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Improve stack overflow recovery

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It's now possible to use sigaltstack() to recover from stack overflows
on Windows. Several bugs in sigaltstack() have been fixed, for all our
supported platforms. There's a newer better example showing how to use
this, along with three independent unit tests just to further showcase
the various techniques.
This commit is contained in:
Justine Tunney 2023-10-04 07:07:43 -07:00
parent 1694edf85c
commit 4631d34d0d
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GPG key ID: BE714B4575D6E328
24 changed files with 590 additions and 274 deletions
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52
test/libc/thread/pthread_create_test.c
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@ -255,58 +255,6 @@ TEST(pthread_cleanup, pthread_normal) {
ASSERT_TRUE(g_cleanup2);
}
////////////////////////////////////////////////////////////////////////////////
jmp_buf recover;
volatile bool smashed_stack;
void CrashHandler(int sig, siginfo_t *si, void *ctx) {
kprintf("kprintf avoids overflowing %G %p\n", si->si_signo, si->si_addr);
smashed_stack = true;
ASSERT_TRUE(__is_stack_overflow(si, ctx));
longjmp(recover, 123);
}
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) {
int jumpcode;
struct sigaction sa, o1, o2;
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, &o1);
sigaction(SIGSEGV, &sa, &o2);
if (!(jumpcode = setjmp(recover))) {
exit(pStackOverflow(pStackOverflow, 0));
}
ASSERT_EQ(123, jumpcode);
sigaction(SIGSEGV, &o2, 0);
sigaction(SIGBUS, &o1, 0);
return 0;
}
TEST(cosmo, altstack_thread) {
pthread_t th;
if (IsWindows()) return;
pthread_create(&th, 0, MyPosixThread, 0);
pthread_join(th, 0);
ASSERT_TRUE(smashed_stack);
}
////////////////////////////////////////////////////////////////////////////////
// BENCHMARKS