Hi Kazu,
On Thu, Aug 25, 2022 at 10:20 AM HAGIO KAZUHITO(萩尾 一仁)
<k-hagio-ab@xxxxxxx> wrote:
>
> 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 ?
>
Sure, it looks better to me. Thanks for the suggestion! I will update the patch.
Thanks,
Tao Liu
> Thanks,
> Kazu
>
>
> >
> > Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
> > ---
> > 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);
--
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