Re: [Crash-utility] Handle the NT_PRSTATUS lost for the "bt" command

OK, now I'm getting confused... I note that currently __diskdump_memory_dump() does this: for (i = 0; i< dd->num_prstatus_notes; i++) { fprintf(fp, " notes[%d]: %lx\n", i, (ulong)dd->nt_prstatus_percpu[i]); } But your patch does this: nrcpus = kt->kernel_NR_CPUS ? kt->kernel_NR_CPUS : NR_CPUS; for (i = 0; i< nrcpus; i++) { if (dd->nt_prstatus_percpu[i] == NULL) { fprintf(fp, " notes[%d]: (not saved)\n", i); continue; } fprintf(fp, " notes[%d]: %lx\n", i, (ulong)dd->nt_prstatus_percpu[i]); } Now surely we don't want to dump "NR_CPUS" notes pointers, unless there actually are that many cpus in the system. For example, in RHEL6 sets CONFIG_NR_CPUS to 4096 for x86_64, but rarely do we see a dumpfile with that many cpus. So I would prefer that the for loop continue to be bounded by "dd->num_prstatus_notes".

However, given that process_elf32_notes() and process_elf64_notes() do a cursory test of each note by checking for the NT_PRSTATUS type, I'm presuming that in your dumpfile, dd->num_prstatus_notes must be equal to 1, correct?

void process_elf64_notes(void *note_buf, unsigned long size_note) { Elf64_Nhdr *nt; size_t index, len = 0; int num = 0; for (index = 0; index< size_note; index += len) { nt = note_buf + index; if(nt->n_type == NT_PRSTATUS) { dd->nt_prstatus_percpu[num] = nt; num++; } len = sizeof(Elf64_Nhdr); len = roundup(len + nt->n_namesz, 4); len = roundup(len + nt->n_descsz, 4); } if (num> 0) { pc->flags2 |= ELF_NOTES; dd->num_prstatus_notes = num; } return; } But then map_cpus_to_prstatus_kdump_cmprs() remaps the notes without modifying the dd->num_prstatus_notes counter. So then there's this: void * diskdump_get_prstatus_percpu(int cpu) { if ((cpu< 0) || (cpu>= dd->num_prstatus_notes)) return NULL; return dd->nt_prstatus_percpu[cpu]; } So in a case such as your example, where cpu 2 was the only cpu that saved its notes, the function above would incorrectly return NULL when called with diskdump_get_prstatus_percpu(2). What am I missing?

Dave -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility