+ tools-mm-add-script-to-display-page-state-for-a-given-pid-and-vaddr.patch added to mm-new branch

+ tools-mm-add-script-to-display-page-state-for-a-given-pid-and-vaddr.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: tools/mm: add script to display page state for a given PID and VADDR
has been added to the -mm mm-new branch.  Its filename is
     tools-mm-add-script-to-display-page-state-for-a-given-pid-and-vaddr.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/tools-mm-add-script-to-display-page-state-for-a-given-pid-and-vaddr.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
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
@@ -18678,6 +18678,11 @@ 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()
_

Patches currently in -mm which might be from liuye@kylinos.cn are

tools-mm-add-script-to-display-page-state-for-a-given-pid-and-vaddr.patch