What is the global named event object equivalent in Unix? I need to create a named event-like object in unix so that another process can set it
pseudocode in Win32:
HANDLE hEvent=CreateEvent(...,"Global\\CSAPP");
while(1)
{
WaitForSingleObject(hEvent);
...
}
In another process:
HANDLE hEvent=OpenEvent(...,"Global\\CSAPP");
SetEvent(hEvent);
You are probably looking for a named semaphore.
int initial = 0;
sem_t *sem = sem_open("/global_name", O_CREAT, 0644, initial);
/* Down ("Wait"). */
sem_wait(sem);
/* Up ("Set") . */
sem_post(sem);
Related
In the following program I print to the console using two different functions
#include <windows.h>
int main() {
HANDLE h = GetStdHandle(STD_OUTPUT_HANDLE);
DWORD byteswritten;
WriteConsole(h, "WriteConsole", 12, &byteswritten, NULL);
WriteFile(h, "WriteFile", 9, &byteswritten, NULL);
}
If when I execute this program and redirect it's output using a > out.txt or a 1> out.txt nothing gets printed to the console (as expected) but the contents of out.txt are only
WriteFile
What is different between the two that allows calls to WriteFile to be redirected to the file and calls to WriteConsole to go to ... nowhere
Tested with gcc and msvc on windows 10
WriteConsole only works with console screen handles, not files nor pipes.
If you are only writing ASCII content you can use WriteFile for everything.
If you need to write Unicode characters you can use GetConsoleMode to detect the handle type, it fails for everything that is not a console handle.
When doing raw output like this you also have to deal with the BOM if the handle is redirected to a file.
This blog post is a good starting point for dealing with Unicode in the Windows console...
Edit 2021:
Windows 10 now has the ConPTY API (aka pseudo-console), which basically allows any program to act like the console for another program, thus enables capturing output that is directly written to the console.
This renders my original answer obsolete for Windows versions that support ConPTY.
Original answer:
From the reference:
WriteConsole fails if it is used with a standard handle that is
redirected to a file. If an application processes multilingual output
that can be redirected, determine whether the output handle is a
console handle (one method is to call the GetConsoleMode function and
check whether it succeeds). If the handle is a console handle, call
WriteConsole. If the handle is not a console handle, the output is
redirected and you should call WriteFile to perform the I/O.
This is only applicable if you control the source code of the application that you want to redirect. I recently had to redirect output from a closed-source application that unconditionally called WriteConsole() so it could not be redirected normally.
Reading the console screen buffer (as suggested by this answer) prooved to be unreliable, so I used Microsoft Detours library to hook the WriteConsole() API in the target process and call WriteFile() if necessary. Otherwise call the original WriteConsole() function.
I created a hook DLL based on the example of Using Detours:
#include <windows.h>
#include <detours.h>
// Target pointer for the uninstrumented WriteConsoleW API.
//
auto WriteConsoleW_orig = &WriteConsoleW;
// Detour function that replaces the WriteConsoleW API.
//
BOOL WINAPI WriteConsoleW_hooked(
_In_ HANDLE hConsoleOutput,
_In_ const VOID *lpBuffer,
_In_ DWORD nNumberOfCharsToWrite,
_Out_ LPDWORD lpNumberOfCharsWritten,
_Reserved_ LPVOID lpReserved
)
{
// Check if this actually is a console screen buffer handle.
DWORD mode;
if( GetConsoleMode( hConsoleOutput, &mode ) )
{
// Forward to the original WriteConsoleW() function.
return WriteConsoleW_orig( hConsoleOutput, lpBuffer, nNumberOfCharsToWrite, lpNumberOfCharsWritten, lpReserved );
}
else
{
// This is a redirected handle (e. g. a file or a pipe). We multiply with sizeof(WCHAR), because WriteFile()
// expects the number of bytes, but WriteConsoleW() gets passed the number of characters.
BOOL result = WriteFile( hConsoleOutput, lpBuffer, nNumberOfCharsToWrite * sizeof(WCHAR), lpNumberOfCharsWritten, nullptr );
// WriteFile() returns number of bytes written, but WriteConsoleW() has to return the number of characters written.
if( lpNumberOfCharsWritten )
*lpNumberOfCharsWritten /= sizeof(WCHAR);
return result;
}
}
// DllMain function attaches and detaches the WriteConsoleW_hooked detour to the
// WriteConsoleW target function. The WriteConsoleW target function is referred to
// through the WriteConsoleW_orig target pointer.
//
BOOL WINAPI DllMain(HINSTANCE hinst, DWORD dwReason, LPVOID reserved)
{
if (DetourIsHelperProcess()) {
return TRUE;
}
if (dwReason == DLL_PROCESS_ATTACH) {
DetourRestoreAfterWith();
DetourTransactionBegin();
DetourUpdateThread(GetCurrentThread());
DetourAttach(&(PVOID&)WriteConsoleW_orig, WriteConsoleW_hooked);
DetourTransactionCommit();
}
else if (dwReason == DLL_PROCESS_DETACH) {
DetourTransactionBegin();
DetourUpdateThread(GetCurrentThread());
DetourDetach(&(PVOID&)WriteConsoleW_orig, WriteConsoleW_hooked);
DetourTransactionCommit();
}
return TRUE;
}
Note: In the WriteFile() branch I don't write a BOM (byte order mark), because it is not always wanted (e. g. when redirecting to a pipe instead of a file or when appending to an existing file). An application that is using the DLL to redirect process output to a file can simply write the UTF-16 LE BOM on its own before launching the redirected process.
The target process is created using DetourCreateProcessWithDllExW(), specifying the name of our hook DLL as argument for the lpDllName parameter. The other arguments are identical to how you create a redirected process via the CreateProcessW() API. I won't go into detail, because these are all well documented.
The code below can be used to redirect console output if the other party uses WriteConsole. The code reads the output via a hidden console screen buffer. I've written this code to intercept debug output some directshow drivers write to the console. Directshow drivers have the habit of doing things drivers should not do, like writing unwanted logfiles, writing to console and crashing.
// info to redirected console output
typedef struct tagRedConInfo
{
// hidden console
HANDLE hCon;
// old console handles
HANDLE hOldConOut;
HANDLE hOldConErr;
// buffer to read screen content
CHAR_INFO *BufData;
INT BufSize;
//
} TRedConInfo;
//------------------------------------------------------------------------------
// GLOBALS
//------------------------------------------------------------------------------
// initial handles
HANDLE gv_hOldConOut;
HANDLE gv_hOldConErr;
//------------------------------------------------------------------------------
// PROTOTYPES
//------------------------------------------------------------------------------
/* init redirecting the console output */
BOOL Shell_InitRedirectConsole(BOOL,TRedConInfo*);
/* done redirecting the console output */
BOOL Shell_DoneRedirectConsole(TRedConInfo*);
/* read string from hidden console, then clear */
BOOL Shell_ReadRedirectConsole(TRedConInfo*,TCHAR*,INT);
/* clear buffer of hidden console */
BOOL Shell_ClearRedirectConsole(TRedConInfo*);
//------------------------------------------------------------------------------
// IMPLEMENTATIONS
//------------------------------------------------------------------------------
/***************************************/
/* init redirecting the console output */
/***************************************/
BOOL Shell_InitRedirectConsole(BOOL in_SetStdHandles, TRedConInfo *out_RcInfo)
{
/* locals */
HANDLE lv_hCon;
SECURITY_ATTRIBUTES lv_SecAttr;
// preclear structure
memset(out_RcInfo, 0, sizeof(TRedConInfo));
// prepare inheritable handle just in case an api spans an external process
memset(&lv_SecAttr, 0, sizeof(SECURITY_ATTRIBUTES));
lv_SecAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
lv_SecAttr.bInheritHandle = TRUE;
// create hidden console buffer
lv_hCon = CreateConsoleScreenBuffer(
GENERIC_READ|GENERIC_WRITE, FILE_SHARE_READ|FILE_SHARE_WRITE,
&lv_SecAttr, CONSOLE_TEXTMODE_BUFFER, 0);
// failed to create console buffer?
if (lv_hCon == INVALID_HANDLE_VALUE)
return FALSE;
// store
out_RcInfo->hCon = lv_hCon;
// set as standard handles for own process?
if (in_SetStdHandles)
{
// mutex the globals
WaitForGlobalVarMutex();
// remember the old handles
out_RcInfo->hOldConOut = GetStdHandle(STD_OUTPUT_HANDLE);
out_RcInfo->hOldConErr = GetStdHandle(STD_ERROR_HANDLE);
// set hidden console as std output
SetStdHandle(STD_OUTPUT_HANDLE, lv_hCon);
SetStdHandle(STD_ERROR_HANDLE, lv_hCon);
// is this the first instance?
if (!gv_hOldConOut)
{
// inform our own console output code about the old handles so our own
// console will be writing to the real console, only console output from
// other parties will write to the hidden console
gv_hOldConOut = out_RcInfo->hOldConOut;
gv_hOldConErr = out_RcInfo->hOldConErr;
}
// release mutex
ReleaseGlobalVarMutex();
}
// done
return TRUE;
}
/***************************************/
/* done redirecting the console output */
/***************************************/
BOOL Shell_DoneRedirectConsole(TRedConInfo *in_RcInfo)
{
// validate
if (!in_RcInfo->hCon)
return FALSE;
// restore original handles?
if (in_RcInfo->hOldConOut)
{
// mutex the globals
WaitForGlobalVarMutex();
// restore original handles
SetStdHandle(STD_OUTPUT_HANDLE, in_RcInfo->hOldConOut);
SetStdHandle(STD_ERROR_HANDLE, in_RcInfo->hOldConErr);
// was this the first instance?
if (in_RcInfo->hOldConOut == gv_hOldConOut)
{
// clear
gv_hOldConOut = NULL;
gv_hOldConErr = NULL;
}
// release mutex
ReleaseGlobalVarMutex();
}
// close the console handle
CloseHandle(in_RcInfo->hCon);
// free read buffer
if (in_RcInfo->BufData)
MemFree(in_RcInfo->BufData);
// clear structure
memset(in_RcInfo, 0, sizeof(TRedConInfo));
// done
return TRUE;
}
/***********************************************/
/* read string from hidden console, then clear */
/***********************************************/
BOOL Shell_ReadRedirectConsole(TRedConInfo *in_RcInfo, TCHAR *out_Str, INT in_MaxLen)
{
/* locals */
TCHAR lv_C;
INT lv_X;
INT lv_Y;
INT lv_W;
INT lv_H;
INT lv_N;
INT lv_Len;
INT lv_Size;
INT lv_PrvLen;
COORD lv_DstSze;
COORD lv_DstOfs;
DWORD lv_Written;
SMALL_RECT lv_SrcRect;
CHAR_INFO *lv_BufData;
CONSOLE_SCREEN_BUFFER_INFO lv_Info;
// preclear output
out_Str[0] = 0;
// validate
if (!in_RcInfo->hCon)
return FALSE;
// reserve character for eos
--in_MaxLen;
// get current buffer info
if (!GetConsoleScreenBufferInfo(in_RcInfo->hCon, &lv_Info))
return FALSE;
// check whether there is something at all
if (!lv_Info.dwSize.X || !lv_Info.dwSize.Y)
return FALSE;
// limit the buffer passed onto read call otherwise it
// will fail with out-of-resources error
lv_DstSze.X = (INT16)(lv_Info.dwSize.X);
lv_DstSze.Y = (INT16)(lv_Info.dwSize.Y < 8 ? lv_Info.dwSize.Y : 8);
// size of buffer needed
lv_Size = lv_DstSze.X * lv_DstSze.Y * sizeof(CHAR_INFO);
// is previous buffer too small?
if (!in_RcInfo->BufData || in_RcInfo->BufSize < lv_Size)
{
// free old buffer
if (in_RcInfo->BufData)
MemFree(in_RcInfo->BufData);
// allocate read buffer
if ((in_RcInfo->BufData = (CHAR_INFO*)MemAlloc(lv_Size)) == NULL)
return FALSE;
// store new size
in_RcInfo->BufSize = lv_Size;
}
// always write to (0,0) in buffer
lv_DstOfs.X = 0;
lv_DstOfs.Y = 0;
// init src rectangle
lv_SrcRect.Left = 0;
lv_SrcRect.Top = 0;
lv_SrcRect.Right = lv_DstSze.X;
lv_SrcRect.Bottom = lv_DstSze.Y;
// buffer to local
lv_BufData = in_RcInfo->BufData;
// start at first string position in output
lv_Len = 0;
// loop until no more rows to read
do
{
// read buffer load
if (!ReadConsoleOutput(in_RcInfo->hCon, lv_BufData, lv_DstSze, lv_DstOfs, &lv_SrcRect))
return FALSE;
// w/h of actually read content
lv_W = lv_SrcRect.Right - lv_SrcRect.Left + 1;
lv_H = lv_SrcRect.Bottom - lv_SrcRect.Top + 1;
// remember previous position
lv_PrvLen = lv_Len;
// loop through rows of buffer
for (lv_Y = 0; lv_Y < lv_H; ++lv_Y)
{
// reset output position of current row
lv_N = 0;
// loop through columns
for (lv_X = 0; lv_X < lv_W; ++lv_X)
{
// is output full?
if (lv_Len + lv_N > in_MaxLen)
break;
// get character from screen buffer, ignore attributes
lv_C = lv_BufData[lv_Y * lv_DstSze.X + lv_X].Char.UnicodeChar;
// append character
out_Str[lv_Len + lv_N++] = lv_C;
}
// remove spaces at the end of the line
while (lv_N > 0 && out_Str[lv_Len+lv_N-1] == ' ')
--lv_N;
// if row was not blank
if (lv_N > 0)
{
// update output position
lv_Len += lv_N;
// is output not full?
if (lv_Len + 2 < in_MaxLen)
{
// append cr/lf
out_Str[lv_Len++] = '\r';
out_Str[lv_Len++] = '\n';
}
}
}
// update screen position
lv_SrcRect.Top = (INT16)(lv_SrcRect.Top + lv_H);
lv_SrcRect.Bottom = (INT16)(lv_SrcRect.Bottom + lv_H);
// until nothing is added or no more screen rows
} while (lv_PrvLen != lv_Len && lv_SrcRect.Bottom < lv_Info.dwSize.Y);
// remove last cr/lf
if (lv_Len > 2)
lv_Len -= 2;
// append eos
out_Str[lv_Len] = 0;
// total screen buffer size in characters
lv_Size = lv_Info.dwSize.X * lv_Info.dwSize.Y;
// clear the buffer with spaces
FillConsoleOutputCharacter(in_RcInfo->hCon, ' ', lv_Size, lv_DstOfs, &lv_Written);
// reset cursor position to (0,0)
SetConsoleCursorPosition(in_RcInfo->hCon, lv_DstOfs);
// done
return TRUE;
}
/**********************************/
/* clear buffer of hidden console */
/**********************************/
BOOL Shell_ClearRedirectConsole(TRedConInfo *in_RcInfo)
{
/* locals */
INT lv_Size;
COORD lv_ClrOfs;
DWORD lv_Written;
CONSOLE_SCREEN_BUFFER_INFO lv_Info;
// validate
if (!in_RcInfo->hCon)
return FALSE;
// get current buffer info
if (!GetConsoleScreenBufferInfo(in_RcInfo->hCon, &lv_Info))
return FALSE;
// clear from (0,0) onward
lv_ClrOfs.X = 0;
lv_ClrOfs.Y = 0;
// total screen buffer size in characters
lv_Size = lv_Info.dwSize.X * lv_Info.dwSize.Y;
// clear the buffer with spaces
FillConsoleOutputCharacter(in_RcInfo->hCon, ' ', lv_Size, lv_ClrOfs, &lv_Written);
// reset cursor position to (0,0)
SetConsoleCursorPosition(in_RcInfo->hCon, lv_ClrOfs);
// done
return TRUE;
}
I'm desperately trying to create a child process and redirect its output to new pipes and read from those pipes, but I just can't get it to work. I am very new the Win32API, please be nice to me. :)
After having failed on using the Win32API "normally", I created wrappers to focus on finding an error in the logic and/or order of API calls. You can find the interface for the wrappers below. Since most of the methods directly translate to Win32API calls, it should (hopefully) not be an obstacle to answering this question.
I get the same behaviour with using the wrapper classes as I have experienced originally.
I've read a lot of online resources about this topic and one says something different than the other. The one that has been most useful until now was https://msdn.microsoft.com/en-us/library/windows/desktop/ms682499(v=vs.85).aspx, especially this information (emphasis mine):
The parent process uses the opposite ends of these two pipes to write to the child process's input and read from the child process's output. As specified in the STARTUPINFO structure, these handles are also inheritable. However, these handles must not be inherited. Therefore, before creating the child process, the parent process uses the SetHandleInformation function to ensure that the write handle for the child process's standard input and the read handle for the child process's standard input cannot be inherited. For more information, see Pipes.
Before I found this topic and closed the ends that I'm not using from the parent process side, I head ReadFile() blocking forever on the standard output read handle of the child process. Now, it always immediately returns that the pipe is broken.
This is how I create the Pipes and Process:
Popen(const String& command, const String& args,
Bool use_current_pipes = false, Bool merge_stderr = true)
{
Bool ok = true;
_error = 0;
ZeroMemory(&_pi, sizeof(_pi));
STARTUPINFO si;
ZeroMemory(&si, sizeof(si));
si.cb = sizeof(si);
if (!use_current_pipes) {
// Create pipes for standard input, output and error.
_stdin = Pipe(true);
_stdout = Pipe(true);
if (_stdout && merge_stderr)
_stderr = _stdout.Duplicate();
else
_stderr = Pipe(true);
if (_stdin && _stdout && _stderr) {
_stdin.w.SetInheritable(false);
_stderr.r.SetInheritable(false);
_stdout.r.SetInheritable(false);
si.hStdInput = _stdin.r.Get();
si.hStdOutput = _stdout.w.Get();
si.hStdError = _stderr.w.Get();
si.dwFlags |= STARTF_USESTDHANDLES;
}
else {
ok = false;
}
}
else {
si.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
si.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
si.hStdError = GetStdHandle(STD_ERROR_HANDLE);
si.dwFlags |= STARTF_USESTDHANDLES;
}
// Create the process. Enclose the actual command in quotes.
ok = ok && CreateProcess(
nullptr, // command might contain whitespace, pass it quoted in arg 2 instead.
AutoString("\"" + command + "\" " + args),
nullptr, // Process handle not inheritable
nullptr, // Thread handle not inheritable
true, // handles are inherited
0, // No creation flags
nullptr, // Use parent's environment block
nullptr, // Use parent's starting directory
&si, // Pointer to STARTUPINFO
&_pi); // Pointer to PROCESS_INFORMATION
// Something went wrong? Well, bad.
if (!ok) {
_error = GetLastError();
}
// Close the handles that have been inherited by the child process
// and to which we don't need access to, otherwise they will not
// close when the child exits.
_stdin.r.Close();
_stdout.w.Close();
_stderr.w.Close();
}
And this is how I read from the standard output (_stdout.r):
UInt Read(UInt num_bytes, char* buffer) {
if (!_stdout.r) return 0;
DWORD bytes_read = 0;
if (!ReadFile(_stdout.r.Get(), buffer, num_bytes - 1, &bytes_read, nullptr)) {
_error = GetLastError();
ConsoleOut("[ERROR]: ReadFile() : " + String::IntToString((Int32) _error));
if (_error == ERROR_BROKEN_PIPE) {
ConsoleOut("No Wait, the Pipe is just broken.");
_error = 0; // that's fine
}
return 0;
}
buffer[bytes_read] = '\0';
return bytes_read;
}
When I comment out the last lines of the Popen constructor (closing the pipe handles that are not used from the parent process) ReadFile() blocks forever. With these lines enabled, the Pipe is always immediately broken (the child process exits pretty quickly).
Question
Can someone see what is wrong in my code/logic?
If not, I would already appreciate if there is a complete working example of opening a child process and reading its output
Wrapper Interface
struct Handle {
HANDLE h;
explicit Handle();
explicit Handle(HANDLE h);
Handle(Handle&& other);
Handle& operator = (Handle&& other);
~Handle();
void Close();
HANDLE Get();
HANDLE Release();
Handle Duplicate(DWORD options = DUPLICATE_SAME_ACCESS, HANDLE src_proc = nullptr, HANDLE dst_proc = nullptr) const;
DWORD GetInfo() const; // uses GetHandleInformation
void SetInheritable(bool inheritable) const; // uses SetHandleInformation
bool GetInheritable() const;
operator bool() const;
explicit Handle(const Handle&) = delete;
Handle* operator = (const Handle&) = delete;
};
struct Pipe {
Handle r, w;
DWORD error;
explicit Pipe();
explicit Pipe(bool inheritable);
Pipe(Pipe&& other);
Pipe& operator = (Pipe&& other);
~Pipe();
void Close();
Pipe Duplicate(DWORD options = DUPLICATE_SAME_ACCESS, HANDLE src_proc = nullptr, HANDLE dst_proc = nullptr) const;
operator bool() const;
explicit Pipe(const Pipe&) = delete;
Pipe* operator = (const Pipe&) = delete;
};
Without using either threads or overlapped I/O, you risk deadlock. The child process could be trying to read from its stdin or waiting for space in its stdout buffer so it can write, you cannot tell which, and when you choose wrong, you get the observed behavior. The blocking read on the child's output means you guessed wrong, and it is actually waiting for input.
Read Raymond Chen's blog article Be careful when redirecting both a process's stdin and stdout to pipes, for you can easily deadlock which I also linked in your earlier question today. It specifically calls out the horrible brokenness in the very same sample you linked in your question.
Can someone please tell me how to go about creating a maximum of N instances of an application in MFC?
Also, if N instances are running, and one instance gets closed, then one new instance can be created (but no more than N instances can run at any one time).
Thank you in advance.
a.
You can create a global semaphore that up to n process instances can enter. The n+1 th instance of your process will fail to enter the semaphore. Of course you should select a short timeout for the locking operation so you can present a meaningful feedback to the user.
For the semaphore stuff you can take a look at MSDN.
I'd use lock files. In your CMyApp::InitInstance() add:
CString Path;
// better get the path to the global app data or local user app data folder,
// depending on if you want to allow the three instances machine-wide or per user.
// Windows' file system virtualization will make GetModuleFileName() per user:
DWORD dw = GetModuleFileName(m_hInstance,
Path.GetBuffer(MAX_PATH), MAX_PATH);
Path.ReleaseBuffer();
// strip "exe" from filename and replace it with "lock"
Path = Path.Left(Path.GetLength()-3) + T("lock");
int i;
// better have the locking file in your class and do a clean Close on ExitInstance()!
CFile *pLockingFile = NULL;
for (i = 0; i < 3; i++) // restrict to three instances
{
CString Counter;
Counter.Format(T("%d"), i);
TRY
{
pLockingFile = new CFile(Path + Counter,
CFile::modeCreate|CFile::modeWrite|CFile::shareExclusive);
pLockingFile.Close();
break; // got an instance slot
}
CATCH( CFileException, e )
{
// maybe do something else here, if file open fails
}
END_CATCH
if (i >= 3)
return TRUE; // close instance, no slot available
}
Edit: To lock the software machine-wide, retrieve the common app folder using the following function instead of calling GetModuleFileName().
#pragma warning(disable: 4996) // no risk, no fun
BOOL GetCommonAppDataPath(char *path)
{
*path = '\0';
if (SHGetSpecialFolderPath(NULL, path, CSIDL_COMMON_APPDATA, TRUE))
{
strcat(path, T("\\MyApplication")); // usually found under C:\ProgramData\MyApplication
DWORD dwFileStat = GetFileAttributes(path);
if (dwFileStat == 0xffffffff) // no MyApplication directory yet?
CreateDirectory(path, NULL); // create it
dwFileStat = GetFileAttributes(path); // 2nd try, just to be sure
if (dwFileStat == 0xffffffff || !(dwFileStat & FILE_ATTRIBUTE_DIRECTORY))
return FALSE;
return TRUE;
}
return FALSE;
}
Note: This will only work from Vista on. If you have XP, writing to a global directory is an easy task, e.g. C:\Windows\Temp. I have put the function in a helper dll I only load if the OS is Vista or higher. Otherwise your software won't start because of unresolved references in system dlls.
I made a kext to use my system call instead of an existing system call on reference to
Re-routing System Calls.
During a test, I wonder which process calls this systemcall.
I need to allow applications to continue normally except the specified process.
Is there anything that obtain the information of calling process?
If you take a look at the source for the regular implementation of the ptrace system call you can see that it works with the struct proc representing the calling process that's passed in as the first argument:
int
ptrace(struct proc *p, struct ptrace_args *uap, int32_t *retval)
{
// …
if (uap->req == PT_DENY_ATTACH) {
proc_lock(p);
if (ISSET(p->p_lflag, P_LTRACED)) {
proc_unlock(p);
KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_FRCEXIT) | DBG_FUNC_NONE,
p->p_pid, W_EXITCODE(ENOTSUP, 0), 4, 0, 0);
exit1(p, W_EXITCODE(ENOTSUP, 0), retval);
/* drop funnel before we return */
thread_exception_return();
/* NOTREACHED */
}
SET(p->p_lflag, P_LNOATTACH);
proc_unlock(p);
return(0);
}
You can use the functions in <sys/proc.h> to get information on the given process, such as proc_pid to find the pid.
I'm porting old linux kernel code for newer version 2.6.32.
There is a part that copies a file descriptor. The idea was to allocate a new file descriptor and a new struct file and use them with another f_op and , leaving all other fields of struct file equivalent to original's.
How do I do this in a modern kernel?
I've written an approximate implementation but I don't know whether i should call file_get, path_get or do others use counter incrementation.
struct file * copy_file(const struct file * iOrig, int * oNewFd) {
if (!orig)
return 0;
*oNewFd = get_unused_fd();
if (*oNewFd < 0)
return 0;
struct file * rv = alloc_file(orig->f_path.mnt, orig->f_path.dentry, orig->f_path.mode, orig->f_op);
if (!rv)
goto free_fd;
fd_install(fd, rv);
return rv;
free_fd:
put_unused_fd(*oNewFd)
return 0;
}
P.S. In fact having all fileds of original file copied is not neccessary. I just need to allow a new set of file operations in user-space. So creating a new descriptor owned by current with a given f_op will do.
path_get sounds fine. Check out an example here http://tomoyo.sourceforge.jp/cgi-bin/lxr/source/fs/pipe.c#L1046 and you'll be able to find more refs there if you need them.