[PATCH] sample/hw_breakpoint: avoid sample hw_breakpoint recursion for arm/arm64

[wangxu]

From: Wang Xu <wangx...@huawei.com>

For x86/ppc, hw_breakpoint is triggered after the instruction is
executed.

For arm/arm64, which is triggered before the instruction executed.
Arm/arm64 skips the instruction by using single step. But it only
supports default overflow_handler.

This patch provides a chance to avoid sample hw_breakpoint recursion
for arm/arm64 by adding 'struct perf_event_attr.bp_step'.

Signed-off-by: Wang Xu <wangx...@huawei.com>
---
 include/linux/perf_event.h              | 3 +++
 include/uapi/linux/perf_event.h         | 3 ++-
 samples/hw_breakpoint/data_breakpoint.c | 1 +
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 61448c1..f270eb7 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1024,6 +1024,9 @@ extern int perf_event_output(struct perf_event *event,
                return true;
        if (unlikely(event->overflow_handler == perf_event_output_backward))
                return true;
+       /* avoid sample hw_breakpoint recursion */
+       if (unlikely(event->attr.bp_step))
+               return true;
        return false;
 }
 
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index bb7b271..95b81c2 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -375,7 +375,8 @@ struct perf_event_attr {
                                ksymbol        :  1, /* include ksymbol events 
*/
                                bpf_event      :  1, /* include bpf events */
                                aux_output     :  1, /* generate AUX records 
instead of events */
-                               __reserved_1   : 32;
+                               bp_step        :  1,
+                               __reserved_1   : 31;
 
        union {
                __u32           wakeup_events;    /* wakeup every n events */
diff --git a/samples/hw_breakpoint/data_breakpoint.c 
b/samples/hw_breakpoint/data_breakpoint.c
index c585047..9fe1351 100644
--- a/samples/hw_breakpoint/data_breakpoint.c
+++ b/samples/hw_breakpoint/data_breakpoint.c
@@ -46,6 +46,7 @@ static int __init hw_break_module_init(void)
        attr.bp_addr = kallsyms_lookup_name(ksym_name);
        attr.bp_len = HW_BREAKPOINT_LEN_4;
        attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
+       attr.bp_step = true;
 
        sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler, 
NULL);
        if (IS_ERR((void __force *)sample_hbp)) {
-- 
1.8.5.6