Simplify TSDInfo by removing a duplicate definition

interpreter/perl/instance.go

@@ -85,12 +85,7 @@ func (i *perlInstance) UpdateLibcInfo(ebpf interpreter.EbpfHandler, pid libpf.PI
 		Version:    d.version,
 		StateAddr:  uint64(d.stateAddr) + uint64(i.bias),
 		StateInTSD: stateInTSD,
-
-		TsdInfo: support.TSDInfo{
-			Offset:     libcInfo.TSDInfo.Offset,
-			Multiplier: libcInfo.TSDInfo.Multiplier,
-			Indirect:   libcInfo.TSDInfo.Indirect,
-		},
+		TsdInfo:    libcInfo.TSDInfo,
 
 		Interpreter_curcop:       uint16(vms.interpreter.curcop),
 		Interpreter_curstackinfo: uint16(vms.interpreter.curstackinfo),

interpreter/python/python.go

@@ -378,12 +378,7 @@ func (p *pythonInstance) UpdateLibcInfo(ebpf interpreter.EbpfHandler, pid libpf.
 	cdata := support.PyProcInfo{
 		AutoTLSKeyAddr: uint64(d.autoTLSKey) + uint64(p.bias),
 		Version:        d.version,
-
-		TsdInfo: support.TSDInfo{
-			Offset:     libcInfo.TSDInfo.Offset,
-			Multiplier: libcInfo.TSDInfo.Multiplier,
-			Indirect:   libcInfo.TSDInfo.Indirect,
-		},
+		TsdInfo:        libcInfo.TSDInfo,
 
 		PyThreadState_frame:            uint8(vm.PyThreadState.Frame),
 		PyCFrame_current_frame:         uint8(vm.PyCFrame.CurrentFrame),

libc/libc.go

@@ -9,32 +9,17 @@ import (
 	"regexp"
 
 	"go.opentelemetry.io/ebpf-profiler/libpf/pfelf"
+	"go.opentelemetry.io/ebpf-profiler/support"
 )
 
+type TSDInfo = support.TSDInfo
+
 // LibcInfo contains introspection information extracted from the C-library
 type LibcInfo struct {
 	// TSDInfo is the TSDInfo extracted for this C-library
 	TSDInfo TSDInfo
 }
 
-// TSDInfo contains information to access C-library's Thread Specific Data from eBPF
-type TSDInfo struct {
-	// Offset is the pointer difference from "tpbase" pointer to the C-library
-	// specific struct pthread's member containing the thread specific data:
-	// .tsd (musl) or .specific (glibc).
-	// Note: on x86_64 it's positive value, and arm64 it is negative value as
-	// "tpbase" register has different purpose and pointer value per platform ABI.
-	Offset int16
-
-	// Multiplier is the TSD specific value array element size.
-	// Typically 8 bytes on 64bit musl and 16 bytes on 64bit glibc
-	Multiplier uint8
-
-	// Indirect is a flag indicating if the "tpbase + Offset" points to a member
-	// which is a pointer the array (musl) and not the array itself (glibc).
-	Indirect uint8
-}
-
 // This code analyzes the C-library provided POSIX defined function which is used
 // to read thread-specific data (TSD):
 //   void *pthread_getspecific(pthread_key_t key);
@@ -97,21 +82,21 @@ func ExtractLibcInfo(ef *pfelf.File) (*LibcInfo, error) {
 	}
 
 	return &LibcInfo{
-		TSDInfo: *tsdinfo,
+		TSDInfo: tsdinfo,
 	}, nil
 }
 
-// ExtractTSDInfo extracts the introspection data for pthread thread specific data.
-func extractTSDInfo(ef *pfelf.File) (*TSDInfo, error) {
+// extractTSDInfo extracts the introspection data for pthread thread specific data.
+func extractTSDInfo(ef *pfelf.File) (TSDInfo, error) {
 	_, code, err := ef.SymbolData("__pthread_getspecific", 2048)
 	if err != nil {
 		_, code, err = ef.SymbolData("pthread_getspecific", 2048)
 		if err != nil {
-			return nil, fmt.Errorf("unable to read 'pthread_getspecific': %s", err)
+			return TSDInfo{}, fmt.Errorf("unable to read 'pthread_getspecific': %s", err)
 		}
 	}
 	if len(code) < 8 {
-		return nil, fmt.Errorf("getspecific function size is %d", len(code))
+		return TSDInfo{}, fmt.Errorf("getspecific function size is %d", len(code))
 	}
 
 	var info TSDInfo
@@ -121,10 +106,10 @@ func extractTSDInfo(ef *pfelf.File) (*TSDInfo, error) {
 	case elf.EM_X86_64:
 		info, err = extractTSDInfoX86(code)
 	default:
-		return nil, fmt.Errorf("unsupported arch %s", ef.Machine.String())
+		return TSDInfo{}, fmt.Errorf("unsupported arch %s", ef.Machine.String())
 	}
 	if err != nil {
-		return nil, fmt.Errorf("failed to extract getspecific data: %s", err)
+		return TSDInfo{}, fmt.Errorf("failed to extract getspecific data: %s", err)
 	}
-	return &info, nil
+	return info, nil
 }

support/ebpf/types.h

@@ -391,8 +391,17 @@ _Static_assert(sizeof(Frame) == 3 * 8, "frame padding not working as expected");
 
 // TSDInfo contains data needed to extract Thread Specific Data (TSD) values
 typedef struct TSDInfo {
+  // Offset is the pointer difference from "tpbase" pointer to the C-library
+  // specific struct pthread's member containing the thread specific data:
+  // .tsd (musl) or .specific (glibc).
+  // Note: on x86_64 it's positive value, and arm64 it is negative value as
+  // "tpbase" register has different purpose and pointer value per platform ABI.
   s16 offset;
+  // Multiplier is the TSD specific value array element size.
+  // Typically 8 bytes on 64bit musl and 16 bytes on 64bit glibc
   u8 multiplier;
+  // Indirect is a flag indicating if the "tpbase + Offset" points to a member
+  // which is a pointer the array (musl) and not the array itself (glibc).
   u8 indirect;
 } TSDInfo;