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Implementation:
C/C++ handling:
==============
we change /proc/sys/kernel/core_pattern to invoke abrtd helper to save
the coredump of crashing app:
* helper source code: http://git.fedorahosted.org/git/abrt.git?p=abrt.git;a=blob_plain;f=src/Hooks/abrt-hook-python.cpp
the code responsible for this:
#define CORE_PATTERN "|/usr/libexec/abrt-hook-ccpp" "/var/spool/abrt" %p %s %u"
ofstream fOutCorePattern;
fOutCorePattern.open(CORE_PATTERN_IFACE);
if (fOutCorePattern.is_open())
{
fOutCorePattern << CORE_PATTERN << endl;
fOutCorePattern.close();
}
%p - pid
%s - signal
%u - uid
when some crash occurs abrt-hook-ccpp is invoked to store the coredump and some other info
read from /proc/<pid>/:
executable:
char buf[sizeof("/proc/%u/exe") + sizeof(int)*3];
sprintf(buf, "/proc/%u/exe", (int)pid);
readlink(buf);
cmdline:
char path[sizeof("/proc/%u/cmdline") + sizeof(int)*3];
sprintf(path, "/proc/%u/cmdline", (int)pid);
both is saved to file in /var/spool/abrt/ccpp-<time>-<pid> readable
only by owner the crashed process:
int fd = open(pPath, O_WRONLY | O_TRUNC | O_CREAT, 0666);
if(fd){
do {
n = write(fd, buf, count);
} while (n < 0 && errno == EINTR);
}
when the hook is done it signalize the daemon (be removing the lock file) and
daemon process the written info and saves some aditional information:
analyzer : name of the plugin used to analyze the crash (ccpp, python)
component : source package name
description : package description (will be removed soon)
kernel : kernel version
release : Fedora release string
uid : uid of the owner of the crashed app
architecture : architecture (i386, x86_64,etc)
package : package name
reason : e.g "Process was terminated by signal 11 (Segmentation fault)"
time : unix time of the crash
2. send dbus signal (broadcast) about new crash, this signal contains two informations:
1. uid of the app owner
2. package name
This is all what happens when some app crashes, the next step is to process
the coredump and extract the backtrace. This is done on user demand by calling
getReport(UUID) method or automatically if admin sets it in /etc/abrt/abrt.conf
* UUID is unique id of the crash in the database, every user is allowed to see only
his own crashes or kerneloops crashes
- see http://git.fedorahosted.org/git/abrt.git?p=abrt.git;a=blob;f=lib/Plugins/SQLite3.cpp line 394
for more details
1. processing coredump:
a) determine if the crashed binary belongs to some installed package
if it does then:
b) daemon tries to install the debuginfo issuing this command:
execlp("abrt-action-install-debuginfo", "abrt-action-install-debuginfo", coredump, tempdir, debuginfo_dirs, NULL);
abrt-action-install-debuginfo is a shell script using elfutils to get build-ids from coredump and the use
"yum provides" and "yumdownloader" to determine and download the missing debuginfo packages
* script source code: http://git.fedorahosted.org/git/abrt.git?p=abrt.git;a=blob_plain;f=src/Daemon/abrt-action-install-debuginfo
c) run gdb and get backtrace from coredump:
see http://git.fedorahosted.org/git/abrt.git?p=abrt.git;a=blob_plain;f=lib/Plugins/CCpp.cpp line 260
- gdb is run with the same privileges as the crashed app (setregid, setreuid)
d) BT is saved to same directory where the coredump is
Once the backtrace is processed all data from the /var/spool/abrt/ccpp-<time>-<pid> is sent
over dbus to the client and then user can edit the backtrace. When user is happy about
the report and command the client (gui, tui) to send the it, the client sends the data back
to the daemon calling the Report(data) method over the dbus. The actual reporting is done by
the respective plugin which is loaded in daemon.
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