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Make execve() linger when it can't spoof parent

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It's now possible to use execve() when the parent process isn't built by
cosmo. In such cases, the current process will kill all threads and then
linger around, waiting for the newly created process to die, and then we
propagate its exit code to the parent. This should help bazel and others

Allocating private anonymous memory is now 5x faster on Windows. This is
thanks to VirtualAlloc() which is faster than the file mapping APIs. The
fork() function also now goes 30% faster, since we are able to avoid the
VirtualProtect() calls on mappings in most cases now.

Fixes #1253
This commit is contained in:
Justine Tunney 2025-01-04 21:11:53 -08:00
parent c97a858470
commit 42a3bb729a
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GPG key ID: BE714B4575D6E328
40 changed files with 612 additions and 656 deletions
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84
test/libc/calls/stackoverflow5_test.c
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@ -16,22 +16,28 @@
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include <cosmo.h>
#include <limits.h>
#include <pthread.h>
#include <signal.h>
#include <unistd.h>
#include "libc/assert.h"
#include "libc/calls/calls.h"
#include "libc/calls/struct/sigaction.h"
#include "libc/calls/struct/siginfo.h"
#include "libc/runtime/runtime.h"
#include "libc/sysv/consts/sa.h"
#include "libc/sysv/consts/sig.h"
#include "libc/sysv/consts/ss.h"
#include "libc/thread/thread.h"
#include "libc/thread/tls.h"
/**
* stack overflow recovery technique #5
* use the cosmo posix threads extensions
* stack overflow test #5
* - make sure fork() preserves sigaltstack()
* - make sure fork() preserves guard page status
*/
sig_atomic_t smashed_stack;
jmp_buf recover;
void CrashHandler(int sig) {
smashed_stack = true;
pthread_exit(0);
void CrashHandler(int sig, siginfo_t *si, void *ctx) {
unassert(__is_stack_overflow(si, ctx));
longjmp(recover, 123);
}
int StackOverflow(int d) {
@ -44,42 +50,40 @@ int StackOverflow(int d) {
}
void *MyPosixThread(void *arg) {
exit(StackOverflow(1));
int pid;
unassert(__get_tls()->tib_sigstack_addr);
unassert((pid = fork()) != -1);
if (!pid) {
int jumpcode;
if (!(jumpcode = setjmp(recover))) {
StackOverflow(1);
_Exit(1);
}
unassert(123 == jumpcode);
} else {
int ws;
unassert(wait(&ws) != -1);
unassert(!ws);
pthread_exit(0);
}
return 0;
}
int main() {
// choose the most dangerously small size possible
size_t sigstacksize = sysconf(_SC_MINSIGSTKSZ) + 2048;
// setup signal handler
struct sigaction sa;
sa.sa_flags = SA_SIGINFO | SA_ONSTACK;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_ONSTACK;
sa.sa_handler = CrashHandler;
if (sigaction(SIGBUS, &sa, 0))
return 1;
if (sigaction(SIGSEGV, &sa, 0))
return 2;
sa.sa_sigaction = CrashHandler;
unassert(!sigaction(SIGBUS, &sa, 0));
unassert(!sigaction(SIGSEGV, &sa, 0));
// create thread with signal stack
pthread_t id;
pthread_t th;
pthread_attr_t attr;
if (pthread_attr_init(&attr))
return 3;
if (pthread_attr_setguardsize(&attr, getpagesize()))
return 4;
if (pthread_attr_setsigaltstacksize_np(&attr, sigstacksize))
return 5;
if (pthread_create(&id, &attr, MyPosixThread, 0))
return 6;
if (pthread_attr_destroy(&attr))
return 7;
if (pthread_join(id, 0))
return 8;
if (!smashed_stack)
return 9;
CheckForMemoryLeaks();
unassert(!pthread_attr_init(&attr));
unassert(!pthread_attr_setguardsize(&attr, getpagesize()));
unassert(!pthread_attr_setsigaltstacksize_np(&attr, SIGSTKSZ));
unassert(!pthread_create(&th, &attr, MyPosixThread, 0));
unassert(!pthread_attr_destroy(&attr));
unassert(!pthread_join(th, 0));
}