Re: [Crash-utility] Can't read stack contents from qemu dump

----- Original Message ----- Presumably the latter. If you do a "task -R stack ffffffff82016500", I'm presuming that it shows the stack base address is ffffffff82000000. And the looking at the stackbase/stacktop values, the crash utility is presuming an 8K stack: bt: invalid RSP: ffffffff82003dc8 bt->stackbase/stacktop: ffffffff82000000/ffffffff82002000 cpu: 0 But the RSP is ffffffff82003dc8, which puts its beyond the 8K stack size, so I'm presuming that the kernel is actually using 16K stacks. The most recent kernel I have is 4.16.0-0.rc6.git3.1.fc29.x86_64, which uses 16K stacks. Here is how the crash utility determines the stack size. The x86_64 stacksize starts out with a default size of 2 pages, as set here in x86_64_init(PRE_SYMTAB): case PRE_SYMTAB: ... [ cut ] ... machdep->stacksize = machdep->pagesize * 2; ... Then later on in task_init(), it gets resized as shown here, where the STACKSIZE() macro is machdep->stacksize: if (VALID_SIZE(task_union) && (SIZE(task_union) != STACKSIZE())) { error(WARNING, "\nnon-standard stack size: %ld\n", len = SIZE(task_union)); machdep->stacksize = len; } else if (VALID_SIZE(thread_union) && ((len = SIZE(thread_union)) != STACKSIZE())) machdep->stacksize = len; The "task_union" no longer exists, and so it checks whether the "thread_union" is larger than the default stacksize, and resets the size appropriately. On my 4.16.0-0.rc6.git3.1.fc29.x86_64 kernel, here is the thread_union: crash> thread_union union thread_union { struct task_struct task; unsigned long stack[2048]; } SIZE: 16384 And so it gets reset: crash> help -m | grep stacksize stacksize: 16384 crash> You can debug it from there. Let me know what you find. Thanks, Dave