Make improvements

- Document redbean's argon2 module
- Fix regressions in cthreads library
- Make testlib work better with threads
- Give the cthreads library lots of love
- Remove some of the stdio assembly code
- Implement getloadavg() across platforms
- Code size optimizations for errnos, etc.
- Only check for signals in main thread on Windows
- Make errnos for dup2 / dup3 consistent with posix

This change also fixes a bug in the argon2 module, where the NUL
terminator was being included in the hash encoded ascii string. This
shouldn't require any database migrations to folks who found this module
and productionized it, since the argon2 library treats it as a c string.

libc/runtime/clone.c

@@ -23,13 +23,16 @@
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/asan.internal.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/intrin/spinlock.h"
+#include "libc/limits.h"
 #include "libc/nexgen32e/threaded.h"
 #include "libc/nt/runtime.h"
 #include "libc/nt/thread.h"
 #include "libc/nt/thunk/msabi.h"
 #include "libc/runtime/runtime.h"
 #include "libc/sysv/consts/clone.h"
+#include "libc/sysv/consts/futex.h"
 #include "libc/sysv/consts/nr.h"
 #include "libc/sysv/consts/nrlinux.h"
 #include "libc/sysv/errfuns.h"
@@ -121,7 +124,7 @@ static textwindows int CloneWindows(int (*func)(void *), char *stk,
   wt->func = func;
   wt->arg = arg;
   wt->tls = flags & CLONE_SETTLS ? tls : 0;
-  if ((h = CreateThread(0, 0, (void *)WinThreadEntry, wt, 0, &wt->utid))) {
+  if ((h = CreateThread(0, 4096, (void *)WinThreadEntry, wt, 0, &wt->utid))) {
     CloseHandle(h);
     return wt->tid;
   } else {
@@ -134,8 +137,7 @@ static textwindows int CloneWindows(int (*func)(void *), char *stk,
 
 void XnuThreadThunk(void *pthread, int machport, void *(*func)(void *),
                     void *arg, intptr_t *stack, unsigned xnuflags);
-asm(".local\tXnuThreadThunk\n"
-    "XnuThreadThunk:\n\t"
+asm("XnuThreadThunk:\n\t"
     "xor\t%ebp,%ebp\n\t"
     "mov\t%r8,%rsp\n\t"
     "and\t$-16,%rsp\n\t"
@@ -168,7 +170,7 @@ XnuThreadMain(void *pthread, int tid, int (*func)(void *arg), void *arg,
   //                                %r10 = uint32_t sem);
   asm volatile("movl\t$0,%0\n\t"         // *wt->ztid = 0
                "xor\t%%r10d,%%r10d\n\t"  // sem = 0
-               "syscall\n\t"             // _Exit1()
+               "syscall\n\t"             // __bsdthread_terminate()
                "ud2"
                : "=m"(*wt->ztid)
                : "a"(0x2000000 | 361), "D"(0), "S"(0), "d"(0)
@@ -218,7 +220,7 @@ static wontreturn void FreebsdThreadMain(void *p) {
   // we no longer use the stack after this point
   // void thr_exit(%rdi = long *state);
   asm volatile("movl\t$0,%0\n\t"  // *wt->ztid = 0
-               "syscall"          // _Exit1()
+               "syscall"          // thr_exit()
                : "=m"(*wt->ztid)
                : "a"(431), "D"(0)
                : "rcx", "r11", "memory");
@@ -294,11 +296,14 @@ OpenbsdThreadMain(struct CloneArgs *wt) {
   // although ideally there should be a better solution.
   //
   // void __threxit(%rdi = int32_t *notdead);
-  asm volatile("mov\t%3,%%rsp\n\t"
-               "movl\t$0,%0\n\t"  // *wt->ztid = 0
-               "syscall"          // _Exit1()
+  asm volatile("mov\t%2,%%rsp\n\t"
+               "movl\t$0,(%%rdi)\n\t"  // *wt->ztid = 0
+               "syscall\n\t"           // futex()
+               "mov\t$302,%%eax\n\t"   // __threxit()
+               "syscall"
                : "=m"(*wt->ztid)
-               : "a"(302), "D"(0), "r"(wt->pstack)
+               : "a"(83), "m"(wt->pstack), "D"(wt->ztid), "S"(FUTEX_WAKE),
+                 "d"(INT_MAX)
                : "rcx", "r11", "memory");
   unreachable;
 }
@@ -337,7 +342,7 @@ static wontreturn void NetbsdThreadMain(void *arg, int (*func)(void *arg),
   // we no longer use the stack after this point
   // %eax = int __lwp_exit(void);
   asm volatile("movl\t$0,%2\n\t"  // *wt->ztid = 0
-               "syscall\n\t"      // _Exit1()
+               "syscall\n\t"      // __lwp_exit()
                "ud2"
                : "=a"(ax), "=d"(dx), "=m"(*ztid)
                : "0"(310)
@@ -504,7 +509,7 @@ int sys_clone_linux(int flags, char *stk, int *ptid, int *ctid, void *tls,
  */
 int clone(int (*func)(void *), void *stk, size_t stksz, int flags, void *arg,
           int *ptid, void *tls, size_t tlssz, int *ctid) {
-  int rc;
+  int rc, maintid;
   struct CloneArgs *wt;
 
   // transition program to threaded state
@@ -517,13 +522,14 @@ int clone(int (*func)(void *), void *stk, size_t stksz, int flags, void *arg,
       STRACE("clone() tls/non-tls mixed order");
       return einval();
     }
+    maintid = gettid();
     __initialize_tls(tibdefault);
-    *(int *)((char *)tibdefault + 0x38) = gettid();
+    *(int *)((char *)tibdefault + 0x38) = maintid;
     *(int *)((char *)tibdefault + 0x3c) = __errno;
     __install_tls(tibdefault);
-    __threaded = true;
+    __threaded = maintid;
   } else if (flags & CLONE_THREAD) {
-    __threaded = true;
+    __threaded = gettid();
   }
 
   if (IsAsan() &&