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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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110
examples/stackoverflow.c
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@ -1,110 +0,0 @@
#if 0
/*─────────────────────────────────────────────────────────────────╗
│ To the extent possible under law, Justine Tunney has waived │
│ all copyright and related or neighboring rights to this file, │
│ as it is written in the following disclaimers: │
│ • http://unlicense.org/ │
│ • http://creativecommons.org/publicdomain/zero/1.0/ │
╚─────────────────────────────────────────────────────────────────*/
#endif
#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
*
* @see test/libc/thread/stackoverflow1_test.c
* @see test/libc/thread/stackoverflow2_test.c
* @see test/libc/thread/stackoverflow3_test.c
*/
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_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;
ASSERT_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;
ctx->uc_mcontext.SP -= 8;
}
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;
}
int main(int argc, char *argv[]) {
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);
ASSERT_SYS(0, 0, sigaltstack(0, &ss));
ASSERT_EQ(SS_DISABLE, ss.ss_flags);
}