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selftests/bpf: Fix BPF_KRETPROBE macro and use it in attach_probe test

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For kretprobes, there is no point in capturing input arguments from pt_regs,
as they are going to be, most probably, clobbered by the time probed kernel
function returns. So switch BPF_KRETPROBE to accept zero or one argument
(optional return result).

Fixes: ac065870d9 ("selftests/bpf: Add BPF_PROG, BPF_KPROBE, and BPF_KRETPROBE macros")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200229231112.1240137-4-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-02-29 15:11:11 -08:00 committed by Alexei Starovoitov
parent fd56e00584
commit 396f544ed5
3 changed files with 11 additions and 11 deletions
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13
tools/testing/selftests/bpf/bpf_trace_helpers.h
View File

@ -96,15 +96,16 @@ typeof(name(0)) name(struct pt_regs *ctx) \
static __always_inline typeof(name(0)) ____##name(struct pt_regs *ctx, ##args)
#define ___bpf_kretprobe_args0() ctx
#define ___bpf_kretprobe_argsN(x, args...) \
___bpf_kprobe_args(args), (void *)PT_REGS_RET(ctx)
#define ___bpf_kretprobe_args1(x) \
___bpf_kretprobe_args0(), (void *)PT_REGS_RET(ctx)
#define ___bpf_kretprobe_args(args...) \
___bpf_apply(___bpf_kretprobe_args, ___bpf_empty(args))(args)
___bpf_apply(___bpf_kretprobe_args, ___bpf_narg(args))(args)
/*
* BPF_KRETPROBE is similar to BPF_KPROBE, except, in addition to listing all
* input kprobe arguments, one last extra argument has to be specified, which
* captures kprobe return value.
* BPF_KRETPROBE is similar to BPF_KPROBE, except, it only provides optional
* return value (in addition to `struct pt_regs *ctx`), but no input
* arguments, because they will be clobbered by the time probed function
* returns.
*/
#define BPF_KRETPROBE(name, args...) \
name(struct pt_regs *ctx); \

3
tools/testing/selftests/bpf/progs/test_attach_probe.c
View File

@ -4,6 +4,7 @@
#include <linux/ptrace.h>
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include "bpf_trace_helpers.h"
int kprobe_res = 0;
int kretprobe_res = 0;
@ -18,7 +19,7 @@ int handle_kprobe(struct pt_regs *ctx)
}
SEC("kretprobe/sys_nanosleep")
int handle_kretprobe(struct pt_regs *ctx)
int BPF_KRETPROBE(handle_kretprobe)
{
kretprobe_res = 2;
return 0;

6
tools/testing/selftests/bpf/progs/test_overhead.c
View File

@ -17,11 +17,9 @@ int BPF_KPROBE(prog1, struct task_struct *tsk, const char *buf, bool exec)
}
SEC("kretprobe/__set_task_comm")
int BPF_KRETPROBE(prog2,
struct task_struct *tsk, const char *buf, bool exec,
int ret)
int BPF_KRETPROBE(prog2, int ret)
{
return !PT_REGS_PARM1(ctx) && ret;
return ret;
}
SEC("raw_tp/task_rename")