11:02 a.m.
On Thu, Nov 19, 2015 at 11:50:22AM -0500, Dave Anderson wrote:
----- Original Message -----
> QEMU can generate both non-makedumpfile (just elf) and makedumpfile
> formatted kdumps. In neither case will crash_notes have prstatus, as
> crash_kexec doesn't run in the kernel, however the elf notes will
> contain the prstatus, and we can dig them out of there.
Hi Andrew,
Refresh my memory -- without the patch, what does "bt" do when run
against the active tasks from QEMU generated dumps?
On initial loading a couple warnings are output
WARNING: invalid note (n_type != NT_PRSTATUS)
WARNING: cannot retrieve registers for active tasks
When attempting 'bt', crash segfaults
PID: 2424 TASK: ffffffc057a46e00 CPU: 1 COMMAND: "bash"
bt: WARNING: cannot determine starting stack frame for task ffffffc057a46e00
Segmentation fault
Thanks,
drew
Dave
> ---
> arm.c | 22 ++++++++++++++++++++++
> arm64.c | 22 ++++++++++++++++++++++
> defs.h | 1 +
> netdump.c | 21 +++++++++++++++++++++
> 4 files changed, 66 insertions(+)
>
> diff --git a/arm.c b/arm.c
> index ffc7c06d0f42c..8fc3d48a8ac89 100644
> --- a/arm.c
> +++ b/arm.c
> @@ -597,6 +597,28 @@ arm_get_crash_notes(void)
> note = (Elf32_Nhdr *)buf;
> p = buf + sizeof(Elf32_Nhdr);
>
> + /*
> + * dumpfiles created with qemu won't have crash_notes, but there will
> + * be elf notes.
> + */
> + 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(Elf32_Nhdr);
> +
> + if (sizeof(Elf32_Nhdr) + roundup(note->n_namesz, 4) +
> + note->n_descsz == notesz)
> + BCOPY((char *)note, buf, notesz);
> + }
> + }
> +
> if (note->n_type != NT_PRSTATUS) {
> error(WARNING, "invalid note (n_type != NT_PRSTATUS)\n");
> goto fail;
> diff --git a/arm64.c b/arm64.c
> index 6187b96d25a4d..91b35787e6942 100644
> --- a/arm64.c
> +++ b/arm64.c
> @@ -1827,6 +1827,28 @@ arm64_get_crash_notes(void)
> note = (Elf64_Nhdr *)buf;
> p = buf + sizeof(Elf64_Nhdr);
>
> + /*
> + * dumpfiles created with qemu won't have crash_notes, but there will
> + * be elf notes.
> + */
> + 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);
> + }
> + }
> +
> if (note->n_type != NT_PRSTATUS) {
> error(WARNING, "invalid note (n_type != NT_PRSTATUS)\n");
> goto fail;
> diff --git a/defs.h b/defs.h
> index 1bcd1b3b177db..981b030cc6688 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -5722,6 +5722,7 @@ void dump_registers_for_qemu_mem_dump(void);
> void kdump_backup_region_init(void);
> void display_regs_from_elf_notes(int, FILE *);
> void display_ELF_note(int, int, void *, FILE *);
> +void *netdump_get_prstatus_percpu(int);
> #define PRSTATUS_NOTE (1)
> #define QEMU_NOTE (2)
>
> diff --git a/netdump.c b/netdump.c
> index bfa818fdef8e1..3ff49f0577c23 100644
> --- a/netdump.c
> +++ b/netdump.c
> @@ -2345,6 +2345,27 @@ dump_Elf64_Nhdr(Elf64_Off offset, int store)
> return len;
> }
>
> +void *
> +netdump_get_prstatus_percpu(int cpu)
> +{
> + int online;
> +
> + if ((cpu < 0) || (cpu >= nd->num_prstatus_notes))
> + return NULL;
> +
> + /*
> + * If no cpu mapping was done, then there must be
> + * a one-to-one relationship between the number
> + * of online cpus and the number of notes.
> + */
> + if ((online = get_cpus_online()) &&
> + (online == kt->cpus) &&
> + (online != nd->num_prstatus_notes))
> + return NULL;
> +
> + return nd->nt_prstatus_percpu[cpu];
> +}
> +
> /*
> * Send the request to the proper architecture hander.
> */
> --
> 2.4.3
>
>