Fix arm64/musl gilstate addressing

parca-dev · May 23, 2024 · 06fbe08 · 06fbe08
1 parent bf30888
commit 06fbe08
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Showing 2 changed files with 33 additions and 18 deletions.
diff --git a/pkg/runtime/python/interpreter.go b/pkg/runtime/python/interpreter.go
@@ -29,6 +29,7 @@ import (
 	runtimedata "github.com/parca-dev/runtime-data/pkg/python"
 
 	"github.com/parca-dev/parca-agent/pkg/runtime"
+	"github.com/parca-dev/parca-agent/pkg/runtime/libc"
 )
 
 var (
@@ -168,7 +169,7 @@ func newInterpreter(proc procfs.Proc) (*interpreter, error) {
 	}, nil
 }
 
-func (i interpreter) threadStateAddress() (uint64, error) {
+func (i interpreter) threadStateAddress(libcImp libc.LibcImplementation) (uint64, error) {
 	const37_11, err := semver.NewConstraint(">=3.7.x-0")
 	if err != nil {
 		return 0, fmt.Errorf("new constraint: %w", err)
@@ -190,7 +191,7 @@ func (i interpreter) threadStateAddress() (uint64, error) {
 			return 0, nil
 		}
 		fmt.Printf("python_new %s got addr = %p, tstate_current offset=%d\n", i.version.String(), unsafe.Pointer(uintptr(addr+uint64(initialState.ThreadStateCurrent))), initialState.ThreadStateCurrent)
-		return addr + uint64(initialState.ThreadStateCurrent), nil
+		return addr + uint64(initialState.ThreadStateCurrent) - interpreterGILAddressOffset(libcImp), nil
 	// Older versions (<3.7.0) of Python do not have the _PyRuntime struct.
 	default:
 		addr, err := i.findAddressOf(pythonThreadStateSymbol) // _PyThreadState_Current
@@ -225,7 +226,16 @@ func (i interpreter) interpreterAddress() (uint64, error) {
 	}
 }
 
-func (i interpreter) tlsKey() (uint64, error) {
+// mutex are 8 bytes smaller on arm64/musl and there are two
+// in the PyRuntime object in front of the gilstate.
+func interpreterGILAddressOffset(libcImp libc.LibcImplementation) uint64 {
+	if libcImp == libc.LibcMusl && goruntime.GOARCH == "arm64" {
+		return 16
+	}
+	return 0
+}
+
+func (i interpreter) tlsKey(libcImp libc.LibcImplementation) (uint64, error) {
 	pyRuntimeAddr, err := i.findAddressOf(pythonRuntimeSymbol) // _PyRuntime
 	if err != nil {
 		return 0, fmt.Errorf("findAddressOf: %w", err)
@@ -234,7 +244,7 @@ func (i interpreter) tlsKey() (uint64, error) {
 	if err != nil {
 		return 0, fmt.Errorf("get initial state: %w", err)
 	}
-	tssKeyAddr := pyRuntimeAddr + uint64(initialState.AutoTSSKey)
+	tssKeyAddr := pyRuntimeAddr + uint64(initialState.AutoTSSKey) - interpreterGILAddressOffset(libcImp)
 	tssKeyLayout := initialState.PyTSS
 
 	tss := make([]byte, tssKeyLayout.Size)

diff --git a/pkg/runtime/python/python.go b/pkg/runtime/python/python.go
@@ -154,14 +154,31 @@ func InterpreterInfo(proc procfs.Proc) (*Info, error) {
 	}
 	defer interpreter.Close()
 
-	threadStateAddress, err := interpreter.threadStateAddress()
+	libcInfo, err := libc.NewLibcInfo(proc)
+	if err != nil {
+		above312, err := semver.NewConstraint(">=3.12.0-0")
+		if err != nil {
+			return nil, fmt.Errorf("python version: %s, libc info: %w", interpreter.version.String(), err)
+		}
+		if above312.Check(interpreter.version) {
+			// It's only critical to have the libc info for Python 3.12 and above.
+			return nil, fmt.Errorf("python version: %s, libc info: %w", interpreter.version.String(), err)
+		}
+	}
+
+	libcImp := libc.LibcGlibc
+	if libcInfo != nil {
+		libcImp = libcInfo.Implementation
+	}
+
+	threadStateAddress, err := interpreter.threadStateAddress(libcImp)
 	if err != nil {
 		return nil, fmt.Errorf("python version: %s, thread state address: %w", interpreter.version.String(), err)
 	}
 
 	var tlsKey uint64
 	if threadStateAddress == 0 {
-		tlsKey, err = interpreter.tlsKey()
+		tlsKey, err = interpreter.tlsKey(libcImp)
 		if err != nil {
 			return nil, fmt.Errorf("python version: %s, tls key: %w", interpreter.version.String(), err)
 		}
@@ -175,18 +192,6 @@ func InterpreterInfo(proc procfs.Proc) (*Info, error) {
 		return nil, fmt.Errorf("invalid address, python version: %s, interpreter address: 0x%016x", interpreter.version.String(), interpreterAddress)
 	}
 
-	libcInfo, err := libc.NewLibcInfo(proc)
-	if err != nil {
-		above312, err := semver.NewConstraint(">=3.12.0-0")
-		if err != nil {
-			return nil, fmt.Errorf("python version: %s, libc info: %w", interpreter.version.String(), err)
-		}
-		if above312.Check(interpreter.version) {
-			// It's only critical to have the libc info for Python 3.12 and above.
-			return nil, fmt.Errorf("python version: %s, libc info: %w", interpreter.version.String(), err)
-		}
-	}
-
 	return &Info{
 		rt: runtime.Runtime{
 			Name:          "Python",