On Fri, Nov 13, 2020 at 04:08:03PM -0800, Ian Rogers wrote: > To ensure the stack frames are on the stack tail calls optimizations > need to be inhibited. If your compiler supports an attribute use it, > otherwise use an asm volatile barrier. > > The barrier fix was suggested here: > https://lore.kernel.org/lkml/20201028081123.gt2...@hirez.programming.kicks-ass.net/ > > Fixes: 9ae1e990f1ab ("perf tools: Remove broken __no_tail_call > attribute")
missing SOB LGTM and test is passing for me ;-) Tested-by: Jiri Olsa <jo...@redhat.com> jirka > --- > tools/perf/tests/dwarf-unwind.c | 39 +++++++++++++++++++++++++++------ > 1 file changed, 32 insertions(+), 7 deletions(-) > > diff --git a/tools/perf/tests/dwarf-unwind.c b/tools/perf/tests/dwarf-unwind.c > index 83638097c3bc..c8ce86bceea8 100644 > --- a/tools/perf/tests/dwarf-unwind.c > +++ b/tools/perf/tests/dwarf-unwind.c > @@ -24,6 +24,23 @@ > /* For bsearch. We try to unwind functions in shared object. */ > #include <stdlib.h> > > +/* > + * The test will assert frames are on the stack but tail call optimizations > lose > + * the frame of the caller. Clang can disable this optimization on a called > + * function but GCC currently (11/2020) lacks this attribute. The barrier is > + * used to inhibit tail calls in these cases. > + */ > +#ifdef __has_attribute > +#if __has_attribute(disable_tail_calls) > +#define NO_TAIL_CALL_ATTRIBUTE __attribute__((disable_tail_calls)) > +#define NO_TAIL_CALL_BARRIER > +#endif > +#endif > +#ifndef NO_TAIL_CALL_ATTRIBUTE > +#define NO_TAIL_CALL_ATTRIBUTE > +#define NO_TAIL_CALL_BARRIER __asm__ __volatile__("" : : : "memory"); > +#endif > + > static int mmap_handler(struct perf_tool *tool __maybe_unused, > union perf_event *event, > struct perf_sample *sample, > @@ -95,7 +112,7 @@ static int unwind_entry(struct unwind_entry *entry, void > *arg) > return strcmp((const char *) symbol, funcs[idx]); > } > > -noinline int test_dwarf_unwind__thread(struct thread *thread) > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__thread(struct thread > *thread) > { > struct perf_sample sample; > unsigned long cnt = 0; > @@ -126,7 +143,7 @@ noinline int test_dwarf_unwind__thread(struct thread > *thread) > > static int global_unwind_retval = -INT_MAX; > > -noinline int test_dwarf_unwind__compare(void *p1, void *p2) > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__compare(void *p1, > void *p2) > { > /* Any possible value should be 'thread' */ > struct thread *thread = *(struct thread **)p1; > @@ -145,7 +162,7 @@ noinline int test_dwarf_unwind__compare(void *p1, void > *p2) > return p1 - p2; > } > > -noinline int test_dwarf_unwind__krava_3(struct thread *thread) > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_3(struct thread > *thread) > { > struct thread *array[2] = {thread, thread}; > void *fp = &bsearch; > @@ -164,14 +181,22 @@ noinline int test_dwarf_unwind__krava_3(struct thread > *thread) > return global_unwind_retval; > } > > -noinline int test_dwarf_unwind__krava_2(struct thread *thread) > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_2(struct thread > *thread) > { > - return test_dwarf_unwind__krava_3(thread); > + int ret; > + > + ret = test_dwarf_unwind__krava_3(thread); > + NO_TAIL_CALL_BARRIER; > + return ret; > } > > -noinline int test_dwarf_unwind__krava_1(struct thread *thread) > +NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_1(struct thread > *thread) > { > - return test_dwarf_unwind__krava_2(thread); > + int ret; > + > + ret = test_dwarf_unwind__krava_2(thread); > + NO_TAIL_CALL_BARRIER; > + return ret; > } > > int test__dwarf_unwind(struct test *test __maybe_unused, int subtest > __maybe_unused) > -- > 2.29.2.299.gdc1121823c-goog >