Hi Lianbo,
On Thu, Sep 1, 2022 at 3:28 PM lijiang <lijiang@xxxxxxxxxx> wrote:
>
> Hi, Tao
> Thank you for the fix.
> On Thu, Aug 25, 2022 at 8:00 PM <crash-utility-request@xxxxxxxxxx> wrote:
>>
>> Date: Thu, 25 Aug 2022 14:42:45 +0800
>> From: Tao Liu <ltao@xxxxxxxxxx>
>> To: crash-utility@xxxxxxxxxx
>> Subject: [PATCH v2] Fix kmem failing to print task
>> context when address is vmalloced stack
>> Message-ID: <20220825064243.71447-1-ltao@xxxxxxxxxx>
>> Content-Type: text/plain; charset="US-ASCII"; x-default=true
>>
>> 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.
>>
>> 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)
>>
>> VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE
>> ffff94eb9102c640 ffff94eb9102b140 ffffb7efce9b8000 - ffffb7efce9bd000 20480
>>
>
> I have one question: If the given physical address falls in the vmalloc area, it won't print the task context, is that expected? For example:
>
Thanks for pointing it out. Hmm... I didn't consider the physical
address case as vtop does. I will improve the patch and send v3.
Thanks,
Tao Liu
> [1] Before this patch: the "kmem + physical/virtual address" has the same output asbelow.
>
> 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
>
> crash> kmem 1883700e28 <----- vtop 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
>
> [2] After this patch: the "kmem + physical/virtual address" has different output asbelow.
> crash> kmem ffffb7efce9bbe28
> PID: 847
> COMMAND: "khungtaskd"
> TASK: ffff94f8038f4000 [THREAD_INFO: ffff94f8038f4000]
> CPU: 72
> STATE: TASK_RUNNING (PANIC)
>
> VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE
> ffff94eb9102c640 ffff94eb9102b140 ffffb7efce9b8000 - ffffb7efce9bd000 20480
>
> PAGE PHYSICAL MAPPING INDEX CNT FLAGS
> ffffdd28220dc000 1883700000 0 0 1 50000000000000
>
> crash> kmem 1883700e28 <----- vtop 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
>
>
> Thanks.
> Lianbo
>
>> PAGE PHYSICAL MAPPING INDEX CNT FLAGS
>> ffffdd28220dc000 1883700000 0 0 1 50000000000000
>>
>> Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
>> ---
>>
>> v1 -> v2: 1) Remove goto to print task context and vmlist.
>> 2) Update commit log to show the change.
>>
>> ---
>> memory.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/memory.c b/memory.c
>> index 7339f0c..9ab5781 100644
>> --- a/memory.c
>> +++ b/memory.c
>> @@ -13477,6 +13477,10 @@ 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");
>> + }
>> if (kvtop(NULL, mi->spec_addr, &paddr, 0)) {
>> mi->flags = orig_flags | VMLIST_VERIFY;
>> dump_vmlist(mi);
>> --
>> 2.33.1
>>
>>
>>
>> ------------------------------
>>
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>>
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