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mpv/osdep/subprocess-win.c

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/*
* This file is part of mpv.
*
* mpv is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* mpv is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
*/
#include <windows.h>
#include <string.h>
#include "osdep/subprocess.h"
#include "osdep/io.h"
#include "osdep/windows_utils.h"
#include "mpv_talloc.h"
#include "common/common.h"
#include "stream/stream.h"
#include "misc/bstr.h"
#include "misc/thread_tools.h"
// Internal CRT FD flags
#define FOPEN (0x01)
#define FPIPE (0x08)
#define FDEV (0x40)
static void write_arg(bstr *cmdline, char *arg)
{
// Empty args must be represented as an empty quoted string
if (!arg[0]) {
bstr_xappend(NULL, cmdline, bstr0("\"\""));
return;
}
// If the string doesn't have characters that need to be escaped, it's best
// to leave it alone for the sake of Windows programs that don't process
// quoted args correctly.
if (!strpbrk(arg, " \t\"")) {
bstr_xappend(NULL, cmdline, bstr0(arg));
return;
}
// If there are characters that need to be escaped, write a quoted string
bstr_xappend(NULL, cmdline, bstr0("\""));
// Escape the argument. To match the behavior of CommandLineToArgvW,
// backslashes are only escaped if they appear before a quote or the end of
// the string.
int num_slashes = 0;
for (int pos = 0; arg[pos]; pos++) {
switch (arg[pos]) {
case '\\':
// Count consecutive backslashes
num_slashes++;
break;
case '"':
// Write the argument up to the point before the quote
bstr_xappend(NULL, cmdline, (struct bstr){arg, pos});
arg += pos;
pos = 0;
// Double backslashes preceding the quote
for (int i = 0; i < num_slashes; i++)
bstr_xappend(NULL, cmdline, bstr0("\\"));
num_slashes = 0;
// Escape the quote itself
bstr_xappend(NULL, cmdline, bstr0("\\"));
break;
default:
num_slashes = 0;
}
}
// Write the rest of the argument
bstr_xappend(NULL, cmdline, bstr0(arg));
// Double backslashes at the end of the argument
for (int i = 0; i < num_slashes; i++)
bstr_xappend(NULL, cmdline, bstr0("\\"));
bstr_xappend(NULL, cmdline, bstr0("\""));
}
// Convert an array of arguments to a properly escaped command-line string
static wchar_t *write_cmdline(void *ctx, char *argv0, char **args)
{
// argv0 should always be quoted. Otherwise, arguments may be interpreted as
// part of the program name. Also, it can't contain escape sequences.
bstr cmdline = {0};
bstr_xappend_asprintf(NULL, &cmdline, "\"%s\"", argv0);
if (args) {
for (int i = 0; args[i]; i++) {
bstr_xappend(NULL, &cmdline, bstr0(" "));
write_arg(&cmdline, args[i]);
}
}
wchar_t *wcmdline = mp_from_utf8(ctx, cmdline.start);
talloc_free(cmdline.start);
return wcmdline;
}
static void delete_handle_list(void *p)
{
LPPROC_THREAD_ATTRIBUTE_LIST list = p;
DeleteProcThreadAttributeList(list);
}
// Create a PROC_THREAD_ATTRIBUTE_LIST that specifies exactly which handles are
// inherited by the subprocess
static LPPROC_THREAD_ATTRIBUTE_LIST create_handle_list(void *ctx,
HANDLE *handles, int num)
{
// Get required attribute list size
SIZE_T size = 0;
if (!InitializeProcThreadAttributeList(NULL, 1, 0, &size)) {
if (GetLastError() != ERROR_INSUFFICIENT_BUFFER)
return NULL;
}
// Allocate attribute list
LPPROC_THREAD_ATTRIBUTE_LIST list = talloc_size(ctx, size);
if (!InitializeProcThreadAttributeList(list, 1, 0, &size))
goto error;
talloc_set_destructor(list, delete_handle_list);
if (!UpdateProcThreadAttribute(list, 0, PROC_THREAD_ATTRIBUTE_HANDLE_LIST,
handles, num * sizeof(HANDLE), NULL, NULL))
goto error;
return list;
error:
talloc_free(list);
return NULL;
}
// Helper method similar to sparse_poll, skips NULL handles
static int sparse_wait(HANDLE *handles, unsigned num_handles)
{
unsigned w_num_handles = 0;
HANDLE w_handles[MP_SUBPROCESS_MAX_FDS + 2];
int map[MP_SUBPROCESS_MAX_FDS + 2];
if (num_handles > MP_ARRAY_SIZE(w_handles))
return -1;
for (unsigned i = 0; i < num_handles; i++) {
if (!handles[i])
continue;
w_handles[w_num_handles] = handles[i];
map[w_num_handles] = i;
w_num_handles++;
}
if (w_num_handles == 0)
return -1;
DWORD i = WaitForMultipleObjects(w_num_handles, w_handles, FALSE, INFINITE);
i -= WAIT_OBJECT_0;
if (i >= w_num_handles)
return -1;
return map[i];
}
// Wrapper for ReadFile that treats ERROR_IO_PENDING as success
static int async_read(HANDLE file, void *buf, unsigned size, OVERLAPPED* ol)
{
if (!ReadFile(file, buf, size, NULL, ol))
return (GetLastError() == ERROR_IO_PENDING) ? 0 : -1;
return 0;
}
static bool is_valid_handle(HANDLE h)
{
// _get_osfhandle can return -2 "when the file descriptor is not associated
// with a stream"
return h && h != INVALID_HANDLE_VALUE && (intptr_t)h != -2;
}
static wchar_t *convert_environ(void *ctx, char **env)
{
// Environment size in wchar_ts, including the trailing NUL
size_t env_size = 1;
for (int i = 0; env[i]; i++) {
int count = MultiByteToWideChar(CP_UTF8, 0, env[i], -1, NULL, 0);
if (count <= 0)
abort();
env_size += count;
}
wchar_t *ret = talloc_array(ctx, wchar_t, env_size);
size_t pos = 0;
for (int i = 0; env[i]; i++) {
int count = MultiByteToWideChar(CP_UTF8, 0, env[i], -1,
ret + pos, env_size - pos);
if (count <= 0)
abort();
pos += count;
}
return ret;
}
void mp_subprocess2(struct mp_subprocess_opts *opts,
struct mp_subprocess_result *res)
{
wchar_t *tmp = talloc_new(NULL);
DWORD r;
HANDLE share_hndls[MP_SUBPROCESS_MAX_FDS] = {0};
int share_hndl_count = 0;
HANDLE wait_hndls[MP_SUBPROCESS_MAX_FDS + 2] = {0};
int wait_hndl_count = 0;
struct {
HANDLE handle;
bool handle_close;
char crt_flags;
HANDLE read;
OVERLAPPED read_ol;
char *read_buf;
} fd_data[MP_SUBPROCESS_MAX_FDS] = {0};
// The maximum target FD is limited because FDs have to fit in two sparse
// arrays in STARTUPINFO.lpReserved2, which has a maximum size of 65535
// bytes. The first four bytes are the handle count, followed by one byte
// per handle for flags, and an intptr_t per handle for the HANDLE itself.
static const int crt_fd_max = (65535 - sizeof(int)) / (1 + sizeof(intptr_t));
int crt_fd_count = 0;
// If the function exits before CreateProcess, there was an init error
*res = (struct mp_subprocess_result){ .error = MP_SUBPROCESS_EINIT };
STARTUPINFOEXW si = {
.StartupInfo = {
.cb = sizeof si,
.dwFlags = STARTF_USESTDHANDLES | STARTF_FORCEOFFFEEDBACK,
},
};
PROCESS_INFORMATION pi = {0};
for (int n = 0; n < opts->num_fds; n++) {
if (opts->fds[n].fd >= crt_fd_max) {
// Target FD is too big to fit in the CRT FD array
res->error = MP_SUBPROCESS_EUNSUPPORTED;
goto done;
}
if (opts->fds[n].fd >= crt_fd_count)
crt_fd_count = opts->fds[n].fd + 1;
if (opts->fds[n].src_fd >= 0) {
HANDLE src_handle = (HANDLE)_get_osfhandle(opts->fds[n].src_fd);
// Invalid handles are just ignored. This is because sometimes the
// standard handles are invalid in Windows, like in GUI processes.
// In this case mp_subprocess2 callers should still be able to
// blindly forward the standard FDs.
if (!is_valid_handle(src_handle))
continue;
DWORD type = GetFileType(src_handle);
bool is_console_handle = false;
switch (type & 0xff) {
case FILE_TYPE_DISK:
fd_data[n].crt_flags = FOPEN;
break;
case FILE_TYPE_CHAR:
fd_data[n].crt_flags = FOPEN | FDEV;
is_console_handle = GetConsoleMode(src_handle, &(DWORD){0});
break;
case FILE_TYPE_PIPE:
fd_data[n].crt_flags = FOPEN | FPIPE;
break;
case FILE_TYPE_UNKNOWN:
continue;
}
if (is_console_handle) {
// Some Windows versions have bugs when duplicating console
// handles, or when adding console handles to the CreateProcess
// handle list, so just use the handle directly for now. Console
// handles treat inheritance weirdly, so this should still work.
fd_data[n].handle = src_handle;
} else {
// Instead of making the source handle inheritable, just
// duplicate it to an inheritable handle
if (!DuplicateHandle(GetCurrentProcess(), src_handle,
GetCurrentProcess(), &fd_data[n].handle, 0,
TRUE, DUPLICATE_SAME_ACCESS))
goto done;
fd_data[n].handle_close = true;
share_hndls[share_hndl_count++] = fd_data[n].handle;
}
} else if (opts->fds[n].on_read && !opts->detach) {
fd_data[n].read_ol.hEvent = CreateEventW(NULL, TRUE, FALSE, NULL);
if (!fd_data[n].read_ol.hEvent)
goto done;
struct w32_create_anon_pipe_opts o = {
.server_flags = PIPE_ACCESS_INBOUND | FILE_FLAG_OVERLAPPED,
.client_inheritable = true,
};
if (!mp_w32_create_anon_pipe(&fd_data[n].read, &fd_data[n].handle, &o))
goto done;
fd_data[n].handle_close = true;
wait_hndls[n] = fd_data[n].read_ol.hEvent;
wait_hndl_count++;
fd_data[n].crt_flags = FOPEN | FPIPE;
fd_data[n].read_buf = talloc_size(tmp, 4096);
share_hndls[share_hndl_count++] = fd_data[n].handle;
} else {
DWORD access;
if (opts->fds[n].fd == 0) {
access = FILE_GENERIC_READ;
} else if (opts->fds[n].fd <= 2) {
access = FILE_GENERIC_WRITE | FILE_READ_ATTRIBUTES;
} else {
access = FILE_GENERIC_READ | FILE_GENERIC_WRITE;
}
SECURITY_ATTRIBUTES sa = {
.nLength = sizeof sa,
.bInheritHandle = TRUE,
};
fd_data[n].crt_flags = FOPEN | FDEV;
fd_data[n].handle = CreateFileW(L"NUL", access,
FILE_SHARE_READ | FILE_SHARE_WRITE,
&sa, OPEN_EXISTING, 0, NULL);
fd_data[n].handle_close = true;
}
switch (opts->fds[n].fd) {
case 0:
si.StartupInfo.hStdInput = fd_data[n].handle;
break;
case 1:
si.StartupInfo.hStdOutput = fd_data[n].handle;
break;
case 2:
si.StartupInfo.hStdError = fd_data[n].handle;
break;
}
}
// Convert the UTF-8 environment into a UTF-16 Windows environment block
wchar_t *env = NULL;
if (opts->env)
env = convert_environ(tmp, opts->env);
// Convert the args array to a UTF-16 Windows command-line string
char **args = opts->args && opts->args[0] ? &opts->args[1] : 0;
wchar_t *cmdline = write_cmdline(tmp, opts->exe, args);
// Get pointers to the arrays in lpReserved2. This is an undocumented data
// structure used by MSVCRT (and other frameworks and runtimes) to emulate
// FD inheritance. The format is unofficially documented here:
// <https://web.archive.org/web/20221014190010/
// https://www.catch22.net/tuts/undocumented-createprocess>
si.StartupInfo.cbReserved2 = sizeof(int) + crt_fd_count * (1 + sizeof(intptr_t));
si.StartupInfo.lpReserved2 = talloc_size(tmp, si.StartupInfo.cbReserved2);
char *crt_buf_flags = si.StartupInfo.lpReserved2 + sizeof(int);
char *crt_buf_hndls = crt_buf_flags + crt_fd_count;
memcpy(si.StartupInfo.lpReserved2, &crt_fd_count, sizeof(int));
// Fill the handle array with INVALID_HANDLE_VALUE, for unassigned handles
for (int n = 0; n < crt_fd_count; n++) {
HANDLE h = INVALID_HANDLE_VALUE;
memcpy(crt_buf_hndls + n * sizeof(intptr_t), &h, sizeof(intptr_t));
}
for (int n = 0; n < opts->num_fds; n++) {
crt_buf_flags[opts->fds[n].fd] = fd_data[n].crt_flags;
memcpy(crt_buf_hndls + opts->fds[n].fd * sizeof(intptr_t),
&fd_data[n].handle, sizeof(intptr_t));
}
DWORD flags = CREATE_UNICODE_ENVIRONMENT | EXTENDED_STARTUPINFO_PRESENT;
// Specify which handles are inherited by the subprocess. If this isn't
// specified, the subprocess inherits all inheritable handles, which could
// include handles created by other threads. See:
// <https://web.archive.org/web/20121127222200/
// http://blogs.msdn.com/b/oldnewthing/archive/2011/12/16/10248328.aspx>
si.lpAttributeList = create_handle_list(tmp, share_hndls, share_hndl_count);
// If we have a console, the subprocess will automatically attach to it so
// it can receive Ctrl+C events. If we don't have a console, prevent the
// subprocess from creating its own console window by specifying
// CREATE_NO_WINDOW. GetConsoleCP() can be used to reliably determine if we
// have a console or not (Cygwin uses it too.)
if (!GetConsoleCP())
flags |= CREATE_NO_WINDOW;
if (!CreateProcessW(NULL, cmdline, NULL, NULL, TRUE, flags, env, NULL,
&si.StartupInfo, &pi))
goto done;
talloc_free(cmdline);
talloc_free(env);
talloc_free(si.StartupInfo.lpReserved2);
talloc_free(si.lpAttributeList);
CloseHandle(pi.hThread);
for (int n = 0; n < opts->num_fds; n++) {
if (fd_data[n].handle_close && is_valid_handle(fd_data[n].handle))
CloseHandle(fd_data[n].handle);
fd_data[n].handle = NULL;
if (fd_data[n].read) {
// Do the first read operation on each pipe
if (async_read(fd_data[n].read, fd_data[n].read_buf, 4096,
&fd_data[n].read_ol))
{
CloseHandle(fd_data[n].read);
wait_hndls[n] = fd_data[n].read = NULL;
wait_hndl_count--;
}
}
}
if (opts->detach) {
res->error = MP_SUBPROCESS_OK;
goto done;
}
res->error = MP_SUBPROCESS_EGENERIC;
wait_hndls[MP_SUBPROCESS_MAX_FDS] = pi.hProcess;
wait_hndl_count++;
if (opts->cancel)
wait_hndls[MP_SUBPROCESS_MAX_FDS + 1] = mp_cancel_get_event(opts->cancel);
DWORD exit_code;
while (wait_hndl_count) {
int n = sparse_wait(wait_hndls, MP_ARRAY_SIZE(wait_hndls));
if (n >= 0 && n < MP_SUBPROCESS_MAX_FDS) {
// Complete the read operation on the pipe
if (!GetOverlappedResult(fd_data[n].read, &fd_data[n].read_ol, &r, TRUE)) {
CloseHandle(fd_data[n].read);
wait_hndls[n] = fd_data[n].read = NULL;
wait_hndl_count--;
} else {
opts->fds[n].on_read(opts->fds[n].on_read_ctx,
fd_data[n].read_buf, r);
// Begin the next read operation on the pipe
if (async_read(fd_data[n].read, fd_data[n].read_buf, 4096,
&fd_data[n].read_ol))
{
CloseHandle(fd_data[n].read);
wait_hndls[n] = fd_data[n].read = NULL;
wait_hndl_count--;
}
}
} else if (n == MP_SUBPROCESS_MAX_FDS) { // pi.hProcess
GetExitCodeProcess(pi.hProcess, &exit_code);
res->exit_status = exit_code;
CloseHandle(pi.hProcess);
wait_hndls[n] = pi.hProcess = NULL;
wait_hndl_count--;
} else if (n == MP_SUBPROCESS_MAX_FDS + 1) { // opts.cancel
if (pi.hProcess) {
TerminateProcess(pi.hProcess, 1);
res->error = MP_SUBPROCESS_EKILLED_BY_US;
goto done;
}
} else {
goto done;
}
}
res->error = MP_SUBPROCESS_OK;
done:
for (int n = 0; n < opts->num_fds; n++) {
if (is_valid_handle(fd_data[n].read)) {
// Cancel any pending I/O (if the process was killed)
CancelIo(fd_data[n].read);
GetOverlappedResult(fd_data[n].read, &fd_data[n].read_ol, &r, TRUE);
CloseHandle(fd_data[n].read);
}
if (fd_data[n].handle_close && is_valid_handle(fd_data[n].handle))
CloseHandle(fd_data[n].handle);
if (fd_data[n].read_ol.hEvent)
CloseHandle(fd_data[n].read_ol.hEvent);
}
if (pi.hProcess)
CloseHandle(pi.hProcess);
talloc_free(tmp);
}
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