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Put more thought into i/o polyfills

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wait4() is now solid enough to run `make -j100` on Windows. You can now
use MSG_DONTWAIT on Windows. There was a handle leak in accept() that's
been fixed. Our WIN32 overlapped i/o code has been simplified. Priority
class now inherits into subprocesses, so the verynice command will work
and the signal mask will now be inherited by execve() and posix_spawn()
This commit is contained in:
Justine Tunney 2023-11-06 16:38:44 -08:00
parent 736fdb757a
commit e961385e55
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52 changed files with 679 additions and 487 deletions
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test/libc/calls/stackoverflow3_test.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2023 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/struct/sigaction.h"
#include "libc/calls/struct/sigaltstack.h"
#include "libc/calls/struct/siginfo.h"
#include "libc/calls/struct/ucontext.internal.h"
#include "libc/calls/ucontext.h"
#include "libc/intrin/kprintf.h"
#include "libc/limits.h"
#include "libc/mem/gc.internal.h"
#include "libc/mem/mem.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/sysconf.h"
#include "libc/sysv/consts/sa.h"
#include "libc/sysv/consts/sig.h"
#include "libc/sysv/consts/ss.h"
#include "libc/testlib/testlib.h"
#include "libc/thread/thread.h"
/**
* stack overflow recovery technique #3
* rewrite thread cpu state to call pthread_exit
* this method returns gracefully from signal handlers
* unfortunately it relies on cpu architecture knowledge
*/
volatile bool smashed_stack;
void Exiter(void *rc) {
struct sigaltstack ss;
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(0, ss.ss_flags);
pthread_exit(rc);
}
void CrashHandler(int sig, siginfo_t *si, void *arg) {
ucontext_t *ctx = arg;
struct sigaltstack ss;
ASSERT_FALSE(smashed_stack);
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(SS_ONSTACK, ss.ss_flags);
kprintf("kprintf avoids overflowing %G %p\n", si->si_signo, si->si_addr);
smashed_stack = true;
// EXPECT_TRUE(__is_stack_overflow(si, ctx));
//
// the backtrace will look like this
//
// 0x000000000042561d: pthread_exit at pthread_exit.c:99
// 0x0000000000418777: Exiter at stackoverflow2_test.c:40
// 0x00000000004186d8: CrashHandler at stackoverflow2_test.c:49
// 0x000000000041872a: StackOverflow at stackoverflow2_test.c:53
// 0x000000000041872a: StackOverflow at stackoverflow2_test.c:53
// 0x000000000041872a: StackOverflow at stackoverflow2_test.c:53
// ...
//
ctx->uc_mcontext.ARG0 = 123;
ctx->uc_mcontext.PC = (long)Exiter;
ctx->uc_mcontext.SP += 32768;
ctx->uc_mcontext.SP &= -16;
#ifdef __x86_64__
*(long *)(ctx->uc_mcontext.SP -= 8) = ctx->uc_mcontext.PC;
#elif defined(__aarch64__)
*(long *)(ctx->uc_mcontext.SP -= 8) = ctx->uc_mcontext.regs[30];
*(long *)(ctx->uc_mcontext.SP -= 8) = ctx->uc_mcontext.regs[29];
ctx->uc_mcontext.BP = ctx->uc_mcontext.SP;
#else
#error "unsupported architecture"
#endif
}
int StackOverflow(int f(), int n) {
if (n < INT_MAX) {
return f(f, n + 1) - 1;
} else {
return INT_MAX;
}
}
int (*pStackOverflow)(int (*)(), int) = StackOverflow;
void *MyPosixThread(void *arg) {
struct sigaction sa;
struct sigaltstack ss;
ss.ss_flags = 0;
ss.ss_size = sysconf(_SC_MINSIGSTKSZ) + 4096;
ss.ss_sp = gc(malloc(ss.ss_size));
ASSERT_SYS(0, 0, sigaltstack(&ss, 0));
sa.sa_flags = SA_SIGINFO | SA_ONSTACK; // <-- important
sigemptyset(&sa.sa_mask);
sa.sa_sigaction = CrashHandler;
sigaction(SIGBUS, &sa, 0);
sigaction(SIGSEGV, &sa, 0);
exit(pStackOverflow(pStackOverflow, 0));
return 0;
}
TEST(stackoverflow, standardStack_altStack_thread_teleport) {
void *res;
pthread_t th;
struct sigaltstack ss;
smashed_stack = false;
pthread_create(&th, 0, MyPosixThread, 0);
pthread_join(th, &res);
ASSERT_EQ((void *)123L, res);
ASSERT_TRUE(smashed_stack);
// this should be SS_DISABLE but ShowCrashReports() creates an alt stack
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(0, ss.ss_flags);
}