[Crash-utility] [PATCH 11/16] MIPS64: Fixes for the gathering of the active task registers for the 'bt' command
Youling Tang
tangyouling at loongson.cn
Wed Mar 10 09:21:29 UTC 2021
On 03/10/2021 09:19 AM, HAGIO KAZUHITO(萩尾 一仁) wrote:
> -----Original Message-----
>> dumpfiles:
>> (1) If ELF notes are not available, read them from the kernel's
>> crash_notes.
> This is reverse? i.e. If kernel's crash_notes are not available,
> read them from ELF notes.
Yes, If crash_notes is available, crash_notes will be used first, otherwise
it will be read from ELF notes.
Thanks,
Youling
> Thanks,
> Kazu
>
>> (2) If an online CPUs did not save its ELF notes, then adjust
>> the mapping of each ELF note to its CPU accordingly.
>>
>> E.g. With this patch:
>> crash> bt
>> PID: 4768 TASK: 9800000243bcf200 CPU: 3 COMMAND: "bash"
>> #0 [980000024291f930] __crash_kexec at ffffffff802fff84
>> #1 [980000024291faa0] panic at ffffffff80248cac
>> #2 [980000024291fb40] die at ffffffff8021b338
>> #3 [980000024291fb70] do_page_fault at ffffffff802315e0
>> #4 [980000024291fbd0] tlb_do_page_fault_1 at ffffffff80239388
>> #5 [980000024291fd00] sysrq_handle_crash at ffffffff8085d308
>> #6 [980000024291fd10] __handle_sysrq at ffffffff8085d9e0
>> #7 [980000024291fd60] write_sysrq_trigger at ffffffff8085e020
>> #8 [980000024291fd80] proc_reg_write at ffffffff804762f0
>> #9 [980000024291fda0] __vfs_write at ffffffff803f3138
>>
>> Signed-off-by: Huacai Chen <chenhuacai at loongson.cn>
>> Signed-off-by: Youling Tang <tangyouling at loongson.cn>
>> ---
>> mips64.c | 203 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 202 insertions(+), 1 deletion(-)
>>
>> diff --git a/mips64.c b/mips64.c
>> index 57a7f41..d949af4 100644
>> --- a/mips64.c
>> +++ b/mips64.c
>> @@ -42,7 +42,9 @@ static void mips64_get_stack_frame(struct bt_info *bt, ulong *pcp, ulong *spp);
>> static int mips64_get_dumpfile_stack_frame(struct bt_info *bt,
>> ulong *nip, ulong *ksp);
>> static int mips64_get_frame(struct bt_info *bt, ulong *pcp, ulong *spp);
>> -
>> +static int mips64_init_active_task_regs(void);
>> +static int mips64_get_crash_notes(void);
>> +static int mips64_get_elf_notes(void);
>>
>> /*
>> * 3 Levels paging PAGE_SIZE=16KB
>> @@ -806,6 +808,192 @@ mips64_get_frame(struct bt_info *bt, ulong *pcp, ulong *spp)
>> return TRUE;
>> }
>>
>> +static int
>> +mips64_init_active_task_regs(void)
>> +{
>> + int retval;
>> +
>> + retval = mips64_get_crash_notes();
>> + if (retval == TRUE)
>> + return retval;
>> +
>> + return mips64_get_elf_notes();
>> +}
>> +
>> +/*
>> + * Retrieve task registers for the time of the crash.
>> + */
>> +static int
>> +mips64_get_crash_notes(void)
>> +{
>> + struct machine_specific *ms = machdep->machspec;
>> + ulong crash_notes;
>> + Elf64_Nhdr *note;
>> + ulong offset;
>> + char *buf, *p;
>> + ulong *notes_ptrs;
>> + ulong i;
>> +
>> + /*
>> + * crash_notes contains per cpu memory for storing cpu states
>> + * in case of system crash.
>> + */
>> + if (!symbol_exists("crash_notes"))
>> + return FALSE;
>> +
>> + crash_notes = symbol_value("crash_notes");
>> +
>> + notes_ptrs = (ulong *)GETBUF(kt->cpus*sizeof(notes_ptrs[0]));
>> +
>> + /*
>> + * Read crash_notes for the first CPU. crash_notes are in standard ELF
>> + * note format.
>> + */
>> + if (!readmem(crash_notes, KVADDR, ¬es_ptrs[kt->cpus-1],
>> + sizeof(notes_ptrs[kt->cpus-1]), "crash_notes",
>> + RETURN_ON_ERROR)) {
>> + error(WARNING, "cannot read crash_notes\n");
>> + FREEBUF(notes_ptrs);
>> + return FALSE;
>> + }
>> +
>> + if (symbol_exists("__per_cpu_offset")) {
>> +
>> + /*
>> + * Add __per_cpu_offset for each cpu to form the pointer to the notes
>> + */
>> + for (i = 0; i < kt->cpus; i++)
>> + notes_ptrs[i] = notes_ptrs[kt->cpus-1] + kt->__per_cpu_offset[i];
>> + }
>> +
>> + buf = GETBUF(SIZE(note_buf));
>> +
>> + if (!(panic_task_regs = calloc((size_t)kt->cpus, sizeof(*panic_task_regs))))
>> + error(FATAL, "cannot calloc panic_task_regs space\n");
>> +
>> + for (i = 0; i < kt->cpus; i++) {
>> +
>> + if (!readmem(notes_ptrs[i], KVADDR, buf, SIZE(note_buf), "note_buf_t",
>> + RETURN_ON_ERROR)) {
>> + error(WARNING,
>> + "cannot find NT_PRSTATUS note for cpu: %d\n", i);
>> + goto fail;
>> + }
>> +
>> + /*
>> + * Do some sanity checks for this note before reading registers from it.
>> + */
>> + note = (Elf64_Nhdr *)buf;
>> + p = buf + sizeof(Elf64_Nhdr);
>> +
>> + /*
>> + * dumpfiles created with qemu won't have crash_notes, but there will
>> + * be elf notes; dumpfiles created by kdump do not create notes for
>> + * offline cpus.
>> + */
>> + if (note->n_namesz == 0 && (DISKDUMP_DUMPFILE() || KDUMP_DUMPFILE())) {
>> + if (DISKDUMP_DUMPFILE())
>> + note = diskdump_get_prstatus_percpu(i);
>> + else if (KDUMP_DUMPFILE())
>> + note = netdump_get_prstatus_percpu(i);
>> + if (note) {
>> + /*
>> + * SIZE(note_buf) accounts for a "final note", which is a
>> + * trailing empty elf note header.
>> + */
>> + long notesz = SIZE(note_buf) - sizeof(Elf64_Nhdr);
>> +
>> + if (sizeof(Elf64_Nhdr) + roundup(note->n_namesz, 4) +
>> + note->n_descsz == notesz)
>> + BCOPY((char *)note, buf, notesz);
>> + } else {
>> + error(WARNING,
>> + "cannot find NT_PRSTATUS note for cpu: %d\n", i);
>> + continue;
>> + }
>> + }
>> +
>> + /*
>> + * Check the sanity of NT_PRSTATUS note only for each online cpu.
>> + */
>> + if (note->n_type != NT_PRSTATUS) {
>> + error(WARNING, "invalid NT_PRSTATUS note (n_type != NT_PRSTATUS)\n");
>> + goto fail;
>> + }
>> + if (!STRNEQ(p, "CORE")) {
>> + error(WARNING, "invalid NT_PRSTATUS note (name != \"CORE\"\n");
>> + goto fail;
>> + }
>> +
>> + /*
>> + * Find correct location of note data. This contains elf_prstatus
>> + * structure which has registers etc. for the crashed task.
>> + */
>> + offset = sizeof(Elf64_Nhdr);
>> + offset = roundup(offset + note->n_namesz, 4);
>> + p = buf + offset; /* start of elf_prstatus */
>> +
>> + BCOPY(p + OFFSET(elf_prstatus_pr_reg), &panic_task_regs[i],
>> + sizeof(panic_task_regs[i]));
>> + }
>> +
>> + /*
>> + * And finally we have the registers for the crashed task. This is
>> + * used later on when dumping backtrace.
>> + */
>> + ms->crash_task_regs = panic_task_regs;
>> +
>> + FREEBUF(buf);
>> + FREEBUF(notes_ptrs);
>> + return TRUE;
>> +
>> +fail:
>> + FREEBUF(buf);
>> + FREEBUF(notes_ptrs);
>> + free(panic_task_regs);
>> + return FALSE;
>> +}
>> +
>> +static int
>> +mips64_get_elf_notes(void)
>> +{
>> + struct machine_specific *ms = machdep->machspec;
>> + int i;
>> +
>> + if (!DISKDUMP_DUMPFILE() && !KDUMP_DUMPFILE())
>> + return FALSE;
>> +
>> + panic_task_regs = calloc(kt->cpus, sizeof(*panic_task_regs));
>> + if (!panic_task_regs)
>> + error(FATAL, "cannot calloc panic_task_regs space\n");
>> +
>> + for (i = 0; i < kt->cpus; i++) {
>> + Elf64_Nhdr *note = NULL;
>> + size_t len;
>> +
>> + if (DISKDUMP_DUMPFILE())
>> + note = diskdump_get_prstatus_percpu(i);
>> + else if (KDUMP_DUMPFILE())
>> + note = netdump_get_prstatus_percpu(i);
>> +
>> + if (!note) {
>> + error(WARNING,
>> + "cannot find NT_PRSTATUS note for cpu: %d\n", i);
>> + continue;
>> + }
>> +
>> + len = sizeof(Elf64_Nhdr);
>> + len = roundup(len + note->n_namesz, 4);
>> +
>> + BCOPY((char *)note + len + OFFSET(elf_prstatus_pr_reg),
>> + &panic_task_regs[i], sizeof(panic_task_regs[i]));
>> + }
>> +
>> + ms->crash_task_regs = panic_task_regs;
>> +
>> + return TRUE;
>> +}
>> +
>> /*
>> * Accept or reject a symbol from the kernel namelist.
>> */
>> @@ -959,9 +1147,22 @@ mips64_init(int when)
>> mips64_stackframe_init();
>> if (!machdep->hz)
>> machdep->hz = 250;
>> + MEMBER_OFFSET_INIT(elf_prstatus_pr_reg, "elf_prstatus",
>> + "pr_reg");
>> + STRUCT_SIZE_INIT(note_buf, "note_buf_t");
>> break;
>>
>> case POST_VM:
>> + /*
>> + * crash_notes contains machine specific information about the
>> + * crash. In particular, it contains CPU registers at the time
>> + * of the crash. We need this information to extract correct
>> + * backtraces from the panic task.
>> + */
>> + if (!ACTIVE() && !mips64_init_active_task_regs())
>> + error(WARNING,
>> + "cannot retrieve registers for active task%s\n\n",
>> + kt->cpus > 1 ? "s" : "");
>> break;
>> }
>> }
>> --
>> 2.1.0
More information about the Crash-utility
mailing list