[PATCH V4 04/13] kprobes: Add perf ksymbol events for kprobe insn pages

Adrian Hunter
2020-03-04T09:07:40Z

Symbols are needed for tools to describe instruction addresses. Pages
allocated for kprobe's purposes need symbols to be created for them.
Add such symbols to be visible via perf ksymbol events.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
---
include/uapi/linux/perf_event.h | 5 +++++
kernel/kprobes.c | 12 ++++++++++++
2 files changed, 17 insertions(+)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index bae9e9d2d897..9b38ac04c110 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -1031,6 +1031,11 @@ enum perf_event_type {
enum perf_record_ksymbol_type {
PERF_RECORD_KSYMBOL_TYPE_UNKNOWN = 0,
PERF_RECORD_KSYMBOL_TYPE_BPF = 1,
+ /*
+ * Out of line code such as kprobe-replaced instructions or optimized
+ * kprobes.
+ */
+ PERF_RECORD_KSYMBOL_TYPE_OOL = 2,
PERF_RECORD_KSYMBOL_TYPE_MAX /* non-ABI */
};

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 229d1b596690..f880eb2189c0 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -35,6 +35,7 @@
#include <linux/ftrace.h>
#include <linux/cpu.h>
#include <linux/jump_label.h>
+#include <linux/perf_event.h>

#include <asm/sections.h>
#include <asm/cacheflush.h>
@@ -184,6 +185,10 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
kip->cache = c;
list_add_rcu(&kip->list, &c->pages);
slot = kip->insns;
+
+ /* Record the perf ksymbol register event after adding the page */
+ perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_OOL, (u64)kip->insns,
+ PAGE_SIZE, false, c->sym);
out:
mutex_unlock(&c->mutex);
return slot;
@@ -202,6 +207,13 @@ static int collect_one_slot(struct kprobe_insn_page *kip, int idx)
* next time somebody inserts a probe.
*/
if (!list_is_singular(&kip->list)) {
+ /*
+ * Record perf ksymbol unregister event before removing
+ * the page.
+ */
+ perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_OOL,
+ (u64)kip->insns, PAGE_SIZE, true,
+ kip->cache->sym);
list_del_rcu(&kip->list);
synchronize_rcu();
kip->cache->free(kip->insns);
--
2.17.1