[PATCH v2 4/6] tracing/kprobes: Support perf-style return probe
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: 2020-09-01 07:57:17
Also in:
lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Support perf-style return probe ("SYMBOL%return") in kprobe events.
This will allow boot-time tracing user to define a return probe event.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
kernel/trace/trace_kprobe.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index aefb6065b508..391361b67c8f 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c@@ -709,6 +709,18 @@ static inline void sanitize_event_name(char *name) *name = '_'; } +static inline bool split_return_suffix(char *symbol) +{ + char *p = strchr(symbol, '%'); + + if (p && !strcmp(p, "%return")) { + *p = '\0'; + return true; + } + + return false; +} + static int trace_kprobe_create(int argc, const char *argv[]) { /*
@@ -717,6 +729,9 @@ static int trace_kprobe_create(int argc, const char *argv[]) * p[:[GRP/]EVENT] [MOD:]KSYM[+OFFS]|KADDR [FETCHARGS] * - Add kretprobe: * r[MAXACTIVE][:[GRP/]EVENT] [MOD:]KSYM[+0] [FETCHARGS] + * Or + * p:[GRP/]EVENT] [MOD:]KSYM[+0]%return [FETCHARGS] + * * Fetch args: * $retval : fetch return value * $stack : fetch stack address
@@ -746,7 +761,6 @@ static int trace_kprobe_create(int argc, const char *argv[]) switch (argv[0][0]) { case 'r': is_return = true; - flags |= TPARG_FL_RETURN; break; case 'p': break;
@@ -804,12 +818,17 @@ static int trace_kprobe_create(int argc, const char *argv[]) symbol = kstrdup(argv[1], GFP_KERNEL); if (!symbol) return -ENOMEM; + + is_return = split_return_suffix(symbol) || is_return; + /* TODO: support .init module functions */ ret = traceprobe_split_symbol_offset(symbol, &offset); if (ret || offset < 0 || offset > UINT_MAX) { trace_probe_log_err(0, BAD_PROBE_ADDR); goto parse_error; } + if (is_return) + flags |= TPARG_FL_RETURN; if (kprobe_on_func_entry(NULL, symbol, offset)) flags |= TPARG_FL_FENTRY; if (offset && is_return && !(flags & TPARG_FL_FENTRY)) {