| From: Ye Liu <liuye@kylinos.cn> |
| Subject: tools/mm: add script to display page state for a given PID and VADDR |
| Date: Fri, 30 May 2025 13:58:55 +0800 |
| |
| 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> |
| --- |
| |
| MAINTAINERS | 5 + |
| tools/mm/show_page_info.py | 169 +++++++++++++++++++++++++++++++++++ |
| 2 files changed, 174 insertions(+) |
| |
| --- a/MAINTAINERS~tools-mm-add-script-to-display-page-state-for-a-given-pid-and-vaddr |
| +++ a/MAINTAINERS |
| @@ -18818,6 +18818,11 @@ 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@kylinos.cn> |
| +S: Maintained |
| +F: tools/mm/show_page_info.py |
| + |
| PANASONIC LAPTOP ACPI EXTRAS DRIVER |
| M: Kenneth Chan <kenneth.t.chan@gmail.com> |
| L: platform-driver-x86@vger.kernel.org |
| diff --git a/tools/mm/show_page_info.py a/tools/mm/show_page_info.py |
| new file mode 100644 |
| --- /dev/null |
| +++ a/tools/mm/show_page_info.py |
| @@ -0,0 +1,169 @@ |
| +#!/usr/bin/env drgn |
| +# SPDX-License-Identifier: GPL-2.0-only |
| +# Copyright (C) 2025 Ye Liu <liuye@kylinos.cn> |
| + |
| +import argparse |
| +import sys |
| +from drgn import Object, FaultError, PlatformFlags, cast |
| +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. |
| +""" |
| + |
| +def format_page_data(page): |
| + """ |
| + Format raw page data into a readable hex dump with "RAW:" prefix. |
| + |
| + :param page: drgn.Object instance representing the page. |
| + :return: Formatted string of memory contents. |
| + """ |
| + try: |
| + address = page.value_() |
| + size = prog.type("struct page").size |
| + |
| + if prog.platform.flags & PlatformFlags.IS_64_BIT: |
| + word_size = 8 |
| + else: |
| + word_size = 4 |
| + num_words = size // word_size |
| + |
| + values = [] |
| + for i in range(num_words): |
| + word_address = address + i * word_size |
| + word = prog.read_word(word_address) |
| + values.append(f"{word:0{word_size * 2}x}") |
| + |
| + lines = [f"RAW: {' '.join(values[i:i + 4])}" for i in range(0, len(values), 4)] |
| + |
| + return "\n".join(lines) |
| + |
| + except FaultError as e: |
| + return f"Error reading memory: {e}" |
| + except Exception as e: |
| + return f"Unexpected error: {e}" |
| + |
| +def get_memcg_info(page): |
| + """Retrieve memory cgroup information for a page.""" |
| + try: |
| + MEMCG_DATA_OBJEXTS = prog.constant("MEMCG_DATA_OBJEXTS").value_() |
| + MEMCG_DATA_KMEM = prog.constant("MEMCG_DATA_KMEM").value_() |
| + mask = prog.constant('__NR_MEMCG_DATA_FLAGS').value_() - 1 |
| + memcg_data = page.memcg_data.read_() |
| + if memcg_data & MEMCG_DATA_OBJEXTS: |
| + slabobj_ext = cast("struct slabobj_ext *", memcg_data & ~mask) |
| + memcg = slabobj_ext.objcg.memcg.value_() |
| + elif memcg_data & MEMCG_DATA_KMEM: |
| + objcg = cast("struct obj_cgroup *", memcg_data & ~mask) |
| + memcg = objcg.memcg.value_() |
| + else: |
| + memcg = cast("struct mem_cgroup *", memcg_data & ~mask) |
| + |
| + if memcg.value_() == 0: |
| + return "none", "/sys/fs/cgroup/memory/" |
| + cgrp = memcg.css.cgroup |
| + return cgroup_name(cgrp).decode(), f"/sys/fs/cgroup/memory{cgroup_path(cgrp).decode()}" |
| + except FaultError as e: |
| + return "unknown", f"Error retrieving memcg info: {e}" |
| + except Exception as e: |
| + return "unknown", f"Unexpected error: {e}" |
| + |
| +def show_page_state(page, addr, mm, pid, task): |
| + """Display detailed information about a page.""" |
| + try: |
| + print(f'PID: {pid} Comm: {task.comm.string_().decode()} mm: {hex(mm)}') |
| + try: |
| + print(format_page_data(page)) |
| + except FaultError as e: |
| + print(f"Error reading page data: {e}") |
| + fields = { |
| + "Page Address": hex(page.value_()), |
| + "Page Flags": decode_page_flags(page), |
| + "Page Size": prog["PAGE_SIZE"].value_(), |
| + "Page PFN": hex(page_to_pfn(page).value_()), |
| + "Page Physical": hex(page_to_phys(page).value_()), |
| + "Page Virtual": hex(page_to_virt(page).value_()), |
| + "Page Refcount": page._refcount.counter.value_(), |
| + "Page Mapcount": page._mapcount.counter.value_(), |
| + "Page Index": hex(page.__folio_index.value_()), |
| + "Page Memcg Data": hex(page.memcg_data.value_()), |
| + } |
| + |
| + memcg_name, memcg_path = get_memcg_info(page) |
| + fields["Memcg Name"] = memcg_name |
| + fields["Memcg Path"] = memcg_path |
| + fields["Page Mapping"] = hex(page.mapping.value_()) |
| + fields["Page Anon/File"] = "Anon" if page.mapping.value_() & 0x1 else "File" |
| + |
| + try: |
| + vma = vma_find(mm, addr) |
| + fields["Page VMA"] = hex(vma.value_()) |
| + fields["VMA Start"] = hex(vma.vm_start.value_()) |
| + fields["VMA End"] = hex(vma.vm_end.value_()) |
| + except FaultError as e: |
| + fields["Page VMA"] = "Unavailable" |
| + fields["VMA Start"] = "Unavailable" |
| + fields["VMA End"] = "Unavailable" |
| + print(f"Error retrieving VMA information: {e}") |
| + |
| + # Calculate the maximum field name length for alignment |
| + max_field_len = max(len(field) for field in fields) |
| + |
| + # Print aligned fields |
| + for field, value in fields.items(): |
| + print(f"{field}:".ljust(max_field_len + 2) + f"{value}") |
| + |
| + # Additional information about the page |
| + 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:'.ljust(max_field_len + 2)}{hex(compound_head(page).value_())}") |
| + print(f"{'Compound Order:'.ljust(max_field_len + 2)}{compound_order(page).value_()}") |
| + print(f"{'Number of Pages:'.ljust(max_field_len + 2)}{compound_nr(page).value_()}") |
| + else: |
| + print("This page is not part of a compound page.") |
| + except FaultError as e: |
| + print(f"Error accessing page state: {e}") |
| + except Exception as e: |
| + print(f"Unexpected error: {e}") |
| + |
| +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: |
| + sys.exit(f"Error: Invalid virtual address format: {args.vaddr}") |
| + |
| + try: |
| + 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: |
| + sys.exit(f"Address {hex(vaddr)} is not mapped.") |
| + except FaultError as e: |
| + sys.exit(f"Error accessing task or memory: {e}") |
| + except Exception as e: |
| + sys.exit(f"Unexpected error: {e}") |
| + |
| +if __name__ == "__main__": |
| + main() |
| _ |
