From 0cbc124bce8c527eb14c87f634683c5bcf4299c7 Mon Sep 17 00:00:00 2001 From: Maninder Singh Date: Tue, 16 Mar 2021 16:07:10 +0530 Subject: mm/slub: Fix backtrace of objects to handle redzone adjustment This commit fixes commit 8e7f37f2aaa5 ("mm: Add mem_dump_obj() to print source of memory block"). With current code, the backtrace of allocated object is incorrect: / # cat /proc/meminfo [ 14.969843] slab kmalloc-64 start c8ab0140 data offset 64 pointer offset 0 size 64 allocated at 0x6b6b6b6b [ 14.970635] 0x6b6b6b6b [ 14.970794] 0x6b6b6b6b [ 14.970932] 0x6b6b6b6b [ 14.971077] 0x6b6b6b6b [ 14.971202] 0x6b6b6b6b [ 14.971317] 0x6b6b6b6b [ 14.971423] 0x6b6b6b6b [ 14.971635] 0x6b6b6b6b [ 14.971740] 0x6b6b6b6b [ 14.971871] 0x6b6b6b6b [ 14.972229] 0x6b6b6b6b [ 14.972363] 0x6b6b6b6b [ 14.972505] 0xa56b6b6b [ 14.972631] 0xbbbbbbbb [ 14.972734] 0xc8ab0400 [ 14.972891] meminfo_proc_show+0x40/0x4fc The reason is that the object address was not adjusted for the red zone. With this fix, the backtrace is correct: / # cat /proc/meminfo [ 14.870782] slab kmalloc-64 start c8ab0140 data offset 64 pointer offset 128 size 64 allocated at meminfo_proc_show+0x40/0x4f4 [ 14.871817] meminfo_proc_show+0x40/0x4f4 [ 14.872035] seq_read_iter+0x18c/0x4c4 [ 14.872229] proc_reg_read_iter+0x84/0xac [ 14.872433] generic_file_splice_read+0xe8/0x17c [ 14.872621] splice_direct_to_actor+0xb8/0x290 [ 14.872747] do_splice_direct+0xa0/0xe0 [ 14.872896] do_sendfile+0x2d0/0x438 [ 14.873044] sys_sendfile64+0x12c/0x140 [ 14.873229] ret_fast_syscall+0x0/0x58 [ 14.873372] 0xbe861de4 Acked-by: Vlastimil Babka Signed-off-by: Vaneet Narang Signed-off-by: Maninder Singh Signed-off-by: Paul E. McKenney --- mm/slub.c | 1 + 1 file changed, 1 insertion(+) (limited to 'mm/slub.c') diff --git a/mm/slub.c b/mm/slub.c index feda53ae62ba..8f2d13508ec9 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4002,6 +4002,7 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page) !(s->flags & SLAB_STORE_USER)) return; #ifdef CONFIG_SLUB_DEBUG + objp = fixup_red_left(s, objp); trackp = get_track(s, objp, TRACK_ALLOC); kpp->kp_ret = (void *)trackp->addr; #ifdef CONFIG_STACKTRACE -- cgit v1.2.3 From e548eaa116d858f07816d41e24835a41f7e7d270 Mon Sep 17 00:00:00 2001 From: Maninder Singh Date: Tue, 16 Mar 2021 16:07:11 +0530 Subject: mm/slub: Add Support for free path information of an object This commit adds enables a stack dump for the last free of an object: slab kmalloc-64 start c8ab0140 data offset 64 pointer offset 0 size 64 allocated at meminfo_proc_show+0x40/0x4fc [ 20.192078] meminfo_proc_show+0x40/0x4fc [ 20.192263] seq_read_iter+0x18c/0x4c4 [ 20.192430] proc_reg_read_iter+0x84/0xac [ 20.192617] generic_file_splice_read+0xe8/0x17c [ 20.192816] splice_direct_to_actor+0xb8/0x290 [ 20.193008] do_splice_direct+0xa0/0xe0 [ 20.193185] do_sendfile+0x2d0/0x438 [ 20.193345] sys_sendfile64+0x12c/0x140 [ 20.193523] ret_fast_syscall+0x0/0x58 [ 20.193695] 0xbeeacde4 [ 20.193822] Free path: [ 20.193935] meminfo_proc_show+0x5c/0x4fc [ 20.194115] seq_read_iter+0x18c/0x4c4 [ 20.194285] proc_reg_read_iter+0x84/0xac [ 20.194475] generic_file_splice_read+0xe8/0x17c [ 20.194685] splice_direct_to_actor+0xb8/0x290 [ 20.194870] do_splice_direct+0xa0/0xe0 [ 20.195014] do_sendfile+0x2d0/0x438 [ 20.195174] sys_sendfile64+0x12c/0x140 [ 20.195336] ret_fast_syscall+0x0/0x58 [ 20.195491] 0xbeeacde4 Acked-by: Vlastimil Babka Co-developed-by: Vaneet Narang Signed-off-by: Vaneet Narang Signed-off-by: Maninder Singh Signed-off-by: Paul E. McKenney --- mm/slab.h | 1 + mm/slab_common.c | 12 +++++++++++- mm/slub.c | 7 +++++++ mm/util.c | 2 +- 4 files changed, 20 insertions(+), 2 deletions(-) (limited to 'mm/slub.c') diff --git a/mm/slab.h b/mm/slab.h index 18c1927cd196..7189daa0c586 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -640,6 +640,7 @@ struct kmem_obj_info { struct kmem_cache *kp_slab_cache; void *kp_ret; void *kp_stack[KS_ADDRS_COUNT]; + void *kp_free_stack[KS_ADDRS_COUNT]; }; void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page); #endif diff --git a/mm/slab_common.c b/mm/slab_common.c index f8833d3e5d47..92e3aa78bb4d 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -564,7 +564,7 @@ EXPORT_SYMBOL_GPL(kmem_valid_obj); * depends on the type of object and on how much debugging is enabled. * For a slab-cache object, the fact that it is a slab object is printed, * and, if available, the slab name, return address, and stack trace from - * the allocation of that object. + * the allocation and last free path of that object. * * This function will splat if passed a pointer to a non-slab object. * If you are not sure what type of object you have, you should instead @@ -609,6 +609,16 @@ void kmem_dump_obj(void *object) break; pr_info(" %pS\n", kp.kp_stack[i]); } + + if (kp.kp_free_stack[0]) + pr_cont(" Free path:\n"); + + for (i = 0; i < ARRAY_SIZE(kp.kp_free_stack); i++) { + if (!kp.kp_free_stack[i]) + break; + pr_info(" %pS\n", kp.kp_free_stack[i]); + } + } EXPORT_SYMBOL_GPL(kmem_dump_obj); #endif diff --git a/mm/slub.c b/mm/slub.c index 8f2d13508ec9..deec894a1345 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4011,6 +4011,13 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page) if (!kpp->kp_stack[i]) break; } + + trackp = get_track(s, objp, TRACK_FREE); + for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) { + kpp->kp_free_stack[i] = (void *)trackp->addrs[i]; + if (!kpp->kp_free_stack[i]) + break; + } #endif #endif } diff --git a/mm/util.c b/mm/util.c index a8bf17f18a81..0b6dd9d81da7 100644 --- a/mm/util.c +++ b/mm/util.c @@ -983,7 +983,7 @@ int __weak memcmp_pages(struct page *page1, struct page *page2) * depends on the type of object and on how much debugging is enabled. * For example, for a slab-cache object, the slab name is printed, and, * if available, the return address and stack trace from the allocation - * of that object. + * and last free path of that object. */ void mem_dump_obj(void *object) { -- cgit v1.2.3