On Thu, Jul 25, 2024 at 7:59 AM Tao Liu <l...@redhat.com> wrote:
> Hi Lijiang,
>
> On Wed, Jul 24, 2024 at 6:37 PM lijiang <liji...@redhat.com> wrote:
> >
> > Hi, Tao
> >
> > On Tue, Jul 23, 2024 at 2:24 PM lijiang <liji...@redhat.com> wrote:
> >>
> >> On Tue, Jul 23, 2024 at 1:55 PM Tao Liu <l...@redhat.com> wrote:
> >>>
> >>> Hi Aditya & Lianbo,
> >>>
> >>> On Mon, Jun 24, 2024 at 11:46 PM Aditya Gupta <adit...@linux.ibm.com>
> wrote:
> >>> >
> >>> > Hello Lianbo,
> >>> >
> >>> > On 24/06/24 05:32PM, lijiang wrote:
> >>> > > > <...snip...>
> >>> > > >
> >>> > > > Before:
> >>> > > > crash> gdb bt
> >>> > > > #0 0xffffffff816a8f65 in context_switch ...
> >>> > > > #1 __schedule () ...
> >>> > > > #2 0xffffffff816a94e9 in schedule ...
> >>> > > > #3 0xffffffff816a86fd in schedule_hrtimeout_range_clock ...
> >>> > > > #4 0xffffffff816a8733 in schedule_hrtimeout_range ...
> >>> > > > #5 0xffffffff8124bb7e in ep_poll ...
> >>> > > > #6 0xffffffff8124d00d in SYSC_epoll_wait ...
> >>> > > > #7 SyS_epoll_wait ...
> >>> > > > #8 <signal handler called>
> >>> > > > #9 0x00007f0449407923 in ?? ()
> >>> > > > #10 0xffff880100000001 in ?? ()
> >>> > > > #11 0xffff880169b3c010 in ?? ()
> >>> > > > #12 0x0000000000000040 in irq_stack_union ()
> >>> > > > #13 0xffff880169b3c058 in ?? ()
> >>> > > > #14 0xffff880169b3c048 in ?? ()
> >>> > > > #15 0xffff880169b3c050 in ?? ()
> >>> > > > #16 0x0000000000000000 in ?? ()
> >>> > > >
> >>> > > > After:
> >>> > > > crash> gdb bt
> >>> > > > #0 0xffffffff816a8f65 in context_switch ...
> >>> > > > #1 __schedule () ...
> >>> > > > #2 0xffffffff816a94e9 in schedule () ...
> >>> > > > #3 0xffffffff816a86fd in schedule_hrtimeout_range_clock ...
> >>> > > > #4 0xffffffff816a8733 in schedule_hrtimeout_range ...
> >>> > > > #5 0xffffffff8124bb7e in ep_poll ...
> >>> > > > #6 0xffffffff8124d00d in SYSC_epoll_wait ...
> >>> > > > #7 SyS_epoll_wait ...
> >>> > > > #8 <signal handler called>
> >>> > > > #9 0x00007f0449407923 in ?? ()
> >>> > > >
> >>> > > >
> >>> > > It seems that there are still some non-kernel addresses that do
> not get
> >>> > > filtered. Can you help double check?
> >>>
> >>> Yes, it is a non-kernel address which does not get filtered.
> >>>
> >>> > >
> >>> > >
> >>> > > For example:
> >>> > >
> >>> > > crash> gdb bt
> >>> > > #0 crash_setup_regs (newregs=0xffffb5bb4f197938, oldregs=0x0) at
> >>> > > ./arch/x86/include/asm/kexec.h:114
> >>> > > #1 0xffffffff8e61e32e in __crash_kexec (regs=regs@entry=0x0) at
> >>> > > kernel/crash_core.c:122
> >>> > > #2 0xffffffff8e51a64d in panic (fmt=fmt@entry=0xffffffff8fa51609
> "sysrq
> >>> > > triggered crash\n") at kernel/panic.c:366
> >>> > > #3 0xffffffff8ec21f86 in sysrq_handle_crash (key=<optimized out>)
> at
> >>> > > drivers/tty/sysrq.c:154
> >>> > > #4 0xffffffff8ec22550 in __handle_sysrq (key=<optimized out>,
> >>> > > check_mask=check_mask@entry=false) at drivers/tty/sysrq.c:612
> >>> > > #5 0xffffffff8ec22bf5 in write_sysrq_trigger (file=<optimized
> out>,
> >>> > > buf=<optimized out>, count=2, ppos=<optimized out>) at
> >>> > > drivers/tty/sysrq.c:1183
> >>> > > #6 0xffffffff8e935ae5 in pde_write (ppos=<optimized out>,
> count=<optimized
> >>> > > out>, buf=<optimized out>, file=0xffffb5bb4f197938,
> pde=0xffff98338b78e0c0)
> >>> > > at fs/proc/inode.c:334
> >>> > > #7 proc_reg_write (file=0xffffb5bb4f197938, buf=0x0, count=1,
> ppos=0x0) at
> >>> > > fs/proc/inode.c:346
> >>> > > #8 0xffffffff8e88d382 in vfs_write (file=file@entry
> =0xffff98338b789200,
> >>> > > buf=buf@entry=0x5614d58a22c0 <error: Cannot access memory at
> address
> >>> > > 0x5614d58a22c0>, count=count@entry=2,
> >>> > > pos=pos@entry=0xffffb5bb4f197b78)
> at
> >>> > > fs/read_write.c:588
> >>> > > #9 0xffffffff8e88d9ff in ksys_write (fd=<optimized out>,
> >>> > > buf=0x5614d58a22c0 <error: Cannot access memory at address
> 0x5614d58a22c0>,
> >>> > > count=2) at fs/read_write.c:643
> >>> > > #10 0xffffffff8f124429 in do_syscall_x64 (nr=1,
> regs=0xffffb5bb4f197f58) at
> >>> > > arch/x86/entry/common.c:52
> >>> > > #11 do_syscall_64 (regs=0xffffb5bb4f197f58, nr=1) at
> >>> > > arch/x86/entry/common.c:83
> >>> > > #12 0xffffffff8f20012b in entry_SYSCALL_64 () at
> >>> > > arch/x86/entry/entry_64.S:121
> >>> > > #13 0x00007f9a147f69e0 in ?? ()
> >>> > >
> >>> > > The frame #13 looks like a non-kernel address.
> >>>
> >>> The address usually to be the user space address before entering
> >>> kernel, you can see it by:
> >>>
> >>> crash> gdb bt
> >>> ...snip...
> >>> #7 SyS_epoll_wait ...
> >>> #8 <signal handler called>
> >>> #9 0x00007f0449407923 in ?? ()
> >>>
> >>> crash> bt
> >>> ...snip...
> >>> #6 [ffff880169b3bf80] system_call_fastpath at ffffffff816b5009
> >>> RIP: 00007f0449407923 ...
> >>>
> >>> So I think leaving the last frame here is useful and shouldn't be
> >>> filtered. Though it looks like some garbage data, it can help for some
> >>> experienced users...
> >>
> >>
> >>
> >> Hmm, normally it should be filtered, otherwise this looks weird.
> >>
> >> Let me dig into the details and see if that can be filtered out.
> >
> >
> Thanks for your patch!
>
> > Can you help try this? I saw the non-kernel addresses are filtered out.
> >
> > + #ifdef CRASH_MERGE
> > + extern "C" int is_kvaddr(ulong);
> > + #endif
> >
> > static void
> > print_frame (const frame_print_options &fp_opts,
> > frame_info *frame, int print_level,
> > enum print_what print_what, int print_args,
> > struct symtab_and_line sal)
> > {
> > struct gdbarch *gdbarch = get_frame_arch (frame);
> > struct ui_out *uiout = current_uiout;
> > enum language funlang = language_unknown;
> > struct value_print_options opts;
> > struct symbol *func;
> > CORE_ADDR pc = 0;
> > int pc_p;
> >
> > pc_p = get_frame_pc_if_available (frame, &pc);
> > + #ifdef CRASH_MERGE
> > + if (!is_kvaddr(pc))
> > + return;
> > + #endif
> > ...
> > }
>
> Your code change is "stop printing for non-kernel address", however I
> would prefer to "stop stack unwinding for non-kernel address", so I
>
Yes, they are different.
If "stop stack unwinding for non-kernel address" won't truncate the
backtrace, I would also prefer it.
Otherwise I would prefer another one.
> think it is better to modify it within the for loop, this is where
> stack unwinding happens.
>
> for (fi = trailing; fi && count--; fi = get_prev_frame (fi))
> ...
> print_frame_info (fp_opts, fi, 1, LOCATION, 1, 0);
>
> I made the following code change:
>
> for (fi = trailing; fi && count--; fi = get_prev_frame (fi))
> {
> QUIT;
> ...
> + CORE_ADDR pc = 0;
> + get_frame_pc_if_available (fi, &pc);
> + if (!is_kvaddr(pc)) {
> + fi = NULL;
> + break;
> + }
> print_frame_info (fp_opts, fi, 1, LOCATION, 1, 0);
>
> With the change:
>
> crash> gdb bt
> #0 blk_mq_rq_timed_out (req=0xffff880fdb246000,
> reserved=reserved@entry=false) at block/blk-mq.c:640
> #1 0xffffffff8130504c in blk_mq_check_expired
> (hctx=hctx@entry=0xffff880fda56bc00, rq=<optimized out>,
> priv=priv@entry=0xffff880fcf68fde8, reserved=reserved@entry=false) at
> block/blk-mq.c:697
> #2 0xffffffff81305eb4 in bt_for_each
> (hctx=hctx@entry=0xffff880fda56bc00, bt=bt@entry=0xffff88014c14c310,
> off=32, fn=fn@entry=0xffffffff81304ff0 <blk_mq_check_expired>,
> data=data@entry=0xffff880fcf68fde8, reserved=reserved@entry=false) at
> block/blk-mq-tag.c:431
> #3 0xffffffff8130686e in blk_mq_queue_tag_busy_iter
> (q=q@entry=0xffff88004912a340, fn=fn@entry=0xffffffff81304ff0
> <blk_mq_check_expired>, priv=priv@entry=0xffff880fcf68fde8) at
> block/blk-mq-tag.c:530
> #4 0xffffffff81301d2b in blk_mq_timeout_work
> (work=0xffff88004912ab68) at block/blk-mq.c:730
> #5 0xffffffff810a881a in process_one_work
> (worker=worker@entry=0xffff880fd86efa00, work=0xffff88004912ab68) at
> kernel/workqueue.c:2252
> #6 0xffffffff810a94e6 in worker_thread (__worker=0xffff880fd86efa00)
> at kernel/workqueue.c:2380
> #7 0xffffffff810b098f in kthread (_create=0xffff8801695f7d38) at
> kernel/kthread.c:202
> #8 <signal handler called>
>
^^^^^^^^^^^^^^^^^^^^^^^^
What's this for?
Thanks
Lianbo
> crash>
>
> What do you think?
>
> Thanks,
> Tao Liu
>
> >
> > Thanks
> > Lianbo
> >
> >>
> >> Thanks
> >> Lianbo
> >>
> >>>
> >>> >
> >>> > True. Though it seems to be okay for it to print the last frame with
> a
> >>> > non-kernel address, as in this snippet from gdb:
> >>> >
> >>> > for (fi = trailing; fi && count--; fi = get_prev_frame (fi))
> >>> > ...
> >>> > print_frame_info (fp_opts, fi, 1, LOCATION, 1, 0);
> >>> >
> >>> > Seems that frame #13, fi was not NULL.
> >>> >
> >>> > Seeing Tao's change, it compares the current frame's NIP/PC to see if
> >>> > it should return NULL (which I think is nice and works). Here the
> >>> > 'this_frame' would have been frame 12, (which would have called
> >>> > `'get_prev_frame' to get the frame 13)
> >>> >
> >>> > ```
> >>> > frame_pc_p = get_frame_pc_if_available (this_frame, &frame_pc);
> >>> > #ifdef CRASH_MERGE
> >>> > if (!is_kvaddr(frame_pc)) {
> >>> > return NULL;
> >>> > }
> >>> > #endif
> >>> > ```
> >>> >
> >>> > Tao's condition will hit when 'get_prev_frame(this_frame=frame#13)'
> will
> >>> > be called to get the frame #14, which will return NULL and hence
> break
> >>> > out of the loop.
> >>> >
> >>> > This is based on what I recall and a quick look at the
> implementation,
> >>> > please feel free to correct Lianbo/Tao.
> >>>
> >>> Thanks Aditya for the detailed inspection, which I didn't dive into.
> >>> When I notice the last frame to be the userspace address, I just keep
> >>> it as it is.
> >>>
> >>> Thanks,
> >>> Tao Liu
> >>>
> >>>
> >>> >
> >>> > Thanks,
> >>> > Aditya Gupta
> >>> >
> >>> >
> >>> > >
> >>> > >
> >>> > > Thanks
> >>> > > Lianbo
> >>> > >
> >>> > >
> >>> > > > Cc: Sourabh Jain <sourabhj...@linux.ibm.com>
> >>> > > > Cc: Hari Bathini <hbath...@linux.ibm.com>
> >>> > > > Cc: Mahesh J Salgaonkar <mah...@linux.ibm.com>
> >>> > > > Cc: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
> >>> > > > Cc: Lianbo Jiang <liji...@redhat.com>
> >>> > > > Cc: HAGIO KAZUHITO(萩尾 一仁) <k-hagio...@nec.com>
> >>> > > > Cc: Tao Liu <l...@redhat.com>
> >>> > > > Cc: Alexey Makhalov <alexey.makha...@broadcom.com>
> >>> > > > Signed-off-by: Tao Liu <l...@redhat.com>
> >>> > > > ---
> >>> > > > defs.h | 1 +
> >>> > > > gdb-10.2.patch | 26 ++++++++++++++++++++++++++
> >>> > > > gdb_interface.c | 6 ++++++
> >>> > > > 3 files changed, 33 insertions(+)
> >>> > > >
> >>> > > > diff --git a/defs.h b/defs.h
> >>> > > > index 012ffdc..c0e6a29 100644
> >>> > > > --- a/defs.h
> >>> > > > +++ b/defs.h
> >>> > > > @@ -7902,6 +7902,7 @@ extern unsigned char
> *gdb_prettyprint_arrays;
> >>> > > > extern unsigned int *gdb_repeat_count_threshold;
> >>> > > > extern unsigned char *gdb_stop_print_at_null;
> >>> > > > extern unsigned int *gdb_output_radix;
> >>> > > > +int is_kvaddr(ulong);
> >>> > > >
> >>> > > > /*
> >>> > > > * gdb/top.c
> >>> > > > diff --git a/gdb-10.2.patch b/gdb-10.2.patch
> >>> > > > index 0bed96a..3ed40c0 100644
> >>> > > > --- a/gdb-10.2.patch
> >>> > > > +++ b/gdb-10.2.patch
> >>> > > > @@ -16171,3 +16171,29 @@ exit 0
> >>> > > > }
> >>> > > >
> >>> > > > /*
> >>> > > > +--- gdb-10.2/gdb/frame.c.orig
> >>> > > > ++++ gdb-10.2/gdb/frame.c
> >>> > > > +@@ -2331,6 +2331,10 @@ inside_entry_func (frame_info
> *this_frame)
> >>> > > > + This function should not contain target-dependent tests,
> such as
> >>> > > > + checking whether the program-counter is zero. */
> >>> > > > +
> >>> > > > ++#ifdef CRASH_MERGE
> >>> > > > ++extern "C" int is_kvaddr(ulong);
> >>> > > > ++#endif
> >>> > > > ++
> >>> > > > + struct frame_info *
> >>> > > > + get_prev_frame (struct frame_info *this_frame)
> >>> > > > + {
> >>> > > > +@@ -2353,7 +2357,11 @@ get_prev_frame (struct frame_info
> *this_frame)
> >>> > > > + get_frame_id (this_frame);
> >>> > > > +
> >>> > > > + frame_pc_p = get_frame_pc_if_available (this_frame,
> &frame_pc);
> >>> > > > +-
> >>> > > > ++#ifdef CRASH_MERGE
> >>> > > > ++ if (!is_kvaddr(frame_pc)) {
> >>> > > > ++ return NULL;
> >>> > > > ++ }
> >>> > > > ++#endif
> >>> > > > + /* tausq/2004-12-07: Dummy frames are skipped because it
> doesn't make
> >>> > > > much
> >>> > > > + sense to stop unwinding at a dummy frame. One place
> where a dummy
> >>> > > > + frame may have an address "inside_main_func" is on HPUX.
> On HPUX,
> >>> > > > the
> >>> > > > diff --git a/gdb_interface.c b/gdb_interface.c
> >>> > > > index b13d5fd..e76ecc6 100644
> >>> > > > --- a/gdb_interface.c
> >>> > > > +++ b/gdb_interface.c
> >>> > > > @@ -947,6 +947,12 @@ gdb_lookup_module_symbol(ulong addr, ulong
> *offset)
> >>> > > > }
> >>> > > > }
> >>> > > >
> >>> > > > +int
> >>> > > > +is_kvaddr(ulong addr)
> >>> > > > +{
> >>> > > > + return IS_KVADDR(addr);
> >>> > > > +}
> >>> > > > +
> >>> > > > /*
> >>> > > > * Used by gdb_interface() to catch gdb-related errors, if
> desired.
> >>> > > > */
> >>> > > > --
> >>> > > > 2.40.1
> >>> > > >
> >>> >
> >>>
>
>
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