linux-kernel - [PATCH 4/6] scripts/gdb: set vabits_actual based on TCR

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Date: Wed, 19 Jun 2024 15:49:09 +0800
From: Kuan-Ying Lee <kuan-ying.lee@...onical.com>
To: kuan-ying.lee@...onical.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Kieran Bingham <kbingham@...nel.org>,
	Ard Biesheuvel <ardb@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/6] scripts/gdb: set vabits_actual based on TCR_EL1

We encounter the following issue after commit 9cce9c6c2c3b ("arm64: mm: Handle
LVA support as a CPU feature").

(gdb) lx-slabinfo
Python Exception <class 'gdb.error'>: No symbol "vabits_actual" in current context.
Error occurred in Python: No symbol "vabits_actual" in current context.

We set vabits_actual based on TCR_EL1 value when
VA_BITS is bigger than 48.

Fixes: 9cce9c6c2c3b ("arm64: mm: Handle LVA support as a CPU feature")
Signed-off-by: Kuan-Ying Lee <kuan-ying.lee@...onical.com>
---
 scripts/gdb/linux/mm.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/scripts/gdb/linux/mm.py b/scripts/gdb/linux/mm.py
index f8b9be3f43e8..200def0e4b9a 100644
--- a/scripts/gdb/linux/mm.py
+++ b/scripts/gdb/linux/mm.py
@@ -48,7 +48,9 @@ class aarch64_page_ops():
         self.VA_BITS = constants.LX_CONFIG_ARM64_VA_BITS
         if self.VA_BITS > 48:
             self.VA_BITS_MIN = 48
-            self.vabits_actual = gdb.parse_and_eval('vabits_actual')
+            tcr_el1 = gdb.execute("info registers $TCR_EL1", to_string=True)
+            tcr_el1 = int(tcr_el1.split()[1], 16)
+            self.vabits_actual = 64 - ((tcr_el1 >> 16) & 63)
         else:
             self.VA_BITS_MIN = self.VA_BITS
             self.vabits_actual = self.VA_BITS
-- 
2.34.1