3:40 a.m.
Hi Tao,
> > <...snip...>
> >
> > Currently I'm still struggling with some failing cases of x86_64
> > unwinding. So I didn't arrange my patchsets, along with the patch
> > commit log well, since they are all "trial" patches.
> >
> > I agree the patch "ppc64 arbitrary task stack unwind support" is
> > better to go with the ppc patch series. But I suggest we make some
> > modifications for it:
> >
> > 1) I'm OK with it being a stand alone patch, or merging the code
> > changes of this one into your previous patches, but I prefer the
> > latter one :)
> >
> > 2) If you'd like to go with a stand alone patch, could you please
> > rewrite a commit log and title for this one?
>
> Sure, I am okay with either. Let's go with the latter one you suggested,
> in that case I will add the line adding 'need_free' in 'bt_info'
> structure also, to make that work. By the way, shouldn't it be
> 'FREEBUF(bt_info.stackbuf)' instead of 'FREEBUF(pt_regs)' ?
No it isn't. Let's take a look at the code in
https://github.com/liutgnu/crash-dev/blob/master/x86_64.c#L5006:
x86_64_get_stack_frame():
For non active tasks, bt->machdep = user_regs, user_regs is allocated
here and get the regs value from stack frame. However for active
tasks, bt->machdep is get from get_netdump_regs_x86_64(), the values
are get from vmcore's elf note section.
Then in x86_64_get_cpu_reg(), pt_regs = (struct
x86_64_user_regs_struct *)bt_info.machdep, so the regs value will be
get from pt_regs. And if the pt_regs is allocated in
x86_64_get_stack_frame(), it should be freed. Else if pt_regs are
allocated from get_netdump_regs_x86_64(), then we don't need to do
anything.
So back to your question, ppc64 case is the same as x86_64, so we
should use FREEBUF(pt_regs) here.
In additiion, in
https://github.com/liutgnu/crash-dev/blob/master/ppc64.c#L2509:
ppc64_get_cpu_reg(), there is both 'FREEBUF(bt_info.stackbuf)' and
'FREEBUF(pt_regs)', they deal with different buffer release.
Thank you for the detailed explanation !
Understood. After reading, went through the code again, it all makes
sense.
Thanks,
Aditya Gupta
>
> Thanks,
> Tao Liu
>
>
>
>
>
> >
> > Also, should I add you as a co-author of the patch ?
> >
> > Thanks,
> > Aditya Gupta
> >
> > >
> > > Thanks,
> > > Tao Liu
> > >
> > >
> > > >
> > > > To test various gdb passthroughs:
> > > >
> > > > (crash) set
> > > > (crash) set gdb on
> > > > gdb> thread
> > > > gdb> bt
> > > > gdb> info threads
> > > > gdb> info threads
> > > > gdb> info locals
> > > > gdb> info variables irq_rover_lock
> > > > gdb> info args
> > > > gdb> thread 2
> > > > gdb> set gdb off
> > > > (crash) set
> > > > (crash) set -c 6
> > > > (crash) gdb thread
> > > > (crash) bt
> > > > (crash) gdb bt
> > > > (crash) frame
> > > > (crash) gdb up
> > > > (crash) gdb down
> > > > (crash) info locals
> > > >
> > > > Known Issues:
> > > > =============
> > > >
> > > > 1. In gdb mode, 'bt' might fail to show backtrace in few
vmcores collected
> > > > from older kernels. This is a known issue due to register mismatch,
and
> > > > its fix has been merged upstream:
> > > >
> > > > This can also cause some 'invalid kernel virtual address'
errors during gdb
> > > > unwinding the stack registers
> > > >
> > > > Commit:
https://github.com/torvalds/linux/commit/b684c09f09e7a6af3794d4233ef78581...
> > > >
> > > > Fixing GDB passthroughs on other architectures
> > > > ==============================================
> > > >
> > > > Much of the work for making gdb passthroughs like 'gdb bt',
'gdb
> > > > thread', 'gdb info locals' etc. has been done by the
patches introducing
> > > > 'machdep->get_cpu_reg' and this series fixing some issues
in that.
> > > >
> > > > Other architectures should be able to fix these gdb functionalities
by
> > > > simply implementing 'machdep->get_cpu_reg (cpu, regno,
...)'.
> > > >
> > > > The reasoning behind that has been explained with a diagram in commit
> > > > description of patch #1
> > > >
> > > > I will assist with my findings/observations fixing it on ppc64
whenever needed.
> > > >
> > > > Changelog:
> > > > ==========
> > > >
> > > > V9:
> > > > + minor change in patch #5: sync gdb context on a 'set' and
'set -p'
> > > > + add taoliu's patch for using current context, and fixes in
ppc64_get_cpu_reg
> > > >
> > > > V8:
> > > > + use get_active_task instead of depending on CURRENT_CONTEXT in
ppc64_get_cpu_reg
> > > > + rebase to upstream/master (5977936c0a91)
> > > >
> > > > V7:
> > > > + move changes in gdb-10.2.patch to the end (minor change in patch
#3,4,5)
> > > > + fix a memory leak in ppc64_get_cpu_reg (minor change in patch #1)
> > > > + use ascii diagram in patch #1 description
> > > >
> > > > V6:
> > > > + changes in patch #5: fix bug introduced in v5 that caused initial
gdb thread
> > > > to be thread 1
> > > >
> > > > V5:
> > > > + changes in patch #1: made ppc64_get_cpu_reg static, and remove
unreachable
> > > > code
> > > > + changes in patch #3: fixed typo 'ppc64_renum' instead of
'ppc64_regnum',
> > > > remove unneeded if condition
> > > > + changes in patch #5: implement refresh regcache on per thread,
instead of all
> > > > threads at once
> > > >
> > > > V4:
> > > > + fix segmentation fault in live debugging (change in patch #1)
> > > > + mention live debugging not supported in cover letter and patch #1
> > > > + fixed some checkpatch warnings (change in patch #5)
> > > >
> > > > V3:
> > > > + default gdb thread will be the crashing thread, instead of being
> > > > thread '0'
> > > > + synchronise crash cpu and gdb thread context
> > > > + fix bug in gdb_interface, that replaced gdb's output stream,
losing
> > > > output in some cases, such as info threads and extra output in info
> > > > variables
> > > > + fix 'info threads'
> > > >
> > > > RFC V2:
> > > > - removed patch implementing 'frame', 'up',
'down' in crash
> > > > - updated the cover letter by removing the mention of those commands
other
> > > > than the respective gdb passthrough
> > > >
> > > > Aditya Gupta (5):
> > > > ppc64: correct gdb passthroughs by implementing
machdep->get_cpu_reg
> > > > remove 'frame' from prohibited commands list
> > > > synchronise cpu context changes between crash/gdb
> > > > fix gdb_interface: restore gdb's output streams at end of
> > > > gdb_interface
> > > > fix 'info threads' command
> > > >
> > > > crash_target.c | 44 ++++++++++++++++
> > > > defs.h | 130
+++++++++++++++++++++++++++++++++++++++++++++++-
> > > > gdb-10.2.patch | 110 +++++++++++++++++++++++++++++++++++++++-
> > > > gdb_interface.c | 2 +-
> > > > kernel.c | 47 +++++++++++++++--
> > > > ppc64.c | 95 +++++++++++++++++++++++++++++++++--
> > > > task.c | 14 ++++++
> > > > tools.c | 2 +-
> > > > 8 files changed, 434 insertions(+), 10 deletions(-)
> > > >
> > > > --
> > > > 2.41.0
> > > >
> > >
> >
>