[lldb-dev] How to redirect stdin/out/err to different pty?
Piotr Rak
piotr.rak at gmail.com
Wed Mar 26 14:01:33 PDT 2014
Also other option is that we don't have O_CREAT in flags and we get ENOENT
from open().... but again can not check that today.
2014-03-26 21:52 GMT+01:00 Piotr Rak <piotr.rak at gmail.com>:
> No, closing before dup2 is not required, it should close fd and it should
> be also atomic. I am wondering now if LLDB sets FileActions like it was
> expecting that we use posix_spawn.
>
> I can not check it today... but will look at it tomorrow or during weekend.
>
>
> 2014-03-26 21:33 GMT+01:00 Greg Clayton <gclayton at apple.com>:
>
> Looks like you might need to look at:
>>
>> ProcessMonitor::Launch(LaunchArgs *args)
>>
>> It is what does the fork + exec.
>>
>> It also looks like no matter what is sent to
>> ProcessMonitor::Launch(LaunchArgs *args) for stdin, stdout, stderr, Linux
>> _always_ launches using a pseudo terminal by doing:
>>
>> lldb_utility::PseudoTerminal terminal;
>> if ((pid = terminal.Fork(err_str, err_len)) == -1)
>>
>>
>> If you look at the "terminal.Fork()" code you will see that it actually
>> sets stdin/out/err to the slave slide of the pseudo terminal, so there is
>> no telling if the code in ProcessMonitor::Launch():
>>
>> if (stdin_path != NULL && stdin_path[0])
>> if (!DupDescriptor(stdin_path, STDIN_FILENO, O_RDONLY))
>> exit(eDupStdinFailed);
>>
>> if (stdout_path != NULL && stdout_path[0])
>> if (!DupDescriptor(stdout_path, STDOUT_FILENO, O_WRONLY |
>> O_CREAT))
>> exit(eDupStdoutFailed);
>>
>> if (stderr_path != NULL && stderr_path[0])
>> if (!DupDescriptor(stderr_path, STDERR_FILENO, O_WRONLY |
>> O_CREAT))
>> exit(eDupStderrFailed);
>>
>>
>> Will work? ProcessMonitor::DupDescriptor() does:
>>
>>
>> bool
>> ProcessMonitor::DupDescriptor(const char *path, int fd, int flags)
>> {
>> int target_fd = open(path, flags, 0666);
>>
>> if (target_fd == -1)
>> return false;
>>
>> return (dup2(target_fd, fd) == -1) ? false : true;
>> }
>>
>> I would assume you would need to call close() on stdin/out/err first?
>> Again the PseudoTerminal::Fork() has always already setup stdin/out/err to
>> the slave side and the DupDescriptor calls are probably failing.
>>
>> Greg
>>
>>
>> On Mar 26, 2014, at 12:26 PM, Piotr Rak <piotr.rak at gmail.com> wrote:
>>
>> > Hi,
>> >
>> > That got me curious and now I am bit confused how it works, and it
>> should be really simple.
>> >
>> > I've checked Greg's example, it will just exit before main doing
>> nothing.
>> > I've no idea why yet, however I attached my perfect tracee:
>> >
>> > extern "C" void _start()
>> > {
>> > __asm__ volatile (
>> > "again:;"
>> > "int $0x03;"
>> > "jmp again;"
>> > "movl $1,%eax;"
>> > "xorl %ebx, %ebx;"
>> > "int $0x80;"
>> > );
>> > }
>> > ls -al /proc/`pidof hello`/fd
>> >
>> > lrwx------ 1 prak prak 64 03-26 19:42 0 -> /dev/pts/19
>> > lrwx------ 1 prak prak 64 03-26 19:42 1 -> /dev/pts/19
>> > lrwx------ 1 prak prak 64 03-26 19:42 2 -> /dev/pts/19
>> > lrwx------ 1 prak prak 64 03-26 19:42 3 -> /dev/ptmx
>> > lrwx------ 1 prak prak 64 03-26 19:42 5 -> /dev/pts/19
>> >
>> > ls -al /proc/`pidof lldb`/fd
>> >
>> > lrwx------ 1 prak prak 64 03-26 19:43 0 -> /dev/pts/16
>> > lrwx------ 1 prak prak 64 03-26 19:43 1 -> /dev/pts/16
>> > lrwx------ 1 prak prak 64 03-26 19:43 2 -> /dev/pts/16
>> > lrwx------ 1 prak prak 64 03-26 19:43 3 -> /dev/ptmx
>> > lrwx------ 1 prak prak 64 03-26 19:43 4 -> /dev/ptmx
>> > lr-x------ 1 prak prak 64 03-26 19:43 5 -> pipe:[1301667]
>> > l-wx------ 1 prak prak 64 03-26 19:43 6 -> pipe:[1301667]
>> > lr-x------ 1 prak prak 64 03-26 19:43 7 -> pipe:[1299830]
>> > l-wx------ 1 prak prak 64 03-26 19:43 8 -> pipe:[1299830]
>> >
>> > So it was spawned as usual using fork() by Linux/ProcessMonitor.cpp
>> > And it was given slave pts, lldb however has no '/tmp/out.txt' file
>> anywhere.
>> >
>> > Should this for this case?:
>> > a) be passed opened to inferior before exec, or
>> > b) lldb should read master pty and write to /tmp/out.txt
>> >
>> > I would guess that should be a:
>> >
>> > But probably then:
>> >
>> > SetSTDIOFileDescriptor(m_monitor->GetTerminalFD());
>> >
>> > from ProcessPosix::DoLaunch() ProcessPosix.cpp:253 after creating
>> process spoils the fun.
>> > Also std{in,err,path)_path had to be empty here.
>> >
>> > Cheers,
>> > /Piotr
>> >
>> >
>> > 2014-03-26 19:08 GMT+01:00 Greg Clayton <gclayton at apple.com>:
>> > Seems like we are having some problem re-directing to terminals and
>> files that exist. I would try debugging through the launch process and see
>> who is doing what with file re-direction. It works on MacOSX just fine, so
>> this is probably a linux only issue. Linux does fork() + exec() so some
>> code in there isn't doing the right things.
>> >
>> > % lldb
>> > (lldb) settings set target.output-path /tmp/out.txt
>> > (lldb) file /bin/ls
>> > Current executable set to '/bin/ls' (x86_64).
>> > (lldb) run /tmp/
>> > (lldb) Process 65933 launched: '/bin/ls' (x86_64)
>> > Process 65933 exited with status = 0 (0x00000000)
>> > (lldb) q
>> >
>> > % cat /tmp/out.txt
>> > launch-B6FwKk
>> > launch-OEyacj
>> > launchd-142.5fRyOk
>> > launchd-175.RBU3HO
>> > launchd-193.Asuh1k
>> > launchd-2701.dSHLJu
>> > launchd-738.U2ACnW
>> > out.txt
>> >
>> > % xcrun lldb
>> > (lldb) settings set target.output-path /tmp/out.txt
>> > (lldb) file /bin/ls
>> > Current executable set to '/bin/ls' (x86_64).
>> > (lldb) run /
>> > (lldb) Process 65940 launched: '/bin/ls' (x86_64)
>> > Process 65940 exited with status = 0 (0x00000000)
>> > (lldb) q
>> > lldb:/tmp % cat /tmp/out.txt
>> > AppleInternal
>> > Applications
>> > Library
>> > Network
>> > SWE
>> > System
>> > Users
>> > Volumes
>> > bin
>> > cores
>> > dev
>> > etc
>> > home
>> > mach_kernel
>> > net
>> >
>> >
>> > So this works on Darwin and needs to be fixed on Linux.
>> >
>> > Greg
>> >
>> > On Mar 25, 2014, at 7:15 AM, Eran Ifrah <eran.ifrah at gmail.com> wrote:
>> >
>> > > Hello Greg,
>> > > Thanks for the input. It still does not work ( I rewrote my terminal
>> code to look similar to lldb's PseudoTerminal, and it is still not working)
>> > >
>> > > To simplify things, I tried some basic things with the command line
>> tool 'lldb':
>> > >
>> > > I created a file ~/.lldbinit with the following content:
>> > >
>> > > eran at eran-linux: ~/llvm/build/bin $ cat ~/.lldbinit
>> > > settings set target.output-path /tmp/dbg.out
>> > > eran at eran-linux: ~/llvm/build/bin $
>> > >
>> > > I then ran lldb while having tail -f /tmp/dbg.out& in another
>> terminal to see if the stdout is being redirected
>> > >
>> > > Now, this is the interesting part:
>> > > In the first run when the file /tmp/dbg.out was empty - the
>> redirection worked (tail showed the debuggee stdout)
>> > > In the second run (and later) - nothing was written to the file
>> > >
>> > > However, if I truncate the file using the below command:
>> > >
>> > > $ > /tmp/dbg.out
>> > >
>> > > and run lldb again - I see the stdout again - but same as before only
>> for the first time (i.e. as long as the file is empty the stdout was
>> redirected)
>> > >
>> > > The next thing I tried was to use a terminal name for redirection:
>> > >
>> > > - Open a new terminal and type `tty` (in my case it gave /dev/pts/19 )
>> > > - Edit the ~/.lldbinit: settings set target.output-path /dev/pts/19
>> > > - Start lldb and verify that the setting is set properly by running:
>> settings show target.output-path
>> > > - Run the program under lldb - the output is not redirected (i.e. it
>> is show in the same console where I ran lldb)
>> > >
>> > > Any ideas?
>> > >
>> > > P.S.
>> > > Sorry if this looks like a voodoo, but this is what I am getting
>> here... ;)
>> > >
>> > > Eran
>> > >
>> > >
>> > >
>> > >
>> > >
>> > > On Mon, Mar 24, 2014 at 6:46 PM, Greg Clayton <gclayton at apple.com>
>> wrote:
>> > > Check out the PseudoTerminal class in
>> trunk/source/Utility/PseudoTerminal.cpp.
>> > >
>> > > See the function named PseudoTerminal::OpenFirstAvailableMaster(...).
>> You must call posix_openpt, grantpt, and unlockpt. I am guessing that
>> because you aren't calling grantpt and granting access to the slave you are
>> failing to be able to use the slave in your child process.
>> > >
>> > > Greg Clayton
>> > >
>> > > On Mar 23, 2014, at 11:32 AM, Eran Ifrah <eran.ifrah at gmail.com>
>> wrote:
>> > >
>> > > > Sure, thanks for the help so far
>> > > > Eran
>> > > >
>> > > >
>> > > > On Sun, Mar 23, 2014 at 8:31 PM, Piotr Rak <piotr.rak at gmail.com>
>> wrote:
>> > > > I am sorry, but nothing obvious comes to me right now, probably
>> you'll need to wait for Monday, when people more familiar with lldb will be
>> able to help you debug this problem.
>> > > >
>> > > >
>> > > > 2014-03-23 16:07 GMT+01:00 Eran Ifrah <eran.ifrah at gmail.com>:
>> > > >
>> > > >
>> > > >
>> > > >
>> > > > On Sun, Mar 23, 2014 at 4:29 PM, Piotr Rak <piotr.rak at gmail.com>
>> wrote:
>> > > > Sorry I misinformed you about posix_spawn - it is not true for
>> Linux and FreeBSD at least, it will use ordinary fork.
>> > > >
>> > > >
>> > > > 2014-03-23 15:23 GMT+01:00 Piotr Rak <piotr.rak at gmail.com>:
>> > > >
>> > > >
>> > > > Hi,
>> > > >
>> > > > 2014-03-23 14:04 GMT+01:00 Eran Ifrah <eran.ifrah at gmail.com>:
>> > > >
>> > > > Thanks for your pointer Piotr. Here is the code I am using to open
>> a pseudo-terminal (there is the UI part, which I left out):
>> > > >
>> > > > char __name[128];
>> > > > memset(__name, 0, sizeof(__name));
>> > > >
>> > > > int master(-1);
>> > > > m_slave = -1;
>> > > > if(openpty(&master, &m_slave, __name, NULL, NULL) != 0)
>> > > > return wxT("");
>> > > >
>> > > > // disable ECHO
>> > > > struct termios termio;
>> > > > tcgetattr(master, &termio);
>> > > > termio.c_lflag = ICANON;
>> > > > termio.c_oflag = ONOCR | ONLRET;
>> > > > tcsetattr(master, TCSANOW, &termio);
>> > > >
>> > > > m_tty = wxString(__name, wxConvUTF8);
>> > > >
>> > > > At the end, m_tty contains a string name (e.g. /dev/pts/19 ).
>> > > > Note that the above code works flawlessly when using it with gdb
>> (i.e. if I pass this "/dev/pts/19" to gdb's switch -tty=/dev/pts/19 I will
>> get all the inferior output/err/input to my internal terminal)
>> > > >
>> > > > However, doing the same with LLDB (using C++ API not the command
>> line , i.e. passing "/dev/pts/19" as an argument to SBTarget::Launch(...))
>> I get nothing as output...
>> > > >
>> > > > Looks sane to me.
>> > > >
>> > > > Also, I am not sure I am following the idea behind replacing the
>> "Launch" function with my own fork(), looking at the code of Launch()
>> suggests that it does more than a simple fork...
>> > > >
>> > > >
>> > > > That was my idea to debug issue if nothing else helps.
>> > > > Or rather bisect on which side it really is, sorry if I did not
>> make it clear...
>> > > > So I was trying suggest replacing SBTarget::Launch with fork,
>> write to child stdout/err, and see if that works alone....
>> > > >
>> > > > SBTarget::Launch is usually actually posix_spawn right now, it uses
>> posix_spawnattr_addopen to open descriptors for your specified paths, and
>> should open it 3 times - given current implementation - even it is just one
>> file.
>> > > >
>> > > > Have you inspected SBProcess and SBError returned by
>> SBTarget::Launch?
>> > > >
>> > > > I checked IsValid() on both and its OK for both. I can actually run
>> "next" Continue etc and seems to be working. Its just that I can't seem to
>> redirect the stdout/err to my own console.
>> > > >
>> > > >
>> > > > Do you see your inferior process is indeed launching, just not
>> displaying anything?
>> > > > Yes, ps -ef shows the debugee
>> > > >
>> > > > Do you have an option to check if those terminals are actually
>> being opened (like examining /proc/<pid>/fd for linux)?
>> > > > The terminal is opened. Like I mentioned in my previous email,
>> using the _same_ code with gdb works
>> > > > I also have a standalone terminal application which I wrote which
>> is also using the same set of classes all of the are working for couple of
>> years now without any problems
>> > > >
>> > > > I also tried this:
>> > > > I typed in my konsole 'tty' and used that as the input for Launch -
>> it also seems to have no effect
>> > > >
>> > > >
>> > > >
>> > > > Good luck,
>> > > > /Piotr
>> > > >
>> > > > Any more hints?
>> > > > Eran
>> > > >
>> > > >
>> > > >
>> > > > On Sat, Mar 22, 2014 at 9:36 PM, Piotr Rak <piotr.rak at gmail.com>
>> wrote:
>> > > > Hi,
>> > > >
>> > > > It should.
>> > > > Have you opened master pseudoterminal like?:
>> > > >
>> > > > int fd = posix_openpt(flags); // open("/dev/ptmx") might work here
>> too but less portable;
>> > > > grantpt(fd);
>> > > > unlockpt(fd);
>> > > >
>> > > > Depending on target you might need some bizarre ioctls here, but
>> assuming you are using Linux/FreeBSD/MacOSX
>> > > > you should be fine.
>> > > >
>> > > > If you had already master pseudo-terminal file descriptor you can
>> skip steps above.
>> > > >
>> > > > You can use ptsname for master file descriptor it will return you
>> name of slave pseudo-terminal for your master.
>> > > > Later you can pass name returned by ptsname(fd) as Launch arguments.
>> > > >
>> > > > If above won't work you can try replacing Launch() call with
>> ordinary fork, and in child process:
>> > > >
>> > > > slavefd = open(slavename, O_RDWR);
>> > > >
>> > > > dup2(0, slavefd);
>> > > > dup2(1, slavefd);
>> > > > dup2(2, slavefd);
>> > > >
>> > > > And see if that works alone for you...
>> > > >
>> > > > Good luck,
>> > > > /Piotr
>> > > >
>> > > >
>> > > > 2014-03-22 19:29 GMT+01:00 Eran Ifrah <eran.ifrah at gmail.com>:
>> > > > Hello,
>> > > >
>> > > > I am trying to use the C++ API with good success so far.
>> > > > I am now at a point where I want to redirect stdin/out/err of the
>> inferior to my application (my application creates a separate pseudo
>> terminal window)
>> > > >
>> > > > Looking at the SBTarget::Launch, I thought that simply passing
>> "/dev/pts/<some-number>" as the 3rd, 4th and 5th argument will do the trick
>> .. well, it did not.
>> > > > I am missing something basic here, can anyone shed some light
>> please? or give an example (better) of how to achieve this?
>> > > >
>> > > > Thanks!
>> > > >
>> > > > --
>> > > > Eran Ifrah
>> > > > Author of codelite, a cross platform open source C/C++ IDE:
>> http://www.codelite.org
>> > > > wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>> > > >
>> > > > _______________________________________________
>> > > > lldb-dev mailing list
>> > > > lldb-dev at cs.uiuc.edu
>> > > > http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>> > > >
>> > > >
>> > > >
>> > > >
>> > > >
>> > > > --
>> > > > Eran Ifrah
>> > > > Author of codelite, a cross platform open source C/C++ IDE:
>> http://www.codelite.org
>> > > > wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>> > > >
>> > > >
>> > > >
>> > > >
>> > > >
>> > > > --
>> > > > Eran Ifrah
>> > > > Author of codelite, a cross platform open source C/C++ IDE:
>> http://www.codelite.org
>> > > > wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>> > > >
>> > > >
>> > > >
>> > > >
>> > > > --
>> > > > Eran Ifrah
>> > > > Author of codelite, a cross platform open source C/C++ IDE:
>> http://www.codelite.org
>> > > > wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>> > > > _______________________________________________
>> > > > lldb-dev mailing list
>> > > > lldb-dev at cs.uiuc.edu
>> > > > http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
>> > >
>> > >
>> > >
>> > >
>> > > --
>> > > Eran Ifrah
>> > > Author of codelite, a cross platform open source C/C++ IDE:
>> http://www.codelite.org
>> > > wxCrafter, a wxWidgets RAD: http://wxcrafter.codelite.org
>> >
>> >
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/lldb-dev/attachments/20140326/7efe49d2/attachment.html>
More information about the lldb-dev
mailing list