[RFC PATCH 5/9] fprobe: Skip exit_handler if entry_handler returns !0
From: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Date: 2022-11-08 15:50:12
Also in:
lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [security & lsm] (security audit and enforcement using bpf), bpf [tracing], library code, the rest, tracing · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, KP Singh, Matt Bobrowski, Song Liu, Andrew Morton, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
From: Masami Hiramatsu (Google) <mhiramat@kernel.org> Skip hooking function return and calling exit_handler if the entry_handler() returns !0. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> --- include/linux/fprobe.h | 4 ++-- kernel/trace/bpf_trace.c | 15 +++++++++++++-- kernel/trace/fprobe.c | 14 +++++++++----- lib/test_fprobe.c | 7 +++++-- samples/fprobe/fprobe_example.c | 5 +++-- 5 files changed, 32 insertions(+), 13 deletions(-)
diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
index 678f741a7b33..47fefc7f363b 100644
--- a/include/linux/fprobe.h
+++ b/include/linux/fprobe.h@@ -34,8 +34,8 @@ struct fprobe { size_t entry_data_size; int nr_maxactive; - void (*entry_handler)(struct fprobe *fp, unsigned long entry_ip, - struct pt_regs *regs, void *entry_data); + int (*entry_handler)(struct fprobe *fp, unsigned long entry_ip, + struct pt_regs *regs, void *entry_data); void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip, struct pt_regs *regs, void *entry_data); };
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 68c369452680..dadcddb6a429 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c@@ -2623,12 +2623,23 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link, return err; } -static void +static int kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip, struct pt_regs *regs, void *data) { struct bpf_kprobe_multi_link *link; + link = container_of(fp, struct bpf_kprobe_multi_link, fp); + kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs); + return 0; +} + +static void +kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip, + struct pt_regs *regs, void *data) +{ + struct bpf_kprobe_multi_link *link; + link = container_of(fp, struct bpf_kprobe_multi_link, fp); kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs); }
@@ -2754,7 +2765,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr goto error; if (flags & BPF_F_KPROBE_MULTI_RETURN) - link->fp.exit_handler = kprobe_multi_link_handler; + link->fp.exit_handler = kprobe_multi_link_exit_handler; else link->fp.entry_handler = kprobe_multi_link_handler;
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index f222848571f2..9abb3905bc8e 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c@@ -27,7 +27,7 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip, struct rethook_node *rh = NULL; struct fprobe *fp; void *entry_data = NULL; - int bit; + int bit, ret; fp = container_of(ops, struct fprobe, ops); if (fprobe_disabled(fp))
@@ -52,11 +52,15 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip, } if (fp->entry_handler) - fp->entry_handler(fp, ip, ftrace_get_regs(fregs), entry_data); - - if (rh) - rethook_hook(rh, ftrace_get_regs(fregs), true); + ret = fp->entry_handler(fp, ip, ftrace_get_regs(fregs), entry_data); + /* If entry_handler returns !0, nmissed is not counted. */ + if (rh) { + if (ret) + rethook_recycle(rh); + else + rethook_hook(rh, ftrace_get_regs(fregs), true); + } out: ftrace_test_recursion_unlock(bit); }
diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
index 976fb3f7cb01..e78176d252ae 100644
--- a/lib/test_fprobe.c
+++ b/lib/test_fprobe.c@@ -37,7 +37,7 @@ static noinline u32 fprobe_selftest_nest_target(u32 value, u32 (*nest)(u32)) return nest(value + 2); } -static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip, +static notrace int fp_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs, void *data) { KUNIT_EXPECT_FALSE(current_test, preemptible());
@@ -51,6 +51,8 @@ static notrace void fp_entry_handler(struct fprobe *fp, unsigned long ip, *(u32 *)data = entry_val; } else KUNIT_EXPECT_NULL(current_test, data); + + return 0; } static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,
@@ -74,10 +76,11 @@ static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip, KUNIT_EXPECT_NULL(current_test, data); } -static notrace void nest_entry_handler(struct fprobe *fp, unsigned long ip, +static notrace int nest_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs, void *data) { KUNIT_EXPECT_FALSE(current_test, preemptible()); + return 0; } static notrace void nest_exit_handler(struct fprobe *fp, unsigned long ip,
diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c
index dd794990ad7e..4efc8feb6277 100644
--- a/samples/fprobe/fprobe_example.c
+++ b/samples/fprobe/fprobe_example.c@@ -48,8 +48,8 @@ static void show_backtrace(void) stack_trace_print(stacks, len, 24); } -static void sample_entry_handler(struct fprobe *fp, unsigned long ip, - struct pt_regs *regs, void *data) +static int sample_entry_handler(struct fprobe *fp, unsigned long ip, + struct pt_regs *regs, void *data) { if (use_trace) /*
@@ -62,6 +62,7 @@ static void sample_entry_handler(struct fprobe *fp, unsigned long ip, nhit++; if (stackdump) show_backtrace(); + return 0; } static void sample_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs,