Re: [Crash-utility] [PATCH] crash: Do not use bt -t flag in panic_search()

On Mon, 3 Aug 2015 13:16:19 -0400 (EDT) Dave Anderson <anderson(a)redhat.com&gt; wrote: > > > ----- Original Message ----- > > On Mon, 03 Aug 2015 12:30:22 -0400 > > Dave Anderson <anderson(a)prospeed.net&gt; wrote: > > > > > > > > > > > Ah, it must be because of the common user-kernel virtual address space on > > > s390x? > > > > Yes we have overlapping virtual address ranges for kernel and user space and user > > space registers are stored at the start of the kernel stack. > > > > But I am not sure, if that is the reason here (have to verify this). > > > > Doesn't the -t option check all the stack memory and looks for valid symbol > > addresses? So IMO everything found there could be by chance the address > > of panic. Why is this no problem on x86? > > I'm not sure what you mean. How could it be there by chance? Are you talking > about a highly unlikely situation where a user-space exception frame at the top > of the kernel stack happens to have a register containing a kernel virtual address > that's within the panic() function? My assumption was that in "print_stack_text_syms()" in the following loop everything on the stack is checked for kernel symbols: for (i = (esp - bt->stackbase)/sizeof(ulong); i < LONGS_PER_STACK; i++) { Besides of function call return addresses there are local variables on the stack. If a variable "by chance" contains an address inside the "panic" function, we will incorrectly assume that we have the panic task. Is this understanding wrong? Michael