[PATCH] slub: extend slub debug to handle multiple slabs

[PATCH] slub: extend slub debug to handle multiple slabs

[Aaron Tomlin]

Extend the slub_debug syntax to "slub_debug=<flags>[,<slub>]*", where <slub>
may contain an asterisk at the end.  For example, the following would poison
all kmalloc slabs:

	slub_debug=P,kmalloc*

and the following would apply the default flags to all kmalloc and all block IO
slabs:

	slub_debug=,bio*,kmalloc*

Please note that a similar patch was posted by Iliyan Malchev some time ago but
was never merged:

	https://marc.info/?l=linux-mm&m=131283905330474&w=2


Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
---
 Documentation/vm/slub.rst | 12 +++++++++---
 mm/slub.c                 | 34 +++++++++++++++++++++++++++++++---
 2 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/Documentation/vm/slub.rst b/Documentation/vm/slub.rst
index 3a775fd64e2d..195928808bac 100644
--- a/Documentation/vm/slub.rst
+++ b/Documentation/vm/slub.rst
@@ -36,9 +36,10 @@ debugging is enabled. Format:
 
 slub_debug=<Debug-Options>
 	Enable options for all slabs
-slub_debug=<Debug-Options>,<slab name>
-	Enable options only for select slabs
 
+slub_debug=<Debug-Options>,<slab name1>,<slab name2>,...
+	Enable options only for select slabs (no spaces
+	after a comma)
 
 Possible debug options are::
 
@@ -62,7 +63,12 @@ Trying to find an issue in the dentry cache? Try::
 
 	slub_debug=,dentry
 
-to only enable debugging on the dentry cache.
+to only enable debugging on the dentry cache.  You may use an asterisk at the
+end of the slab name, in order to cover all slabs with the same prefix.  For
+example, here's how you can poison the dentry cache as well as all kmalloc
+slabs:
+
+	slub_debug=P,kmalloc-*,dentry
 
 Red zoning and tracking may realign the slab.  We can just apply sanity checks
 to the dentry cache with::
diff --git a/mm/slub.c b/mm/slub.c
index 8da34a8af53d..27281867cbe0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1283,9 +1283,37 @@ slab_flags_t kmem_cache_flags(unsigned int object_size,
 	/*
 	 * Enable debugging if selected on the kernel commandline.
 	 */
-	if (slub_debug && (!slub_debug_slabs || (name &&
-		!strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs)))))
-		flags |= slub_debug;
+
+	char *end, *n, *glob;
+	int len = strlen(name);
+
+	/* If slub_debug = 0, it folds into the if conditional. */
+	if (!slub_debug_slabs)
+		return flags | slub_debug;
+
+	n = slub_debug_slabs;
+	while (*n) {
+		int cmplen;
+
+		end = strchr(n, ',');
+		if (!end)
+			end = n + strlen(n);
+
+		glob = strnchr(n, end - n, '*');
+		if (glob)
+			cmplen = glob - n;
+		else
+			cmplen = max(len, end - n);
+
+		if (!strncmp(name, n, cmplen)) {
+			flags |= slub_debug;
+			break;
+		}
+
+		if (!*end)
+			break;
+		n = end + 1;
+	}
 
 	return flags;
 }
-- 
2.14.4

Re: [PATCH] slub: extend slub debug to handle multiple slabs

[kbuild test robot]

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Hi Aaron,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.19-rc3 next-20180910]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Aaron-Tomlin/slub-extend-slub-debug-to-handle-multiple-slabs/20180911-030241
config: x86_64-randconfig-x008-201836 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from include/asm-generic/bug.h:18:0,
                    from arch/x86/include/asm/bug.h:83,
                    from include/linux/bug.h:5,
                    from include/linux/mmdebug.h:5,
                    from include/linux/mm.h:9,
                    from mm/slub.c:13:
   mm/slub.c: In function 'kmem_cache_flags':
   include/linux/kernel.h:845:29: warning: comparison of distinct pointer types lacks a cast
      (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
                                ^
   include/linux/kernel.h:859:4: note: in expansion of macro '__typecheck'
      (__typecheck(x, y) && __no_side_effects(x, y))
       ^~~~~~~~~~~
   include/linux/kernel.h:869:24: note: in expansion of macro '__safe_cmp'
     __builtin_choose_expr(__safe_cmp(x, y), \
                           ^~~~~~~~~~
   include/linux/kernel.h:885:19: note: in expansion of macro '__careful_cmp'
    #define max(x, y) __careful_cmp(x, y, >)
                      ^~~~~~~~~~~~~
>> mm/slub.c:1306:13: note: in expansion of macro 'max'
       cmplen = max(len, end - n);
                ^~~

vim +/max +1306 mm/slub.c

  1278	
  1279	slab_flags_t kmem_cache_flags(unsigned int object_size,
  1280		slab_flags_t flags, const char *name,
  1281		void (*ctor)(void *))
  1282	{
  1283		/*
  1284		 * Enable debugging if selected on the kernel commandline.
  1285		 */
  1286	
  1287		char *end, *n, *glob;
  1288		int len = strlen(name);
  1289	
  1290		/* If slub_debug = 0, it folds into the if conditional. */
  1291		if (!slub_debug_slabs)
  1292			return flags | slub_debug;
  1293	
  1294		n = slub_debug_slabs;
  1295		while (*n) {
  1296			int cmplen;
  1297	
  1298			end = strchr(n, ',');
  1299			if (!end)
  1300				end = n + strlen(n);
  1301	
  1302			glob = strnchr(n, end - n, '*');
  1303			if (glob)
  1304				cmplen = glob - n;
  1305			else
> 1306				cmplen = max(len, end - n);
  1307	
  1308			if (!strncmp(name, n, cmplen)) {
  1309				flags |= slub_debug;
  1310				break;
  1311			}
  1312	
  1313			if (!*end)
  1314				break;
  1315			n = end + 1;
  1316		}
  1317	
  1318		return flags;
  1319	}
  1320	#else /* !CONFIG_SLUB_DEBUG */
  1321	static inline void setup_object_debug(struct kmem_cache *s,
  1322				struct page *page, void *object) {}
  1323	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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