On Mon, Feb 09, 2015 at 11:13:51PM +0000, Rui Paulo wrote:
> Author: rpaulo
> Date: Mon Feb 9 23:13:50 2015
> New Revision: 278479
> URL: https://svnweb.freebsd.org/changeset/base/278479
>
> Log:
> Notify devd(8) when a process crashed.
>
> This change implements a notification (via devctl) to userland when
> the kernel produces coredumps after a process has crashed.
> devd can then run a specific command to produce a human readable crash
> report. The command is most usually a helper that runs gdb/lldb
> commands on the file/coredump pair. It's possible to use this
> functionality for implementing automatic generation of crash reports.
>
> devd(8) will be notified of the full path of the binary that crashed and
> the full path of the coredump file.
Arguably, there should be a knob, probably sysctl, to turn the
functionality off. I definitely do not want this on crash boxes used for
userspace debugging. Even despite the example handler is inactive.
>
> Modified:
> head/etc/devd.conf
> head/sys/kern/kern_sig.c
>
> Modified: head/etc/devd.conf
> ==============================================================================
> --- head/etc/devd.conf Mon Feb 9 23:04:30 2015 (r278478)
> +++ head/etc/devd.conf Mon Feb 9 23:13:50 2015 (r278479)
> @@ -325,4 +325,16 @@ notify 100 {
> action "/usr/sbin/automount -c";
> };
>
> +# Handle userland coredumps.
> +# This commented out handler makes it possible to run an
> +# automated debugging session after the core dump is generated.
> +# Replace action with a proper coredump handler, but be aware that
> +# it will run with elevated privileges.
> +notify 10 {
> + match "system" "kernel";
> + match "subsystem" "signal";
> + match "type" "coredump";
> + action "logger $comm $core";
> +};
> +
> */
>
> Modified: head/sys/kern/kern_sig.c
> ==============================================================================
> --- head/sys/kern/kern_sig.c Mon Feb 9 23:04:30 2015 (r278478)
> +++ head/sys/kern/kern_sig.c Mon Feb 9 23:13:50 2015 (r278479)
> @@ -46,6 +46,7 @@ __FBSDID("$FreeBSD$");
> #include <sys/signalvar.h>
> #include <sys/vnode.h>
> #include <sys/acct.h>
> +#include <sys/bus.h>
> #include <sys/capsicum.h>
> #include <sys/condvar.h>
> #include <sys/event.h>
> @@ -3237,6 +3238,9 @@ coredump(struct thread *td)
> void *rl_cookie;
> off_t limit;
> int compress;
> + char *data = NULL;
> + size_t len;
> + char *fullpath, *freepath = NULL;
>
> #ifdef COMPRESS_USER_CORES
> compress = compress_user_cores;
> @@ -3322,9 +3326,36 @@ close:
> error1 = vn_close(vp, FWRITE, cred, td);
> if (error == 0)
> error = error1;
> + else
> + goto out;
> + /*
> + * Notify the userland helper that a process triggered a core dump.
> + * This allows the helper to run an automated debugging session.
> + */
> + len = MAXPATHLEN * 2 + 5 /* comm= */ + 5 /* core= */ + 1;
It is much cleaner to use static const char arrays for the names,
and use sizeof() - 1 instead of hard-coding commented constants.
> + data = malloc(len, M_TEMP, M_NOWAIT);
Why is this allocation M_NOWAIT ?
> + if (data == NULL)
> + goto out;
> + if (vn_fullpath_global(td, p->p_textvp, &fullpath, &freepath) != 0)
> + goto out;
> + snprintf(data, len, "comm=%s", fullpath);
> + if (freepath != NULL) {
> + free(freepath, M_TEMP);
Checks for NULL pointer before free(9) are redundant.
> + freepath = NULL;
> + }
> + if (vn_fullpath_global(td, vp, &fullpath, &freepath) != 0)
> + goto out;
> + snprintf(data, len, "%s core=%s", data, fullpath);
This is weird, and highly depends on the implementation details, supplying
the same string as target and source. IMO strcat(9) is enough there.
> + devctl_notify("kernel", "signal", "coredump", data);
> + free(name, M_TEMP);
> +out:
> #ifdef AUDIT
> audit_proc_coredump(td, name, error);
> #endif
> + if (freepath != NULL)
> + free(freepath, M_TEMP);
> + if (data != NULL)
> + free(data, M_TEMP);
> free(name, M_TEMP);
> return (error);
> }
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