On Mon, Mar 15, 2021 at 11:57:53AM -0500, madvenka@xxxxxxxxxxxxxxxxxxx wrote: > In summary, task pt_regs->stackframe is where a successful stack trace ends. > .if \el == 0 > - mov x29, xzr > + stp xzr, xzr, [sp, #S_STACKFRAME] > .else > stp x29, x22, [sp, #S_STACKFRAME] > - add x29, sp, #S_STACKFRAME > .endif > + add x29, sp, #S_STACKFRAME For both user and kernel threads this patch (at least by itself) results in an additional record being reported in stack traces with a NULL function pointer since it keeps the existing record where it is and adds this new fixed record below it. This is addressed for the kernel later in the series, by "arm64: Terminate the stack trace at TASK_FRAME and EL0_FRAME", but will still be visible to other unwinders such as debuggers. I'm not sure that this *matters* but it might and should at least be called out more explicitly. If we are going to add the extra record there would probably be less potential for confusion if we pointed it at some sensibly named dummy function so anything or anyone that does see it on the stack doesn't get confused by a NULL.
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