Re: [Crash-utility] [PATCH v2] Fix kmem failing to print task context when address is vmalloced stack

On 2022/09/01 17:15, 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. >>> >>> 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. For physical address, a context is not shown also without CONFIG_VMAP_STACK. crash> kmem ffff9288bc977f00 PID: 1 COMMAND: "systemd" TASK: ffff9288bc978000 [THREAD_INFO: ffff9288bc974000] CPU: 10 STATE: TASK_INTERRUPTIBLE PAGE PHYSICAL MAPPING INDEX CNT FLAGS ffffd91fc1f25dc0 7c977000 0 0 0 1fffff00000000 crash> kmem 7c977f00 PAGE PHYSICAL MAPPING INDEX CNT FLAGS ffffd91fc1f25dc0 7c977000 0 0 0 1fffff00000000 Some information for virtual address is not shown with physical address, it's kind of expected. And we have the ptov command, personally I don't think it needs to do. but if you change this behavior, it might be good in a separate patch.

Thanks, Kazu