Make vmlinux detection automatic and use Perf's default objdump
when -d is specified. This will make it easier for a test to use the
script without having to provide arguments. And similarly for users.

Reviewed-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: James Clark <james.clark@linaro.org>
---
 .../scripts/python/arm-cs-trace-disasm.py     | 63 ++++++++++++++++---
 1 file changed, 55 insertions(+), 8 deletions(-)

diff --git a/tools/perf/scripts/python/arm-cs-trace-disasm.py b/tools/perf/scripts/python/arm-cs-trace-disasm.py
index 45f682a8b34d..02e957d037ea 100755
--- a/tools/perf/scripts/python/arm-cs-trace-disasm.py
+++ b/tools/perf/scripts/python/arm-cs-trace-disasm.py
@@ -12,25 +12,48 @@ from os import path
 import re
 from subprocess import *
 import argparse
+import platform
 
-from perf_trace_context import perf_set_itrace_options, \
-	perf_sample_insn, perf_sample_srccode
+from perf_trace_context import perf_sample_srccode, perf_config_get
 
 # Below are some example commands for using this script.
+# Note a --kcore recording is required for accurate decode
+# due to the alternatives patching mechanism. However this
+# script only supports reading vmlinux for disassembly dump,
+# meaning that any patched instructions will appear
+# as unpatched, but the instruction ranges themselves will
+# be correct. In addition to this, source line info comes
+# from Perf, and when using kcore there is no debug info. The
+# following lists the supported features in each mode:
+#
+# +-----------+-----------------+------------------+------------------+
+# | Recording | Accurate decode | Source line dump | Disassembly dump |
+# +-----------+-----------------+------------------+------------------+
+# | --kcore   | yes             | no               | yes              |
+# | normal    | no              | yes              | yes              |
+# +-----------+-----------------+------------------+------------------+
+#
+# Output disassembly with objdump and auto detect vmlinux
+# (when running on same machine.)
+#  perf script -s scripts/python/arm-cs-trace-disasm.py -d
 #
-# Output disassembly with objdump:
-#  perf script -s scripts/python/arm-cs-trace-disasm.py \
-#		-- -d objdump -k path/to/vmlinux
 # Output disassembly with llvm-objdump:
 #  perf script -s scripts/python/arm-cs-trace-disasm.py \
 #		-- -d llvm-objdump-11 -k path/to/vmlinux
+#
 # Output only source line and symbols:
 #  perf script -s scripts/python/arm-cs-trace-disasm.py
 
+def default_objdump():
+	config = perf_config_get("annotate.objdump")
+	return config if config else "objdump"
+
 # Command line parsing.
 args = argparse.ArgumentParser()
-args.add_argument("-k", "--vmlinux", help="Set path to vmlinux file")
-args.add_argument("-d", "--objdump", help="Set path to objdump executable file"),
+args.add_argument("-k", "--vmlinux",
+		  help="Set path to vmlinux file. Omit to autodetect if running on same machine")
+args.add_argument("-d", "--objdump", nargs="?", const=default_objdump(),
+		  help="Show disassembly. Can also be used to change the objdump path"),
 args.add_argument("-v", "--verbose", action="store_true", help="Enable debugging log")
 options = args.parse_args()
 
@@ -45,6 +68,17 @@ glb_source_file_name	= None
 glb_line_number		= None
 glb_dso			= None
 
+kver = platform.release()
+vmlinux_paths = [
+	f"/usr/lib/debug/boot/vmlinux-{kver}.debug",
+	f"/usr/lib/debug/lib/modules/{kver}/vmlinux",
+	f"/lib/modules/{kver}/build/vmlinux",
+	f"/usr/lib/debug/boot/vmlinux-{kver}",
+	f"/boot/vmlinux-{kver}",
+	f"/boot/vmlinux",
+	f"vmlinux"
+]
+
 def get_optional(perf_dict, field):
        if field in perf_dict:
                return perf_dict[field]
@@ -55,12 +89,25 @@ def get_offset(perf_dict, field):
 		return "+%#x" % perf_dict[field]
 	return ""
 
+def find_vmlinux():
+	if hasattr(find_vmlinux, "path"):
+		return find_vmlinux.path
+
+	for v in vmlinux_paths:
+		if os.access(v, os.R_OK):
+			find_vmlinux.path = v
+			break
+	else:
+		find_vmlinux.path = None
+
+	return find_vmlinux.path
+
 def get_dso_file_path(dso_name, dso_build_id):
 	if (dso_name == "[kernel.kallsyms]" or dso_name == "vmlinux"):
 		if (options.vmlinux):
 			return options.vmlinux;
 		else:
-			return dso_name
+			return find_vmlinux() if find_vmlinux() else dso_name
 
 	if (dso_name == "[vdso]") :
 		append = "/vdso"
-- 
2.34.1