Re: [Crash-utility] question about phys_base

At 02/29/2012 09:04 AM, HATAYAMA Daisuke Wrote: > From: Dave Anderson <anderson(a)redhat.com&gt; > Subject: Re: [Crash-utility] question about phys_base > Date: Tue, 28 Feb 2012 09:44:09 -0500 (EST) > >> >> >> ----- Original Message ----- >>> At 02/28/2012 04:52 PM, HATAYAMA Daisuke Wrote: >> >>>>>> In general, such characteristic should not be used. You should prepare >>>>>> a solid interface. Even if using them, it should be limited to as >>>>>> workaround to avoid some issue. >>>>>> >>>>>> Why not use qemu's CPU state? Include it as note information with good >>>>>> name, and we can use it to distinguish which. Like: >>>>>> >>>>>> $ readelf -n vmcore >>>>>> >>>>>> Notes at offset 0x000001c8 with length 0x00000838: >>>>>> Owner Data size Description >>>>>> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >>>>>> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >>>>>> QEMU 0x00000557 Unknown note type: (0x00000000) >>>>>> >>>>>> Or QEMUCPUState is better? >>>>> >>>>> Good idea. I will try it, and hope gdb can also work. >>>>> >>>> >>>> Tools basically ignore unknown notes. Looking into gdb, it appears to >>>> ignore unknown information. >>>> >>>> static bfd_boolean >>>> elfcore_grok_note (bfd *abfd, Elf_Internal_Note *note) >>>> { >>>> const struct elf_backend_data *bed = get_elf_backend_data (abfd); >>>> >>>> switch (note->type) >>>> { >>>> default: >>>> return TRUE; >>>> <cut> >>>> >>>> You might need to add new command to output contents of new note if >>>> it's necessary. >>> >>> My goal is: >>> 1. gdb uses NT_PRSTATUS, and can work well >>> 2. crash uses unknown notes, and can get phys_base from it. >>> >>> Another question: >>> >>> What is QEMUCPUState? I donot find its definition? >> >> It's just the note's name character string. Either "QEMU", "QEMUCPUState", >> or whatever unique character string you prefer would suffice. >> >>> What note->type shoule be for "QEMU"? If we choose an unused value, the >>> value may be used in the future. >> >> Why not do the same thing as the "VMCOREINFO" note, and leave it >> as an "illegal/unknown" type of 0:: >> >> $ cat /usr/include/elf.h >> ... [ cut ] ... >> >> /* Legal values for note segment descriptor types for core files. */ >> >> #define NT_PRSTATUS 1 /* Contains copy of prstatus struct */ >> #define NT_FPREGSET 2 /* Contains copy of fpregset struct */ >> #define NT_PRPSINFO 3 /* Contains copy of prpsinfo struct */ >> ... >> $ >> >> $ readelf -a vmcore >> ... [ cut ] ... >> >> Notes at offset 0x00000190 with length 0x00000f1c: >> Owner Data size Description >> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >> CORE 0x00000150 NT_PRSTATUS (prstatus structure) >> VMCOREINFO 0x000003e4 Unknown note type: (0x00000000) >> $ >> > > It looks OK to me for now. > > But rigorously, it might be better to give it a name QEMU and then > prepare variety of information such as NT_CPUSTATE and others to be > needed later. I see. I think we should decide what information should be stored in QEMUCPUState. The CPUState in qemu cannot be used directly, because it may be changed in the furture. I think all CPU register should be stored in QEMUCPUState. Do we need other information?