Date: Fri, 30 Aug 2024 10:33:03 -0000
From: qiwu.chen@transsion.com
Subject: [Crash-utility] [PATCH] kmem: fix the determination for slab
        page
To: devel@lists.crash-utility.osci.io
Message-ID: <20240830103303.2824.23557@lists.crash-utility.osci.io>
Content-Type: text/plain; charset="utf-8"

The determination for a slab page is changed since kernel commit
8db00ad564617 which migrates PG_slab flag from page flags to the
lower 16 bit of the page type.

Before apply this patch:
crash> kmem -s ffff000002aa4100
kmem: address is not allocated in slab subsystem: ffff000002aa4100

After apply this patch:
crash> kmem -s ffff000002aa4100
CACHE             OBJSIZE  ALLOCATED     TOTAL  SLABS  SSIZE  NAME
ffff00000140f900     4096         94       126     18    32k  task_struct
  SLAB              MEMORY            NODE  TOTAL  ALLOCATED  FREE
  fffffdffc00aa800  ffff000002aa0000     0      7          5     2
  FREE / [ALLOCATED]
  [ffff000002aa4100]

Signed-off-by: qiwu.chen <qiwu.chen@transsion.com>
---
 defs.h   |  1 +
 memory.c | 23 +++++++++++++++++++----
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/defs.h b/defs.h
index e9eb9e3..9ef7f97 100644
--- a/defs.h
+++ b/defs.h
@@ -2289,6 +2289,7 @@ struct offset_table {                    /* stash of commonly-used offsets */
        long track_cpu;
        long track_when;
        long track_handle;
+       long page_page_type;
 };

 struct size_table {         /* stash of commonly-used sizes */
diff --git a/memory.c b/memory.c
index 7bf8f86..f9ad6e4 100644
--- a/memory.c
+++ b/memory.c
@@ -509,6 +509,8 @@ vm_init(void)
                ANON_MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head");
        MEMBER_OFFSET_INIT(page_private, "page", "private");
        MEMBER_OFFSET_INIT(page_freelist, "page", "freelist");
+       if (MEMBER_EXISTS("page", "page_type"))
+               MEMBER_OFFSET_INIT(page_page_type, "page", "page_type");

        MEMBER_OFFSET_INIT(mm_struct_pgd, "mm_struct", "pgd");

@@ -10114,7 +10116,7 @@ static char *
 vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose)
 {
        physaddr_t paddr;
-       ulong page, cache, page_flags;
+       ulong page, cache, page_flags, page_type;

         if (!kvtop(NULL, vaddr, &paddr, 0)) {
                if (verbose)
@@ -10143,7 +10145,10 @@ vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose)
                                readmem(compound_head(page)+OFFSET(page_flags), KVADDR,
                                        &page_flags, sizeof(ulong), "page.flags",
                                        FAULT_ON_ERROR);
-                               if (!(page_flags & (1 << vt->PG_slab)))
+                               readmem(page + OFFSET(page_page_type), KVADDR, &page_type,
+                                       sizeof(ulong), "page type", FAULT_ON_ERROR);
+                               if (!(page_flags & (1 << vt->PG_slab)) &&
+                                       !(page_type & (1 << vt->PG_slab)))
                                        return NULL;
                        } else
                                return NULL;
@@ -20688,7 +20693,7 @@ char *
 is_slab_page(struct meminfo *si, char *buf)
 {
        int i, cnt;
-       ulong page_slab, page_flags, name;
+       ulong page_slab, page_flags, page_type, name;
         ulong *cache_list;
         char *retval;

@@ -20703,7 +20708,17 @@ is_slab_page(struct meminfo *si, char *buf)
            RETURN_ON_ERROR|QUIET))
                return NULL;

-       if (!(page_flags & (1 << vt->PG_slab)))
+       if (!readmem(si->spec_addr + OFFSET(page_page_type), KVADDR,
+           &page_type, sizeof(ulong), "page.page_type",
+           RETURN_ON_ERROR|QUIET))
+               return NULL;
+
+       /*
+        * PG_slab is migrated from the page flags to the lower 16 bit
+        * of the page type since linux commit 8db00ad564617.
+        */
+       if (!(page_flags & (1 << vt->PG_slab)) &&
+               !(page_type & (1 << vt->PG_slab)))
                return NULL;

        if (!readmem(si->spec_addr + OFFSET(page_slab), KVADDR,
--
2.25.1