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glibc/posix/sysconf.c
H.J. Lu 6c57d32048 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.
2021-02-01 11:00:52 -08:00

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/* Copyright (C) 1991-2021 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 <errno.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <unistd.h>
#include <time.h>
#include <limits.h>
#include <sys/param.h>
#include <sys/sysinfo.h>
/* Get the value of the system variable NAME. */
long int
__sysconf (int name)
{
switch (name)
{
default:
__set_errno (EINVAL);
return -1;
case _SC_TZNAME_MAX:
return -1;
case _SC_CHARCLASS_NAME_MAX:
#ifdef CHARCLASS_NAME_MAX
return CHARCLASS_NAME_MAX;
#else
return -1;
#endif
case _SC_COLL_WEIGHTS_MAX:
#ifdef COLL_WEIGHTS_MAX
return COLL_WEIGHTS_MAX;
#else
return -1;
#endif
case _SC_EQUIV_CLASS_MAX:
#ifdef EQUIV_CLASS_MAX
return EQUIV_CLASS_MAX;
#else
return -1;
#endif
case _SC_2_LOCALEDEF:
#ifdef _POSIX2_LOCALEDEF
return _POSIX2_LOCALEDEF;
#else
return -1;
#endif
case _SC_NPROCESSORS_CONF:
return __get_nprocs_conf ();
case _SC_NPROCESSORS_ONLN:
return __get_nprocs ();
case _SC_PHYS_PAGES:
return __get_phys_pages ();
case _SC_AVPHYS_PAGES:
return __get_avphys_pages ();
case _SC_ATEXIT_MAX:
/* We have no limit since we use lists. */
return INT_MAX;
case _SC_PASS_MAX:
/* We have no limit but since the return value might be used to
allocate a buffer we restrict the value. */
return BUFSIZ;
case _SC_CHAR_BIT:
return CHAR_BIT;
case _SC_CHAR_MAX:
return CHAR_MAX;
case _SC_CHAR_MIN:
return CHAR_MIN;
case _SC_INT_MAX:
return INT_MAX;
case _SC_INT_MIN:
return INT_MIN;
case _SC_LONG_BIT:
return sizeof (long int) * CHAR_BIT;
case _SC_WORD_BIT:
return sizeof (int) * CHAR_BIT;
case _SC_MB_LEN_MAX:
return MB_LEN_MAX;
case _SC_NZERO:
return NZERO;
case _SC_SSIZE_MAX:
return _POSIX_SSIZE_MAX;
case _SC_SCHAR_MAX:
return SCHAR_MAX;
case _SC_SCHAR_MIN:
return SCHAR_MIN;
case _SC_SHRT_MAX:
return SHRT_MAX;
case _SC_SHRT_MIN:
return SHRT_MIN;
case _SC_UCHAR_MAX:
return UCHAR_MAX;
case _SC_UINT_MAX:
return UINT_MAX;
case _SC_ULONG_MAX:
return ULONG_MAX;
case _SC_USHRT_MAX:
return USHRT_MAX;
case _SC_GETGR_R_SIZE_MAX:
return NSS_BUFLEN_GROUP;
case _SC_GETPW_R_SIZE_MAX:
return NSS_BUFLEN_PASSWD;
case _SC_ARG_MAX:
case _SC_CHILD_MAX:
case _SC_CLK_TCK:
case _SC_NGROUPS_MAX:
case _SC_OPEN_MAX:
case _SC_STREAM_MAX:
case _SC_JOB_CONTROL:
case _SC_SAVED_IDS:
case _SC_REALTIME_SIGNALS:
case _SC_PRIORITY_SCHEDULING:
case _SC_TIMERS:
case _SC_ASYNCHRONOUS_IO:
case _SC_PRIORITIZED_IO:
case _SC_SYNCHRONIZED_IO:
case _SC_FSYNC:
case _SC_MAPPED_FILES:
case _SC_MEMLOCK:
case _SC_MEMLOCK_RANGE:
case _SC_MEMORY_PROTECTION:
case _SC_MESSAGE_PASSING:
case _SC_SEMAPHORES:
case _SC_SHARED_MEMORY_OBJECTS:
case _SC_AIO_LISTIO_MAX:
case _SC_AIO_MAX:
case _SC_AIO_PRIO_DELTA_MAX:
case _SC_DELAYTIMER_MAX:
case _SC_MQ_OPEN_MAX:
case _SC_MQ_PRIO_MAX:
case _SC_VERSION:
case _SC_PAGESIZE:
case _SC_RTSIG_MAX:
case _SC_SEM_NSEMS_MAX:
case _SC_SEM_VALUE_MAX:
case _SC_SIGQUEUE_MAX:
case _SC_TIMER_MAX:
case _SC_PII:
case _SC_PII_XTI:
case _SC_PII_SOCKET:
case _SC_PII_OSI:
case _SC_POLL:
case _SC_SELECT:
case _SC_UIO_MAXIOV:
case _SC_PII_INTERNET_STREAM:
case _SC_PII_INTERNET_DGRAM:
case _SC_PII_OSI_COTS:
case _SC_PII_OSI_CLTS:
case _SC_PII_OSI_M:
case _SC_T_IOV_MAX:
case _SC_BC_BASE_MAX:
case _SC_BC_DIM_MAX:
case _SC_BC_SCALE_MAX:
case _SC_BC_STRING_MAX:
case _SC_EXPR_NEST_MAX:
case _SC_LINE_MAX:
case _SC_RE_DUP_MAX:
case _SC_2_VERSION:
case _SC_2_C_BIND:
case _SC_2_C_DEV:
case _SC_2_FORT_DEV:
case _SC_2_SW_DEV:
case _SC_2_CHAR_TERM:
case _SC_2_C_VERSION:
case _SC_2_UPE:
case _SC_THREADS:
case _SC_THREAD_SAFE_FUNCTIONS:
case _SC_LOGIN_NAME_MAX:
case _SC_TTY_NAME_MAX:
case _SC_THREAD_DESTRUCTOR_ITERATIONS:
case _SC_THREAD_KEYS_MAX:
case _SC_THREAD_STACK_MIN:
case _SC_THREAD_THREADS_MAX:
case _SC_THREAD_ATTR_STACKADDR:
case _SC_THREAD_ATTR_STACKSIZE:
case _SC_THREAD_PRIORITY_SCHEDULING:
case _SC_THREAD_PRIO_INHERIT:
case _SC_THREAD_PRIO_PROTECT:
case _SC_THREAD_PROCESS_SHARED:
case _SC_XOPEN_VERSION:
case _SC_XOPEN_XCU_VERSION:
case _SC_XOPEN_UNIX:
case _SC_XOPEN_CRYPT:
case _SC_XOPEN_ENH_I18N:
case _SC_XOPEN_SHM:
case _SC_XOPEN_XPG2:
case _SC_XOPEN_XPG3:
case _SC_XOPEN_XPG4:
case _SC_NL_ARGMAX:
case _SC_NL_LANGMAX:
case _SC_NL_MSGMAX:
case _SC_NL_NMAX:
case _SC_NL_SETMAX:
case _SC_NL_TEXTMAX:
case _SC_XBS5_ILP32_OFF32:
case _SC_XBS5_ILP32_OFFBIG:
case _SC_XBS5_LP64_OFF64:
case _SC_XBS5_LPBIG_OFFBIG:
case _SC_POSIX_V6_ILP32_OFF32:
case _SC_POSIX_V6_ILP32_OFFBIG:
case _SC_POSIX_V6_LP64_OFF64:
case _SC_POSIX_V6_LPBIG_OFFBIG:
case _SC_POSIX_V7_ILP32_OFF32:
case _SC_POSIX_V7_ILP32_OFFBIG:
case _SC_POSIX_V7_LP64_OFF64:
case _SC_POSIX_V7_LPBIG_OFFBIG:
case _SC_XOPEN_LEGACY:
case _SC_XOPEN_REALTIME:
case _SC_XOPEN_REALTIME_THREADS:
case _SC_MINSIGSTKSZ:
case _SC_SIGSTKSZ:
break;
}
__set_errno (ENOSYS);
return -1;
}
weak_alias (__sysconf, sysconf)
libc_hidden_def (__sysconf)
stub_warning (sysconf)
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