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Subject[PATCH 37/38] perf probe: Fix build when DWARF support libraries not present
Date
From: Arnaldo Carvalho de Melo <acme@redhat.com>

On a freshly installed system, after libelf-dev is installed we get:

CC /tmp/build/perf/util/probe-event.o
util/probe-event.c: In function ‘try_to_find_probe_trace_events’:
util/probe-event.c:753:46: error: unused parameter ‘target’ [-Werror=unused-parameter]
int max_tevs __maybe_unused, const char *target)
^
CC /tmp/build/perf/util/cgroup.o
util/probe-event.c: At top level:
util/probe-event.c:193:12: error: ‘get_text_start_address’ defined but not used [-Werror=unused-function]
static int get_text_start_address(const char *exec, unsigned long *address)
^
cc1: all warnings being treated as errors
make[1]: *** [/tmp/build/perf/util/probe-event.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make: *** [install] Error 2

Fix it by enclosing functions only used when those libraries are installed
under the suitable preprocessor define and using __maybe_unused to a function
that is only built when DWARF support is disabled.

Problem introduced in this changeset:

commit fb7345bbf7fad9bf72ef63a19c707970b9685812
Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Date: Thu Dec 26 05:41:53 2013 +0000

perf probe: Support basic dwarf-based operations on uprobe events

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-73kc2fopt81517hrdgdra18o@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/probe-event.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 86ed8580c3cb..a4ee6b4a840f 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -172,6 +172,7 @@ const char *kernel_get_module_path(const char *module)
return (dso) ? dso->long_name : NULL;
}

+#ifdef HAVE_DWARF_SUPPORT
/* Copied from unwind.c */
static Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
GElf_Shdr *shp, const char *name)
@@ -217,6 +218,7 @@ out:
elf_end(elf);
return ret;
}
+#endif

static int init_user_exec(void)
{
@@ -750,7 +752,8 @@ static int kprobe_convert_to_perf_probe(struct probe_trace_point *tp,

static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
struct probe_trace_event **tevs __maybe_unused,
- int max_tevs __maybe_unused, const char *target)
+ int max_tevs __maybe_unused,
+ const char *target __maybe_unused)
{
if (perf_probe_event_need_dwarf(pev)) {
pr_warning("Debuginfo-analysis is not supported.\n");
--
1.8.1.4
--
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