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-rw-r--r--NEWS5
-rw-r--r--bits/confname.h8
-rw-r--r--bits/sigstksz.h21
-rw-r--r--elf/dl-support.c5
-rw-r--r--elf/dl-sysdep.c9
-rw-r--r--include/bits/sigstack.h5
-rw-r--r--include/bits/sigstksz.h7
-rw-r--r--include/features.h11
-rw-r--r--manual/conf.texi21
-rw-r--r--manual/creature.texi6
-rw-r--r--posix/sysconf.c3
-rw-r--r--signal/Makefile5
-rw-r--r--signal/signal.h1
-rw-r--r--signal/tst-minsigstksz-5.c84
-rw-r--r--sysdeps/generic/ldsodefs.h3
-rw-r--r--sysdeps/unix/sysv/linux/bits/sigstksz.h33
-rw-r--r--sysdeps/unix/sysv/linux/ia64/sysconf-sigstksz.h27
-rw-r--r--sysdeps/unix/sysv/linux/sysconf-sigstksz.h38
-rw-r--r--sysdeps/unix/sysv/linux/sysconf.c9
-rw-r--r--sysdeps/unix/sysv/linux/x86/dl-minsigstacksize.h83
-rw-r--r--sysdeps/unix/sysv/linux/x86/include/bits/sigstack.h5
-rw-r--r--sysdeps/x86/cpu-features.c3
-rw-r--r--sysdeps/x86/dl-minsigstacksize.h27
23 files changed, 416 insertions, 3 deletions
diff --git a/NEWS b/NEWS
index 4ac2849e23..7e535c990e 100644
--- a/NEWS
+++ b/NEWS
@@ -33,6 +33,11 @@ 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 --list-tunables argument which prints
   all the supported tunables.  This option is disable if glibc is
   configured with tunables disabled (--enable-tunables=no).
diff --git a/bits/confname.h b/bits/confname.h
index 8068bda273..ec6cd07957 100644
--- a/bits/confname.h
+++ b/bits/confname.h
@@ -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'.  */
diff --git a/bits/sigstksz.h b/bits/sigstksz.h
new file mode 100644
index 0000000000..5535d873b5
--- /dev/null
+++ b/bits/sigstksz.h
@@ -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
diff --git a/elf/dl-support.c b/elf/dl-support.c
index 7abb65d8e3..7fc2ee78e2 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -142,6 +142,8 @@ 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;
@@ -307,6 +309,9 @@ _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)
diff --git a/elf/dl-sysdep.c b/elf/dl-sysdep.c
index 0658c17da6..bd5066fe3b 100644
--- a/elf/dl-sysdep.c
+++ b/elf/dl-sysdep.c
@@ -115,6 +115,11 @@ _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)
       {
@@ -179,6 +184,9 @@ _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
       }
 
@@ -306,6 +314,7 @@ _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 },
diff --git a/include/bits/sigstack.h b/include/bits/sigstack.h
new file mode 100644
index 0000000000..eea939f59d
--- /dev/null
+++ b/include/bits/sigstack.h
@@ -0,0 +1,5 @@
+#include_next <bits/sigstack.h>
+
+#if !defined _ISOMAC && !defined CONSTANT_MINSIGSTKSZ
+# define CONSTANT_MINSIGSTKSZ MINSIGSTKSZ
+#endif
diff --git a/include/bits/sigstksz.h b/include/bits/sigstksz.h
new file mode 100644
index 0000000000..2ca891e918
--- /dev/null
+++ b/include/bits/sigstksz.h
@@ -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
diff --git a/include/features.h b/include/features.h
index c6ff971346..eb97470afa 100644
--- a/include/features.h
+++ b/include/features.h
@@ -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
diff --git a/manual/conf.texi b/manual/conf.texi
index f959b00bb6..ba9847aaa4 100644
--- a/manual/conf.texi
+++ b/manual/conf.texi
@@ -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
diff --git a/manual/creature.texi b/manual/creature.texi
index 31208ccb2b..5090735e4f 100644
--- a/manual/creature.texi
+++ b/manual/creature.texi
@@ -258,6 +258,12 @@ checks are applied. If defined to @math{3}, @theglibc{} may also use
 checks that may have an additional performance overhead.
 @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)}
diff --git a/posix/sysconf.c b/posix/sysconf.c
index bb9e132e5c..67d17ca0f8 100644
--- a/posix/sysconf.c
+++ b/posix/sysconf.c
@@ -266,6 +266,9 @@ __sysconf (int name)
     case _SC_XOPEN_REALTIME:
     case _SC_XOPEN_REALTIME_THREADS:
 
+    case _SC_MINSIGSTKSZ:
+    case _SC_SIGSTKSZ:
+
       break;
     }
 
diff --git a/signal/Makefile b/signal/Makefile
index e89c308889..3d8cab1f50 100644
--- a/signal/Makefile
+++ b/signal/Makefile
@@ -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
diff --git a/signal/signal.h b/signal/signal.h
index 6463c98e11..b17203c99c 100644
--- a/signal/signal.h
+++ b/signal/signal.h
@@ -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.
diff --git a/signal/tst-minsigstksz-5.c b/signal/tst-minsigstksz-5.c
new file mode 100644
index 0000000000..d657d2f4e6
--- /dev/null
+++ b/signal/tst-minsigstksz-5.c
@@ -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>
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index aab7245e93..9720a4e446 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -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;
 
diff --git a/sysdeps/unix/sysv/linux/bits/sigstksz.h b/sysdeps/unix/sysv/linux/bits/sigstksz.h
new file mode 100644
index 0000000000..926508f2b4
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/bits/sigstksz.h
@@ -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
diff --git a/sysdeps/unix/sysv/linux/ia64/sysconf-sigstksz.h b/sysdeps/unix/sysv/linux/ia64/sysconf-sigstksz.h
new file mode 100644
index 0000000000..7e5ceba151
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/ia64/sysconf-sigstksz.h
@@ -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;
+}
diff --git a/sysdeps/unix/sysv/linux/sysconf-sigstksz.h b/sysdeps/unix/sysv/linux/sysconf-sigstksz.h
new file mode 100644
index 0000000000..64d450b22c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/sysconf-sigstksz.h
@@ -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;
+}
diff --git a/sysdeps/unix/sysv/linux/sysconf.c b/sysdeps/unix/sysv/linux/sysconf.c
index bfad5b6858..366fcef01e 100644
--- a/sysdeps/unix/sysv/linux/sysconf.c
+++ b/sysdeps/unix/sysv/linux/sysconf.c
@@ -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;
     }
diff --git a/sysdeps/unix/sysv/linux/x86/dl-minsigstacksize.h b/sysdeps/unix/sysv/linux/x86/dl-minsigstacksize.h
new file mode 100644
index 0000000000..6088bbc99e
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/dl-minsigstacksize.h
@@ -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;
+    }
+}
diff --git a/sysdeps/unix/sysv/linux/x86/include/bits/sigstack.h b/sysdeps/unix/sysv/linux/x86/include/bits/sigstack.h
new file mode 100644
index 0000000000..208754c497
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/include/bits/sigstack.h
@@ -0,0 +1,5 @@
+#include_next <bits/sigstack.h>
+
+#ifndef _ISOMAC
+# define CONSTANT_MINSIGSTKSZ 0
+#endif
diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index 73b0a4dc9a..7996ed0cd2 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -21,6 +21,7 @@
 #include <get-isa-level.h>
 #include <cacheinfo.h>
 #include <dl-cacheinfo.h>
+#include <dl-minsigstacksize.h>
 
 #if HAVE_TUNABLES
 extern void TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *)
@@ -364,6 +365,8 @@ get_common_indices (struct cpu_features *cpu_features,
 		   cpu_features->features[CPUID_INDEX_19].cpuid.ebx,
 		   cpu_features->features[CPUID_INDEX_19].cpuid.ecx,
 		   cpu_features->features[CPUID_INDEX_19].cpuid.edx);
+
+  dl_check_minsigstacksize (cpu_features);
 }
 
 _Static_assert (((index_arch_Fast_Unaligned_Load
diff --git a/sysdeps/x86/dl-minsigstacksize.h b/sysdeps/x86/dl-minsigstacksize.h
new file mode 100644
index 0000000000..959871c970
--- /dev/null
+++ b/sysdeps/x86/dl-minsigstacksize.h
@@ -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;
+}
generated by cgit-pink 1.4.1 (git 2.36.1) at 2024-06-29 23:27:12 +0000