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Date: Fri, 12 Feb 2016 10:11:23 -0600
From: Tom Zanussi <tom.zanussi@...ux.intel.com>
To: ast@...mgrid.com, rostedt@...dmis.org
Cc: masami.hiramatsu.pt@...achi.com, namhyung@...nel.org,
peterz@...radead.org, linux-kernel@...r.kernel.org,
Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: [RFC][PATCH 05/10] eBPF/tracing: Add eBPF trace event field access helpers
Add two eBPF helper functions for accessing trace event contents:
- bpf_trace_event_field_read() - grab integer field contents from trace events
- bpf_trace_event_field_read_string() - grab string contents from trace events
Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
---
include/uapi/linux/bpf.h | 18 ++++++++++
kernel/bpf/verifier.c | 2 +-
kernel/trace/bpf_trace.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 106 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index df6a7ff..4045ce9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -270,6 +270,24 @@ enum bpf_func_id {
* Return: 0 on success
*/
BPF_FUNC_perf_event_output,
+
+ /**
+ * bpf_trace_event_field_read(ctx, field_name) - read trace event field contents
+ * @ctx: struct trace_event_context*
+ * @field_name: ftrace_event_field name
+ * Return: value of field in ctx->record
+ */
+ BPF_FUNC_trace_event_field_read,
+
+ /**
+ * bpf_trace_event_field_read_string(ctx, field_name, dest, size) - read trace event field string
+ * @ctx: struct trace_event_context*
+ * @field_name: ftrace_event_field name
+ * @dest: destination string buffer
+ * @size: destination string buffer size
+ * Return: value of field in ctx->record
+ */
+ BPF_FUNC_trace_event_field_read_string,
__BPF_FUNC_MAX_ID,
};
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a7945d1..2b877ff 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -245,7 +245,7 @@ static const struct {
} func_limit[] = {
{BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
- {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output},
+ {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_trace_event_field_read_string},
};
static void print_verifier_state(struct verifier_env *env)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 78dbac0..eb78c28 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -326,6 +326,89 @@ static struct bpf_prog_type_list kprobe_tl = {
.type = BPF_PROG_TYPE_KPROBE,
};
+static u64 bpf_trace_event_field_read(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+ struct trace_event_context *ctx;
+ struct ftrace_event_field *field;
+ char *field_name;
+ u64 val;
+
+ ctx = (struct trace_event_context *) (long) r1;
+ field_name = (char *) (long) r2;
+
+ field = trace_find_event_field(ctx->call, field_name);
+
+ if (unlikely(!field))
+ return -ENOENT;
+
+ val = field->accessor(field, ctx->record);
+
+ return val;
+}
+
+static const struct bpf_func_proto bpf_trace_event_field_read_proto = {
+ .func = bpf_trace_event_field_read,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_PTR_TO_STACK,
+};
+
+static int event_field_strlen(struct ftrace_event_field *field, void *rec)
+{
+ int size;
+
+ if (field->filter_type == FILTER_DYN_STRING)
+ size = *(u32 *)(rec + field->offset) >> 16;
+ else if (field->filter_type == FILTER_PTR_STRING)
+ size = strlen((char *)(rec + field->offset));
+ else
+ size = field->size;
+
+ return size;
+}
+
+static u64 bpf_trace_event_field_read_string(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+ struct ftrace_event_field *field;
+ struct trace_event_context *ctx;
+ char *field_name;
+ int size, len;
+ void *dst;
+ u64 val;
+
+ ctx = (struct trace_event_context *) (long) r1;
+ field_name = (char *) (long) r2;
+
+ field = trace_find_event_field(ctx->call, field_name);
+ if (unlikely(!field))
+ return -ENOENT;
+
+ val = field->accessor(field, ctx->record);
+
+ dst = (void *)(long)r3;
+ size = (int)r4;
+
+ len = event_field_strlen(field, ctx->record);
+ if (len > size - 1)
+ len = size - 1;
+
+ memset(dst, '\0', size);
+ memcpy(dst, (char *)val, len);
+
+ return 0;
+}
+
+static const struct bpf_func_proto bpf_trace_event_field_read_string_proto = {
+ .func = bpf_trace_event_field_read_string,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_PTR_TO_STACK,
+ .arg3_type = ARG_PTR_TO_STACK,
+ .arg4_type = ARG_CONST_STACK_SIZE,
+};
+
static const struct bpf_func_proto *
trace_event_prog_func_proto(enum bpf_func_id func_id)
{
@@ -356,6 +439,10 @@ trace_event_prog_func_proto(enum bpf_func_id func_id)
return &bpf_perf_event_read_proto;
case BPF_FUNC_perf_event_output:
return &bpf_perf_event_output_proto;
+ case BPF_FUNC_trace_event_field_read:
+ return &bpf_trace_event_field_read_proto;
+ case BPF_FUNC_trace_event_field_read_string:
+ return &bpf_trace_event_field_read_string_proto;
default:
return NULL;
}
--
1.9.3
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