bcc/tools-slabratetop-Fix-error-incomplete-definition-of.patch

From 01b7a5320857676f4f5b610db588d4e7d14a2372 Mon Sep 17 00:00:00 2001
From: Rong Tao <rongtao@cestc.cn>
Date: Sun, 22 Jan 2023 15:44:46 +0800
Subject: [PATCH] tools/slabratetop: Fix error: incomplete definition of type
 'struct slab'

kernel commit 40f3bf0cb04c("mm: Convert struct page to struct slab in functions
used by other subsystems") introduce slab_address() function, commit 6e48a966dfd1
("mm/kasan: Convert to struct folio and struct slab") linux/kasan.h adds a
dependency on the slab struct, This leads to the following problems:

    $ sudo ./slabratetop.py
    In file included from /virtual/main.c:13:
    include/linux/slub_def.h:162:26: warning: call to undeclared function 'slab_address';
    ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
            void *object = x - (x - slab_address(slab)) % cache->size;
                                    ^
    include/linux/slub_def.h:162:46: error: invalid operands to binary expression ('void *' and 'unsigned int')
            void *object = x - (x - slab_address(slab)) % cache->size;
                               ~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~
    include/linux/slub_def.h:164:8: error: incomplete definition of type 'struct slab'
                    (slab->objects - 1) * cache->size;
                     ~~~~^
    include/linux/kasan.h:13:8: note: forward declaration of 'struct slab'
    struct slab;
           ^
    ...

At first, I wanted to fix this with a kernel patch [1], however, bcc as a
downstream project of the kernel, this issue should be solved inside the bcc
project. This is agreed by kernel maintainer and bcc maintainer @yonghong-song.

This solution is provided by @yonghong-song [0].

[0] https://github.com/iovisor/bcc/issues/4438
[1] https://lore.kernel.org/all/tencent_ABA832E296819D1053D6C625ADCAF76BC706@qq.com/

Signed-off-by: Rong Tao <rongtao@cestc.cn>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/slabratetop.py | 76 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/tools/slabratetop.py b/tools/slabratetop.py
index ac44b2bd..8fbcac5e 100755
--- a/tools/slabratetop.py
+++ b/tools/slabratetop.py
@@ -14,6 +14,9 @@
 # Licensed under the Apache License, Version 2.0 (the "License")
 #
 # 15-Oct-2016   Brendan Gregg   Created this.
+# 23-Jan-2023   Rong Tao        Introduce kernel internal data structure and
+#                               functions to temporarily solve problem for
+#                               >=5.16(TODO: fix this workaround)
 
 from __future__ import print_function
 from bcc import BPF
@@ -65,6 +68,79 @@ bpf_text = """
 // 5.9, but it does not hurt to have it here for versions 5.4 to 5.8.
 struct memcg_cache_params {};
 
+// introduce kernel interval slab structure and slab_address() function, solved
+// 'undefined' error for >=5.16. TODO: we should fix this workaround if BCC
+// framework support BTF/CO-RE.
+struct slab {
+    unsigned long __page_flags;
+
+#if defined(CONFIG_SLAB)
+
+    struct kmem_cache *slab_cache;
+    union {
+        struct {
+            struct list_head slab_list;
+            void *freelist; /* array of free object indexes */
+            void *s_mem;    /* first object */
+        };
+        struct rcu_head rcu_head;
+    };
+    unsigned int active;
+
+#elif defined(CONFIG_SLUB)
+
+    struct kmem_cache *slab_cache;
+    union {
+        struct {
+            union {
+                struct list_head slab_list;
+#ifdef CONFIG_SLUB_CPU_PARTIAL
+                struct {
+                    struct slab *next;
+                        int slabs;      /* Nr of slabs left */
+                };
+#endif
+            };
+            /* Double-word boundary */
+            void *freelist;         /* first free object */
+            union {
+                unsigned long counters;
+                struct {
+                    unsigned inuse:16;
+                    unsigned objects:15;
+                    unsigned frozen:1;
+                };
+            };
+        };
+        struct rcu_head rcu_head;
+    };
+    unsigned int __unused;
+
+#elif defined(CONFIG_SLOB)
+
+    struct list_head slab_list;
+    void *__unused_1;
+    void *freelist;         /* first free block */
+    long units;
+    unsigned int __unused_2;
+
+#else
+#error "Unexpected slab allocator configured"
+#endif
+
+    atomic_t __page_refcount;
+#ifdef CONFIG_MEMCG
+    unsigned long memcg_data;
+#endif
+};
+
+// slab_address() will not be used, and NULL will be returned directly, which
+// can avoid adaptation of different kernel versions
+static inline void *slab_address(const struct slab *slab)
+{
+    return NULL;
+}
+
 #ifdef CONFIG_SLUB
 #include <linux/slub_def.h>
 #else
-- 
2.39.1