mirror of https://github.com/torvalds/linux.git
tools/mm: add script to display page state for a given PID and VADDR
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 0x7fc988181000
PID: 1 Comm: systemd mm: 0xffff8d22c4089700
RAW: 0017ffffc000416c fffff939062ff708 fffff939062ffe08 ffff8d23062a12a8
RAW: 0000000000000000 ffff8d2323438f60 0000002500000007 ffff8d23203ff500
Page Address: 0xfffff93905664e00
Page Flags: PG_referenced|PG_uptodate|PG_lru|PG_head|PG_active|
PG_private|PG_reported|PG_has_hwpoisoned
Page Size: 4096
Page PFN: 0x159938
Page Physical: 0x159938000
Page Virtual: 0xffff8d2319938000
Page Refcount: 37
Page Mapcount: 7
Page Index: 0x0
Page Memcg Data: 0xffff8d23203ff500
Memcg Name: init.scope
Memcg Path: /sys/fs/cgroup/memory/init.scope
Page Mapping: 0xffff8d23062a12a8
Page Anon/File: File
Page VMA: 0xffff8d22e06e0e40
VMA Start: 0x7fc988181000
VMA End: 0x7fc988185000
This page is part of a compound page.
This page is the head page of a compound page.
Head Page: 0xfffff93905664e00
Compound Order: 2
Number of Pages: 4
Link: https://lkml.kernel.org/r/20250530055855.687067-1-ye.liu@linux.dev
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Tested-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Omar Sandoval <osandov@osandov.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ye Liu
Andrew Morton
parent
af827e0904
commit
fee8870a09
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@ -18818,6 +18818,11 @@ F: Documentation/mm/page_table_check.rst
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F: include/linux/page_table_check.h
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F: mm/page_table_check.c
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PAGE STATE DEBUG SCRIPT
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M: Ye Liu <liuye@kylinos.cn>
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S: Maintained
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F: tools/mm/show_page_info.py
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PANASONIC LAPTOP ACPI EXTRAS DRIVER
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M: Kenneth Chan <kenneth.t.chan@gmail.com>
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L: platform-driver-x86@vger.kernel.org
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@ -0,0 +1,169 @@
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#!/usr/bin/env drgn
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# SPDX-License-Identifier: GPL-2.0-only
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# Copyright (C) 2025 Ye Liu <liuye@kylinos.cn>
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import argparse
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import sys
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from drgn import Object, FaultError, PlatformFlags, cast
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from drgn.helpers.linux import find_task, follow_page, page_size
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from drgn.helpers.linux.mm import (
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decode_page_flags, page_to_pfn, page_to_phys, page_to_virt, vma_find,
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PageSlab, PageCompound, PageHead, PageTail, compound_head, compound_order, compound_nr
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)
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from drgn.helpers.linux.cgroup import cgroup_name, cgroup_path
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DESC = """
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This is a drgn script to show the page state.
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For more info on drgn, visit https://github.com/osandov/drgn.
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"""
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def format_page_data(page):
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"""
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Format raw page data into a readable hex dump with "RAW:" prefix.
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:param page: drgn.Object instance representing the page.
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:return: Formatted string of memory contents.
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"""
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try:
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address = page.value_()
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size = prog.type("struct page").size
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if prog.platform.flags & PlatformFlags.IS_64_BIT:
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word_size = 8
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else:
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word_size = 4
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num_words = size // word_size
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values = []
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for i in range(num_words):
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word_address = address + i * word_size
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word = prog.read_word(word_address)
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values.append(f"{word:0{word_size * 2}x}")
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lines = [f"RAW: {' '.join(values[i:i + 4])}" for i in range(0, len(values), 4)]
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return "\n".join(lines)
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except FaultError as e:
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return f"Error reading memory: {e}"
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except Exception as e:
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return f"Unexpected error: {e}"
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def get_memcg_info(page):
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"""Retrieve memory cgroup information for a page."""
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try:
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MEMCG_DATA_OBJEXTS = prog.constant("MEMCG_DATA_OBJEXTS").value_()
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MEMCG_DATA_KMEM = prog.constant("MEMCG_DATA_KMEM").value_()
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mask = prog.constant('__NR_MEMCG_DATA_FLAGS').value_() - 1
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memcg_data = page.memcg_data.read_()
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if memcg_data & MEMCG_DATA_OBJEXTS:
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slabobj_ext = cast("struct slabobj_ext *", memcg_data & ~mask)
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memcg = slabobj_ext.objcg.memcg.value_()
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elif memcg_data & MEMCG_DATA_KMEM:
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objcg = cast("struct obj_cgroup *", memcg_data & ~mask)
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memcg = objcg.memcg.value_()
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else:
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memcg = cast("struct mem_cgroup *", memcg_data & ~mask)
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if memcg.value_() == 0:
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return "none", "/sys/fs/cgroup/memory/"
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cgrp = memcg.css.cgroup
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return cgroup_name(cgrp).decode(), f"/sys/fs/cgroup/memory{cgroup_path(cgrp).decode()}"
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except FaultError as e:
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return "unknown", f"Error retrieving memcg info: {e}"
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except Exception as e:
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return "unknown", f"Unexpected error: {e}"
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def show_page_state(page, addr, mm, pid, task):
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"""Display detailed information about a page."""
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try:
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print(f'PID: {pid} Comm: {task.comm.string_().decode()} mm: {hex(mm)}')
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try:
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print(format_page_data(page))
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except FaultError as e:
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print(f"Error reading page data: {e}")
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fields = {
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"Page Address": hex(page.value_()),
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"Page Flags": decode_page_flags(page),
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"Page Size": prog["PAGE_SIZE"].value_(),
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"Page PFN": hex(page_to_pfn(page).value_()),
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"Page Physical": hex(page_to_phys(page).value_()),
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"Page Virtual": hex(page_to_virt(page).value_()),
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"Page Refcount": page._refcount.counter.value_(),
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"Page Mapcount": page._mapcount.counter.value_(),
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"Page Index": hex(page.__folio_index.value_()),
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"Page Memcg Data": hex(page.memcg_data.value_()),
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}
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memcg_name, memcg_path = get_memcg_info(page)
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fields["Memcg Name"] = memcg_name
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fields["Memcg Path"] = memcg_path
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fields["Page Mapping"] = hex(page.mapping.value_())
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fields["Page Anon/File"] = "Anon" if page.mapping.value_() & 0x1 else "File"
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try:
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vma = vma_find(mm, addr)
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fields["Page VMA"] = hex(vma.value_())
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fields["VMA Start"] = hex(vma.vm_start.value_())
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fields["VMA End"] = hex(vma.vm_end.value_())
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except FaultError as e:
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fields["Page VMA"] = "Unavailable"
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fields["VMA Start"] = "Unavailable"
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fields["VMA End"] = "Unavailable"
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print(f"Error retrieving VMA information: {e}")
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# Calculate the maximum field name length for alignment
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max_field_len = max(len(field) for field in fields)
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# Print aligned fields
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for field, value in fields.items():
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print(f"{field}:".ljust(max_field_len + 2) + f"{value}")
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# Additional information about the page
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if PageSlab(page):
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print("This page belongs to the slab allocator.")
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if PageCompound(page):
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print("This page is part of a compound page.")
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if PageHead(page):
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print("This page is the head page of a compound page.")
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if PageTail(page):
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print("This page is the tail page of a compound page.")
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print(f"{'Head Page:'.ljust(max_field_len + 2)}{hex(compound_head(page).value_())}")
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print(f"{'Compound Order:'.ljust(max_field_len + 2)}{compound_order(page).value_()}")
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print(f"{'Number of Pages:'.ljust(max_field_len + 2)}{compound_nr(page).value_()}")
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else:
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print("This page is not part of a compound page.")
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except FaultError as e:
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print(f"Error accessing page state: {e}")
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except Exception as e:
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print(f"Unexpected error: {e}")
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def main():
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"""Main function to parse arguments and display page state."""
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parser = argparse.ArgumentParser(description=DESC, formatter_class=argparse.RawTextHelpFormatter)
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parser.add_argument('pid', metavar='PID', type=int, help='Target process ID (PID)')
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parser.add_argument('vaddr', metavar='VADDR', type=str, help='Target virtual address in hexadecimal format (e.g., 0x7fff1234abcd)')
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args = parser.parse_args()
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try:
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vaddr = int(args.vaddr, 16)
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except ValueError:
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sys.exit(f"Error: Invalid virtual address format: {args.vaddr}")
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try:
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task = find_task(args.pid)
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mm = task.mm
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page = follow_page(mm, vaddr)
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if page:
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show_page_state(page, vaddr, mm, args.pid, task)
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else:
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sys.exit(f"Address {hex(vaddr)} is not mapped.")
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except FaultError as e:
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sys.exit(f"Error accessing task or memory: {e}")
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except Exception as e:
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sys.exit(f"Unexpected error: {e}")
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if __name__ == "__main__":
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main()
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