Re: [PATCH tracing/kprobes v4] perf: Add perf probe subcommand for kprobe-event setup helper
From: Frédéric Weisbecker
Date: Mon Oct 12 2009 - 06:32:51 EST
2009/10/8 Masami Hiramatsu <mhiramat@xxxxxxxxxx>:
> Add perf probe subcommand for kprobe-event setup helper to perf command.
> This allows user to define kprobe events by C expressions (C line numbers,
> C function names, and C local variables).
>
> Usage
> -----
> perf probe [<options>] -P 'PROBEDEF' [-P 'PROBEDEF' ...]
>
> -k, --vmlinux <file> vmlinux/module pathname
> -P, --probe <p|r:[GRP/]NAME FUNC[+OFFS][@SRC]|@SRC:LINE [ARG ...]>
> probe point definition, where
> p: kprobe probe
> r: kretprobe probe
> GRP: Group name (optional)
> NAME: Event name
> FUNC: Function name
> OFFS: Offset from function entry (in byte)
> SRC: Source code path
> LINE: Line number
> ARG: Probe argument (local variable name or
> kprobe-tracer argument format is supported.)
>
> Changes in v4:
> - Add _GNU_SOURCE macro for strndup().
>
> Changes in v3:
> - Remove -r option because perf always be used for online kernel.
> - Check malloc/calloc results.
>
> Changes in v2:
> - Check synthesized string length.
> - Rename perf kprobe to perf probe.
> - Use spaces for separator and update usage comment.
> - Check error paths in parse_probepoint().
> - Check optimized-out variables.
>
> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Mike Galbraith <efault@xxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
> Cc: Jim Keniston <jkenisto@xxxxxxxxxx>
> Cc: Frank Ch. Eigler <fche@xxxxxxxxxx>
> ---
>
[...]
> +/* Default vmlinux search paths */
> +#define NR_SEARCH_PATH 3
> +const char *default_search_path[NR_SEARCH_PATH] = {
> +"/lib/modules/%s/build/vmlinux", /* Custom build kernel */
> +"/usr/lib/debug/lib/modules/%s/vmlinux", /* Red Hat debuginfo */
> +"/boot/vmlinux-debug-%s", /* Ubuntu */
> +};
[...]
> +static int open_default_vmlinux(void)
> +{
> + struct utsname uts;
> + char fname[MAX_PATH_LEN];
> + int fd, ret, i;
> +
> + ret = uname(&uts);
> + if (ret) {
> + debug("uname() failed.\n");
> + return -errno;
> + }
> + session.release = uts.release;
> + for (i = 0; i < NR_SEARCH_PATH; i++) {
> + ret = snprintf(fname, MAX_PATH_LEN,
> + default_search_path[i], session.release);
> + if (ret >= MAX_PATH_LEN || ret < 0) {
> + debug("Filename(%d,%s) is too long.\n", i, uts.release);
> + errno = E2BIG;
> + return -E2BIG;
> + }
> + debug("try to open %s\n", fname);
> + fd = open(fname, O_RDONLY);
> + if (fd >= 0)
> + break;
> + }
> + return fd;
> +}
We have a kind of kernel path finder already inside perf. It might be
encapsulated
inside the load_kernel() helper, I don't remember exactly.
It would be better to make use of such centralized and already
existing facility.
The patchset looks good. I'll apply and push it soon.
Thanks a lot!
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