diff --git a/libc/bionic/sysconf.cpp b/libc/bionic/sysconf.cpp
index 9ffb58e..571370c 100644
--- a/libc/bionic/sysconf.cpp
+++ b/libc/bionic/sysconf.cpp
@@ -240,7 +240,7 @@
     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_DELAYTIMER_MAX:    return _POSIX_DELAYTIMER_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;
@@ -308,11 +308,11 @@
     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:             return -1;
+    case _SC_TRACE_EVENT_FILTER:      return -1;
     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_INHERIT:     return -1;
+    case _SC_TRACE_LOG:         return -1;
     case _SC_TRACE_NAME_MAX:    return -1;
     case _SC_TRACE_SYS_MAX:     return -1;
     case _SC_TRACE_USER_EVENT_MAX:    return -1;
@@ -321,7 +321,7 @@
     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_STREAMS:     return -1;
     case _SC_XOPEN_UUCP:        return -1;
 
     case _SC_LEVEL1_ICACHE_SIZE:      return __sysconf_caches()->l1_i.size;
diff --git a/libc/include/bits/sysconf.h b/libc/include/bits/sysconf.h
index 8607adf..ecf26ba 100644
--- a/libc/include/bits/sysconf.h
+++ b/libc/include/bits/sysconf.h
@@ -26,172 +26,324 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _BITS_SYSCONF_H_
-#define _BITS_SYSCONF_H_
+#pragma once
 
 #include <sys/cdefs.h>
 
-/* as listed by Posix sysconf() description */
-/* most of these will return -1 and ENOSYS  */
-
-#define _SC_ARG_MAX             0x0000
-#define _SC_BC_BASE_MAX         0x0001
-#define _SC_BC_DIM_MAX          0x0002
-#define _SC_BC_SCALE_MAX        0x0003
-#define _SC_BC_STRING_MAX       0x0004
-#define _SC_CHILD_MAX           0x0005
-#define _SC_CLK_TCK             0x0006
-#define _SC_COLL_WEIGHTS_MAX    0x0007
-#define _SC_EXPR_NEST_MAX       0x0008
-#define _SC_LINE_MAX            0x0009
-#define _SC_NGROUPS_MAX         0x000a
-#define _SC_OPEN_MAX            0x000b
-#define _SC_PASS_MAX            0x000c
-#define _SC_2_C_BIND            0x000d
-#define _SC_2_C_DEV             0x000e
-#define _SC_2_C_VERSION         0x000f  /* Obsolescent in POSIX.1-2008, TODO: remove it. */
-#define _SC_2_CHAR_TERM         0x0010
-#define _SC_2_FORT_DEV          0x0011
-#define _SC_2_FORT_RUN          0x0012
-#define _SC_2_LOCALEDEF         0x0013
-#define _SC_2_SW_DEV            0x0014
-#define _SC_2_UPE               0x0015
-#define _SC_2_VERSION           0x0016
-#define _SC_JOB_CONTROL         0x0017
-#define _SC_SAVED_IDS           0x0018
-#define _SC_VERSION             0x0019
-#define _SC_RE_DUP_MAX          0x001a
-#define _SC_STREAM_MAX          0x001b
-#define _SC_TZNAME_MAX          0x001c
-#define _SC_XOPEN_CRYPT         0x001d
-#define _SC_XOPEN_ENH_I18N      0x001e
-#define _SC_XOPEN_SHM           0x001f
-#define _SC_XOPEN_VERSION       0x0020
-#define _SC_XOPEN_XCU_VERSION   0x0021  /* Obsolescent in POSIX.1-2008, TODO: remove it. */
-#define _SC_XOPEN_REALTIME      0x0022
-#define _SC_XOPEN_REALTIME_THREADS  0x0023
-#define _SC_XOPEN_LEGACY        0x0024
-#define _SC_ATEXIT_MAX          0x0025
-#define _SC_IOV_MAX             0x0026
+/** sysconf() query for the maximum number of bytes of exec() arguments. */
+#define _SC_ARG_MAX 0x0000
+/** sysconf() query for bc(1) behavior equivalent to _POSIX2_BC_BASE_MAX. */
+#define _SC_BC_BASE_MAX 0x0001
+/** sysconf() query for bc(1) behavior equivalent to _POSIX2_BC_DIM_MAX. */
+#define _SC_BC_DIM_MAX 0x0002
+/** sysconf() query for bc(1) behavior equivalent to _POSIX2_BC_SCALE_MAX. */
+#define _SC_BC_SCALE_MAX 0x0003
+/** sysconf() query for bc(1) behavior equivalent to _POSIX2_BC_STRING_MAX. */
+#define _SC_BC_STRING_MAX 0x0004
+/** sysconf() query equivalent to RLIMIT_NPROC. */
+#define _SC_CHILD_MAX 0x0005
+/** sysconf() query equivalent to AT_CLKTCK. */
+#define _SC_CLK_TCK 0x0006
+/** sysconf() query for collation behavior equivalent to _POSIX2_COLL_WEIGHTS_MAX. */
+#define _SC_COLL_WEIGHTS_MAX 0x0007
+/** sysconf() query for expr(1) behavior equivalent to _POSIX2_EXPR_NEST_MAX. */
+#define _SC_EXPR_NEST_MAX 0x0008
+/** sysconf() query for command-line tool behavior equivalent to _POSIX2_LINE_MAX. */
+#define _SC_LINE_MAX 0x0009
+/** sysconf() query equivalent to NGROUPS_MAX. */
+#define _SC_NGROUPS_MAX 0x000a
+/** sysconf() query equivalent to RLIMIT_NOFILE. */
+#define _SC_OPEN_MAX 0x000b
+/** sysconf() query equivalent to PASS_MAX. */
+#define _SC_PASS_MAX 0x000c
+/** sysconf() query equivalent to _POSIX2_C_BIND. */
+#define _SC_2_C_BIND 0x000d
+/** sysconf() query equivalent to _POSIX2_C_DEV. */
+#define _SC_2_C_DEV 0x000e
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_2_C_VERSION 0x000f
+/** sysconf() query equivalent to _POSIX2_CHAR_TERM. */
+#define _SC_2_CHAR_TERM 0x0010
+/** sysconf() query equivalent to _POSIX2_FORT_DEV. */
+#define _SC_2_FORT_DEV 0x0011
+/** sysconf() query equivalent to _POSIX2_FORT_RUN. */
+#define _SC_2_FORT_RUN 0x0012
+/** sysconf() query equivalent to _POSIX2_LOCALEDEF. */
+#define _SC_2_LOCALEDEF 0x0013
+/** sysconf() query equivalent to _POSIX2_SW_DEV. */
+#define _SC_2_SW_DEV 0x0014
+/** sysconf() query equivalent to _POSIX2_UPE. */
+#define _SC_2_UPE 0x0015
+/** sysconf() query equivalent to _POSIX2_VERSION. */
+#define _SC_2_VERSION 0x0016
+/** sysconf() query equivalent to _POSIX_JOB_CONTROL. */
+#define _SC_JOB_CONTROL 0x0017
+/** sysconf() query equivalent to _POSIX_SAVED_IDS. */
+#define _SC_SAVED_IDS 0x0018
+/** sysconf() query equivalent to _POSIX_VERSION. */
+#define _SC_VERSION 0x0019
+/** sysconf() query equivalent to _POSIX_RE_DUP_MAX. */
+#define _SC_RE_DUP_MAX 0x001a
+/** sysconf() query equivalent to FOPEN_MAX. */
+#define _SC_STREAM_MAX 0x001b
+/** sysconf() query equivalent to _POSIX_TZNAME_MAX. */
+#define _SC_TZNAME_MAX 0x001c
+/** sysconf() query equivalent to _XOPEN_CRYPT. */
+#define _SC_XOPEN_CRYPT 0x001d
+/** sysconf() query equivalent to _XOPEN_ENH_I18N. */
+#define _SC_XOPEN_ENH_I18N 0x001e
+/** sysconf() query equivalent to _XOPEN_SHM. */
+#define _SC_XOPEN_SHM 0x001f
+/** sysconf() query equivalent to _XOPEN_VERSION. */
+#define _SC_XOPEN_VERSION 0x0020
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_XOPEN_XCU_VERSION 0x0021
+/** sysconf() query equivalent to _XOPEN_REALTIME. */
+#define _SC_XOPEN_REALTIME 0x0022
+/** sysconf() query equivalent to _XOPEN_REALTIME_THREADS. */
+#define _SC_XOPEN_REALTIME_THREADS 0x0023
+/** sysconf() query equivalent to _XOPEN_LEGACY. */
+#define _SC_XOPEN_LEGACY 0x0024
+/** sysconf() query for the maximum number of atexit() handlers. Unlimited on Android. */
+#define _SC_ATEXIT_MAX 0x0025
+/** sysconf() query equivalent to IOV_MAX. */
+#define _SC_IOV_MAX 0x0026
+/** Same as _SC_IOV_MAX. */
 #define _SC_UIO_MAXIOV _SC_IOV_MAX
-#define _SC_PAGESIZE            0x0027
-#define _SC_PAGE_SIZE           0x0028
-#define _SC_XOPEN_UNIX          0x0029
-#define _SC_XBS5_ILP32_OFF32    0x002a  /* Obsolescent in POSIX.1-2008, TODO: remove it. */
-#define _SC_XBS5_ILP32_OFFBIG   0x002b  /* Obsolescent in POSIX.1-2008, TODO: remove it. */
-#define _SC_XBS5_LP64_OFF64     0x002c  /* Obsolescent in POSIX.1-2008, TODO: remove it. */
-#define _SC_XBS5_LPBIG_OFFBIG   0x002d  /* Obsolescent in POSIX.1-2008, TODO: remove it. */
-#define _SC_AIO_LISTIO_MAX      0x002e
-#define _SC_AIO_MAX             0x002f
+/** Same as _SC_PAGE_SIZE. */
+#define _SC_PAGESIZE 0x0027
+/** sysconf() query equivalent to getpagesize(). */
+#define _SC_PAGE_SIZE 0x0028
+/** sysconf() query equivalent to _XOPEN_UNIX. */
+#define _SC_XOPEN_UNIX 0x0029
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_XBS5_ILP32_OFF32 0x002a
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_XBS5_ILP32_OFFBIG 0x002b
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_XBS5_LP64_OFF64 0x002c
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_XBS5_LPBIG_OFFBIG 0x002d
+/** sysconf() query equivalent to _POSIX_AIO_LISTIO_MAX. */
+#define _SC_AIO_LISTIO_MAX 0x002e
+/** sysconf() query equivalent to _POSIX_AIO_MAX. */
+#define _SC_AIO_MAX 0x002f
+/** Unimplemented on Android. */
 #define _SC_AIO_PRIO_DELTA_MAX  0x0030
-#define _SC_DELAYTIMER_MAX      0x0031
-#define _SC_MQ_OPEN_MAX         0x0032
-#define _SC_MQ_PRIO_MAX         0x0033
-#define _SC_RTSIG_MAX           0x0034
-#define _SC_SEM_NSEMS_MAX       0x0035
-#define _SC_SEM_VALUE_MAX       0x0036
-#define _SC_SIGQUEUE_MAX        0x0037
-#define _SC_TIMER_MAX           0x0038
-#define _SC_ASYNCHRONOUS_IO     0x0039
-#define _SC_FSYNC               0x003a
-#define _SC_MAPPED_FILES        0x003b
-#define _SC_MEMLOCK             0x003c
-#define _SC_MEMLOCK_RANGE       0x003d
-#define _SC_MEMORY_PROTECTION   0x003e
-#define _SC_MESSAGE_PASSING     0x003f
-#define _SC_PRIORITIZED_IO      0x0040
+/** sysconf() query equivalent to _POSIX_DELAYTIMER_MAX. */
+#define _SC_DELAYTIMER_MAX 0x0031
+/** sysconf() query equivalent to _POSIX_MQ_OPEN_MAX. */
+#define _SC_MQ_OPEN_MAX 0x0032
+/** sysconf() query equivalent to _POSIX_MQ_PRIO_MAX. */
+#define _SC_MQ_PRIO_MAX 0x0033
+/** sysconf() query equivalent to RTSIG_MAX. Constant on Android. */
+#define _SC_RTSIG_MAX 0x0034
+/** sysconf() query equivalent to _POSIX_SEM_NSEMS_MAX. Constant on Android. */
+#define _SC_SEM_NSEMS_MAX 0x0035
+/** sysconf() query equivalent to SEM_VALUE_MAX. Constant on Android. */
+#define _SC_SEM_VALUE_MAX 0x0036
+/** sysconf() query equivalent to _POSIX_SIGQUEUE_MAX. */
+#define _SC_SIGQUEUE_MAX 0x0037
+/** sysconf() query equivalent to _POSIX_TIMER_MAX. */
+#define _SC_TIMER_MAX 0x0038
+/** sysconf() query equivalent to _POSIX_ASYNCHRONOUS_IO. */
+#define _SC_ASYNCHRONOUS_IO 0x0039
+/** sysconf() query equivalent to _POSIX_FSYNC. */
+#define _SC_FSYNC 0x003a
+/** sysconf() query equivalent to _POSIX_MAPPED_FILES. */
+#define _SC_MAPPED_FILES 0x003b
+/** sysconf() query equivalent to _POSIX_MEMLOCK. */
+#define _SC_MEMLOCK 0x003c
+/** sysconf() query equivalent to _POSIX_MEMLOCK_RANGE. */
+#define _SC_MEMLOCK_RANGE 0x003d
+/** sysconf() query equivalent to _POSIX_MEMORY_PROTECTION. */
+#define _SC_MEMORY_PROTECTION 0x003e
+/** sysconf() query equivalent to _POSIX_MESSAGE_PASSING. */
+#define _SC_MESSAGE_PASSING 0x003f
+/** sysconf() query equivalent to _POSIX_PRIORITIZED_IO. */
+#define _SC_PRIORITIZED_IO 0x0040
+/** sysconf() query equivalent to _POSIX_PRIORITY_SCHEDULING. */
 #define _SC_PRIORITY_SCHEDULING 0x0041
-#define _SC_REALTIME_SIGNALS    0x0042
-#define _SC_SEMAPHORES          0x0043
-#define _SC_SHARED_MEMORY_OBJECTS  0x0044
-#define _SC_SYNCHRONIZED_IO     0x0045
-#define _SC_TIMERS              0x0046
-#define _SC_GETGR_R_SIZE_MAX    0x0047
-#define _SC_GETPW_R_SIZE_MAX    0x0048
-#define _SC_LOGIN_NAME_MAX      0x0049
-#define _SC_THREAD_DESTRUCTOR_ITERATIONS  0x004a
-#define _SC_THREAD_KEYS_MAX     0x004b
-#define _SC_THREAD_STACK_MIN    0x004c
-#define _SC_THREAD_THREADS_MAX  0x004d
-#define _SC_TTY_NAME_MAX        0x004e
-
-#define _SC_THREADS                     0x004f
-#define _SC_THREAD_ATTR_STACKADDR       0x0050
-#define _SC_THREAD_ATTR_STACKSIZE       0x0051
-#define _SC_THREAD_PRIORITY_SCHEDULING  0x0052
-#define _SC_THREAD_PRIO_INHERIT         0x0053
-#define _SC_THREAD_PRIO_PROTECT         0x0054
-#define _SC_THREAD_SAFE_FUNCTIONS       0x0055
-
-#define _SC_NPROCESSORS_CONF            0x0060
-#define _SC_NPROCESSORS_ONLN            0x0061
-#define _SC_PHYS_PAGES                  0x0062
-#define _SC_AVPHYS_PAGES                0x0063
-#define _SC_MONOTONIC_CLOCK             0x0064
-
-#define _SC_2_PBS               0x0065
-#define _SC_2_PBS_ACCOUNTING    0x0066
-#define _SC_2_PBS_CHECKPOINT    0x0067
-#define _SC_2_PBS_LOCATE        0x0068
-#define _SC_2_PBS_MESSAGE       0x0069
-#define _SC_2_PBS_TRACK         0x006a
-#define _SC_ADVISORY_INFO       0x006b
-#define _SC_BARRIERS            0x006c
-#define _SC_CLOCK_SELECTION     0x006d
-#define _SC_CPUTIME             0x006e
-#define _SC_HOST_NAME_MAX       0x006f
-#define _SC_IPV6                0x0070
-#define _SC_RAW_SOCKETS         0x0071
+/** sysconf() query equivalent to _POSIX_REALTIME_SIGNALS. */
+#define _SC_REALTIME_SIGNALS 0x0042
+/** sysconf() query equivalent to _POSIX_SEMAPHORES. */
+#define _SC_SEMAPHORES 0x0043
+/** sysconf() query equivalent to _POSIX_SHARED_MEMORY_OBJECTS. */
+#define _SC_SHARED_MEMORY_OBJECTS 0x0044
+/** sysconf() query equivalent to _POSIX_SYNCHRONIZED_IO. */
+#define _SC_SYNCHRONIZED_IO 0x0045
+/** sysconf() query equivalent to _POSIX_TIMERS. */
+#define _SC_TIMERS 0x0046
+/** sysconf() query for an initial size for getgrgid_r() and getgrnam_r() buffers. */
+#define _SC_GETGR_R_SIZE_MAX 0x0047
+/** sysconf() query for an initial size for getpwuid_r() and getpwnam_r() buffers. */
+#define _SC_GETPW_R_SIZE_MAX 0x0048
+/** sysconf() query equivalent to LOGIN_NAME_MAX. */
+#define _SC_LOGIN_NAME_MAX 0x0049
+/** sysconf() query equivalent to PTHREAD_DESTRUCTOR_ITERATIONS. */
+#define _SC_THREAD_DESTRUCTOR_ITERATIONS 0x004a
+/** sysconf() query equivalent to PTHREAD_KEYS_MAX. */
+#define _SC_THREAD_KEYS_MAX 0x004b
+/** sysconf() query equivalent to PTHREAD_STACK_MIN. */
+#define _SC_THREAD_STACK_MIN 0x004c
+/** sysconf() query for a maximum number of threads. Unlimited on Android. */
+#define _SC_THREAD_THREADS_MAX 0x004d
+/** sysconf() query equivalent to TTY_NAME_MAX. */
+#define _SC_TTY_NAME_MAX 0x004e
+/** sysconf() query equivalent to _POSIX_THREADS. */
+#define _SC_THREADS 0x004f
+/** sysconf() query equivalent to _POSIX_THREAD_ATTR_STACKADDR. */
+#define _SC_THREAD_ATTR_STACKADDR 0x0050
+/** sysconf() query equivalent to _POSIX_THREAD_ATTR_STACKSIZE. */
+#define _SC_THREAD_ATTR_STACKSIZE 0x0051
+/** sysconf() query equivalent to _POSIX_THREAD_PRIORITY_SCHEDULING. */
+#define _SC_THREAD_PRIORITY_SCHEDULING 0x0052
+/** sysconf() query equivalent to _POSIX_THREAD_PRIO_INHERIT. */
+#define _SC_THREAD_PRIO_INHERIT 0x0053
+/** sysconf() query equivalent to _POSIX_THREAD_PRIO_PROTECT. */
+#define _SC_THREAD_PRIO_PROTECT 0x0054
+/** sysconf() query equivalent to _POSIX_THREAD_SAFE_FUNCTIONS. */
+#define _SC_THREAD_SAFE_FUNCTIONS 0x0055
+/** sysconf() query equivalent to get_nprocs_conf(). */
+#define _SC_NPROCESSORS_CONF 0x0060
+/** sysconf() query equivalent to get_nprocs(). */
+#define _SC_NPROCESSORS_ONLN 0x0061
+/** sysconf() query equivalent to get_phys_pages(). */
+#define _SC_PHYS_PAGES 0x0062
+/** sysconf() query equivalent to get_avphys_pages(). */
+#define _SC_AVPHYS_PAGES 0x0063
+/** sysconf() query equivalent to _POSIX_MONOTONIC_CLOCK. */
+#define _SC_MONOTONIC_CLOCK 0x0064
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_2_PBS 0x0065
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_2_PBS_ACCOUNTING 0x0066
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_2_PBS_CHECKPOINT 0x0067
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_2_PBS_LOCATE 0x0068
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_2_PBS_MESSAGE 0x0069
+/** Obsolescent in POSIX.1-2008. */
+#define _SC_2_PBS_TRACK 0x006a
+/** sysconf() query equivalent to _POSIX_ADVISORY_INFO. */
+#define _SC_ADVISORY_INFO 0x006b
+/** sysconf() query equivalent to _POSIX_BARRIERS. */
+#define _SC_BARRIERS 0x006c
+/** sysconf() query equivalent to _POSIX_CLOCK_SELECTION. */
+#define _SC_CLOCK_SELECTION 0x006d
+/** sysconf() query equivalent to _POSIX_CPUTIME. */
+#define _SC_CPUTIME 0x006e
+/** sysconf() query equivalent to _POSIX_HOST_NAME_MAX. */
+#define _SC_HOST_NAME_MAX 0x006f
+/** sysconf() query equivalent to _POSIX_IPV6. */
+#define _SC_IPV6 0x0070
+/** sysconf() query equivalent to _POSIX_RAW_SOCKETS. */
+#define _SC_RAW_SOCKETS 0x0071
+/** sysconf() query equivalent to _POSIX_READER_WRITER_LOCKS. */
 #define _SC_READER_WRITER_LOCKS 0x0072
-#define _SC_REGEXP              0x0073
-#define _SC_SHELL               0x0074
-#define _SC_SPAWN               0x0075
-#define _SC_SPIN_LOCKS          0x0076
-#define _SC_SPORADIC_SERVER     0x0077
-#define _SC_SS_REPL_MAX         0x0078
-#define _SC_SYMLOOP_MAX         0x0079
-#define _SC_THREAD_CPUTIME      0x007a
-#define _SC_THREAD_PROCESS_SHARED       0x007b
-#define _SC_THREAD_ROBUST_PRIO_INHERIT  0x007c
-#define _SC_THREAD_ROBUST_PRIO_PROTECT  0x007d
-#define _SC_THREAD_SPORADIC_SERVER      0x007e
-#define _SC_TIMEOUTS            0x007f
-#define _SC_TRACE               0x0080
-#define _SC_TRACE_EVENT_FILTER  0x0081
-#define _SC_TRACE_EVENT_NAME_MAX  0x0082
-#define _SC_TRACE_INHERIT       0x0083
-#define _SC_TRACE_LOG           0x0084
-#define _SC_TRACE_NAME_MAX      0x0085
-#define _SC_TRACE_SYS_MAX       0x0086
-#define _SC_TRACE_USER_EVENT_MAX  0x0087
-#define _SC_TYPED_MEMORY_OBJECTS  0x0088
-#define _SC_V7_ILP32_OFF32      0x0089
-#define _SC_V7_ILP32_OFFBIG     0x008a
-#define _SC_V7_LP64_OFF64       0x008b
-#define _SC_V7_LPBIG_OFFBIG     0x008c
-#define _SC_XOPEN_STREAMS       0x008d
-#define _SC_XOPEN_UUCP          0x008e
-
-#define _SC_LEVEL1_ICACHE_SIZE      0x008f
-#define _SC_LEVEL1_ICACHE_ASSOC     0x0090
-#define _SC_LEVEL1_ICACHE_LINESIZE  0x0091
-#define _SC_LEVEL1_DCACHE_SIZE      0x0092
-#define _SC_LEVEL1_DCACHE_ASSOC     0x0093
-#define _SC_LEVEL1_DCACHE_LINESIZE  0x0094
-#define _SC_LEVEL2_CACHE_SIZE       0x0095
-#define _SC_LEVEL2_CACHE_ASSOC      0x0096
-#define _SC_LEVEL2_CACHE_LINESIZE   0x0097
-#define _SC_LEVEL3_CACHE_SIZE       0x0098
-#define _SC_LEVEL3_CACHE_ASSOC      0x0099
-#define _SC_LEVEL3_CACHE_LINESIZE   0x009a
-#define _SC_LEVEL4_CACHE_SIZE       0x009b
-#define _SC_LEVEL4_CACHE_ASSOC      0x009c
-#define _SC_LEVEL4_CACHE_LINESIZE   0x009d
+/** sysconf() query equivalent to _POSIX_REGEXP. */
+#define _SC_REGEXP 0x0073
+/** sysconf() query equivalent to _POSIX_SHELL. */
+#define _SC_SHELL 0x0074
+/** sysconf() query equivalent to _POSIX_SPAWN. */
+#define _SC_SPAWN 0x0075
+/** sysconf() query equivalent to _POSIX_SPIN_LOCKS. */
+#define _SC_SPIN_LOCKS 0x0076
+/** sysconf() query equivalent to _POSIX_SPORADIC_SERVER. */
+#define _SC_SPORADIC_SERVER 0x0077
+/** sysconf() query equivalent to _POSIX_SS_REPL_MAX. */
+#define _SC_SS_REPL_MAX 0x0078
+/** sysconf() query equivalent to _POSIX_SYMLOOP_MAX. */
+#define _SC_SYMLOOP_MAX 0x0079
+/** sysconf() query equivalent to _POSIX_THREAD_CPUTIME. */
+#define _SC_THREAD_CPUTIME 0x007a
+/** sysconf() query equivalent to _POSIX_THREAD_PROCESS_SHARED. */
+#define _SC_THREAD_PROCESS_SHARED 0x007b
+/** sysconf() query equivalent to _POSIX_THREAD_ROBUST_PRIO_INHERIT. */
+#define _SC_THREAD_ROBUST_PRIO_INHERIT 0x007c
+/** sysconf() query equivalent to _POSIX_THREAD_ROBUST_PRIO_PROTECT. */
+#define _SC_THREAD_ROBUST_PRIO_PROTECT 0x007d
+/** sysconf() query equivalent to _POSIX_THREAD_SPORADIC_SERVER. */
+#define _SC_THREAD_SPORADIC_SERVER 0x007e
+/** sysconf() query equivalent to _POSIX_TIMEOUTS. */
+#define _SC_TIMEOUTS 0x007f
+/** Unimplemented. */
+#define _SC_TRACE 0x0080
+/** Unimplemented. */
+#define _SC_TRACE_EVENT_FILTER 0x0081
+/** Unimplemented. */
+#define _SC_TRACE_EVENT_NAME_MAX 0x0082
+/** Unimplemented. */
+#define _SC_TRACE_INHERIT 0x0083
+/** Unimplemented. */
+#define _SC_TRACE_LOG 0x0084
+/** Unimplemented. */
+#define _SC_TRACE_NAME_MAX 0x0085
+/** Unimplemented. */
+#define _SC_TRACE_SYS_MAX 0x0086
+/** Unimplemented. */
+#define _SC_TRACE_USER_EVENT_MAX 0x0087
+/** sysconf() query equivalent to _POSIX_TYPED_MEMORY_OBJECTS. */
+#define _SC_TYPED_MEMORY_OBJECTS 0x0088
+/** sysconf() query equivalent to _POSIX_V7_ILP32_OFF32. */
+#define _SC_V7_ILP32_OFF32 0x0089
+/** sysconf() query equivalent to _POSIX_V7_ILP32_OFFBIG. */
+#define _SC_V7_ILP32_OFFBIG 0x008a
+/** sysconf() query equivalent to _POSIX_V7_ILP64_OFF64. */
+#define _SC_V7_LP64_OFF64 0x008b
+/** sysconf() query equivalent to _POSIX_V7_ILP64_OFFBIG. */
+#define _SC_V7_LPBIG_OFFBIG 0x008c
+/** Unimplemented. */
+#define _SC_XOPEN_STREAMS 0x008d
+/** Meaningless in Android, unsupported in every other libc (but defined by POSIX). */
+#define _SC_XOPEN_UUCP 0x008e
+/** sysconf() query for the L1 instruction cache size. Not available on all architectures. */
+#define _SC_LEVEL1_ICACHE_SIZE 0x008f
+/** sysconf() query for the L1 instruction cache associativity. Not available on all architectures. */
+#define _SC_LEVEL1_ICACHE_ASSOC 0x0090
+/** sysconf() query for the L1 instruction cache line size. Not available on all architectures. */
+#define _SC_LEVEL1_ICACHE_LINESIZE 0x0091
+/** sysconf() query for the L1 data cache size. Not available on all architectures. */
+#define _SC_LEVEL1_DCACHE_SIZE 0x0092
+/** sysconf() query for the L1 data cache associativity. Not available on all architectures. */
+#define _SC_LEVEL1_DCACHE_ASSOC 0x0093
+/** sysconf() query for the L1 data cache line size. Not available on all architectures. */
+#define _SC_LEVEL1_DCACHE_LINESIZE 0x0094
+/** sysconf() query for the L2 cache size. Not available on all architectures. */
+#define _SC_LEVEL2_CACHE_SIZE 0x0095
+/** sysconf() query for the L2 cache associativity. Not available on all architectures. */
+#define _SC_LEVEL2_CACHE_ASSOC 0x0096
+/** sysconf() query for the L2 cache line size. Not available on all architectures. */
+#define _SC_LEVEL2_CACHE_LINESIZE 0x0097
+/** sysconf() query for the L3 cache size. Not available on all architectures. */
+#define _SC_LEVEL3_CACHE_SIZE 0x0098
+/** sysconf() query for the L3 cache associativity. Not available on all architectures. */
+#define _SC_LEVEL3_CACHE_ASSOC 0x0099
+/** sysconf() query for the L3 cache line size. Not available on all architectures. */
+#define _SC_LEVEL3_CACHE_LINESIZE 0x009a
+/** sysconf() query for the L4 cache size. Not available on all architectures. */
+#define _SC_LEVEL4_CACHE_SIZE 0x009b
+/** sysconf() query for the L4 cache associativity. Not available on all architectures. */
+#define _SC_LEVEL4_CACHE_ASSOC 0x009c
+/** sysconf() query for the L4 cache line size. Not available on all architectures. */
+#define _SC_LEVEL4_CACHE_LINESIZE 0x009d
 
 __BEGIN_DECLS
 
+/**
+ * [sysconf(3)](https://man7.org/linux/man-pages/man3/sysconf.3.html)
+ * gets system configuration at runtime, corresponding to the given
+ * `_SC_` constant. See the man page for details on how to interpret
+ * the results.
+ *
+ * For `_SC_` constants where an equivalent is given, it's cheaper on Android
+ * to go straight to that function call --- sysconf() is just a multiplexer.
+ * This may not be true on other systems, and other systems may not support the
+ * direct function, so sysconf() can be useful for portability, though despite
+ * POSIX's best efforts, the exact set of constants that return useful results
+ * will also vary by system.
+ */
 long sysconf(int __name);
 
 __END_DECLS
-
-#endif /* _SYS_SYSCONF_H_ */
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index ee772a5..c69db61 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -336,6 +336,13 @@
 
 int acct(const char* _Nullable __path);
 
+/**
+ * [getpagesize(2)](https://man7.org/linux/man-pages/man2/getpagesize.2.html)
+ * returns the system's page size. This is slightly faster than going via
+ * sysconf().
+ *
+ * Returns the system's page size in bytes.
+ */
 int getpagesize(void) __attribute_const__;
 
 long syscall(long __number, ...);