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Spoof PID across execve() on Windows

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It's now possible with cosmo and redbean, to deliver a signal to a child
process after it has called execve(). However the executed program needs
to be compiled using cosmocc. The cosmo runtime WinMain() implementation
now intercepts a _COSMO_PID environment variable that's set by execve().
It ensures the child process will use the same C:\ProgramData\cosmo\sigs
file, which is where kill() will place the delivered signal. We are able
to do this on Windows even better than NetBSD, which has a bug with this

Fixes #1334
This commit is contained in:
Justine Tunney 2024-12-14 12:23:02 -08:00
parent 9cc1bd04b2
commit 26c051c297
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
8 changed files with 187 additions and 21 deletions
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37
libc/runtime/winmain.greg.c
View file

@ -300,6 +300,37 @@ static abi wontreturn void WinInit(const char16_t *cmdline) {
(uintptr_t)(stackaddr + (stacksize - sizeof(struct WinArgs))));
}
static int Atoi(const char16_t *str) {
int c;
unsigned x = 0;
while ((c = *str++)) {
if ('0' <= c && c <= '9') {
x *= 10;
x += c - '0';
} else {
return -1;
}
}
return x;
}
static abi int WinGetPid(const char16_t *var, bool *out_is_inherited) {
uint32_t len;
char16_t val[12];
if ((len = __imp_GetEnvironmentVariableW(var, val, ARRAYLEN(val)))) {
int pid = -1;
if (len < ARRAYLEN(val))
pid = Atoi(val);
__imp_SetEnvironmentVariableW(var, NULL);
if (pid > 0) {
*out_is_inherited = true;
return pid;
}
}
*out_is_inherited = false;
return __imp_GetCurrentProcessId();
}
abi int64_t WinMain(int64_t hInstance, int64_t hPrevInstance,
const char *lpCmdLine, int64_t nCmdShow) {
static atomic_ulong fake_process_signals;
@ -316,10 +347,12 @@ abi int64_t WinMain(int64_t hInstance, int64_t hPrevInstance,
__imp_GetSystemInfo(&si);
__pagesize = si.dwPageSize;
__gransize = si.dwAllocationGranularity;
__pid = __imp_GetCurrentProcessId();
bool pid_is_inherited;
__pid = WinGetPid(u"_COSMO_PID", &pid_is_inherited);
if (!(__sig.process = __sig_map_process(__pid, kNtOpenAlways)))
__sig.process = &fake_process_signals;
atomic_store_explicit(__sig.process, 0, memory_order_release);
if (!pid_is_inherited)
atomic_store_explicit(__sig.process, 0, memory_order_release);
cmdline = __imp_GetCommandLineW();
#if SYSDEBUG
// sloppy flag-only check for early initialization