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fprobe: Skip exit_handler if entry_handler returns !0
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Skip hooking function return and calling exit_handler if the
entry_handler() returns !0.

Link: https://lkml.kernel.org/r/167526699798.433354.10998365726830117303.stgit@mhiramat.roam.corp.google.com

Cc: Florent Revest <revest@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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Masami Hiramatsu (Google) authored and Steven Rostedt (Google) committed Mar 28, 2023
1 parent 7e7ef1b commit 39d9542
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Showing 5 changed files with 32 additions and 13 deletions.
4 changes: 2 additions & 2 deletions include/linux/fprobe.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
};
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15 changes: 13 additions & 2 deletions kernel/trace/bpf_trace.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2644,12 +2644,23 @@ 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);
}
Expand Down Expand Up @@ -2848,7 +2859,7 @@ 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;

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14 changes: 9 additions & 5 deletions kernel/trace/fprobe.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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))
Expand All @@ -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);
}
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7 changes: 5 additions & 2 deletions lib/test_fprobe.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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());
Expand All @@ -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,
Expand All @@ -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,
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5 changes: 3 additions & 2 deletions samples/fprobe/fprobe_example.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
/*
Expand All @@ -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,
Expand Down

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