defined at all for new glibc ABIs.)
strtol_l.c has some similarity to strtol.c in gnulib, but has already
diverged some way (and isn't listed at all at
https://sourceware.org/glibc/wiki/SharedSourceFiles unlike strtoll.c
and strtoul.c); I haven't made any attempts at gnulib compatibility in
the changes to that file.
I note incidentally that inttypes.h and wchar.h are missing the
__nonnull present on declarations of this family of functions in
stdlib.h; I didn't make any changes in that regard for the new
declarations added.
This macro from Mach headers conflicts with how
sysdeps/x86_64/multiarch/strcmp-sse2.S expects it to be defined.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230214173722.428140-3-bugaevc@gmail.com>
* Micro-optimize TLS access using GCC's native support for gs-based
addressing when available;
* Just use THREAD_GETMEM and THREAD_SETMEM instead of more inline
assembly;
* Sync tcbhead_t layout with NPTL, in particular update/fix __private_ss
offset;
* Statically assert that the two offsets that are a part of ABI are what
we expect them to be.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230214173722.428140-2-bugaevc@gmail.com>
ISO C does not support omitting parameter names in function definitions
before C2X,the compiler is giving an error with older versions of gcc and
this commit will resolve the test failure "error: parameter name omitted"
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
These are supposed to stay 32-bit even on 64-bit systems. This matches
BSD and Linux, as well as how these types are already defined in
tioctl.defs
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
