Refactor Go-DI template generation to use location expressions

LICENSE-3rdparty.csv

@@ -2932,6 +2932,7 @@ core,gopkg.in/DataDog/dd-trace-go.v1/appsec/events,Apache-2.0,"Copyright 2016-Pr
 core,gopkg.in/DataDog/dd-trace-go.v1/contrib/internal/httptrace,Apache-2.0,"Copyright 2016-Present Datadog, Inc."
 core,gopkg.in/DataDog/dd-trace-go.v1/contrib/internal/options,Apache-2.0,"Copyright 2016-Present Datadog, Inc."
 core,gopkg.in/DataDog/dd-trace-go.v1/contrib/net/http,Apache-2.0,"Copyright 2016-Present Datadog, Inc."
+core,gopkg.in/DataDog/dd-trace-go.v1/datastreams,Apache-2.0,"Copyright 2016-Present Datadog, Inc."
 core,gopkg.in/DataDog/dd-trace-go.v1/datastreams/options,Apache-2.0,"Copyright 2016-Present Datadog, Inc."
 core,gopkg.in/DataDog/dd-trace-go.v1/ddtrace,Apache-2.0,"Copyright 2016-Present Datadog, Inc."
 core,gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext,Apache-2.0,"Copyright 2016-Present Datadog, Inc."

go.mod

@@ -480,7 +480,7 @@ require (
 	github.com/mitchellh/hashstructure/v2 v2.0.2 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/mkrautz/goar v0.0.0-20150919110319-282caa8bd9da // indirect
-	github.com/moby/buildkit v0.12.5 // indirect
+	github.com/moby/buildkit v0.14.1 // indirect
 	github.com/moby/locker v1.0.1 // indirect
 	github.com/moby/sys/signal v0.7.0 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect

pkg/dynamicinstrumentation/codegen/c/types.h → pkg/dynamicinstrumentation/codegen/c/base_event.h

@@ -1,9 +1,8 @@
-#ifndef DI_TYPES_H
-#define DI_TYPES_H
+#ifndef DI_BASE_EVENT_H
+#define DI_BASE_EVENT_H
 
 #include "ktypes.h"
 
-// NOTE: Be careful when adding fields, alignment should always be to 8 bytes
 struct base_event {
     char probe_id[304];
     __u32 pid;

pkg/dynamicinstrumentation/codegen/c/dynamicinstrumentation.c

@@ -2,49 +2,30 @@
 #include "bpf_tracing.h"
 #include "kconfig.h"
 #include <asm/ptrace.h>
-#include "types.h"
-
-#define MAX_STRING_SIZE {{ .InstrumentationInfo.InstrumentationOptions.StringMaxSize}}
-#define PARAM_BUFFER_SIZE {{ .InstrumentationInfo.InstrumentationOptions.ArgumentsMaxSize}}
-#define STACK_DEPTH_LIMIT 10
-#define MAX_SLICE_SIZE 1800
-#define MAX_SLICE_LENGTH 20
-
-struct {
-    __uint(type, BPF_MAP_TYPE_RINGBUF);
-    __uint(max_entries, 1 << 24);
-} events SEC(".maps");
-
-struct {
-    __uint(type, BPF_MAP_TYPE_ARRAY);
-    __uint(key_size, sizeof(__u32));
-    __uint(value_size, sizeof(char[PARAM_BUFFER_SIZE]));
-    __uint(max_entries, 1);
-} zeroval SEC(".maps");
-
-struct event {
-    struct base_event base;
-    char output[PARAM_BUFFER_SIZE];
-};
+#include "base_event.h"
+#include "macros.h"
+#include "event.h"
+#include "maps.h"
+#include "expressions.h"
 
 SEC("uprobe/{{.GetBPFFuncName}}")
 int {{.GetBPFFuncName}}(struct pt_regs *ctx)
 {
-    bpf_printk("{{.GetBPFFuncName}} probe in {{.ServiceName}} has triggered");
+    log_debug("{{.GetBPFFuncName}} probe in {{.ServiceName}} has triggered");
 
     // reserve space on ringbuffer
     struct event *event;
     event = bpf_ringbuf_reserve(&events, sizeof(struct event), 0);
     if (!event) {
-        bpf_printk("No space available on ringbuffer, dropping event");
+        log_debug("No space available on ringbuffer, dropping event");
         return 0;
     }
 
     char* zero_string;
     __u32 key = 0;
     zero_string = bpf_map_lookup_elem(&zeroval, &key);
     if (!zero_string) {
-        bpf_printk("couldn't lookup zero value in zeroval array map, dropping event for {{.GetBPFFuncName}}");
+        log_debug("couldn't lookup zero value in zeroval array map, dropping event for {{.GetBPFFuncName}}");
         bpf_ringbuf_discard(event, 0);
         return 0;
     }
@@ -72,6 +53,8 @@ int {{.GetBPFFuncName}}(struct pt_regs *ctx)
     __u64 ret_addr = PT_REGS_RET(ctx); // when bpf prog enters, the return address hasn't yet been written to the stack
 
     int i;
+    int j;
+    __u16 n;
     for (i = 1; i < STACK_DEPTH_LIMIT; i++)
     {
         if (bp == 0) {
@@ -83,16 +66,50 @@ int {{.GetBPFFuncName}}(struct pt_regs *ctx)
     }
 
     // Collect parameters
+    __u16 collectionMax = MAX_SLICE_LENGTH;
     __u8 param_type;
     __u16 param_size;
     __u16 slice_length;
+    __u16 *collectionLimit;
+    __u8 stack_counter = 0;
 
-    int outputOffset = 0;
+    int chunk_size = 0;
+    __u64 outputOffset = 0;
+
+    // Set up temporary storage array which is used by some location expressions
+    // to have memory off the stack to work with
+    __u64 *temp_storage = bpf_map_lookup_elem(&temp_storage_array, &key) ;
+    if (!temp_storage) {
+        log_debug("could not lookup temporary storage array");
+        bpf_ringbuf_discard(event, 0);
+        return 0;
+    }
+
+    struct expression_context context = {
+        .ctx = ctx,
+        .output_offset = &outputOffset,
+        .stack_counter = &stack_counter,
+        .event = event,
+        .temp_storage = temp_storage,
+        .zero_string = zero_string
+    };
 
     {{ .InstrumentationInfo.BPFParametersSourceCode }}
 
     bpf_ringbuf_submit(event, 0);
 
+
+    // Drain the stack map for next invocation
+    __u8 m = 0;
+    __u64 placeholder;
+    long pop_ret = 0;
+    for (m = 0; m < stack_counter; m++) {
+        pop_ret = bpf_map_pop_elem(&param_stack, &placeholder);
+        if (pop_ret != 0) {
+            break;
+        }
+    }
+
     return 0;
 }
 

pkg/dynamicinstrumentation/codegen/c/event.h

@@ -0,0 +1,20 @@
+#ifndef DI_EVENT_H
+#define DI_EVENT_H
+
+#include "ktypes.h"
+
+struct event {
+    struct base_event base;
+    char output[PARAM_BUFFER_SIZE];
+};
+
+struct expression_context {
+    __u64 *output_offset;
+    __u8 *stack_counter;
+    struct pt_regs *ctx;
+    struct event *event;
+    __u64 *temp_storage;
+    char *zero_string;
+};
+
+#endif