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platform_bionic/libc/bionic/sysconf.cpp
Elliott Hughes db602e8a47 sysconf(_SC_ARG_MAX): go back to imitating the kernel. 
For reasons explained in the code comment, go back to roughly our old
code. The "new" tests are just the old tests resurrected.

This also passes the current toybox xargs tests, which were the
motivation for going back on our earlier decision.

Test: bionic and toybox tests
Change-Id: I33cbcc04107efe81fdbc8166dc9ae844e471173e
2019-11-15 09:24:35 -08:00

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/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <pthread.h>
#include <stdio.h> // For FOPEN_MAX.
#include <sys/auxv.h>
#include <sys/param.h>
#include <sys/resource.h>
#include <sys/sysinfo.h>
#include <time.h>
#include <unistd.h>
#include "private/bionic_tls.h"
static long __sysconf_rlimit(int resource) {
rlimit rl;
getrlimit(resource, &rl);
return rl.rlim_cur;
}
long sysconf(int name) {
switch (name) {
//
// Things we actually have to calculate...
//
case _SC_ARG_MAX:
// You might think that just returning a constant 128KiB (ARG_MAX) would
// make sense, as this guy did:
//
// https://lkml.org/lkml/2017/11/15/813...
//
// I suspect a 128kB sysconf(_SC_ARG_MAX) is the sanest bet, simply
// because of that "conservative is better than aggressive".
//
// Especially since _technically_ we're still limiting things to that
// 128kB due to the single-string limit.
//
// Linus
//
// In practice that caused us trouble with toybox tests for xargs edge
// cases. The tests assume that they can at least reach the kernel's
// "minimum maximum" of 128KiB, but if we report 128KiB for _SC_ARG_MAX
// and xargs starts subtracting the environment space and so on from that,
// then xargs will think it's run out of space when given 128KiB of data,
// which should always work. See this thread for more:
//
// http://lists.landley.net/pipermail/toybox-landley.net/2019-November/011229.html
//
// So let's resign ourselves to tracking what the kernel actually does.
// Right now (2019, Linux 5.3) that amounts to:
return MAX(MIN(__sysconf_rlimit(RLIMIT_STACK) / 4, 3 * _STK_LIM / 4), ARG_MAX);
case _SC_AVPHYS_PAGES: return get_avphys_pages();
case _SC_CHILD_MAX: return __sysconf_rlimit(RLIMIT_NPROC);
case _SC_CLK_TCK: return static_cast<long>(getauxval(AT_CLKTCK));
case _SC_NPROCESSORS_CONF: return get_nprocs_conf();
case _SC_NPROCESSORS_ONLN: return get_nprocs();
case _SC_OPEN_MAX: return __sysconf_rlimit(RLIMIT_NOFILE);
case _SC_PAGESIZE:
case _SC_PAGE_SIZE:
// _SC_PAGESIZE and _SC_PAGE_SIZE are distinct, but return the same value.
return static_cast<long>(getauxval(AT_PAGESZ));
case _SC_PHYS_PAGES: return get_phys_pages();
//
// Constants...
//
case _SC_BC_BASE_MAX: return _POSIX2_BC_BASE_MAX; // Minimum requirement.
case _SC_BC_DIM_MAX: return _POSIX2_BC_DIM_MAX; // Minimum requirement.
case _SC_BC_SCALE_MAX: return _POSIX2_BC_SCALE_MAX; // Minimum requirement.
case _SC_BC_STRING_MAX: return _POSIX2_BC_STRING_MAX; // Minimum requirement.
case _SC_COLL_WEIGHTS_MAX: return _POSIX2_COLL_WEIGHTS_MAX; // Minimum requirement.
case _SC_EXPR_NEST_MAX: return _POSIX2_EXPR_NEST_MAX; // Minimum requirement.
case _SC_LINE_MAX: return _POSIX2_LINE_MAX; // Minimum requirement.
case _SC_NGROUPS_MAX: return NGROUPS_MAX;
case _SC_PASS_MAX: return PASS_MAX;
case _SC_2_C_BIND: return _POSIX2_C_BIND;
case _SC_2_C_DEV: return _POSIX2_C_DEV;
case _SC_2_CHAR_TERM: return _POSIX2_CHAR_TERM;
case _SC_2_FORT_DEV: return -1;
case _SC_2_FORT_RUN: return -1;
case _SC_2_LOCALEDEF: return _POSIX2_LOCALEDEF;
case _SC_2_SW_DEV: return _POSIX2_SW_DEV;
case _SC_2_UPE: return _POSIX2_UPE;
case _SC_2_VERSION: return _POSIX2_VERSION;
case _SC_JOB_CONTROL: return _POSIX_JOB_CONTROL;
case _SC_SAVED_IDS: return _POSIX_SAVED_IDS;
case _SC_VERSION: return _POSIX_VERSION;
case _SC_RE_DUP_MAX: return _POSIX_RE_DUP_MAX; // Minimum requirement.
case _SC_STREAM_MAX: return FOPEN_MAX;
case _SC_TZNAME_MAX: return _POSIX_TZNAME_MAX; // Minimum requirement.
case _SC_XOPEN_CRYPT: return _XOPEN_CRYPT;
case _SC_XOPEN_ENH_I18N: return _XOPEN_ENH_I18N;
case _SC_XOPEN_SHM: return _XOPEN_SHM;
case _SC_XOPEN_VERSION: return _XOPEN_VERSION;
case _SC_XOPEN_REALTIME: return _XOPEN_REALTIME;
case _SC_XOPEN_REALTIME_THREADS: return _XOPEN_REALTIME_THREADS;
case _SC_XOPEN_LEGACY: return _XOPEN_LEGACY;
case _SC_ATEXIT_MAX: return LONG_MAX; // Unlimited.
case _SC_IOV_MAX: return IOV_MAX;
case _SC_XOPEN_UNIX: return _XOPEN_UNIX;
case _SC_AIO_LISTIO_MAX: return _POSIX_AIO_LISTIO_MAX; // Minimum requirement.
case _SC_AIO_MAX: return _POSIX_AIO_MAX; // Minimum requirement.
case _SC_AIO_PRIO_DELTA_MAX:return 0; // Minimum requirement.
case _SC_DELAYTIMER_MAX: return INT_MAX;
case _SC_MQ_OPEN_MAX: return _POSIX_MQ_OPEN_MAX; // Minimum requirement.
case _SC_MQ_PRIO_MAX: return _POSIX_MQ_PRIO_MAX; // Minimum requirement.
case _SC_RTSIG_MAX: return RTSIG_MAX;
case _SC_SEM_NSEMS_MAX: return _POSIX_SEM_NSEMS_MAX; // Minimum requirement.
case _SC_SEM_VALUE_MAX: return SEM_VALUE_MAX;
case _SC_SIGQUEUE_MAX: return _POSIX_SIGQUEUE_MAX; // Minimum requirement.
case _SC_TIMER_MAX: return _POSIX_TIMER_MAX; // Minimum requirement.
case _SC_ASYNCHRONOUS_IO: return _POSIX_ASYNCHRONOUS_IO;
case _SC_FSYNC: return _POSIX_FSYNC;
case _SC_MAPPED_FILES: return _POSIX_MAPPED_FILES;
case _SC_MEMLOCK: return _POSIX_MEMLOCK;
case _SC_MEMLOCK_RANGE: return _POSIX_MEMLOCK_RANGE;
case _SC_MEMORY_PROTECTION: return _POSIX_MEMORY_PROTECTION;
case _SC_MESSAGE_PASSING: return _POSIX_MESSAGE_PASSING;
case _SC_PRIORITIZED_IO: return _POSIX_PRIORITIZED_IO;
case _SC_PRIORITY_SCHEDULING: return _POSIX_PRIORITY_SCHEDULING;
case _SC_REALTIME_SIGNALS: return _POSIX_REALTIME_SIGNALS;
case _SC_SEMAPHORES: return _POSIX_SEMAPHORES;
case _SC_SHARED_MEMORY_OBJECTS: return _POSIX_SHARED_MEMORY_OBJECTS;
case _SC_SYNCHRONIZED_IO: return _POSIX_SYNCHRONIZED_IO;
case _SC_TIMERS: return _POSIX_TIMERS;
case _SC_GETGR_R_SIZE_MAX: return 1024;
case _SC_GETPW_R_SIZE_MAX: return 1024;
case _SC_LOGIN_NAME_MAX: return LOGIN_NAME_MAX;
case _SC_THREAD_DESTRUCTOR_ITERATIONS: return PTHREAD_DESTRUCTOR_ITERATIONS;
case _SC_THREAD_KEYS_MAX: return PTHREAD_KEYS_MAX;
case _SC_THREAD_STACK_MIN: return PTHREAD_STACK_MIN;
case _SC_THREAD_THREADS_MAX: return -1; // No specific limit.
case _SC_TTY_NAME_MAX: return TTY_NAME_MAX;
case _SC_THREADS: return _POSIX_THREADS;
case _SC_THREAD_ATTR_STACKADDR: return _POSIX_THREAD_ATTR_STACKADDR;
case _SC_THREAD_ATTR_STACKSIZE: return _POSIX_THREAD_ATTR_STACKSIZE;
case _SC_THREAD_PRIORITY_SCHEDULING: return _POSIX_THREAD_PRIORITY_SCHEDULING;
case _SC_THREAD_PRIO_INHERIT: return _POSIX_THREAD_PRIO_INHERIT;
case _SC_THREAD_PRIO_PROTECT: return _POSIX_THREAD_PRIO_PROTECT;
case _SC_THREAD_SAFE_FUNCTIONS: return _POSIX_THREAD_SAFE_FUNCTIONS;
case _SC_MONOTONIC_CLOCK: return _POSIX_MONOTONIC_CLOCK;
case _SC_2_PBS: return -1; // Obsolescent in POSIX.1-2008.
case _SC_2_PBS_ACCOUNTING: return -1; // Obsolescent in POSIX.1-2008.
case _SC_2_PBS_CHECKPOINT: return -1; // Obsolescent in POSIX.1-2008.
case _SC_2_PBS_LOCATE: return -1; // Obsolescent in POSIX.1-2008.
case _SC_2_PBS_MESSAGE: return -1; // Obsolescent in POSIX.1-2008.
case _SC_2_PBS_TRACK: return -1; // Obsolescent in POSIX.1-2008.
case _SC_ADVISORY_INFO: return _POSIX_ADVISORY_INFO;
case _SC_BARRIERS: return _POSIX_BARRIERS;
case _SC_CLOCK_SELECTION: return _POSIX_CLOCK_SELECTION;
case _SC_CPUTIME: return _POSIX_CPUTIME;
case _SC_HOST_NAME_MAX: return _POSIX_HOST_NAME_MAX; // Minimum requirement.
case _SC_IPV6: return _POSIX_IPV6;
case _SC_RAW_SOCKETS: return _POSIX_RAW_SOCKETS;
case _SC_READER_WRITER_LOCKS: return _POSIX_READER_WRITER_LOCKS;
case _SC_REGEXP: return _POSIX_REGEXP;
case _SC_SHELL: return _POSIX_SHELL;
case _SC_SPAWN: return _POSIX_SPAWN;
case _SC_SPIN_LOCKS: return _POSIX_SPIN_LOCKS;
case _SC_SPORADIC_SERVER: return _POSIX_SPORADIC_SERVER;
case _SC_SS_REPL_MAX: return -1;
case _SC_SYMLOOP_MAX: return _POSIX_SYMLOOP_MAX; // Minimum requirement.
case _SC_THREAD_CPUTIME: return _POSIX_THREAD_CPUTIME;
case _SC_THREAD_PROCESS_SHARED: return _POSIX_THREAD_PROCESS_SHARED;
case _SC_THREAD_ROBUST_PRIO_INHERIT: return _POSIX_THREAD_ROBUST_PRIO_INHERIT;
case _SC_THREAD_ROBUST_PRIO_PROTECT: return _POSIX_THREAD_ROBUST_PRIO_PROTECT;
case _SC_THREAD_SPORADIC_SERVER: return _POSIX_THREAD_SPORADIC_SERVER;
case _SC_TIMEOUTS: return _POSIX_TIMEOUTS;
case _SC_TRACE: return -1; // Obsolescent in POSIX.1-2008.
case _SC_TRACE_EVENT_FILTER: return -1; // Obsolescent in POSIX.1-2008.
case _SC_TRACE_EVENT_NAME_MAX: return -1;
case _SC_TRACE_INHERIT: return -1; // Obsolescent in POSIX.1-2008.
case _SC_TRACE_LOG: return -1; // Obsolescent in POSIX.1-2008.
case _SC_TRACE_NAME_MAX: return -1;
case _SC_TRACE_SYS_MAX: return -1;
case _SC_TRACE_USER_EVENT_MAX: return -1;
case _SC_TYPED_MEMORY_OBJECTS: return _POSIX_TYPED_MEMORY_OBJECTS;
case _SC_V7_ILP32_OFF32: return _POSIX_V7_ILP32_OFF32;
case _SC_V7_ILP32_OFFBIG: return _POSIX_V7_ILP32_OFFBIG;
case _SC_V7_LP64_OFF64: return _POSIX_V7_LP64_OFF64;
case _SC_V7_LPBIG_OFFBIG: return _POSIX_V7_LPBIG_OFFBIG;
case _SC_XOPEN_STREAMS: return -1; // Obsolescent in POSIX.1-2008.
case _SC_XOPEN_UUCP: return -1;
// We do not have actual implementations for cache queries.
// It's valid to return 0 as the result is unknown.
case _SC_LEVEL1_ICACHE_SIZE: return 0;
case _SC_LEVEL1_ICACHE_ASSOC: return 0;
case _SC_LEVEL1_ICACHE_LINESIZE: return 0;
case _SC_LEVEL1_DCACHE_SIZE: return 0;
case _SC_LEVEL1_DCACHE_ASSOC: return 0;
case _SC_LEVEL1_DCACHE_LINESIZE: return 0;
case _SC_LEVEL2_CACHE_SIZE: return 0;
case _SC_LEVEL2_CACHE_ASSOC: return 0;
case _SC_LEVEL2_CACHE_LINESIZE: return 0;
case _SC_LEVEL3_CACHE_SIZE: return 0;
case _SC_LEVEL3_CACHE_ASSOC: return 0;
case _SC_LEVEL3_CACHE_LINESIZE: return 0;
case _SC_LEVEL4_CACHE_SIZE: return 0;
case _SC_LEVEL4_CACHE_ASSOC: return 0;
case _SC_LEVEL4_CACHE_LINESIZE: return 0;
default:
errno = EINVAL;
return -1;
}
}
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