Fix typos, extend docs add tracing helper script

Author: Rot127

README.md

@@ -41,12 +41,31 @@ The plugin takes two required arguments:
 
 `bin_path`: The path to the binary emulated. Due to a [QEMU bug](https://gitlab.com/qemu-project/qemu/-/issues/3014) this cannot be inferred.
 `out`: The output file to save the trace into.
+`endianness`: The architecture endanness.
 
 ```bash
-./qemu-sparc64 -plugin file=./contrib/plugins/bap-tracing/libbap_tracing.so,bin_path=<bin_path>,out=<output-file> -d plugin <bin_path>
+./qemu-sparc64 -plugin file=buil/contrib/plugins/bap-tracing/libbap_tracing.so,bin_path=<bin_path>,out=<output-file>,endianness=[b/l] -d plugin <bin_path>
 ls <output-file>
 ```
 
+You can also use the helper shell script:
+
+```bash
+./gen-trace.sh ./build/ sparc64 b <path_to_bin>
+```
+
+> [!NOTE]
+> The trace plugin currently only generates standard frames.
+> This is due to the limitations of the QEMU plugin API.
+>
+> If the traced binary exits due to an exception it can only indirectly be observed.
+> It will produce a standard frame without any logged post register state.
+> Any completed memory read/write might still be logged.
+>
+> If you suspect this, execute the binary with the `execlog` plugin (see `gen-trace.sh`)
+> to check of the execution stops earlier than expected.
+
+
 ## Trace format
 
 The generated trace consists of three parts: the header,

contrib/plugins/bap-tracing/tracing.c

@@ -404,14 +404,14 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
     qemu_plugin_outs("Pass it with 'out=<output_file>'.\n\n");
     exit(1);
   }
-  char *endianess = get_argv_val(argv, argc, "endianess");
-  if (!endianess || (strcmp(endianess, "b") && strcmp(endianess, "l"))) {
-    qemu_plugin_outs("'endianess' argument is missing or is not 'b' or 'l'.\n");
+  char *endianness = get_argv_val(argv, argc, "endianness");
+  if (!endianness || (strcmp(endianness, "b") && strcmp(endianness, "l"))) {
+    qemu_plugin_outs("'endianness' argument is missing or is not 'b' or 'l'.\n");
     qemu_plugin_outs("This is required until QEMU plugins get a richer API.\n");
-    qemu_plugin_outs("Pass it with 'endianess=[b/l]'.\n\n");
+    qemu_plugin_outs("Pass it with 'endianness=[b/l]'.\n\n");
     exit(1);
   }
-  state.is_big_endian = endianess[0] == 'b';
+  state.is_big_endian = endianness[0] == 'b';
 
   state.target_name = g_strdup(info->target_name);
   state.frame_buffer = g_ptr_array_new();

gen-trace.sh

@@ -0,0 +1,17 @@
+#!/bin/sh -x
+
+if [ "$#" -lt 4 ]; then
+  echo "$0 <build_dir> <arch> <endianess=[b/l]> <bin_path> [args...]"
+  echo "<arch> is attached to qemu-<arch>"
+  exit 1
+fi
+
+BUILDIR=$1
+ARCH=$2
+EN=$3
+BIN=$4
+BNAME=$(basename $BIN)
+
+$BUILDIR/qemu-$ARCH -plugin file="$BUILDIR/contrib/plugins/bap-tracing/libbap_tracing.so,bin_path=$BIN",out="$BNAME.trace",endianess="$EN" -d plugin "$BIN" ""${@:5}""
+ls -lh "$BNAME.trace"
+# $BUILDIR/qemu-$ARCH -plugin file="$BUILDIR/contrib/plugins/libexeclog.so" -d plugin "$BIN"