From 7ce7a0e753edd5fbda65cec987d681c65e86960d Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Fri, 25 Sep 2020 13:10:08 -0700
Subject: [PATCH] sysconf: Add _SC_MINSIGSTKSZ/_SC_SIGSTKSZ [BZ #20305]
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.
---
NEWS | 5 ++
bits/confname.h | 8 +-
bits/sigstksz.h | 21 +++++
elf/dl-support.c | 5 ++
elf/dl-sysdep.c | 9 ++
include/bits/sigstack.h | 5 ++
include/bits/sigstksz.h | 7 ++
include/features.h | 11 +++
manual/conf.texi | 21 +++++
manual/creature.texi | 6 ++
posix/sysconf.c | 3 +
signal/Makefile | 5 +-
signal/signal.h | 1 +
signal/tst-minsigstksz-5.c | 84 +++++++++++++++++++
sysdeps/generic/ldsodefs.h | 3 +
sysdeps/unix/sysv/linux/bits/sigstksz.h | 33 ++++++++
.../unix/sysv/linux/ia64/sysconf-sigstksz.h | 27 ++++++
sysdeps/unix/sysv/linux/sysconf-sigstksz.h | 38 +++++++++
sysdeps/unix/sysv/linux/sysconf.c | 9 ++
.../unix/sysv/linux/x86/dl-minsigstacksize.h | 83 ++++++++++++++++++
.../sysv/linux/x86/include/bits/sigstack.h | 5 ++
sysdeps/x86/cpu-features.c | 3 +
sysdeps/x86/dl-minsigstacksize.h | 27 ++++++
23 files changed, 416 insertions(+), 3 deletions(-)
create mode 100644 bits/sigstksz.h
create mode 100644 include/bits/sigstack.h
create mode 100644 include/bits/sigstksz.h
create mode 100644 signal/tst-minsigstksz-5.c
create mode 100644 sysdeps/unix/sysv/linux/bits/sigstksz.h
create mode 100644 sysdeps/unix/sysv/linux/ia64/sysconf-sigstksz.h
create mode 100644 sysdeps/unix/sysv/linux/sysconf-sigstksz.h
create mode 100644 sysdeps/unix/sysv/linux/x86/dl-minsigstacksize.h
create mode 100644 sysdeps/unix/sysv/linux/x86/include/bits/sigstack.h
create mode 100644 sysdeps/x86/dl-minsigstacksize.h
@@ -9,6 +9,11 @@ Version 2.33
Major new features:
+* Add _SC_MINSIGSTKSZ and _SC_SIGSTKSZ. When _SC_SIGSTKSZ_SOURCE or
+ _GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ are no longer
+ constant on Linux. MINSIGSTKSZ is redefined to sysconf(_SC_MINSIGSTKSZ)
+ and SIGSTKSZ is redefined to sysconf (_SC_SIGSTKSZ).
+
* The dynamic linker accepts the --argv0 argument and provides opportunity
to change argv[0] string.
@@ -525,8 +525,14 @@ enum
_SC_THREAD_ROBUST_PRIO_INHERIT,
#define _SC_THREAD_ROBUST_PRIO_INHERIT _SC_THREAD_ROBUST_PRIO_INHERIT
- _SC_THREAD_ROBUST_PRIO_PROTECT
+ _SC_THREAD_ROBUST_PRIO_PROTECT,
#define _SC_THREAD_ROBUST_PRIO_PROTECT _SC_THREAD_ROBUST_PRIO_PROTECT
+
+ _SC_MINSIGSTKSZ,
+#define _SC_MINSIGSTKSZ _SC_MINSIGSTKSZ
+
+ _SC_SIGSTKSZ
+#define _SC_SIGSTKSZ _SC_SIGSTKSZ
};
/* Values for the NAME argument to `confstr'. */
new file mode 100644
@@ -0,0 +1,21 @@
+/* Definition of MINSIGSTKSZ. Generic version.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SIGNAL_H
+# error "Never include <bits/sigstksz.h> directly; use <signal.h> instead."
+#endif
@@ -136,6 +136,8 @@ void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
size_t _dl_pagesize = EXEC_PAGESIZE;
+size_t _dl_minsigstacksize = CONSTANT_MINSIGSTKSZ;
+
int _dl_inhibit_cache;
unsigned int _dl_osversion;
@@ -295,6 +297,9 @@ _dl_aux_init (ElfW(auxv_t) *av)
case AT_RANDOM:
_dl_random = (void *) av->a_un.a_val;
break;
+ case AT_MINSIGSTKSZ:
+ _dl_minsigstacksize = av->a_un.a_val;
+ break;
DL_PLATFORM_AUXV
}
if (seen == 0xf)
@@ -117,6 +117,11 @@ _dl_sysdep_start (void **start_argptr,
user_entry = (ElfW(Addr)) ENTRY_POINT;
GLRO(dl_platform) = NULL; /* Default to nothing known about the platform. */
+ /* NB: Default to a constant CONSTANT_MINSIGSTKSZ. */
+ _Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ),
+ "CONSTANT_MINSIGSTKSZ is constant");
+ GLRO(dl_minsigstacksize) = CONSTANT_MINSIGSTKSZ;
+
for (av = GLRO(dl_auxv); av->a_type != AT_NULL; set_seen (av++))
switch (av->a_type)
{
@@ -181,6 +186,9 @@ _dl_sysdep_start (void **start_argptr,
case AT_RANDOM:
_dl_random = (void *) av->a_un.a_val;
break;
+ case AT_MINSIGSTKSZ:
+ GLRO(dl_minsigstacksize) = av->a_un.a_val;
+ break;
DL_PLATFORM_AUXV
}
@@ -308,6 +316,7 @@ _dl_show_auxv (void)
[AT_SYSINFO_EHDR - 2] = { "SYSINFO_EHDR: 0x", hex },
[AT_RANDOM - 2] = { "RANDOM: 0x", hex },
[AT_HWCAP2 - 2] = { "HWCAP2: 0x", hex },
+ [AT_MINSIGSTKSZ - 2] = { "MINSIGSTKSZ ", dec },
[AT_L1I_CACHESIZE - 2] = { "L1I_CACHESIZE: ", dec },
[AT_L1I_CACHEGEOMETRY - 2] = { "L1I_CACHEGEOMETRY: 0x", hex },
[AT_L1D_CACHESIZE - 2] = { "L1D_CACHESIZE: ", dec },
new file mode 100644
@@ -0,0 +1,5 @@
+#include_next <bits/sigstack.h>
+
+#if !defined _ISOMAC && !defined CONSTANT_MINSIGSTKSZ
+# define CONSTANT_MINSIGSTKSZ MINSIGSTKSZ
+#endif
new file mode 100644
@@ -0,0 +1,7 @@
+/* NB: Don't define MINSIGSTKSZ nor SIGSTKSZ to sysconf (SC_SIGSTKSZ) for
+ glibc build. IS_IN can only be used when _ISOMAC isn't defined. */
+#ifdef _ISOMAC
+# include_next <bits/sigstksz.h>
+#elif IS_IN (libsupport)
+# include_next <bits/sigstksz.h>
+#endif
@@ -48,6 +48,8 @@
_LARGEFILE64_SOURCE Additional functionality from LFS for large files.
_FILE_OFFSET_BITS=N Select default filesystem interface.
_ATFILE_SOURCE Additional *at interfaces.
+ _SC_SIGSTKSZ_SOURCE Select correct (but non compile-time constant)
+ MINSIGSTKSZ and SIGSTKSZ.
_GNU_SOURCE All of the above, plus GNU extensions.
_DEFAULT_SOURCE The default set of features (taking precedence over
__STRICT_ANSI__).
@@ -94,6 +96,8 @@
__USE_FILE_OFFSET64 Define 64bit interface as default.
__USE_MISC Define things from 4.3BSD or System V Unix.
__USE_ATFILE Define *at interfaces and AT_* constants for them.
+ __USE_SC_SIGSTKSZ Define correct (but non compile-time constant)
+ MINSIGSTKSZ and SIGSTKSZ.
__USE_GNU Define GNU extensions.
__USE_FORTIFY_LEVEL Additional security measures used, according to level.
@@ -137,6 +141,7 @@
#undef __USE_FILE_OFFSET64
#undef __USE_MISC
#undef __USE_ATFILE
+#undef __USE_SC_SIGSTKSZ
#undef __USE_GNU
#undef __USE_FORTIFY_LEVEL
#undef __KERNEL_STRICT_NAMES
@@ -213,6 +218,8 @@
# define _DEFAULT_SOURCE 1
# undef _ATFILE_SOURCE
# define _ATFILE_SOURCE 1
+# undef _SC_SIGSTKSZ_SOURCE
+# define _SC_SIGSTKSZ_SOURCE 1
#endif
/* If nothing (other than _GNU_SOURCE and _DEFAULT_SOURCE) is defined,
@@ -388,6 +395,10 @@
# define __USE_ATFILE 1
#endif
+#ifdef _SC_SIGSTKSZ_SOURCE
+# define __USE_SC_SIGSTKSZ 1
+#endif
+
#ifdef _GNU_SOURCE
# define __USE_GNU 1
#endif
@@ -913,6 +913,27 @@ Inquire about the parameter corresponding to @code{NL_SETMAX}.
@item _SC_NL_TEXTMAX
@standards{X/Open, unistd.h}
Inquire about the parameter corresponding to @code{NL_TEXTMAX}.
+
+@item _SC_MINSIGSTKSZ
+@standards{GNU, unistd.h}
+Inquire about the minimum number of bytes of free stack space required
+in order to guarantee successful, non-nested handling of a single signal
+whose handler is an empty function.
+
+@item _SC_SIGSTKSZ
+@standards{GNU, unistd.h}
+Inquire about the suggested minimum number of bytes of stack space
+required for a signal stack.
+
+This is not guaranteed to be enough for any specific purpose other than
+the invocation of a single, non-nested, empty handler, but nonetheless
+should be enough for basic scenarios involving simple signal handlers
+and very low levels of signal nesting (say, 2 or 3 levels at the very
+most).
+
+This value is provided for developer convenience and to ease migration
+from the legacy @code{SIGSTKSZ} constant. Programs requiring stronger
+guarantees should avoid using it if at all possible.
@end vtable
@node Examples of Sysconf
@@ -257,6 +257,12 @@ various library functions. If defined to @math{2}, even stricter
checks are applied.
@end defvr
+@defvr Macro _SC_SIGSTKSZ_SOURCE
+@standards{GNU, (none)}
+If this macro is defined, correct (but non compile-time constant)
+MINSIGSTKSZ and SIGSTKSZ are defined.
+@end defvr
+
@defvr Macro _REENTRANT
@defvrx Macro _THREAD_SAFE
@standards{Obsolete, (none)}
@@ -266,6 +266,9 @@ __sysconf (int name)
case _SC_XOPEN_REALTIME:
case _SC_XOPEN_REALTIME_THREADS:
+ case _SC_MINSIGSTKSZ:
+ case _SC_SIGSTKSZ:
+
break;
}
@@ -31,7 +31,8 @@ headers := signal.h sys/signal.h \
bits/types/sigevent_t.h bits/types/siginfo_t.h \
bits/types/sigset_t.h bits/types/sigval_t.h \
bits/types/stack_t.h bits/types/struct_sigstack.h \
- bits/types/__sigval_t.h bits/signal_ext.h
+ bits/types/__sigval_t.h bits/signal_ext.h \
+ bits/sigstksz.h
routines := signal raise killpg \
sigaction sigprocmask kill \
@@ -48,7 +49,7 @@ routines := signal raise killpg \
tests := tst-signal tst-sigset tst-sigsimple tst-raise tst-sigset2 \
tst-sigwait-eintr tst-sigaction \
tst-minsigstksz-1 tst-minsigstksz-2 tst-minsigstksz-3 \
- tst-minsigstksz-3a tst-minsigstksz-4 \
+ tst-minsigstksz-3a tst-minsigstksz-4 tst-minsigstksz-5 \
tst-sigisemptyset
include ../Rules
@@ -312,6 +312,7 @@ extern int siginterrupt (int __sig, int __interrupt) __THROW
__attribute_deprecated_msg__ ("Use sigaction with SA_RESTART instead");
# include <bits/sigstack.h>
+# include <bits/sigstksz.h>
# include <bits/ss_flags.h>
/* Alternate signal handler stack interface.
new file mode 100644
@@ -0,0 +1,84 @@
+/* Test of signal delivery on an alternate stack with MINSIGSTKSZ size.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <support/check.h>
+#include <support/support.h>
+
+static volatile sig_atomic_t handler_run;
+
+static void
+handler (int signo)
+{
+ /* Clear a bit of on-stack memory. */
+ volatile char buffer[256];
+ for (size_t i = 0; i < sizeof (buffer); ++i)
+ buffer[i] = 0;
+ handler_run = 1;
+}
+
+int
+do_test (void)
+{
+ size_t stack_buffer_size = 64 * 1024 * 1024;
+ void *stack_buffer = xmalloc (stack_buffer_size);
+ void *stack_end = stack_buffer + stack_buffer_size;
+ memset (stack_buffer, 0xCC, stack_buffer_size);
+
+ void *stack_bottom = stack_buffer + (stack_buffer_size + MINSIGSTKSZ) / 2;
+ void *stack_top = stack_bottom + MINSIGSTKSZ;
+ stack_t stack =
+ {
+ .ss_sp = stack_bottom,
+ .ss_size = MINSIGSTKSZ,
+ };
+ if (sigaltstack (&stack, NULL) < 0)
+ FAIL_RET ("sigaltstack: %m\n");
+
+ struct sigaction act =
+ {
+ .sa_handler = handler,
+ .sa_flags = SA_ONSTACK,
+ };
+ if (sigaction (SIGUSR1, &act, NULL) < 0)
+ FAIL_RET ("sigaction: %m\n");
+
+ if (kill (getpid (), SIGUSR1) < 0)
+ FAIL_RET ("kill: %m\n");
+
+ if (handler_run != 1)
+ FAIL_RET ("handler did not run\n");
+
+ for (void *p = stack_buffer; p < stack_bottom; ++p)
+ if (*(unsigned char *) p != 0xCC)
+ FAIL_RET ("changed byte %ld bytes below configured stack\n",
+ (long) (stack_bottom - p));
+ for (void *p = stack_top; p < stack_end; ++p)
+ if (*(unsigned char *) p != 0xCC)
+ FAIL_RET ("changed byte %ld bytes above configured stack\n",
+ (long) (p - stack_top));
+
+ free (stack_buffer);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
@@ -536,6 +536,9 @@ struct rtld_global_ro
/* Cached value of `getpagesize ()'. */
EXTERN size_t _dl_pagesize;
+ /* Cached value of `sysconf (_SC_MINSIGSTKSZ)'. */
+ EXTERN size_t _dl_minsigstacksize;
+
/* Do we read from ld.so.cache? */
EXTERN int _dl_inhibit_cache;
new file mode 100644
@@ -0,0 +1,33 @@
+/* Definition of MINSIGSTKSZ and SIGSTKSZ. Linux version.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SIGNAL_H
+# error "Never include <bits/sigstksz.h> directly; use <signal.h> instead."
+#endif
+
+#if defined __USE_SC_SIGSTKSZ && __USE_SC_SIGSTKSZ
+# include <unistd.h>
+
+/* 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
+#endif
new file mode 100644
@@ -0,0 +1,27 @@
+/* sysconf_sigstksz (). Linux/ia64 version.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* Return sysconf (_SC_SIGSTKSZ). */
+
+static long int
+sysconf_sigstksz (void)
+{
+ _Static_assert (__builtin_constant_p (SIGSTKSZ),
+ "SIGSTKSZ is constant");
+ return SIGSTKSZ;
+}
new file mode 100644
@@ -0,0 +1,38 @@
+/* sysconf_sigstksz (). Linux version.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* Return sysconf (_SC_SIGSTKSZ). */
+
+static long int
+sysconf_sigstksz (void)
+{
+ long int minsigstacksize = GLRO(dl_minsigstacksize);
+ assert (minsigstacksize != 0);
+ _Static_assert (__builtin_constant_p (MINSIGSTKSZ),
+ "MINSIGSTKSZ is constant");
+ if (minsigstacksize < MINSIGSTKSZ)
+ minsigstacksize = MINSIGSTKSZ;
+ /* MAX (MINSIGSTKSZ, sysconf (_SC_MINSIGSTKSZ)) * 4. */
+ long int sigstacksize = minsigstacksize * 4;
+ /* Return MAX (SIGSTKSZ, sigstacksize). */
+ _Static_assert (__builtin_constant_p (SIGSTKSZ),
+ "SIGSTKSZ is constant");
+ if (sigstacksize < SIGSTKSZ)
+ sigstacksize = SIGSTKSZ;
+ return sigstacksize;
+}
@@ -16,6 +16,7 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
+#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
@@ -26,6 +27,7 @@
#include <sys/param.h>
#include <not-cancel.h>
#include <ldsodefs.h>
+#include <sysconf-sigstksz.h>
/* Legacy value of ARG_MAX. The macro is now not defined since the
actual value varies based on the stack size. */
@@ -75,6 +77,13 @@ __sysconf (int name)
}
break;
+ case _SC_MINSIGSTKSZ:
+ assert (GLRO(dl_minsigstacksize) != 0);
+ return GLRO(dl_minsigstacksize);
+
+ case _SC_SIGSTKSZ:
+ return sysconf_sigstksz ();
+
default:
break;
}
new file mode 100644
@@ -0,0 +1,83 @@
+/* Emulate AT_MINSIGSTKSZ. Linux/x86 version.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* Emulate AT_MINSIGSTKSZ with XSAVE. */
+
+static inline void
+dl_check_minsigstacksize (const struct cpu_features *cpu_features)
+{
+ /* Return if AT_MINSIGSTKSZ is provide by kernel. */
+ if (GLRO(dl_minsigstacksize) != 0)
+ return;
+
+ if (cpu_features->basic.max_cpuid >= 0xd
+ && CPU_FEATURES_CPU_P (cpu_features, OSXSAVE))
+ {
+ /* Emulate AT_MINSIGSTKSZ. In Linux kernel, the signal frame data
+ with XSAVE is composed of the following areas and laid out as:
+ ------------------------------
+ | alignment padding |
+ ------------------------------
+ | xsave buffer |
+ ------------------------------
+ | fsave header (32-bit only) |
+ ------------------------------
+ | siginfo + ucontext |
+ ------------------------------
+ */
+
+ unsigned int sigframe_size;
+
+#ifdef __x86_64__
+ /* NB: sizeof(struct rt_sigframe) + 8-byte return address in Linux
+ kernel. */
+ sigframe_size = 440 + 8;
+#else
+ /* NB: sizeof(struct sigframe_ia32) + sizeof(struct fregs_state)) +
+ 4-byte return address + 3 * 4-byte arguments in Linux kernel. */
+ sigframe_size = 736 + 112 + 4 + 3 * 4;
+#endif
+
+ /* Add 15 bytes to align the stack to 16 bytes. */
+ sigframe_size += 15;
+
+ /* Make the space before xsave buffer multiple of 16 bytes. */
+ sigframe_size = ALIGN_UP (sigframe_size, 16);
+
+ /* Add (64 - 16)-byte padding to align xsave buffer at 64 bytes. */
+ sigframe_size += 64 - 16;
+
+ unsigned int eax, ebx, ecx, edx;
+ __cpuid_count (0xd, 0, eax, ebx, ecx, edx);
+
+ /* Add the size of xsave buffer. */
+ sigframe_size += ebx;
+
+ /* Add the size of FP_XSTATE_MAGIC2. */
+#define FP_XSTATE_MAGIC2 0x46505845U
+ sigframe_size += sizeof (FP_XSTATE_MAGIC2);
+
+ GLRO(dl_minsigstacksize) = sigframe_size;
+ }
+ else
+ {
+ /* NB: Default to a constant MINSIGSTKSZ. */
+ _Static_assert (__builtin_constant_p (MINSIGSTKSZ),
+ "MINSIGSTKSZ is constant");
+ GLRO(dl_minsigstacksize) = MINSIGSTKSZ;
+ }
+}
new file mode 100644
@@ -0,0 +1,5 @@
+#include_next <bits/sigstack.h>
+
+#ifndef _ISOMAC
+# define CONSTANT_MINSIGSTKSZ 0
+#endif
@@ -19,6 +19,7 @@
#include <cpuid.h>
#include <dl-hwcap.h>
#include <libc-pointer-arith.h>
+#include <dl-minsigstacksize.h>
#if IS_IN (libc) && !defined SHARED
# include <assert.h>
# include <unistd.h>
@@ -367,6 +368,8 @@ get_common_indices (struct cpu_features *cpu_features,
cpu_features->features[COMMON_CPUID_INDEX_19].cpuid.ebx,
cpu_features->features[COMMON_CPUID_INDEX_19].cpuid.ecx,
cpu_features->features[COMMON_CPUID_INDEX_19].cpuid.edx);
+
+ dl_check_minsigstacksize (cpu_features);
}
_Static_assert (((index_arch_Fast_Unaligned_Load
new file mode 100644
@@ -0,0 +1,27 @@
+/* Emulate AT_MINSIGSTKSZ. Generic x86 version.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* Emulate AT_MINSIGSTKSZ with XSAVE. */
+
+static inline void
+dl_check_minsigstacksize (const struct cpu_features *cpu_features)
+{
+ /* NB: Default to a constant MINSIGSTKSZ. */
+ _Static_assert (__builtin_constant_p (MINSIGSTKSZ),
+ "MINSIGSTKSZ is constant");
+ GLRO(dl_minsigstacksize) = MINSIGSTKSZ;
+}
--
2.28.0