----- Original Message -----
>
> If SLAB_RED_ZONE is enabled, slub adds guard zone of sizeof(void *)
> onto head of slab page (red zone padding of left of object) on v4.6 or
> later.
>
> Without this fix, like following SUPERBLK and [allocate addr] has
> difference.
>
> crash> mount
> MOUNT SUPERBLK TYPE DEVNAME DIRNAME
> ffff88013ae58040 ffff88013ac35698 rootfs rootfs /
> [...]
> crash> kmem ffff88013ac35698
> CACHE NAME OBJSIZE ALLOCATED TOTAL SLABS SSIZE
> ffff88013ac05bc0 kmalloc-4096 4096 118 126 18 32k
> SLAB MEMORY NODE TOTAL ALLOCATED FREE
> ffffea0004eb0c00 ffff88013ac30000 0 7 7 0
> FREE / [ALLOCATED]
> [ffff88013ac35690]
> [...]
Hi Ogawa,
When you enter "kmem ffff88013ac35698", I am presuming that it it shows the [ALLOCATED]
object at ffff88013ac35690 as shown above. If that's true, then in my opinion, it's doing
the right thing.
I understand that the kmalloc caller receives ffff88013ac35698, but with respect to the
slab subsystem itself, the actual address of the slab object is ffff88013ac35690. I worry
about the potential consequences of making such a wholesale change to the kmem command.
Dave
> ---
>
> defs.h | 1 +
> memory.c | 8 ++++++++
> symbols.c | 2 ++
> 3 files changed, 11 insertions(+)
>
> diff -puN memory.c~slub-red_zone-fix memory.c
> --- crash-64/memory.c~slub-red_zone-fix 2017-01-30 10:21:12.123644726 +0900
> +++ crash-64-hirofumi/memory.c 2017-01-30 10:21:12.127644748 +0900
> @@ -723,6 +723,7 @@ vm_init(void)
> MEMBER_OFFSET_INIT(kmem_cache_node, "kmem_cache", "node");
> MEMBER_OFFSET_INIT(kmem_cache_cpu_slab, "kmem_cache", "cpu_slab");
> MEMBER_OFFSET_INIT(kmem_cache_list, "kmem_cache", "list");
> + MEMBER_OFFSET_INIT(kmem_cache_red_left_pad, "kmem_cache", "red_left_pad");
> MEMBER_OFFSET_INIT(kmem_cache_name, "kmem_cache", "name");
> MEMBER_OFFSET_INIT(kmem_cache_flags, "kmem_cache", "flags");
> MEMBER_OFFSET_INIT(kmem_cache_cpu_freelist, "kmem_cache_cpu", "freelist");
> @@ -18442,6 +18443,13 @@ do_slab_slub(struct meminfo *si, int ver
> fprintf(fp, "< SLUB: free list END (%d found) >\n", i);
> }
>
> + if (VALID_MEMBER(kmem_cache_red_left_pad)) {
> +#define SLAB_RED_ZONE 0x00000400UL
> + ulong flags = ULONG(si->cache_buf + OFFSET(kmem_cache_flags));
> + ulong red_left_pad = ULONG(si->cache_buf +
> OFFSET(kmem_cache_red_left_pad));
> + if (flags & SLAB_RED_ZONE)
> + vaddr += red_left_pad;
> + }
> for (p = vaddr; p < vaddr + objects * si->size; p += si->size) {
> hq_open();
> is_free = FALSE;
> diff -puN defs.h~slub-red_zone-fix defs.h
> --- crash-64/defs.h~slub-red_zone-fix 2017-01-30 10:21:12.124644731 +0900
> +++ crash-64-hirofumi/defs.h 2017-02-01 00:11:33.445552457 +0900
> @@ -1696,6 +1696,7 @@ struct offset_table {
> long kmem_cache_align;
> long kmem_cache_name;
> long kmem_cache_list;
> + long kmem_cache_red_left_pad;
> long kmem_cache_node;
> long kmem_cache_cpu_slab;
> long page_inuse;
> diff -puN symbols.c~slub-red_zone-fix symbols.c
> --- crash-64/symbols.c~slub-red_zone-fix 2017-01-30 10:21:12.124644731 +0900
> +++ crash-64-hirofumi/symbols.c 2017-02-01 00:11:33.446552463 +0900
> @@ -9330,6 +9330,8 @@ dump_offset_table(char *spec, ulong make
> OFFSET(kmem_cache_name));
> fprintf(fp, " kmem_cache_list: %ld\n",
> OFFSET(kmem_cache_list));
> + fprintf(fp, " kmem_cache_red_left_pad: %ld\n",
> + OFFSET(kmem_cache_red_left_pad));
> fprintf(fp, " kmem_cache_node: %ld\n",
> OFFSET(kmem_cache_node));
> fprintf(fp, " kmem_cache_cpu_slab: %ld\n",
> _
>
> --
> OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
>
> --
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> Crash-utility@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/crash-utility
>
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