From: Vlastimil Babka <vbabka@xxxxxxx> Subject: mm, slub: extend slub_debug syntax for multiple blocks Patch series "slub_debug fixes and improvements". The slub_debug kernel boot parameter can either apply a single set of options to all caches or a list of caches. There is a use case where debugging is applied for all caches and then disabled at runtime for specific caches, for performance and memory consumption reasons [1]. As runtime changes are dangerous, extend the boot parameter syntax so that multiple blocks of either global or slab-specific options can be specified, with blocks delimited by ';'. This will also support the use case of [1] without runtime changes. For details see the updated Documentation/vm/slub.rst [1] https://lore.kernel.org/r/1383cd32-1ddc-4dac-b5f8-9c42282fa81c@xxxxxxxxxxxxxx [weiyongjun1@xxxxxxxxxx: make parse_slub_debug_flags() static] Link: http://lkml.kernel.org/r/20200702150522.4940-1-weiyongjun1@xxxxxxxxxx Link: http://lkml.kernel.org/r/20200610163135.17364-2-vbabka@xxxxxxx Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Jann Horn <jannh@xxxxxxxxxx> Cc: Roman Gushchin <guro@xxxxxx> Cc: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/admin-guide/kernel-parameters.txt | 2 Documentation/vm/slub.rst | 18 + mm/slub.c | 179 +++++++++----- 3 files changed, 146 insertions(+), 53 deletions(-) --- a/Documentation/admin-guide/kernel-parameters.txt~mm-slub-extend-slub_debug-syntax-for-multiple-blocks +++ a/Documentation/admin-guide/kernel-parameters.txt @@ -4689,7 +4689,7 @@ fragmentation. Defaults to 1 for systems with more than 32MB of RAM, 0 otherwise. - slub_debug[=options[,slabs]] [MM, SLUB] + slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB] Enabling slub_debug allows one to determine the culprit if slab objects become corrupted. Enabling slub_debug can create guard zones around objects and --- a/Documentation/vm/slub.rst~mm-slub-extend-slub_debug-syntax-for-multiple-blocks +++ a/Documentation/vm/slub.rst @@ -41,6 +41,11 @@ slub_debug=<Debug-Options>,<slab name1>, Enable options only for select slabs (no spaces after a comma) +Multiple blocks of options for all slabs or selected slabs can be given, with +blocks of options delimited by ';'. The last of "all slabs" blocks is applied +to all slabs except those that match one of the "select slabs" block. Options +of the first "select slabs" blocks that matches the slab's name are applied. + Possible debug options are:: F Sanity checks on (enables SLAB_DEBUG_CONSISTENCY_CHECKS @@ -83,6 +88,19 @@ switch off debugging for such caches by slub_debug=O +You can apply different options to different list of slab names, using blocks +of options. This will enable red zoning for dentry and user tracking for +kmalloc. All other slabs will not get any debugging enabled:: + + slub_debug=Z,dentry;U,kmalloc-* + +You can also enable options (e.g. sanity checks and poisoning) for all caches +except some that are deemed too performance critical and don't need to be +debugged by specifying global debug options followed by a list of slab names +with "-" as options:: + + slub_debug=FZ;-,zs_handle,zspage + In case you forgot to enable debugging on the kernel command line: It is possible to enable debugging manually when the kernel is up. Look at the contents of:: --- a/mm/slub.c~mm-slub-extend-slub_debug-syntax-for-multiple-blocks +++ a/mm/slub.c @@ -499,7 +499,7 @@ static slab_flags_t slub_debug = DEBUG_D static slab_flags_t slub_debug; #endif -static char *slub_debug_slabs; +static char *slub_debug_string; static int disable_higher_order_debug; /* @@ -1262,68 +1262,132 @@ out: return ret; } -static int __init setup_slub_debug(char *str) +/* + * Parse a block of slub_debug options. Blocks are delimited by ';' + * + * @str: start of block + * @flags: returns parsed flags, or DEBUG_DEFAULT_FLAGS if none specified + * @slabs: return start of list of slabs, or NULL when there's no list + * @init: assume this is initial parsing and not per-kmem-create parsing + * + * returns the start of next block if there's any, or NULL + */ +static char * +parse_slub_debug_flags(char *str, slab_flags_t *flags, char **slabs, bool init) { - slub_debug = DEBUG_DEFAULT_FLAGS; - if (*str++ != '=' || !*str) - /* - * No options specified. Switch on full debugging. - */ - goto out; + bool higher_order_disable = false; - if (*str == ',') + /* Skip any completely empty blocks */ + while (*str && *str == ';') + str++; + + if (*str == ',') { /* * No options but restriction on slabs. This means full * debugging for slabs matching a pattern. */ + *flags = DEBUG_DEFAULT_FLAGS; goto check_slabs; + } + *flags = 0; - slub_debug = 0; - if (*str == '-') - /* - * Switch off all debugging measures. - */ - goto out; - - /* - * Determine which debug features should be switched on - */ - for (; *str && *str != ','; str++) { + /* Determine which debug features should be switched on */ + for (; *str && *str != ',' && *str != ';'; str++) { switch (tolower(*str)) { + case '-': + *flags = 0; + break; case 'f': - slub_debug |= SLAB_CONSISTENCY_CHECKS; + *flags |= SLAB_CONSISTENCY_CHECKS; break; case 'z': - slub_debug |= SLAB_RED_ZONE; + *flags |= SLAB_RED_ZONE; break; case 'p': - slub_debug |= SLAB_POISON; + *flags |= SLAB_POISON; break; case 'u': - slub_debug |= SLAB_STORE_USER; + *flags |= SLAB_STORE_USER; break; case 't': - slub_debug |= SLAB_TRACE; + *flags |= SLAB_TRACE; break; case 'a': - slub_debug |= SLAB_FAILSLAB; + *flags |= SLAB_FAILSLAB; break; case 'o': /* * Avoid enabling debugging on caches if its minimum * order would increase as a result. */ - disable_higher_order_debug = 1; + higher_order_disable = true; break; default: - pr_err("slub_debug option '%c' unknown. skipped\n", - *str); + if (init) + pr_err("slub_debug option '%c' unknown. skipped\n", *str); } } - check_slabs: if (*str == ',') - slub_debug_slabs = str + 1; + *slabs = ++str; + else + *slabs = NULL; + + /* Skip over the slab list */ + while (*str && *str != ';') + str++; + + /* Skip any completely empty blocks */ + while (*str && *str == ';') + str++; + + if (init && higher_order_disable) + disable_higher_order_debug = 1; + + if (*str) + return str; + else + return NULL; +} + +static int __init setup_slub_debug(char *str) +{ + slab_flags_t flags; + char *saved_str; + char *slab_list; + bool global_slub_debug_changed = false; + bool slab_list_specified = false; + + slub_debug = DEBUG_DEFAULT_FLAGS; + if (*str++ != '=' || !*str) + /* + * No options specified. Switch on full debugging. + */ + goto out; + + saved_str = str; + while (str) { + str = parse_slub_debug_flags(str, &flags, &slab_list, true); + + if (!slab_list) { + slub_debug = flags; + global_slub_debug_changed = true; + } else { + slab_list_specified = true; + } + } + + /* + * For backwards compatibility, a single list of flags with list of + * slabs means debugging is only enabled for those slabs, so the global + * slub_debug should be 0. We can extended that to multiple lists as + * long as there is no option specifying flags without a slab list. + */ + if (slab_list_specified) { + if (!global_slub_debug_changed) + slub_debug = 0; + slub_debug_string = saved_str; + } out: if ((static_branch_unlikely(&init_on_alloc) || static_branch_unlikely(&init_on_free)) && @@ -1352,36 +1416,47 @@ slab_flags_t kmem_cache_flags(unsigned i { char *iter; size_t len; + char *next_block; + slab_flags_t block_flags; /* If slub_debug = 0, it folds into the if conditional. */ - if (!slub_debug_slabs) + if (!slub_debug_string) return flags | slub_debug; len = strlen(name); - iter = slub_debug_slabs; - while (*iter) { - char *end, *glob; - size_t cmplen; - - end = strchrnul(iter, ','); - - glob = strnchr(iter, end - iter, '*'); - if (glob) - cmplen = glob - iter; - else - cmplen = max_t(size_t, len, (end - iter)); + next_block = slub_debug_string; + /* Go through all blocks of debug options, see if any matches our slab's name */ + while (next_block) { + next_block = parse_slub_debug_flags(next_block, &block_flags, &iter, false); + if (!iter) + continue; + /* Found a block that has a slab list, search it */ + while (*iter) { + char *end, *glob; + size_t cmplen; + + end = strchrnul(iter, ','); + if (next_block && next_block < end) + end = next_block - 1; + + glob = strnchr(iter, end - iter, '*'); + if (glob) + cmplen = glob - iter; + else + cmplen = max_t(size_t, len, (end - iter)); - if (!strncmp(name, iter, cmplen)) { - flags |= slub_debug; - break; - } + if (!strncmp(name, iter, cmplen)) { + flags |= block_flags; + return flags; + } - if (!*end) - break; - iter = end + 1; + if (!*end || *end == ';') + break; + iter = end + 1; + } } - return flags; + return slub_debug; } #else /* !CONFIG_SLUB_DEBUG */ static inline void setup_object_debug(struct kmem_cache *s, _
