strace: Improvements

- Added some utility functions to the `Context` class.
- Updated the `sockaddr` handler to retrieve the next sibling
rather than the sibling at index 2. This allows the handler to
work for syscalls where the `socklen_t` argument is not the third
one, for example, `_kern_recvfrom`.
- Added the ability to print the `flatArgs` for `_kern_exec` and
`_kern_load_image`.

Change-Id: Ia4cf0a30a5cf972274820bbf068101450db52189
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6498
Reviewed-by: waddlesplash <[email protected]>

src/bin/debug/strace/Context.cpp

@@ -12,6 +12,18 @@
 #include <stdio.h>
 #include <string.h>
 
+
+Parameter *
+Context::GetNextSibling(Parameter *param) const
+{
+	for (int32 i = 0; i + 1 < fSyscall->CountParameters(); i++) {
+		if (fSyscall->ParameterAt(i) == param)
+			return fSyscall->ParameterAt(i + 1);
+	}
+	return NULL;
+}
+
+
 string
 Context::FormatSigned(int64 value, int bytes) const
 {

src/bin/debug/strace/Context.h

@@ -33,10 +33,21 @@ public:
 		return fSyscall->ParameterAt(index);
 	}
 
+	Parameter *GetNextSibling(Parameter *param) const;
+
 	const void *GetValue(Parameter *param) const {
 		return fData + param->Offset();
 	}
 
+	template<typename value_t>
+	value_t ReadValue(Parameter *param) const {
+		const void *address = GetValue(param);
+		if (sizeof(align_t) > sizeof(value_t))
+			return value_t(*(align_t*)address);
+		else
+			return *(value_t*)address;
+	}
+
 	uint64 GetReturnValue() const {
 		return fReturnValue;
 	}

src/bin/debug/strace/Jamfile

@@ -21,6 +21,7 @@ local straceSources =
 	MemoryReader.cpp
 
 	area.cpp
+	exec.cpp
 	fcntl.cpp
 	ioctl.cpp
 	network.cpp

src/bin/debug/strace/NetworkTypes.cpp

@@ -169,17 +169,6 @@ format_pointer(Context &context, flock *lock)
 
 
 
-template<typename value_t>
-static inline value_t
-get_value(const void *address)
-{
-	if (sizeof(align_t) > sizeof(value_t))
-		return value_t(*(align_t*)address);
-	else
-		return *(value_t*)address;
-}
-
-
 static string
 format_signed_number(int32 value)
 {
@@ -192,7 +181,7 @@ format_signed_number(int32 value)
 static string
 read_pollfd(Context &context, void *data)
 {
-	nfds_t numfds = get_value<nfds_t>(context.GetValue(context.GetSibling(1)));
+	nfds_t numfds = context.ReadValue<nfds_t>(context.GetSibling(1));
 	if ((int64)numfds <= 0)
 		return string();
 
@@ -424,10 +413,15 @@ format_pointer(Context &context, sockaddr *saddr)
 
 
 static string
-read_sockaddr(Context &context, void *address)
+read_sockaddr(Context &context, Parameter *param, void *address)
 {
+	param = context.GetNextSibling(param);
+	if (param == NULL)
+		return context.FormatPointer(address);
+
+	socklen_t addrlen = context.ReadValue<socklen_t>(param);
+
 	sockaddr_storage data;
-	socklen_t addrlen = get_value<socklen_t>(context.GetValue(context.GetSibling(2)));
 
 	if (addrlen > sizeof(data))
 		return context.FormatPointer(address);
@@ -443,12 +437,12 @@ read_sockaddr(Context &context, void *address)
 
 template<>
 string
-TypeHandlerImpl<sockaddr *>::GetParameterValue(Context &context, Parameter *,
-	const void *address)
+TypeHandlerImpl<sockaddr *>::GetParameterValue(Context &context,
+	Parameter *param, const void *address)
 {
 	void *data = *(void **)address;
 	if (data != NULL && context.GetContents(Context::SIMPLE_STRUCTS))
-		return read_sockaddr(context, data);
+		return read_sockaddr(context, param, data);
 	return context.FormatPointer(data);
 }
 

src/bin/debug/strace/exec.cpp

@@ -0,0 +1,114 @@
+/*
+ * Copyright 2023, Trung Nguyen, [email protected].
+ * Distributed under the terms of the MIT License.
+ */
+
+
+#include <string.h>
+
+#include <AutoDeleter.h>
+
+#include "strace.h"
+#include "Context.h"
+#include "MemoryReader.h"
+#include "TypeHandler.h"
+
+
+using BPrivate::AutoDeleter;
+
+
+class FlatArgsTypeHandler : public TypeHandler {
+public:
+	string GetParameterValue(Context &context, Parameter *param,
+		const void *address)
+	{
+		size_t flatArgsSize;
+		int32 argCount, envCount;
+		char *flatArgs, *flatArgsEnd;
+		int32 bytesRead;
+		status_t err;
+		ArrayDeleter<char> flatArgsDeleter;
+		string r;
+
+		if (!context.GetContents(Context::COMPLEX_STRUCTS))
+			goto fallback;
+
+		param = context.GetNextSibling(param);
+		if (param == NULL)
+			goto fallback;
+		flatArgsSize = context.ReadValue<size_t>(param);
+
+		param = context.GetNextSibling(param);
+		if (param == NULL)
+			goto fallback;
+		argCount = context.ReadValue<int32>(param);
+
+		param = context.GetNextSibling(param);
+		if (param == NULL)
+			goto fallback;
+		envCount = context.ReadValue<int32>(param);
+
+		flatArgs = new (std::nothrow) char[flatArgsSize + 1];
+		if (flatArgs == NULL)
+			goto fallback;
+
+		flatArgsDeleter.SetTo(flatArgs);
+
+		// Guard with a null byte to prevent faulty buffers.
+		flatArgsEnd = flatArgs + flatArgsSize;
+		*flatArgsEnd = '\0';
+
+		err = context.Reader().Read(*(void **)address, flatArgs, flatArgsSize,
+			bytesRead);
+		if (err != B_OK)
+			goto fallback;
+
+		flatArgs += sizeof(void *) * (argCount + envCount + 2);
+
+		r = "{args = [";
+
+		for (int32 i = 0; i < argCount && flatArgs < flatArgsEnd; i++) {
+			if (i > 0)
+				r += ", ";
+			size_t currentLen = strlen(flatArgs);
+			r += "\"";
+			r += flatArgs;
+			r += "\"";
+			flatArgs += currentLen + 1;
+		}
+
+		r += "], env = [";
+
+		for (int32 i = 0; i < envCount && flatArgs < flatArgsEnd; i++) {
+			if (i > 0)
+				r += ", ";
+			size_t currentLen = strlen(flatArgs);
+			r += "\"";
+			r += flatArgs;
+			r += "\"";
+			flatArgs += currentLen + 1;
+		}
+
+		r += "]}";
+
+		return r;
+	fallback:
+		return context.FormatPointer(address);
+	}
+
+	string GetReturnValue(Context &context, uint64 value)
+	{
+		return context.FormatPointer((void *)value);
+	}
+};
+
+
+void
+patch_exec()
+{
+	Syscall *exec = get_syscall("_kern_exec");
+	exec->GetParameter("flatArgs")->SetHandler(new FlatArgsTypeHandler());
+
+	Syscall *load_image = get_syscall("_kern_load_image");
+	load_image->GetParameter("flatArgs")->SetHandler(new FlatArgsTypeHandler());
+}

src/bin/debug/strace/strace.cpp

@@ -230,6 +230,7 @@ patch_syscalls()
 	// kernel/syscalls.h and have it parsed automatically
 
 	extern void patch_area();
+	extern void patch_exec();
 	extern void patch_fcntl();
 	extern void patch_ioctl();
 	extern void patch_network();
@@ -246,6 +247,7 @@ patch_syscalls()
 	}
 
 	patch_area();
+	patch_exec();
 	patch_fcntl();
 	patch_ioctl();
 	patch_network();