[PATCH v4 03/17] verification/rvgen: Improve rv_dir discovery in RVGenerator

[Gabriele Monaco <gmonaco@redhat.com>]

The RVGenerator class can find the RV directory (kernel/trace/rv) in the
kernel tree to do some auto patching. This works by assuming PWD is
either the kernel tree or tools/verification, which isn't always the
case (e.g. when running from selftests).

Make discovery more robust by relying on the absolute path of the
current script and traversing backwards the right number of times.
This should work from any location if rvgen is in the kernel tree.

Reviewed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
---

Notes:
    V4:
    * Use pathlib's parents array to climb up directories

 tools/verification/rvgen/rvgen/generator.py | 29 ++++++++++++---------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/tools/verification/rvgen/rvgen/generator.py b/tools/verification/rvgen/rvgen/generator.py
index 56f3bd8db850..1c20f7d1905c 100644
--- a/tools/verification/rvgen/rvgen/generator.py
+++ b/tools/verification/rvgen/rvgen/generator.py
@@ -7,6 +7,7 @@
 
 import platform
 import os
+from pathlib import Path
 
 
 class RVGenerator:
@@ -25,27 +26,29 @@ class RVGenerator:
             self.__fill_rv_kernel_dir()
 
     def __fill_rv_kernel_dir(self):
-
-        # first try if we are running in the kernel tree root
-        if os.path.exists(self.rv_dir):
-            return
-
-        # offset if we are running inside the kernel tree from verification/dot2
-        kernel_path = os.path.join("../..", self.rv_dir)
-
-        if os.path.exists(kernel_path):
-            self.rv_dir = kernel_path
+        # find the kernel tree root relative to this file's location
+        resolved_path = Path(__file__).resolve()
+        if len(resolved_path.parents) > 4:
+            kernel_root = resolved_path.parents[4]
+            kernel_path = kernel_root / self.rv_dir
+
+            if kernel_path.exists():
+                self.rv_dir = str(kernel_path)
+                return
+
+        # best effort if rvgen is installed and we are at the root of a kernel tree
+        if Path(self.rv_dir).exists():
             return
 
         if platform.system() != "Linux":
             raise OSError("I can only run on Linux.")
 
-        kernel_path = os.path.join(f"/lib/modules/{platform.release()}/build", self.rv_dir)
+        kernel_path = Path(f"/lib/modules/{platform.release()}/build") / self.rv_dir
 
         # if the current kernel is from a distro this may not be a full kernel tree
         # verify that one of the files we are going to modify is available
-        if os.path.exists(os.path.join(kernel_path, "rv_trace.h")):
-            self.rv_dir = kernel_path
+        if (kernel_path / "rv_trace.h").exists():
+            self.rv_dir = str(kernel_path)
             return
 
         raise FileNotFoundError("Could not find the rv directory, do you have the kernel source installed?")
-- 
2.55.0