support: use cgo to generate Go constants from eBPF

Signed-off-by: Florian Lehner <florian.lehner@elastic.co>

support/generate.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+set -eu
+
+echo "////go:build linux" > types_gen.go
+echo "" >> types_gen.go
+echo "// Copyright The OpenTelemetry Authors" >> types_gen.go
+echo "// SPDX-License-Identifier: Apache-2.0" >> types_gen.go
+echo "" >> types_gen.go
+GOOS=linux go tool cgo -godefs types_def.go >> types_gen.go
+
+sed -i 's/^package support$/package support \/\/ import "go.opentelemetry.io\/ebpf-profiler\/support"/' types_gen.go
+
+if ! diff types_gen.go types.go; then
+    echo "Auto generated and existing code differ"
+    exit 1
+fi
+
+rm -rf _obj/ types_gen.go

support/helper.go

@@ -0,0 +1,29 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+//go:generate bash -c "./generate.sh"
+
+// support maps the definitions from headers in the C world into a nice go way
+package support // import "go.opentelemetry.io/ebpf-profiler/support"
+
+import "fmt"
+
+// EncodeBiasAndUnwindProgram encodes a bias_and_unwind_program value (for C.PIDPageMappingInfo)
+// from a bias and unwind program values.
+// This currently assumes a non-negative bias: this encoding may have to be changed if bias can be
+// negative.
+func EncodeBiasAndUnwindProgram(bias uint64,
+	unwindProgram uint8) (uint64, error) {
+	if (bias >> 56) > 0 {
+		return 0, fmt.Errorf("unsupported bias value (too large): 0x%x", bias)
+	}
+	return bias | (uint64(unwindProgram) << 56), nil
+}
+
+// DecodeBiasAndUnwindProgram decodes the contents of the `bias_and_unwind_program` field in
+// C.PIDPageMappingInfo and returns the corresponding bias and unwind program.
+func DecodeBiasAndUnwindProgram(biasAndUnwindProgram uint64) (bias uint64, unwindProgram uint8) {
+	bias = biasAndUnwindProgram & 0x00FFFFFFFFFFFFFF
+	unwindProgram = uint8(biasAndUnwindProgram >> 56)
+	return bias, unwindProgram
+}

support/types_def.go

@@ -0,0 +1,95 @@
+//go:build ignore
+
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package support // import "go.opentelemetry.io/ebpf-profiler/support"
+
+/*
+#include "./ebpf/types.h"
+#include "./ebpf/frametypes.h"
+*/
+import "C"
+
+const (
+	FrameMarkerUnknown  = C.FRAME_MARKER_UNKNOWN
+	FrameMarkerErrorBit = C.FRAME_MARKER_ERROR_BIT
+	FrameMarkerPython   = C.FRAME_MARKER_PYTHON
+	FrameMarkerNative   = C.FRAME_MARKER_NATIVE
+	FrameMarkerPHP      = C.FRAME_MARKER_PHP
+	FrameMarkerPHPJIT   = C.FRAME_MARKER_PHP_JIT
+	FrameMarkerKernel   = C.FRAME_MARKER_KERNEL
+	FrameMarkerHotSpot  = C.FRAME_MARKER_HOTSPOT
+	FrameMarkerRuby     = C.FRAME_MARKER_RUBY
+	FrameMarkerPerl     = C.FRAME_MARKER_PERL
+	FrameMarkerV8       = C.FRAME_MARKER_V8
+	FrameMarkerDotnet   = C.FRAME_MARKER_DOTNET
+	FrameMarkerAbort    = C.FRAME_MARKER_ABORT
+)
+
+const (
+	ProgUnwindStop    = C.PROG_UNWIND_STOP
+	ProgUnwindNative  = C.PROG_UNWIND_NATIVE
+	ProgUnwindHotspot = C.PROG_UNWIND_HOTSPOT
+	ProgUnwindPython  = C.PROG_UNWIND_PYTHON
+	ProgUnwindPHP     = C.PROG_UNWIND_PHP
+	ProgUnwindRuby    = C.PROG_UNWIND_RUBY
+	ProgUnwindPerl    = C.PROG_UNWIND_PERL
+	ProgUnwindV8      = C.PROG_UNWIND_V8
+	ProgUnwindDotnet  = C.PROG_UNWIND_DOTNET
+)
+
+const (
+	DeltaCommandFlag = C.STACK_DELTA_COMMAND_FLAG
+
+	MergeOpcodeNegative = C.MERGEOPCODE_NEGATIVE
+)
+
+const (
+	EventTypeGenericPID = C.EVENT_TYPE_GENERIC_PID
+)
+
+const MaxFrameUnwinds = C.MAX_FRAME_UNWINDS
+
+const (
+	MetricIDBeginCumulative = C.metricID_BeginCumulative
+)
+
+const (
+	BitWidthPID  = C.BIT_WIDTH_PID
+	BitWidthPage = C.BIT_WIDTH_PAGE
+)
+
+const (
+	// StackDeltaBucket[Smallest|Largest] define the boundaries of the bucket sizes of the various
+	// nested stack delta maps.
+	StackDeltaBucketSmallest = C.STACK_DELTA_BUCKET_SMALLEST
+	StackDeltaBucketLargest  = C.STACK_DELTA_BUCKET_LARGEST
+
+	// StackDeltaPage[Bits|Mask] determine the paging size of stack delta map information
+	StackDeltaPageBits = C.STACK_DELTA_PAGE_BITS
+	StackDeltaPageMask = C.STACK_DELTA_PAGE_MASK
+)
+
+const (
+	HSTSIDIsStubBit       = C.HS_TSID_IS_STUB_BIT
+	HSTSIDHasFrameBit     = C.HS_TSID_HAS_FRAME_BIT
+	HSTSIDStackDeltaBit   = C.HS_TSID_STACK_DELTA_BIT
+	HSTSIDStackDeltaMask  = C.HS_TSID_STACK_DELTA_MASK
+	HSTSIDStackDeltaScale = C.HS_TSID_STACK_DELTA_SCALE
+	HSTSIDSegMapBit       = C.HS_TSID_SEG_MAP_BIT
+	HSTSIDSegMapMask      = C.HS_TSID_SEG_MAP_MASK
+)
+
+const (
+	// PerfMaxStackDepth is the bpf map data array length for BPF_MAP_TYPE_STACK_TRACE traces
+	PerfMaxStackDepth = C.PERF_MAX_STACK_DEPTH
+)
+
+const (
+	TraceOriginUnknown  = C.TRACE_UNKNOWN
+	TraceOriginSampling = C.TRACE_SAMPLING
+	TraceOriginOffCPU   = C.TRACE_OFF_CPU
+)
+
+const OffCPUThresholdMax = C.OFF_CPU_THRESHOLD_MAX