Hi all,
Now that I think about it, being able to continue the process after it hits
a SIGSEGV is very important for Android because the ART runtime (and
dalvik?) use SIGSEGV to detect and generate NullPointerExceptions in Java.
Ideally, on Android, if we see a SIGSEGV at a PC that belongs to jit code
we should probably just transparently continue the process.
Vince
On Wed, May 20, 2015 at 10:01 AM, Eugene Birukov <eugen...@hotmail.com>
wrote:
> Thank you!
>
> I have another concern about this file: why do we use numerical constants
> like 1,2,3,... here instead of symbolic SIGHUP,SIGINT,SIGQUIT,...?
> Linux signal(7) man page gives 3 different values for some signals on
> different platforms. For example, SIGUSR1 could be 30, 10, or 16.
>
> Standard signals
> Linux supports the standard signals listed below. Several signal
> numbers are architecture-dependent, as
> indicated in the "Value" column. (Where three values are given,
> the first one is usually valid for alpha
> and sparc, the middle one for x86, arm, and most other
> architectures, and the last one for mips. (Values
> for parisc are not shown; see the Linux kernel source for
> signal numbering on that architecture.) A -
> denotes that a signal is absent on the corresponding architecture.)
> First the signals described in the original POSIX.1-1990 standard.
> Signal Value Action Comment
>
> ──────────────────────────────────────────────────────────────────────
> SIGHUP 1 Term Hangup detected on controlling
> terminal
> or death of controlling process
> SIGINT 2 Term Interrupt from keyboard
> SIGQUIT 3 Core Quit from keyboard
> SIGILL 4 Core Illegal Instruction
> SIGABRT 6 Core Abort signal from abort(3)
> SIGFPE 8 Core Floating point exception
> SIGKILL 9 Term Kill signal
> SIGSEGV 11 Core Invalid memory reference
> SIGPIPE 13 Term Broken pipe: write to pipe with no
> readers
> SIGALRM 14 Term Timer signal from alarm(2)
> SIGTERM 15 Term Termination signal
> SIGUSR1 30,10,16 Term User-defined signal 1
> SIGUSR2 31,12,17 Term User-defined signal 2
> SIGCHLD 20,17,18 Ign Child stopped or terminated
> ...
>
> Eugene
>
> > From: lab...@google.com
> > Date: Wed, 20 May 2015 11:43:20 +0100
> > Subject: Re: [lldb-dev] LLDB 3.7 swallows real-time signals
> > To: eugen...@hotmail.com
> > CC: lldb-dev@cs.uiuc.edu
>
> >
> > Hello Eugene,
> >
> > thanks for diagnosing this issue. I will commit something similar to
> > LLDB shortly.
> >
> > cheers,
> > pl
> >
> >
> > On 19 May 2015 at 19:52, Eugene Birukov <eugen...@hotmail.com> wrote:
> > > Hello,
> > >
> > > I debugged signal processing a bit, and I think that the right solution
> > > would be just to add these signals to the list of known signals. I.e.
> in
> > > LinuxSignals.cpp:
> > >
> > > void
> > > LinuxSignals::Reset()
> > > {
> > > m_signals.clear();
> > > AddSignal (1, "SIGHUP", "HUP", false, true , true ,
> > > "hangup");
> > > AddSignal (2, "SIGINT", "INT", true , true , true ,
> > > "interrupt");
> > > AddSignal (3, "SIGQUIT", "QUIT", false, true , true , "quit");
> > > AddSignal (4, "SIGILL", "ILL", false, true , true , "illegal
> > > instruction");
> > > AddSignal (5, "SIGTRAP", "TRAP", true , true , true , "trace
> > > trap (not reset when caught)");
> > > AddSignal (6, "SIGABRT", "ABRT", false, true , true ,
> > > "abort()");
> > > AddSignal (6, "SIGIOT", "IOT", false, true , true , "IOT
> > > trap");
> > > AddSignal (7, "SIGBUS", "BUS", false, true , true , "bus
> > > error");
> > > AddSignal (8, "SIGFPE", "FPE", false, true , true ,
> > > "floating point exception");
> > > AddSignal (9, "SIGKILL", "KILL", false, true , true , "kill");
> > > AddSignal (10, "SIGUSR1", "USR1", false, true , true , "user
> > > defined signal 1");
> > > AddSignal (11, "SIGSEGV", "SEGV", false, true , true ,
> > > "segmentation violation");
> > > AddSignal (12, "SIGUSR2", "USR2", false, true , true , "user
> > > defined signal 2");
> > > AddSignal (13, "SIGPIPE", "PIPE", false, true , true , "write
> > > to pipe with reading end closed");
> > > AddSignal (14, "SIGALRM", "ALRM", false, false, false,
> > > "alarm");
> > > AddSignal (15, "SIGTERM", "TERM", false, true , true ,
> > > "termination requested");
> > > AddSignal (16, "SIGSTKFLT", "STKFLT", false, true , true , "stack
> > > fault");
> > > AddSignal (16, "SIGCLD", "CLD", false, false, true , "same as
> > > SIGCHLD");
> > > AddSignal (17, "SIGCHLD", "CHLD", false, false, true , "child
> > > status has changed");
> > > AddSignal (18, "SIGCONT", "CONT", false, true , true , "process
> > > continue");
> > > AddSignal (19, "SIGSTOP", "STOP", true , true , true , "process
> > > stop");
> > > AddSignal (20, "SIGTSTP", "TSTP", false, true , true , "tty
> > > stop");
> > > AddSignal (21, "SIGTTIN", "TTIN", false, true , true ,
> > > "background tty read");
> > > AddSignal (22, "SIGTTOU", "TTOU", false, true , true ,
> > > "background tty write");
> > > AddSignal (23, "SIGURG", "URG", false, true , true , "urgent
> > > data on socket");
> > > AddSignal (24, "SIGXCPU", "XCPU", false, true , true , "CPU
> > > resource exceeded");
> > > AddSignal (25, "SIGXFSZ", "XFSZ", false, true , true , "file
> > > size limit exceeded");
> > > AddSignal (26, "SIGVTALRM", "VTALRM", false, true , true , "virtual
> > > time alarm");
> > > AddSignal (27, "SIGPROF", "PROF", false, false, false,
> > > "profiling time alarm");
> > > AddSignal (28, "SIGWINCH", "WINCH", false, true , true , "window
> > > size changes");
> > > AddSignal (29, "SIGPOLL", "POLL", false, true , true ,
> > > "pollable event");
> > > AddSignal (29, "SIGIO", "IO", false, true , true ,
> > > "input/output ready");
> > > AddSignal (30, "SIGPWR", "PWR", false, true , true , "power
> > > failure");
> > > AddSignal (31, "SIGSYS", "SYS", false, true , true , "invalid
> > > system call");
> > >
> > > // Add real-time signals
> > > for (int rtsig = SIGRTMIN + 1; rtsig < SIGRTMAX; ++rtsig)
> > > {
> > > char signame[16];
> > > char sigdescr[64];
> > > ::snprintf(signame, sizeof(signame), "SIG%d", rtsig);
> > > ::snprintf(sigdescr, sizeof(sigdescr), "Real-time event %d", rtsig);
> > > AddSignal (rtsig, signame, signame, false, true, true, sigdescr);
> > > }
> > > }
> > >
> > > Thanks,
> > > Eugene
> > > ________________________________
> > > From: eugen...@hotmail.com
> > > To: lldb-dev@cs.uiuc.edu
> > > Date: Tue, 19 May 2015 10:22:14 -0700
> > > Subject: [lldb-dev] LLDB 3.7 swallows real-time signals
> > >
> > >
> > > Hi,
> > >
> > > I have a simple program that uses real-time signals on Linux Ubuntu
> 14.04:
> > >
> > >
> > > $ cat rt.cpp
> > > #include <iostream>
> > > #include <sys/mman.h>
> > > #include <signal.h>
> > > #include <assert.h>
> > > #include <sys/types.h>
> > > #include <unistd.h>
> > >
> > > void handler(int sig, siginfo_t* info, void* context)
> > > {
> > > std::cout << "signal " << sig << " received with value " <<
> > > info->si_value.sival_in << "\n";
> > > }
> > > int main()
> > > {
> > > int signo = SIGRTMIN + 1;
> > > if (SIGRTMAX > SIGRTMIN)
> > > {
> > > struct sigaction action;
> > > action.sa_sigaction = handler;
> > > action.sa_flags = SA_SIGINFO;
> > > sigaction(signo, &action, NULL);
> > > for (int i = 0; i < 3; ++i)
> > > {
> > > sigval value;
> > > value.sival_int = i + 10;
> > > sigqueue(getpid(), signo, value);
> > > }
> > > }
> > > else
> > > {
> > > std::cerr << "real-time signals not supported";
> > > }
> > > }
> > >
> > > This program works correctly standalone. GDB is capable of
> intercepting this
> > > signal and continue. LLDB-3.6 that I installed using apt-get does not
> > > intercept the signal but the program still receives it. But LLDB 3.7
> that I
> > > built from sources from http://llvm.org/svn/llvm-project/lldb/trunk
> simply
> > > swallows the signals. I think GDB behavior is the best option, but I
> could
> > > live with 3.6 behavior.
> > >
> > > Is this a known problem? Is there a workaround or fix I can apply
> locally?
> > >
> > > Thanks,
> > > Eugene
> > >
> > > $ cat rt.cpp
> > > #include <iostream>
> > > #include <sys/mman.h>
> > > #include <signal.h>
> > > #include <assert.h>
> > > #include <sys/types.h>
> > > #include <unistd.h>
> > >
> > > void handler(int sig, siginfo_t* info, void* context)
> > > {
> > > std::cout << "signal " << sig << " received with value " <<
> > > info->si_value.sival_in << "\n";
> > > }
> > >
> > > int main()
> > > {
> > > int signo = SIGRTMIN + 1;
> > > if (SIGRTMAX > SIGRTMIN)
> > > {
> > > struct sigaction action;
> > > action.sa_sigaction = handler;
> > > action.sa_flags = SA_SIGINFO;
> > > sigaction(signo, &action, NULL);
> > > for (int i = 0; i < 3; ++i)
> > > {
> > > sigval value;
> > > value.sival_int = i + 10;
> > > sigqueue(getpid(), signo, value);
> > > }
> > > }
> > > else
> > > {
> > > std::cerr << "real-time signals are not supported";
> > > }
> > > }
> > >
> > > $ ./rt
> > > signal 35 received with value 10
> > > signal 35 received with value 11
> > > signal 35 received with value 12
> > >
> > > $ ~/llvm/bin/lldb ./rt
> > > (lldb) target create "./rt"
> > > Current executable set to './rt' (x86_64).
> > > (lldb) pr lau
> > > Process 18697 launched: './rt' (x86_64)
> > > Process 18697 exited with status = 0 (0x00000000)
> > > (lldb) q
> > >
> > > $ lldb-3.6 ./rt
> > > (lldb) target create "./rt"
> > > Current executable set to './rt' (x86_64).
> > > (lldb) pr lau
> > > Process 18674 launching
> > > Process 18674 launched: './rt' (x86_64)
> > > signal 35 received with value 10
> > > signal 35 received with value 11
> > > signal 35 received with value 12
> > > Process 18674 exited with status = 0 (0x00000000)
> > > (lldb) q
> > >
> > > $ gdb --quiet ./rt
> > > Reading symbols from ./rt...done.
> > > (gdb) r
> > > Starting program: /home/eugene/Z/tmp/rt
> > > Program received signal SIG35, Real-time event 35.
> > > 0x00007ffff722cfc4 in __sigqueue (pid=18662, sig=35, val=...) at
> > > ../sysdeps/unix/sysv/linux/sigqueue.c:46
> > > 46 ../sysdeps/unix/sysv/linux/sigqueue.c: No such file or directory.
> > > (gdb) c
> > > Continuing.
> > > signal 35 received with value 10
> > > Program received signal SIG35, Real-time event 35.
> > > 0x00007ffff722cfc4 in __sigqueue (pid=18662, sig=35, val=...) at
> > > ../sysdeps/unix/sysv/linux/sigqueue.c:46
> > > 46 in ../sysdeps/unix/sysv/linux/sigqueue.c
> > > (gdb) c
> > > Continuing.
> > > signal 35 received with value 11
> > > Program received signal SIG35, Real-time event 35.
> > > 0x00007ffff722cfc4 in __sigqueue (pid=18662, sig=35, val=...) at
> > > ../sysdeps/unix/sysv/linux/sigqueue.c:46
> > > 46 in ../sysdeps/unix/sysv/linux/sigqueue.c
> > > (gdb) c
> > > Continuing.
> > > signal 35 received with value 12
> > > [Inferior 1 (process 18662) exited normally]
> > > (gdb) q
> > >
> > >
> > > _______________________________________________ lldb-dev mailing list
> > > lldb-dev@cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
> > >
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> > >
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