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#include "noun.h"
#include "rsignal.h"
#include <windows.h>
int err_win_to_posix(DWORD winerr);
// The current implementation of rsignal_ is single-threaded,
// but it can be extended to multi-threaded by replacing these
// static variables with a thread id-based hash map.
//
static __p_sig_fn_t _fns[SIG_COUNT];
static volatile DWORD _tid;
static HANDLE _hvt;
void rsignal_install_handler(int sig, __p_sig_fn_t fn)
{
if (sig < 0 || sig >= SIG_COUNT)
return;
DWORD newtid = GetCurrentThreadId();
DWORD oldtid = InterlockedExchange((volatile LONG*)&_tid, newtid);
if (oldtid != 0 && oldtid != newtid) {
fprintf(stderr, "\r\nrsignal_install_handler: %lu -> %lu\r\n", oldtid, newtid);
return;
}
__p_sig_fn_t oldfn = InterlockedExchangePointer((PVOID*)&_fns[sig], fn);
if (fn != 0 && oldfn != 0 && oldfn != fn) {
fprintf(stderr, "\r\nrsignal_install_handler: %p -> %p\r\n", oldfn, fn);
}
}
void rsignal_deinstall_handler(int sig)
{
rsignal_install_handler(sig, 0);
}
void rsignal_raise(int sig)
{
if (sig < 0 || sig >= SIG_COUNT)
return;
__p_sig_fn_t oldfn = InterlockedExchangePointer((PVOID*)&_fns[sig], 0);
if (oldfn == 0)
return;
if (_tid == GetCurrentThreadId()) {
oldfn(sig);
return;
}
HANDLE hthread = OpenThread(THREAD_ALL_ACCESS, FALSE, _tid);
if (!hthread) {
fprintf(stderr, "\r\nrsignal_raise: OpenThread(%lu): %lu\r\n", _tid, GetLastError());
return;
}
if (SuspendThread(hthread) < 0) {
fprintf(stderr, "\r\nrsignal_raise: SuspendThread(%lu): %lu\r\n", _tid, GetLastError());
goto cleanup;
}
oldfn(sig);
if (!ResumeThread(hthread)) {
fprintf(stderr, "\r\nrsignal_raise: ResumeThread(%lu): %lu\r\n", _tid, GetLastError());
// abort because the main thread is stuck
abort();
}
cleanup:
CloseHandle(hthread);
}
static void _rsignal_vt_cb(PVOID param, BOOLEAN timedOut)
{
rsignal_raise(SIGVTALRM);
}
int rsignal_setitimer(int type, struct itimerval *in, struct itimerval *out)
{
if (in == 0) {
errno = EFAULT;
return -1;
}
if (type != ITIMER_VIRTUAL || out != 0) {
errno = ENOTSUP;
return -1;
}
if (_hvt != NULL) {
DeleteTimerQueueTimer(NULL, _hvt, NULL);
_hvt = NULL;
}
if (timerisset(&in->it_value) && !CreateTimerQueueTimer(&_hvt, NULL, _rsignal_vt_cb, NULL,
in->it_value.tv_sec * 1000 + in->it_value.tv_usec / 1000,
in->it_interval.tv_sec * 1000 + in->it_interval.tv_usec / 1000, 0))
{
errno = err_win_to_posix(GetLastError());
return -1;
} else {
return 0;
}
}
// direct import from ntdll.dll
extern DWORD64 __imp_KiUserExceptionDispatcher;
static void _rsignal_longjmp(intptr_t* builtin_jb)
{
__builtin_longjmp((void**)builtin_jb, 1);
}
void rsignal_post_longjmp(DWORD tid, intptr_t* builtin_jb)
{
HANDLE hthread = OpenThread(THREAD_ALL_ACCESS, FALSE, tid);
if (!hthread) {
fprintf(stderr, "\r\nrsignal: OpenThread(%lu): %lu\r\n", tid, GetLastError());
return;
}
CONTEXT context;
context.ContextFlags = CONTEXT_CONTROL | CONTEXT_INTEGER;
if (!GetThreadContext(hthread, &context)) {
fprintf(stderr, "\r\nrsignal: GetThreadContext(%lu): %lu\r\n", tid, GetLastError());
goto cleanup;
}
// see if the thread is currently handling a structured exception
// if so, let the handler (usually the libsigsegv handler) finish
// and set up the the signal to run at the exception resume point
// otherwise, passing a parameter to fn is completely unreliable
//
DWORD64 kibase;
PRUNTIME_FUNCTION ki = RtlLookupFunctionEntry(__imp_KiUserExceptionDispatcher, &kibase, NULL);
CONTEXT c = context;
while (1)
{
DWORD64 base, frame;
PRUNTIME_FUNCTION f = RtlLookupFunctionEntry(c.Rip, &base, NULL);
if (!f) break;
if (f == ki)
{
// KiUserExceptionDispatcher has a "bare" frame
// with $rsp pointing to the CONTEXT structure
//
((PCONTEXT)c.Rsp)->Rip = (DWORD64)_rsignal_longjmp;
((PCONTEXT)c.Rsp)->Rcx = (DWORD64)builtin_jb;
goto cleanup;
}
PVOID handler_data;
RtlVirtualUnwind(0, base, c.Rip, f, &c, &handler_data, &frame, NULL);
}
context.Rip = (DWORD64)_rsignal_longjmp;
context.Rcx = (DWORD64)builtin_jb;
if (!SetThreadContext(hthread, &context)) {
fprintf(stderr, "\r\nrsignal: SetThreadContext(%lu): %lu\r\n", tid, GetLastError());
goto cleanup;
}
cleanup:
CloseHandle(hthread);
}
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