scripts/gdb/stackdepot: add stackdepot support

Add support for printing the backtrace of stackdepot handle.

This is the preparation patch for dumping page_owner,
slabtrace usage.

Link: https://lkml.kernel.org/r/20230808083020.22254-6-Kuan-Ying.Lee@mediatek.com
Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Qun-Wei Lin <qun-wei.lin@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

scripts/gdb/linux/constants.py.in

@@ -128,3 +128,4 @@ LX_CONFIG(CONFIG_VMAP_STACK)
 if IS_BUILTIN(CONFIG_NUMA):
     LX_VALUE(CONFIG_NODES_SHIFT)
 LX_CONFIG(CONFIG_DEBUG_VIRTUAL)
+LX_CONFIG(CONFIG_STACKDEPOT)

scripts/gdb/linux/stackdepot.py

@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (c) 2023 MediaTek Inc.
+#
+# Authors:
+#  Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
+#
+
+import gdb
+from linux import utils, constants
+
+if constants.LX_CONFIG_STACKDEPOT:
+    stack_record_type = utils.CachedType('struct stack_record')
+    DEPOT_STACK_ALIGN = 4
+
+def stack_depot_fetch(handle):
+    global DEPOT_STACK_ALIGN
+    global stack_record_type
+
+    stack_depot_disabled = gdb.parse_and_eval('stack_depot_disabled')
+
+    if stack_depot_disabled:
+        raise gdb.GdbError("stack_depot_disabled\n")
+
+    handle_parts_t = gdb.lookup_type("union handle_parts")
+    parts = handle.cast(handle_parts_t)
+    offset = parts['offset'] << DEPOT_STACK_ALIGN
+    pool_index_cached = gdb.parse_and_eval('pool_index')
+
+    if parts['pool_index'] > pool_index_cached:
+        gdb.write("pool index %d out of bounds (%d) for stack id 0x%08x\n" % (parts['pool_index'], pool_index_cached, handle))
+        return gdb.Value(0), 0
+
+    stack_pools = gdb.parse_and_eval('stack_pools')
+
+    try:
+        pool = stack_pools[parts['pool_index']]
+        stack = (pool + gdb.Value(offset).cast(utils.get_size_t_type())).cast(stack_record_type.get_type().pointer())
+        size = int(stack['size'].cast(utils.get_ulong_type()))
+        return stack['entries'], size
+    except Exception as e:
+        gdb.write("%s\n" % e)
+        return gdb.Value(0), 0
+
+def stack_depot_print(handle):
+    if not constants.LX_CONFIG_STACKDEPOT:
+        raise gdb.GdbError("CONFIG_STACKDEPOT is not enabled")
+
+    entries, nr_entries = stack_depot_fetch(handle)
+    if nr_entries > 0:
+        for i in range(0, nr_entries):
+            try:
+                gdb.execute("x /i 0x%x" % (int(entries[i])))
+            except Exception as e:
+                gdb.write("%s\n" % e)

scripts/gdb/vmlinux-gdb.py

@@ -45,3 +45,4 @@ else:
     import linux.radixtree
     import linux.interrupts
     import linux.mm
+    import linux.stackdepot