George Anzinger wrote: > On 01/31/2008 01:36 AM, Jan Kiszka was caught saying: >> Jan Kiszka wrote: >>> George Anzinger wrote: >>>> On 01/30/2008 04:08 PM, Jan Kiszka was caught saying: >>>>> [Here comes a rebased version against latest x86/mm] >>>>> >>>>> In case "kgdbwait" is passed as kernel parameter, KGDB tries to set up >>>>> and connect to the front-end already during early_param evaluation. >>>>> This >>>>> fails on x86 as the exception stack is not yet initialized, > effectively >>>>> delaying kgdbwait until late-init. >>>> >>>> I wonder how much work it would take to just set up the exception >>>> stack and proceed. After all the kgbdwait is there to help debug >>>> very early kernel code... >>> >>> In principle a valid question, but I'm not the one to answer it. I >>> would not feel very well if I had to reorder this critical setup code. >>> Look, we would have to move trap_init in start_kernel before >>> parse_early_param, and that would affect _every_ arch... > > I can not speak to other archs, but for x86 I called trap_init from the > code that caught the kgdbwait. At that time (since I retired, I have > not looked at the actual kernel code) it could be called again later by > the kernel code. I.e. I did not try to reorder the kernel bring up > code, but just added an additional call to trap_init and then only in > the case of finding a kgdbwait. > > As such, this would need to be arch specific... > >>> >> >> BTW, do you know if EXCEPTION_STACK_READY fails for other archs in >> parse_early_param as well? It should, because my under standing of >> trap_init is that it's the functions to arm things like... exception >> handlers? And that raises the question of the deeper purpose of this >> check (and the invocation of kgdb_early_init from the argument parsing >> function). Sigh, KGDB is still a quite improvable piece of code. > > Likely. Once you get it in the main line kernel, one would hope that > other arch code would be forth coming as many more "eyes" will be in play.
Meanwhile I realized that there is early_trap_init - for x86-32 only! I assume now we are only lacking the same for x86-64 to get kgdb running there already during early_param-parsing. Jan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
