[PATCH 0/3] tools/mm: show_page_info.py enhancements and fixes

[PATCH 0/3] tools/mm: show_page_info.py enhancements and fixes

[Ye Liu]

This series improves the show_page_info.py drgn script with bug fixes
and new features:

Patch 1 fixes memory cgroup information retrieval by updating the
obj_cgroup type casting and handling slabobj_ext field name changes
for compatibility with newer kernel versions.

Patch 2 removes the incorrect Page Index field display, as pages
don't have indexes - only folios do.

Patch 3 adds VMA flags decoding and VMA name display to provide
more detailed information about the virtual memory area containing
the page.

These changes ensure the script works correctly with current kernel
memory management structures and provides more comprehensive page
state information.

Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
Actual results：

drgn -s /root/linux-next/vmlinux show_page_info.py 1 7f17c9ab5000

PID: 1 Comm: systemd mm: 0xffff8d796ab73800
RAW: 0017ffffc0020028 fffff2af04d3aa88 fffff2af04d3ab08 ffff8d794703b901
RAW: 00000007f17c9ab5 0000000000000000 0000000100000000 ffff8d79438fd700
Page Address:    0xfffff2af04d3aac0
Page Flags:      PG_uptodate|PG_lru|PG_swapbacked|PG_movable_ops|PG_reported
Page Size:       4096
Page PFN:        0x134eab
Page Physical:   0x134eab000
Page Virtual:    0xffff8d7974eab000
Page Refcount:   1
Page Mapcount:   0
Page Memcg Data: 0xffff8d79438fd700
Memcg Name:      init.scope
Memcg Path:      /sys/fs/cgroup/memory/init.scope
Page Mapping:    0xffff8d794703b901
Page Anon/File:  Anon
Page VMA:        0xffff8d796b0c0cc0
VMA Start:       0x7f17c9ab5000
VMA End:         0x7f17c9ab6000
VMA Flags:       0x8100073 (READ|WRITE|MAYREAD|MAYWRITE|MAYEXEC|ACCOUNT|SOFTDIRTY)
VMA Name:        /usr/lib64/libmount.so.1.1.0
This page is not part of a compound page.

---
Ye Liu (3):
      tools/mm: fix memcg info retrieval in show_page_info.py
      tools/mm: remove Page Index field from show_page_info
      tools/mm: add VMA flags decoding and name display to show_page_info.py

 tools/mm/show_page_info.py | 68 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 60 insertions(+), 8 deletions(-)
---
base-commit: 1fffefb00cc0b0da1f2ae24e3d33364530ea6515
base-tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
change-id: 20261014-show_page_info-12fb720e5592

Best regards,
--  
Ye Liu <ye.liu@linux.dev>

[PATCH 1/3] tools/mm: fix memcg info retrieval in show_page_info.py

[Ye Liu]

From: Ye Liu <liuye@kylinos.cn>

Fix obj_cgroup type casting and slabobj_ext field name compatibility.

Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
 tools/mm/show_page_info.py | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/tools/mm/show_page_info.py b/tools/mm/show_page_info.py
index c46d8ea283d7..9cfb5cac05a3 100644
--- a/tools/mm/show_page_info.py
+++ b/tools/mm/show_page_info.py
@@ -53,17 +53,18 @@ 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_()
+            try:
+                objcg = slabobj_ext._objcg
+            except AttributeError:
+                objcg = slabobj_ext.objcg
+            memcg = objcg.memcg
         else:
-            memcg = cast("struct mem_cgroup *", memcg_data & ~mask)
+            objcg = Object(prog, "struct obj_cgroup *", memcg_data & ~mask)
+            memcg = objcg.memcg
 
         if memcg.value_() == 0:
             return "none", "/sys/fs/cgroup/memory/"

-- 
2.43.0

[PATCH 2/3] tools/mm: remove Page Index field from show_page_info

[Ye Liu]

Pages don't have indexes, folios have indexes. Remove the
__folio_index field access.

Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
 tools/mm/show_page_info.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tools/mm/show_page_info.py b/tools/mm/show_page_info.py
index 9cfb5cac05a3..1fbef3889e91 100644
--- a/tools/mm/show_page_info.py
+++ b/tools/mm/show_page_info.py
@@ -92,7 +92,6 @@ def show_page_state(page, addr, mm, pid, task):
             "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_()),
         }
 

-- 
2.43.0

[PATCH 3/3] tools/mm: add VMA flags decoding and name display to show_page_info.py

[Ye Liu]

From: Ye Liu <liuye@kylinos.cn>

Add support for decoding VMA flags into human-readable format and
displaying VMA names. This provides more detailed information about
the virtual memory area containing the page.

Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
 tools/mm/show_page_info.py | 54 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

diff --git a/tools/mm/show_page_info.py b/tools/mm/show_page_info.py
index 1fbef3889e91..9dc65b4d2b29 100644
--- a/tools/mm/show_page_info.py
+++ b/tools/mm/show_page_info.py
@@ -7,10 +7,11 @@ 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,
+    decode_page_flags, page_to_pfn, page_to_phys, page_to_virt, vma_find, vma_name,
     PageSlab, PageCompound, PageHead, PageTail, compound_head, compound_order, compound_nr
 )
 from drgn.helpers.linux.cgroup import cgroup_name, cgroup_path
+from drgn.helpers.common.format import decode_flags
 
 DESC = """
 This is a drgn script to show the page state.
@@ -75,6 +76,52 @@ def get_memcg_info(page):
     except Exception as e:
         return "unknown", f"Unexpected error: {e}"
 
+def format_vma_flags(flags: int) -> str:
+    """
+    Format VMA flags into a human-readable string.
+
+    :param flags: The VMA flags as an integer.
+    :return: A string representation of the flags.
+    """
+    # VM flags from include/uapi/linux/mm.h
+    # Since Linux 6.19 (commit 2b6a3f061f11), VMA flag bit numbers are defined
+    # in an anonymous enum. For older kernels, we hard-code them.
+    VM_FLAGS = [
+        ("READ", 0x00000001),
+        ("WRITE", 0x00000002),
+        ("EXEC", 0x00000004),
+        ("SHARED", 0x00000008),
+        ("MAYREAD", 0x00000010),
+        ("MAYWRITE", 0x00000020),
+        ("MAYEXEC", 0x00000040),
+        ("MAYSHARE", 0x00000080),
+        ("GROWSDOWN", 0x00000100),
+        ("UFFD_MISSING", 0x00000200),
+        ("PFNMAP", 0x00000400),
+        ("DENYWRITE", 0x00000800),
+        ("EXECUTABLE", 0x00001000),
+        ("LOCKED", 0x00002000),
+        ("IO", 0x00004000),
+        ("SEQ_READ", 0x00008000),
+        ("RAND_READ", 0x00010000),
+        ("DONTCOPY", 0x00020000),
+        ("DONTEXPAND", 0x00040000),
+        ("LOCKONFAULT", 0x00080000),
+        ("ACCOUNT", 0x00100000),
+        ("NORESERVE", 0x00200000),
+        ("HUGETLB", 0x00400000),
+        ("SYNC", 0x00800000),
+        ("ARCH_1", 0x01000000),
+        ("WIPEONFORK", 0x02000000),
+        ("DONTDUMP", 0x04000000),
+        ("SOFTDIRTY", 0x08000000),
+        ("MIXEDMAP", 0x10000000),
+        ("HUGEPAGE", 0x20000000),
+        ("NOHUGEPAGE", 0x40000000),
+        ("MERGEABLE", 0x80000000),
+    ]
+    return decode_flags(flags, VM_FLAGS, bit_numbers=False)
+
 def show_page_state(page, addr, mm, pid, task):
     """Display detailed information about a page."""
     try:
@@ -106,10 +153,15 @@ def show_page_state(page, addr, mm, pid, task):
             fields["Page VMA"] = hex(vma.value_())
             fields["VMA Start"] = hex(vma.vm_start.value_())
             fields["VMA End"] = hex(vma.vm_end.value_())
+            vma_flags_hex = hex(vma.vm_flags.value_())
+            vma_flags_readable = format_vma_flags(vma.vm_flags.value_())
+            fields["VMA Flags"] = f"{vma_flags_hex} ({vma_flags_readable})"
+            fields["VMA Name"] = vma_name(vma).decode()
         except FaultError as e:
             fields["Page VMA"] = "Unavailable"
             fields["VMA Start"] = "Unavailable"
             fields["VMA End"] = "Unavailable"
+            fields["VMA Flags"] = "Unavailable"
             print(f"Error retrieving VMA information: {e}")
 
         # Calculate the maximum field name length for alignment

-- 
2.43.0