Commit 35b6f55a authored Feb 22, 2017 by Naveen N. Rao Committed by Arnaldo Carvalho de Melo Mar 03, 2017

trace/kprobes: Allow return probes with offsets and absolute addresses



Since the kernel includes many non-global functions with same names, we
will need to use offsets from other symbols (typically _text/_stext) or
absolute addresses to place return probes on specific functions. Also,
the core register_kretprobe() API never forbid use of offsets or
absolute addresses with kretprobes.

Allow its use with the trace infrastructure. To distinguish kernels that
support this, update ftrace README to explicitly call this out.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/183e7ce2921a08c9c755ee9a5da3134febc6695b.1487770934.git.naveen.n.rao@linux.vnet.ibm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 90ec5e89

kernel/trace/trace.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -4355,6 +4355,7 @@ static const char readme_msg[] =
		"\t -:[<group>/]<event>\n"
		#ifdef CONFIG_KPROBE_EVENTS
		"\t place: [<module>:]<symbol>[+<offset>]\|<memaddr>\n"
		"place (kretprobe): [<module>:]<symbol>[+<offset>]\|<memaddr>\n"
		#endif
		#ifdef CONFIG_UPROBE_EVENTS
		"\t place: <path>:<offset>\n"

kernel/trace/trace_kprobe.c

+0 −8

Original line number	Diff line number	Diff line
		@@ -680,10 +680,6 @@ static int create_trace_kprobe(int argc, char **argv)
		return -EINVAL;
		}
		if (isdigit(argv[1][0])) {
		if (is_return) {
		pr_info("Return probe point must be a symbol.\n");
		return -EINVAL;
		}
		/* an address specified */
		ret = kstrtoul(&argv[1][0], 0, (unsigned long *)&addr);
		if (ret) {
		@@ -699,10 +695,6 @@ static int create_trace_kprobe(int argc, char **argv)
		pr_info("Failed to parse symbol.\n");
		return ret;
		}
		if (offset && is_return) {
		pr_info("Return probe must be used without offset.\n");
		return -EINVAL;
		}
		}
		argc -= 2; argv += 2;

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