Hi Lianbo,

On 2023/05/18 16:53, HAGIO KAZUHITO(萩尾 一仁) wrote:
> From: Kazuhito Hagio <k-hagio-ab@nec.com>
>
> Kernel commit fb799447ae29 ("x86,objtool: Split UNWIND_HINT_EMPTY in
> two"), which is contained in Linux 6.4 and later kernels, changed
> ORC_TYPE_CALL macro from 0 to 2.  As a result, the "bt" command cannot
> use ORC entries, and can display stale entries in a call trace.
>
>    crash> bt 1
>    PID: 1        TASK: ffff93cd06294180  CPU: 51   COMMAND: "systemd"
>     #0 [ffffb72bc00cbc98] __schedule at ffffffff86e52aae
>     #1 [ffffb72bc00cbd00] schedule at ffffffff86e52f6a
>     #2 [ffffb72bc00cbd18] schedule_hrtimeout_range_clock at ffffffff86e58ef5
>     #3 [ffffb72bc00cbd88] ep_poll at ffffffff8669624d
>     #4 [ffffb72bc00cbe28] do_epoll_wait at ffffffff86696371
>     #5 [ffffb72bc00cbe30] do_timerfd_settime at ffffffff8669902b        <<
>     #6 [ffffb72bc00cbe60] __x64_sys_epoll_wait at ffffffff86696bf0
>     #7 [ffffb72bc00cbeb0] do_syscall_64 at ffffffff86e3feb9
>     #8 [ffffb72bc00cbee0] __task_pid_nr_ns at ffffffff863330d7          <<
>     #9 [ffffb72bc00cbf08] syscall_exit_to_user_mode at ffffffff86e466b2 << stale entries
>    #10 [ffffb72bc00cbf18] do_syscall_64 at ffffffff86e3fec9             <<
>    #11 [ffffb72bc00cbf50] entry_SYSCALL_64_after_hwframe at ffffffff870000aa
>
> Also, kernel commit ffb1b4a41016 added a member to struct orc_entry.
> Although this does not affect the crash's unwinder, its debugging
> information can be displayed incorrectly.
>
> To fix these,
> (1) introduce "kernel_orc_entry_6_4" structure corresponding to 6.4 and
>      abstruction layer "orc_entry" structure in crash,
> (2) switch ORC_TYPE_CALL to 2 or 0 with kernel's orc_entry structure.
>
> Related orc_entry history:
>   v4.14 39358a033b2e introduced struct orc_entry
>   v4.19 d31a580266ee added orc_entry.end member
>   v6.3  ffb1b4a41016 added orc_entry.signal member
>   v6.4  fb799447ae29 removed end member and changed type member to 3 bits
>
> Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
> ---
> v2:
> - better debugging information for orc_entry.{signal,end}.
>
>   defs.h   |  27 ++++++++++++-
>   x86_64.c | 119 +++++++++++++++++++++++++++++++++++++++++++------------
>   2 files changed, 118 insertions(+), 28 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index 21cc760444d1..c1ac347c8e26 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -6354,9 +6354,29 @@ typedef struct __attribute__((__packed__)) {
>           unsigned int sp_reg:4;
>           unsigned int bp_reg:4;
>           unsigned int type:2;
> +        unsigned int signal:1;
>           unsigned int end:1;
>   } kernel_orc_entry;
>   
> +typedef struct __attribute__((__packed__)) {
> +        signed short sp_offset;
> +        signed short bp_offset;
> +        unsigned int sp_reg:4;
> +        unsigned int bp_reg:4;
> +        unsigned int type:3;
> +        unsigned int signal:1;
> +} kernel_orc_entry_6_4;
> +
> +typedef struct orc_entry {
> +        signed short sp_offset;
> +        signed short bp_offset;
> +        unsigned int sp_reg;
> +        unsigned int bp_reg;
> +        unsigned int type;
> +        unsigned int signal;
> +        unsigned int end;
> +} orc_entry;
> +
>   struct ORC_data {
>       int module_ORC;
>       uint lookup_num_blocks;
> @@ -6367,10 +6387,12 @@ struct ORC_data {
>       ulong orc_lookup;
>       ulong ip_entry;
>       ulong orc_entry;
> -     kernel_orc_entry kernel_orc_entry;
> +     orc_entry orc_entry_data;
> +     int has_signal;
> +     int has_end;
>   };
>   
> -#define ORC_TYPE_CALL                   0
> +#define ORC_TYPE_CALL                   ((machdep->flags & ORC_6_4) ? 2 : 0)

>   #define ORC_TYPE_REGS                   1
>   #define ORC_TYPE_REGS_IRET              2
>   #define UNWIND_HINT_TYPE_SAVE           3

These entries are not used in crash so far, remove them?
or add a comment like this?

/* The below entries are not used and must be updated if we use them. */