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Message-Id: <20250421080748.114750-1-ye.liu@linux.dev>
Date: Mon, 21 Apr 2025 16:07:48 +0800
From: Ye Liu <ye.liu@...ux.dev>
To: akpm@...ux-foundation.org
Cc: linux-debuggers@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-mm@...ck.org,
linux-toolchains@...r.kernel.org,
osandov@...ndov.com,
paulmck@...nel.org,
sweettea-kernel@...miny.me,
liuye@...inos.cn,
ye.liu@...ux.dev
Subject: [PATCH v2] tools/mm: Add script to display page state for a given PID and VADDR
From: Ye Liu <liuye@...inos.cn>
Introduces a new drgn script, `show_page_info.py`, which allows users
to analyze the state of a page given a process ID (PID) and a virtual
address (VADDR). This can help kernel developers or debuggers easily
inspect page-related information in a live kernel or vmcore.
The script extracts information such as the page flags, mapping, and
other metadata relevant to diagnosing memory issues.
Output example:
sudo ./show_page_info.py 1 0x7f2c7de4c000
PID : 1 Comm : systemd mm : 0xffff888116b6d440
User Virtual Address : 0x7f2c7de4c000
Page Address : 0xffffea000b3a4000
raw: 0017ffffc000416c ffffea00045d1b08 ffffea000456d408 ffff888104521970
raw: 0000000000000000 ffff8881083fdb60 0000006900000018 ffff888107a41000
Page Flags : PG_referenced|PG_uptodate|PG_lru|PG_head|PG_active|
PG_private|PG_reported
Page Size : 16384
Page PFN : 0x2ce900
Page Physical : 0x2ce900000
Page Virtual : 0xffff8882ce900000
Page Refcount : 105
Page Mapcount : 24
Page Index : 0x0
Page Memcg Data : 0xffff888107a41000
Memcg Name : init.scope
Memcg Path : /sys/fs/cgroup/memory/init.scope
Page Mapping : 0xffff888104521970
Page Anon/File : File
Page VMA : 0xffff888109e135e8
VMA Start : 0x7f2c7de4c000
VMA End : 0x7f2c7de58000
This page is part of a compound page.
This page is the head page of a compound page.
Head Page : 0xffffea000b3a4000
Compound Order : 2
Number of Pages : 4
Signed-off-by: Ye Liu <liuye@...inos.cn>
Changes in v2:
- Move the show_page_info.py file to tools/mm.
- Link to v1: https://lore.kernel.org/all/20250415075024.248232-1-ye.liu@linux.dev/
---
MAINTAINERS | 5 ++
tools/mm/show_page_info.py | 114 +++++++++++++++++++++++++++++++++++++
2 files changed, 119 insertions(+)
create mode 100755 tools/mm/show_page_info.py
diff --git a/MAINTAINERS b/MAINTAINERS
index 17ed0b5ffdd2..85686a30dc72 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18351,6 +18351,11 @@ F: Documentation/mm/page_table_check.rst
F: include/linux/page_table_check.h
F: mm/page_table_check.c
+PAGE STATE DEBUG SCRIPT
+M: Ye Liu <liuye@...inos.cn>
+S: Maintained
+F: tools/mm/show_page_info.py
+
PANASONIC LAPTOP ACPI EXTRAS DRIVER
M: Kenneth Chan <kenneth.t.chan@...il.com>
L: platform-driver-x86@...r.kernel.org
diff --git a/tools/mm/show_page_info.py b/tools/mm/show_page_info.py
new file mode 100755
index 000000000000..e3cccc4743be
--- /dev/null
+++ b/tools/mm/show_page_info.py
@@ -0,0 +1,114 @@
+#!/usr/bin/env drgn
+# SPDX-License-Identifier: GPL-2.0-only
+# Copyright (C) 2025 Ye Liu <liuye@...inos.cn>
+
+import argparse
+from drgn import Object
+from drgn.helpers.linux import find_task, follow_page, page_size
+from drgn.helpers.linux.mm import (
+ decode_page_flags, page_to_pfn, page_to_phys, page_to_virt, vma_find,
+ PageSlab, PageCompound, PageHead, PageTail, compound_head, compound_order, compound_nr
+)
+from drgn.helpers.linux.cgroup import cgroup_name, cgroup_path
+
+DESC = """
+This is a drgn script to show the page state.
+For more info on drgn, visit https://github.com/osandov/drgn.
+"""
+
+MEMCG_DATA_OBJEXTS = 1 << 0
+MEMCG_DATA_KMEM = 1 << 1
+__NR_MEMCG_DATA_FLAGS = 1 << 2
+
+def format_page_data(data):
+ """Format raw page data into a readable hex dump."""
+ chunks = [data[i:i+8] for i in range(0, len(data), 8)]
+ hex_chunks = ["".join(f"{b:02x}" for b in chunk[::-1]) for chunk in chunks]
+ lines = [" ".join(hex_chunks[i:i+4]) for i in range(0, len(hex_chunks), 4)]
+ return "\n".join(f"raw: {line}" for line in lines)
+
+def get_memcg_info(page):
+ """Retrieve memory cgroup information for a page."""
+ memcg_data = page.memcg_data.value_()
+ if memcg_data & MEMCG_DATA_OBJEXTS:
+ memcg_value = 0
+ elif memcg_data & MEMCG_DATA_KMEM:
+ objcg = Object(prog, "struct obj_cgroup *", address=memcg_data & ~__NR_MEMCG_DATA_FLAGS)
+ memcg_value = objcg.memcg.value_()
+ else:
+ memcg_value = memcg_data & ~__NR_MEMCG_DATA_FLAGS
+
+ memcg = Object(prog, "struct mem_cgroup *", address=memcg_value)
+ cgrp = memcg.css.cgroup
+ return cgroup_name(cgrp).decode(), f"/sys/fs/cgroup/memory{cgroup_path(cgrp).decode()}"
+
+def show_page_state(page, addr, mm, pid, task):
+ """Display detailed information about a page."""
+ print(f'PID : {pid} Comm : {task.comm.string_().decode()} mm : {hex(mm)}')
+ print(f'User Virtual Address : {hex(addr)}')
+ print(f'Page Address : {hex(page.value_())}')
+
+ print(format_page_data(prog.read(page.value_(), 64)))
+
+ print(f'Page Flags : {decode_page_flags(page)}')
+ print(f'Page Size : {page_size(page).value_()}')
+ print(f'Page PFN : {hex(page_to_pfn(page).value_())}')
+ print(f'Page Physical : {hex(page_to_phys(page).value_())}')
+ print(f'Page Virtual : {hex(page_to_virt(page).value_())}')
+ print(f'Page Refcount : {page._refcount.counter.value_()}')
+ print(f'Page Mapcount : {page._mapcount.counter.value_()}')
+ print(f'Page Index : {hex(page.index.value_())}')
+ print(f'Page Memcg Data : {hex(page.memcg_data.value_())}')
+
+ memcg_name, memcg_path = get_memcg_info(page)
+ print(f'Memcg Name : {memcg_name}')
+ print(f'Memcg Path : {memcg_path}')
+
+ print(f'Page Mapping : {hex(page.mapping.value_())}')
+ print(f'Page Anon/File : {"Anon" if page.mapping.value_() & 0x1 else "File"}')
+
+ vma = vma_find(mm, addr)
+ print(f'Page VMA : {hex(vma.value_())}')
+ print(f'VMA Start : {hex(vma.vm_start.value_())}')
+ print(f'VMA End : {hex(vma.vm_end.value_())}')
+
+ if PageSlab(page):
+ print("This page belongs to the slab allocator.")
+
+ if PageCompound(page):
+ print("This page is part of a compound page.")
+ if PageHead(page):
+ print("This page is the head page of a compound page.")
+ if PageTail(page):
+ print("This page is the tail page of a compound page.")
+ print(f'Head Page : {hex(compound_head(page).value_())}')
+ print(f'Compound Order : {compound_order(page).value_()}')
+ print(f'Number of Pages : {compound_nr(page).value_()}')
+ else:
+ print("This page is not part of a compound page.")
+
+def main():
+ """Main function to parse arguments and display page state."""
+ parser = argparse.ArgumentParser(description=DESC, formatter_class=argparse.RawTextHelpFormatter)
+ parser.add_argument('pid', metavar='PID', type=int, help='Target process ID (PID)')
+ parser.add_argument('vaddr', metavar='VADDR', type=str, help='Target virtual address in hexadecimal format (e.g., 0x7fff1234abcd)')
+ args = parser.parse_args()
+
+ try:
+ vaddr = int(args.vaddr, 16)
+ except ValueError:
+ print(f"Error: Invalid virtual address format: {args.vaddr}")
+ return
+
+ task = find_task(args.pid)
+ mm = task.mm
+ page = follow_page(mm, vaddr)
+
+ if page:
+ show_page_state(page, vaddr, mm, args.pid, task)
+ else:
+ print(f"Address {hex(vaddr)} is not mapped.")
+
+if __name__ == "__main__":
+ main()
+
--
2.25.1
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