Re: [Crash-utility] [PATCH] Fix kmem failing to print task context when address is vmalloced stack
On 2022/08/24 13:08, Tao Liu wrote:
When kernel enabled CONFIG_VMAP_STACK, stack can be allocated to
vmalloced area. Currently crash didn't handle the case, as a result,
kmem will not print the task context as expected. This patch fix the
bug by checking if the address is a vmalloced stack first.
Good catch, again. Thank you for the patch.
Before:
crash> kmem ffffb7efce9bbe28
VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE
ffff94eb9102c640 ffff94eb9102b140 ffffb7efce9b8000 - ffffb7efce9bd000 20480
PAGE PHYSICAL MAPPING INDEX CNT FLAGS
ffffdd28220dc000 1883700000 0 0 1 50000000000000
After:
crash> kmem ffffb7efce9bbe28
PID: 847
COMMAND: "khungtaskd"
TASK: ffff94f8038f4000 [THREAD_INFO: ffff94f8038f4000]
CPU: 72
STATE: TASK_RUNNING (PANIC)
PAGE PHYSICAL MAPPING INDEX CNT FLAGS
ffffdd28220dc000 1883700000 0 0 1 50000000000000
I feel like it might be better to print the VMAP_AREA info too
even if it's an address of process's stack. For example,
crash> kmem ffff9b6dc017ff50
PID: 1
COMMAND: "systemd"
TASK: ffff8f96c159c8c0 [THREAD_INFO: ffff8f96c159c8c0]
CPU: 6
STATE: TASK_INTERRUPTIBLE
VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE
ffff8f96c7c25080 ffff8f96c7d48dc0 ffff9b6dc017c000 - ffff9b6dc0181000 20480
PAGE PHYSICAL MAPPING INDEX CNT FLAGS
fffff043bb9910c0 ee6443000 0 0 1 17ffffc0000000
So, can we remove the "goto mem_map;" below ?
Thanks,
Kazu
>
> Signed-off-by: Tao Liu <ltao(a)redhat.com>
> ---
> memory.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/memory.c b/memory.c
> index 7339f0c..7a1bf9c 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -13477,6 +13477,11 @@ kmem_search(struct meminfo *mi)
> * Check for a valid mapped address.
> */
> if ((mi->memtype == KVADDR) && IS_VMALLOC_ADDR(mi->spec_addr)) {
> + if ((task = stkptr_to_task(vaddr)) && (tc = task_to_context(task))) {
> + show_context(tc);
> + fprintf(fp, "\n");
> + goto mem_map;
> + }
> if (kvtop(NULL, mi->spec_addr, &paddr, 0)) {
> mi->flags = orig_flags | VMLIST_VERIFY;
> dump_vmlist(mi);