scripts/gdb: change the layout of vmemmap

We need to change the layout of vmemmap in gdb scripts after
commit 32697ff ("arm64: vmemmap: Avoid base2 order of
struct page size to dimension region") changed it.

Link: https://lkml.kernel.org/r/20240619074911.100434-4-kuan-ying.lee@canonical.com
Fixes: 32697ff ("arm64: vmemmap: Avoid base2 order of struct page size to dimension region")
Signed-off-by: Kuan-Ying Lee <kuan-ying.lee@canonical.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: kylee0215

scripts/gdb/linux/mm.py

@@ -89,10 +89,10 @@ def __init__(self):
         self.MODULES_VADDR = self._PAGE_END(self.VA_BITS_MIN)
         self.MODULES_END = self.MODULES_VADDR + self.MODULES_VSIZE
 
-        self.VMEMMAP_SHIFT = (self.PAGE_SHIFT - self.STRUCT_PAGE_MAX_SHIFT)
-        self.VMEMMAP_SIZE = ((self._PAGE_END(self.VA_BITS_MIN) - self.PAGE_OFFSET) >> self.VMEMMAP_SHIFT)
-        self.VMEMMAP_START = (-(1 << (self.VA_BITS - self.VMEMMAP_SHIFT))) & 0xffffffffffffffff
-        self.VMEMMAP_END = self.VMEMMAP_START + self.VMEMMAP_SIZE
+        self.VMEMMAP_RANGE = self._PAGE_END(self.VA_BITS_MIN) - self.PAGE_OFFSET
+        self.VMEMMAP_SIZE = (self.VMEMMAP_RANGE >> self.PAGE_SHIFT) * self.struct_page_size
+        self.VMEMMAP_END = (-(1 * 1024 * 1024 * 1024)) & 0xffffffffffffffff
+        self.VMEMMAP_START = self.VMEMMAP_END - self.VMEMMAP_SIZE
 
         self.VMALLOC_START = self.MODULES_END
         self.VMALLOC_END = self.VMEMMAP_START - 256 * 1024 * 1024