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#ifndef EXIT_PROCESS_H
#define EXIT_PROCESS_H
/*
* This file contains functions to terminate a Win32 process, as gently as
* possible.
*
* At first, we will attempt to inject a thread that calls ExitProcess(). If
* that fails, we will fall back to terminating the entire process tree.
*
* For simplicity, these functions are marked as file-local.
*/
#include <tlhelp32.h>
/*
* Terminates the process corresponding to the process ID and all of its
* directly and indirectly spawned subprocesses.
*
* This way of terminating the processes is not gentle: the processes get
* no chance of cleaning up after themselves (closing file handles, removing
* .lock files, terminating spawned processes (if any), etc).
*/
static int terminate_process_tree(HANDLE main_process, int exit_status)
{
HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
PROCESSENTRY32 entry;
DWORD pids[16384];
int max_len = sizeof(pids) / sizeof(*pids), i, len, ret = 0;
pid_t pid = GetProcessId(main_process);
pids[0] = (DWORD)pid;
len = 1;
/*
* Even if Process32First()/Process32Next() seem to traverse the
* processes in topological order (i.e. parent processes before
* child processes), there is nothing in the Win32 API documentation
* suggesting that this is guaranteed.
*
* Therefore, run through them at least twice and stop when no more
* process IDs were added to the list.
*/
for (;;) {
int orig_len = len;
memset(&entry, 0, sizeof(entry));
entry.dwSize = sizeof(entry);
if (!Process32First(snapshot, &entry))
break;
do {
for (i = len - 1; i >= 0; i--) {
if (pids[i] == entry.th32ProcessID)
break;
if (pids[i] == entry.th32ParentProcessID)
pids[len++] = entry.th32ProcessID;
}
} while (len < max_len && Process32Next(snapshot, &entry));
if (orig_len == len || len >= max_len)
break;
}
for (i = len - 1; i > 0; i--) {
HANDLE process = OpenProcess(PROCESS_TERMINATE, FALSE, pids[i]);
if (process) {
if (!TerminateProcess(process, exit_status))
ret = -1;
CloseHandle(process);
}
}
if (!TerminateProcess(main_process, exit_status))
ret = -1;
CloseHandle(main_process);
return ret;
}
/**
* Determine whether a process runs in the same architecture as the current
* one. That test is required before we assume that GetProcAddress() returns
* a valid address *for the target process*.
*/
static inline int process_architecture_matches_current(HANDLE process)
{
static BOOL current_is_wow = -1;
BOOL is_wow;
if (current_is_wow == -1 &&
!IsWow64Process (GetCurrentProcess(), ¤t_is_wow))
current_is_wow = -2;
if (current_is_wow == -2)
return 0; /* could not determine current process' WoW-ness */
if (!IsWow64Process (process, &is_wow))
return 0; /* cannot determine */
return is_wow == current_is_wow;
}
/**
* Inject a thread into the given process that runs ExitProcess().
*
* Note: as kernel32.dll is loaded before any process, the other process and
* this process will have ExitProcess() at the same address.
*
* This function expects the process handle to have the access rights for
* CreateRemoteThread(): PROCESS_CREATE_THREAD, PROCESS_QUERY_INFORMATION,
* PROCESS_VM_OPERATION, PROCESS_VM_WRITE, and PROCESS_VM_READ.
*
* The idea comes from the Dr Dobb's article "A Safer Alternative to
* TerminateProcess()" by Andrew Tucker (July 1, 1999),
* http://www.drdobbs.com/a-safer-alternative-to-terminateprocess/184416547
*
* If this method fails, we fall back to running terminate_process_tree().
*/
static int exit_process(HANDLE process, int exit_code)
{
DWORD code;
if (GetExitCodeProcess(process, &code) && code == STILL_ACTIVE) {
static int initialized;
static LPTHREAD_START_ROUTINE exit_process_address;
PVOID arg = (PVOID)(intptr_t)exit_code;
DWORD thread_id;
HANDLE thread = NULL;
if (!initialized) {
HINSTANCE kernel32 = GetModuleHandleA("kernel32");
if (!kernel32)
die("BUG: cannot find kernel32");
exit_process_address =
(LPTHREAD_START_ROUTINE)(void (*)(void))
GetProcAddress(kernel32, "ExitProcess");
initialized = 1;
}
if (!exit_process_address ||
!process_architecture_matches_current(process))
return terminate_process_tree(process, exit_code);
thread = CreateRemoteThread(process, NULL, 0,
exit_process_address,
arg, 0, &thread_id);
if (thread) {
CloseHandle(thread);
/*
* If the process survives for 10 seconds (a completely
* arbitrary value picked from thin air), fall back to
* killing the process tree via TerminateProcess().
*/
if (WaitForSingleObject(process, 10000) ==
WAIT_OBJECT_0) {
CloseHandle(process);
return 0;
}
}
return terminate_process_tree(process, exit_code);
}
return 0;
}
#endif
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