Re: [Crash-utility] [PATCH v2] x86_64: Fix "bt" command printing stale entries on Linux 6.4 and later

Hi Lianbo, On 2023/05/18 16:53, HAGIO KAZUHITO(萩尾 一仁) wrote: > From: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > > 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(a)nec.com&gt; > --- > 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. */