bpf: add a bpf_override_function helper

[linux-2.6-block.git] / kernel / trace / bpf_trace.c

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index b143f2a05aff4add19dfe101e2436431aade6edf..e009b7ecf473cf23d2da31e20b97679db50d7af3 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -13,6 +13,10 @@
 #include <linux/filter.h>
 #include <linux/uaccess.h>
 #include <linux/ctype.h>
+#include <linux/kprobes.h>
+#include <asm/kprobes.h>
+
+#include "trace_probe.h"
 #include "trace.h"
 
 u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
@@ -76,6 +80,24 @@ unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
 }
 EXPORT_SYMBOL_GPL(trace_call_bpf);
 
+#ifdef CONFIG_BPF_KPROBE_OVERRIDE
+BPF_CALL_2(bpf_override_return, struct pt_regs *, regs, unsigned long, rc)
+{
+       __this_cpu_write(bpf_kprobe_override, 1);
+       regs_set_return_value(regs, rc);
+       arch_ftrace_kprobe_override_function(regs);
+       return 0;
+}
+
+static const struct bpf_func_proto bpf_override_return_proto = {
+       .func           = bpf_override_return,
+       .gpl_only       = true,
+       .ret_type       = RET_INTEGER,
+       .arg1_type      = ARG_PTR_TO_CTX,
+       .arg2_type      = ARG_ANYTHING,
+};
+#endif
+
 BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
 {
        int ret;
@@ -551,6 +573,10 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
                return &bpf_get_stackid_proto;
        case BPF_FUNC_perf_event_read_value:
                return &bpf_perf_event_read_value_proto;
+#ifdef CONFIG_BPF_KPROBE_OVERRIDE
+       case BPF_FUNC_override_return:
+               return &bpf_override_return_proto;
+#endif
        default:
                return tracing_func_proto(func_id);
        }
@@ -768,6 +794,15 @@ int perf_event_attach_bpf_prog(struct perf_event *event,
        struct bpf_prog_array *new_array;
        int ret = -EEXIST;
 
+       /*
+        * Kprobe override only works for ftrace based kprobes, and only if they
+        * are on the opt-in list.
+        */
+       if (prog->kprobe_override &&
+           (!trace_kprobe_ftrace(event->tp_event) ||
+            !trace_kprobe_error_injectable(event->tp_event)))
+               return -EINVAL;
+
        mutex_lock(&bpf_event_mutex);
 
        if (event->prog)