[#1279 4/4] Generate core dump in libscope.so

[michalbiesek]

This Pull request required merging the following Pull Requests:

• [#1279 1/4] Update libunwind version #1294
• [#1279 2/4] Extend contrib code with coredumper #1295
• [#1279 3/4] Integrate coredumper with scope codebase #1296

In this Pull Request following changes are introduced:

• extending the possible values of SCOPE_ERROR_SIGNAL_HANDLER
• generates the coredump in signal handler based on coredump or full value
• core dump will be generated in /tmp/scope_core.<PID> path

[michalbiesek]

@jrcheli
This is last series of patch, to test it what You can do:

# checkout this branch
git fetch origin
git checkout origin/feat-1279-coredumper-scope-lib -b local_test
# build AppScope

# Start scoping a process (preferably on Your host machine)
sudo SCOPE_ERROR_SIGNAL_HANDLER=full ./bin/linux/x86_64/scope attach --userconfig ./conf/scope.yml <process_name>
# send SIGSEGV signal to the scoped process
kill -SIGSEGV <PID_of_scoped_process>
# the coredump should be available in '/tmp/scope_core.<pid>'
#To run core dump analysis
gdb /usr/bin/redis-server /tmp/scope.<pid>
You should be able at least see information about stack trace using bt

Note: this only works on glibc based distro

Example (redis):
On first terminal

redis-server -p 6780

On second terminal

# 8121124 is redis PID
sudo SCOPE_ERROR_SIGNAL_HANDLER=full ./bin/linux/x86_64/scope attach --userconfig ./conf/scope.yml 812124
sudo kill -SIGSEGV 812124
gdb /usr/bin/redis-server  /tmp/scope_core.812124

[jrcheli]

Looks great. I verified that signals (here SIGFPE) generated within a scoped process works well too...

// gcc -g -o backtrace backtrace.c

#include <stdio.h>
#include <unistd.h>

int
main(void)
{
    printf("Running backtrace\n");
    sleep (5);
    int a = 1;
    int b = 0;
    float val = a/b;

    printf("Exiting backtrace\n");
    return 0;
}

When ran LD_PRELOAD=libscope.so SCOPE_ERROR_SIGNAL_HANDLER=full ./backtrace, I saw nice stacktrace output in /tmp/scope.log, and a perfectly useable core file ( /tmp/scope. ). Everything here works as advertised. Merging!