C23 adds a header <stdbit.h> with various functions and type-generic
macros for bit-manipulation of unsigned integers (plus macro defines
related to endianness). Implement this header for glibc.
The functions have both inline definitions in the header (referenced
by macros defined in the header) and copies with external linkage in
the library (which are implemented in terms of those macros to avoid
duplication). They are documented in the glibc manual. Tests, as
well as verifying results for various inputs (of both the macros and
the out-of-line functions), verify the types of those results (which
showed up a bug in an earlier version with the type-generic macro
stdc_has_single_bit wrongly returning a promoted type), that the
macros can be used at top level in a source file (so don't use ({})),
that they evaluate their arguments exactly once, and that the macros
for the type-specific functions have the expected implicit conversions
to the relevant argument type.
Jakub previously referred to -Wconversion warnings in type-generic
macros, so I've included a test with -Wconversion (but the only
warnings I saw and fixed from that test were actually in inline
functions in the <stdbit.h> header - not anything coming from use of
the type-generic macros themselves).
This implementation of the type-generic macros does not handle
unsigned __int128, or unsigned _BitInt types with a width other than
that of a standard integer type (and C23 doesn't require the header to
handle such types either). Support for those types, using the new
type-generic built-in functions Jakub's added for GCC 14, can
reasonably be added in a followup (along of course with associated
tests).
This implementation doesn't do anything special to handle C++, or have
any tests of functionality in C++ beyond the existing tests that all
headers can be compiled in C++ code; it's not clear exactly what form
this header should take in C++, but probably not one using macros.
DIS ballot comment AT-107 asks for the word "count" to be added to the
names of the stdc_leading_zeros, stdc_leading_ones,
stdc_trailing_zeros and stdc_trailing_ones functions and macros. I
don't think it's likely to be accepted (accepting any technical
comments would mean having an FDIS ballot), but if it is accepted at
the WG14 meeting (22-26 January in Strasbourg, starting with DIS
ballot comment handling) then there would still be time to update
glibc for the renaming before the 2.39 release.
The new functions and header are placed in the stdlib/ directory in
glibc, rather than creating a new toplevel stdbit/ or putting them in
string/ alongside ffs.
Tested for x86_64 and x86.
Includes test for setcontext too.
The test directly checks after longjmp if ZA got disabled and the
ZA contents got saved following the lazy saving scheme. It does not
use ACLE code to verify that gcc can interoperate with glibc.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
For the ZA lazy saving scheme to work, setcontext has to call
__libc_arm_za_disable.
Also fixes swapcontext which uses setcontext internally.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
For the ZA lazy saving scheme to work, longjmp has to call
__libc_arm_za_disable.
In ld.so we assume ZA is not used so longjmp does not need
special support there.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The runtime support routines for the call ABI of the Scalable Matrix
Extension (SME) are mostly in libgcc. Since libc.so cannot depend on
libgcc_s.so have an implementation of __arm_za_disable in libc for
libc internal use in longjmp and similar APIs.
__libc_arm_za_disable follows the same PCS rules as __arm_za_disable,
but it's a hidden symbol so it does not need variant PCS marking.
Using __libc_fatal instead of abort because it can print a message and
works in ld.so too. But for now we don't need SME routines in ld.so.
To check the SME HWCAP in asm, we need the _dl_hwcap2 member offset in
_rtld_global_ro in the shared libc.so, while in libc.a the _dl_hwcap2
object is accessed.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The multibyte character needs to fit into the remaining buffer space,
not the already-written buffer space. Without the fix, we were never
moving the write pointer from the start of the buffer, always using
the single-character fallback buffer.
Fixes commit 04b76b5aa8 ("Don't error out writing
a multibyte character to an unbuffered stream (bug 17522)").
Seeing occasional failures in `__strchrnul_evex512` that are not
consistently reproducible. Hopefully by adding this the next failure
will provide enough information to debug.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Verify that setjmp and longjmp work correctly between user contexts.
Arrange stacks for uctx_func1 and uctx_func2 so that ____longjmp_chk
works when setjmp and longjmp are called from different user contexts.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
When shadow stack is enabled, some CET tests failed when compiled with
GCC 14:
FAIL: elf/tst-cet-legacy-4
FAIL: elf/tst-cet-legacy-5a
FAIL: elf/tst-cet-legacy-6a
which are caused by
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113039
These tests use -fcf-protection -fcf-protection=branch and assume that
-fcf-protection=branch will override -fcf-protection. But this GCC 14
commit:
https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=1c6231c05bdcca
changed the -fcf-protection behavior such that
-fcf-protection -fcf-protection=branch
is treated the same as
-fcf-protection
Use
-fcf-protection -fcf-protection=none -fcf-protection=branch
as the workaround. This fixes BZ #31187.
Tested with GCC 13 and GCC 14 on Intel Tiger Lake.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
* posix/regex.c: [!_LIBC && __GNUC_PREREQ (4, 3)]:
Omit GCC pragmas no longer needed when this file is used as part of Gnulib.
-Wold-style-definition no longer needs to be ignored because the regex
code no longer uses old style definitions. -Wtype-limits no longer
needs to be ignored because Gnulib already arranges for it to be
ignored in the C compiler flags. This patch is taken from Gnulib.
I've updated copyright dates in glibc for 2024. This is the patch for
the changes not generated by scripts/update-copyrights and subsequent
build / regeneration of generated files.
Not all CET enabled applications and libraries have been properly tested
in CET enabled environments. Some CET enabled applications or libraries
will crash or misbehave when CET is enabled. Don't set CET active by
default so that all applications and libraries will run normally regardless
of whether CET is active or not. Shadow stack can be enabled by
$ export GLIBC_TUNABLES=glibc.cpu.hwcaps=SHSTK
at run-time if shadow stack can be enabled by kernel.
NB: This commit can be reverted if it is OK to enable CET by default for
all applications and libraries.
Initially, IBT and SHSTK are marked as active when CPU supports them
and CET are enabled in glibc. They can be disabled early by tunables
before relocation. Since after relocation, GLRO(dl_x86_cpu_features)
becomes read-only, we can't update GLRO(dl_x86_cpu_features) to mark
IBT and SHSTK as inactive. Instead, check the feature_1 field in TCB
to decide if IBT and SHST are active.
Previously, CET was enabled by kernel before passing control to user
space and the startup code must disable CET if applications or shared
libraries aren't CET enabled. Since the current kernel only supports
shadow stack and won't enable shadow stack before passing control to
user space, we need to enable shadow stack during startup if the
application and all shared library are shadow stack enabled. There
is no need to disable shadow stack at startup. Shadow stack can only
be enabled in a function which will never return. Otherwise, shadow
stack will underflow at the function return.
1. GL(dl_x86_feature_1) is set to the CET features which are supported
by the processor and are not disabled by the tunable. Only non-zero
features in GL(dl_x86_feature_1) should be enabled. After enabling
shadow stack with ARCH_SHSTK_ENABLE, ARCH_SHSTK_STATUS is used to check
if shadow stack is really enabled.
2. Use ARCH_SHSTK_ENABLE in RTLD_START in dynamic executable. It is
safe since RTLD_START never returns.
3. Call arch_prctl (ARCH_SHSTK_ENABLE) from ARCH_SETUP_TLS in static
executable. Since the start function using ARCH_SETUP_TLS never returns,
it is safe to enable shadow stack in ARCH_SETUP_TLS.
Sync with Linux kernel 6.6 shadow stack interface. Since only x86-64 is
supported, i386 shadow stack codes are unchanged and CET shouldn't be
enabled for i386.
1. When the shadow stack base in TCB is unset, the default shadow stack
is in use. Use the current shadow stack pointer as the marker for the
default shadow stack. It is used to identify if the current shadow stack
is the same as the target shadow stack when switching ucontexts. If yes,
INCSSP will be used to unwind shadow stack. Otherwise, shadow stack
restore token will be used.
2. Allocate shadow stack with the map_shadow_stack syscall. Since there
is no function to explicitly release ucontext, there is no place to
release shadow stack allocated by map_shadow_stack in ucontext functions.
Such shadow stacks will be leaked.
3. Rename arch_prctl CET commands to ARCH_SHSTK_XXX.
4. Rewrite the CET control functions with the current kernel shadow stack
interface.
Since CET is no longer enabled by kernel, a separate patch will enable
shadow stack during startup.
Code is mostly inspired from the LoongArch one, which has a similar ABI,
with minor changes to support riscv32 and register differences.
This fixes elf/tst-sprof-basic. This also fixes elf/tst-audit1,
elf/tst-audit2 and elf/tst-audit8 with recent binutils snapshots when
--enable-bind-now is used.
Resolves: BZ #31151
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Similar to other printf-like ones. It requires to be in a different
process so we can change the orientation of stdout.
Checked on aarch64, armhf, x86_64, and i686.
It requires to be in a container tests to avoid logging bogus
information on the system. The syslog also requires to be checked in
a different process because the internal printf call will abort with
the internal syslog lock taken (which makes subsequent syslog calls
deadlock).
Checked on aarch64, armhf, x86_64, and i686.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
The fortify wrappers for varargs functions already add fallbacks to
builtins calls if __va_arg_pack is not supported.
Checked on aarch64, armhf, x86_64, and i686.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
_dl_tlsdesc_undefweak and _dl_tlsdesc_dynamic access the thread pointer
via the tcb field in TCB:
_dl_tlsdesc_undefweak:
_CET_ENDBR
movq 8(%rax), %rax
subq %fs:0, %rax
ret
_dl_tlsdesc_dynamic:
...
subq %fs:0, %rax
movq -8(%rsp), %rdi
ret
Since the tcb field in TCB is a pointer, %fs:0 is a 32-bit location,
not 64-bit. It should use "sub %fs:0, %RAX_LP" instead. Since
_dl_tlsdesc_undefweak returns ptrdiff_t and _dl_make_tlsdesc_dynamic
returns void *, RAX_LP is appropriate here for x32 and x86-64. This
fixes BZ #31185.
On x32, I got
FAIL: elf/tst-tlsgap
$ gdb elf/tst-tlsgap
...
open tst-tlsgap-mod1.so
Thread 2 "tst-tlsgap" received signal SIGSEGV, Segmentation fault.
[Switching to LWP 2268754]
_dl_tlsdesc_dynamic () at ../sysdeps/x86_64/dl-tlsdesc.S:108
108 movq (%rsi), %rax
(gdb) p/x $rsi
$4 = 0xf7dbf9005655fb18
(gdb)
This is caused by
_dl_tlsdesc_dynamic:
_CET_ENDBR
/* Preserve call-clobbered registers that we modify.
We need two scratch regs anyway. */
movq %rsi, -16(%rsp)
movq %fs:DTV_OFFSET, %rsi
Since the dtv field in TCB is a pointer, %fs:DTV_OFFSET is a 32-bit
location, not 64-bit. Load the dtv field to RSI_LP instead of rsi.
This fixes BZ #31184.
No bug because this is not visible if glibc is built with
optimization. Otherwise this would be a critical resource leak.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
In permissive mode, don't disable IBT nor SHSTK when dlopening a legacy
shared library if not single threaded since IBT and SHSTK may be still
enabled in other threads. Other threads with IBT or SHSTK enabled will
crash when calling functions in the legacy shared library. Instead, an
error will be issued.
Improve readability and make maintenance easier for dl-feature.c by
modularizing sysdeps/x86/dl-cet.c:
1. Support processors with:
a. Only IBT. Or
b. Only SHSTK. Or
c. Both IBT and SHSTK.
2. Lock CET features only if IBT or SHSTK are enabled and are not
enabled permissively.
This is a minimal regression test for bug 29039 which only affects
targets with TLSDESC and a reproducer requires that
1) Have modid gaps (closed modules) with old generation.
2) Update a DTV to a newer generation (needs a newer dlopen).
3) But do not update the closed gap entry in that DTV.
4) Reuse the modid gap for a new module (another dlopen).
5) Use dynamic TLSDESC in that new module with old generation (bug).
6) Access TLS via this TLSDESC and the now outdated DTV.
However step (3) in practice rarely happens: during DTV update the
entries for closed modids are initialized to "unallocated" and then
dynamic TLSDESC calls __tls_get_addr independently of its generation.
The only exception to this is DTV setup at thread creation (gaps are
initialized to NULL instead of unallocated) or DTV resize where the
gap entries are outside the previous DTV array (again NULL instead
of unallocated, and this requires loading > DTV_SURPLUS modules).
So the bug can only cause NULL (+ offset) dereference, not use after
free. And the easiest way to get (3) is via thread creation.
Note that step (5) requires that the newly loaded module has larger
TLS than the remaining optional static TLS. And for (6) there cannot
be other TLS access or dlopen in the thread that updates the DTV.
Tested on aarch64-linux-gnu.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Added annotations for autovec by GCC and GFortran - this enables GCC
>= 9 to autovectorise math calls at -Ofast.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
