On Mon, Oct 23, 2006 at 02:34:32PM -0400, Dave Anderson wrote: > Rachita Kothiyal wrote: > > > This is because what crash is reporting is the stack address at which > > the return address was pushed on stack, while what the dwarf based bt is > > reporting is the CFA. In most cases, return address is stored at a location > > (CFA - 8). That is why the offset of 0x8. > > > > The low-budget tracer's backtraces are different from the dwarf-tracer > > because when the low-budget tracer is unwinding the stack by trying to read > > kernel text addresses, it actually comes across many addresses which were > > actually not pushed onto stack because of function calls. > > Specially for the panic task on kdumps, where after 'crash_kexec' is called, > > the registers are dumped onto stack(for creating NT_PRSTATUS section), this > > becomes misleading for the low-budget tracer mechanism. Thats why we see > > multiple crash_kexec entries in the backtrace. Static inline functions can > > also aggrevate this problem. > > > > In other cases, stale frames on the stack can also mislead the low-budget > > tracer. > > > > AFAICT, user_regs_struct register offsets are not the culprits here. > > > > Thanks > > Rachita > > So, in other words, if we hardwire the user_regs_struct so that > it uses the NT_PRSTATUS registers all the time, then we get > the second (preferred/better) budget back trace when unwind > is off. > > That being the case, I argue for hardwiring them all the time. Yes, we can(should) do that for all the active tasks. Rachita -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility
