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https://github.com/jart/cosmopolitan.git
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af7bd80430
This change introduces a new deadlock detector for Cosmo's POSIX threads implementation. Error check mutexes will now track a DAG of nested locks and report EDEADLK when a deadlock is theoretically possible. These will occur rarely, but it's important for production hardening your code. You don't even need to change your mutexes to use the POSIX error check mode because `cosmocc -mdbg` will enable error checking on mutexes by default globally. When cycles are found, an error message showing your demangled symbols describing the strongly connected component are printed and then the SIGTRAP is raised, which means you'll also get a backtrace if you're using ShowCrashReports() too. This new error checker is so low-level and so pure that it's able to verify the relationships of every libc runtime lock, including those locks upon which the mutex implementation depends.
119 lines
4.6 KiB
C
119 lines
4.6 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/calls.h"
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#include "libc/errno.h"
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#include "libc/fmt/itoa.h"
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#include "libc/intrin/cmpxchg.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/macros.h"
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#include "libc/nexgen32e/stackframe.h"
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#include "libc/runtime/internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/runtime/stack.h"
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#include "libc/thread/posixthread.internal.h"
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#include "libc/thread/thread.h"
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#include "libc/thread/tls.h"
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/**
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* @fileoverview Plain-text function call logging.
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*
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* Able to log ~2 million function calls per second, which is mostly
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* bottlenecked by system call overhead. Log size is reasonable if piped
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* into gzip.
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*/
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#define MAX_NESTING 512
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#ifdef __x86_64__
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#define DETOUR_SKEW 2
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#elif defined(__aarch64__)
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#define DETOUR_SKEW 8
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#endif
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static struct CosmoFtrace g_ftrace;
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__funline int GetNestingLevelImpl(struct StackFrame *frame) {
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int nesting = -2;
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while (frame && !kisdangerous(frame)) {
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++nesting;
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frame = frame->next;
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}
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return MAX(0, nesting);
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}
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__funline int GetNestingLevel(struct CosmoFtrace *ft, struct StackFrame *sf) {
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int nesting;
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nesting = GetNestingLevelImpl(sf);
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if (nesting < ft->ft_skew)
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ft->ft_skew = nesting;
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nesting -= ft->ft_skew;
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return MIN(MAX_NESTING, nesting);
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}
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/**
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* Prints name of function being called.
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*
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* Whenever a function is called, ftrace_hook() will be called from the
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* function prologue which saves the parameter registers and calls this
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* function, which is responsible for logging the function call.
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*
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* @see ftrace_install()
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*/
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privileged void ftracer(void) {
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long stackuse;
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uintptr_t fn, st;
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struct CosmoTib *tib;
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struct StackFrame *sf;
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struct CosmoFtrace *ft;
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struct PosixThread *pt;
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sf = __builtin_frame_address(0);
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st = (uintptr_t)__argv - sizeof(uintptr_t);
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if (__ftrace <= 0)
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return;
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if (__tls_enabled) {
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tib = __get_tls_privileged();
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if (tib->tib_ftrace <= 0)
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return;
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ft = &tib->tib_ftracer;
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if ((char *)sf >= tib->tib_sigstack_addr &&
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(char *)sf <= tib->tib_sigstack_addr + tib->tib_sigstack_size) {
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st = (uintptr_t)tib->tib_sigstack_addr + tib->tib_sigstack_size;
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} else if ((pt = (struct PosixThread *)tib->tib_pthread) &&
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pt->pt_attr.__stacksize) {
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st = (uintptr_t)pt->pt_attr.__stackaddr + pt->pt_attr.__stacksize;
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}
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} else {
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ft = &g_ftrace;
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}
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stackuse = st - (intptr_t)sf;
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if (_cmpxchg(&ft->ft_once, false, true)) {
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ft->ft_lastaddr = -1;
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ft->ft_skew = GetNestingLevelImpl(sf);
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}
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if (_cmpxchg(&ft->ft_noreentry, false, true)) {
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sf = sf->next;
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fn = sf->addr + DETOUR_SKEW;
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if (fn != ft->ft_lastaddr) {
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kprintf("%rFUN %6P %6H %'18T %'*ld %*s%t\n", ftrace_stackdigs, stackuse,
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GetNestingLevel(ft, sf) * 2, "", fn);
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ft->ft_lastaddr = fn;
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}
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ft->ft_noreentry = false;
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}
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}
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