12:57 a.m.
Hi Lianbo,
Thanks for the reviews.
crash> gdb frame
#0 <unavailable> in ?? ()
Will fix this in V6. It got introduced in V5 due to initial gdb thread
still being thread 1 (CPU 0).
crash> set gdb on
gdb: on
gdb> bt
#0 <unavailable> in ?? ()
#1 0xc0000000000f570c in plpar_hcall_norets_notrace () at
arch/powerpc/platforms/pseries/hvCall.S:111
#2 0xc000000001004dd8 in cede_processor () at
./arch/powerpc/include/asm/plpar_wrappers.h:37
#3 check_and_cede_processor () at drivers/cpuidle/cpuidle-pseries.c:83
#4 0xc000000001005000 in shared_cede_loop (dev=<optimized out>,
drv=<optimized out>, index=<optimized out>) at
drivers/cpuidle/cpuidle-pseries.c:256
#5 0xc000000001004498 in cpuidle_enter_state
(dev=dev@entry=0xc0000001ff5910c0, drv=drv@entry=0xc000000002b8f558
<pseries_idle_driver>, index=index@entry=1) at drivers/cpuidle/cpuidle.c:267
#6 0xc000000000c0eb4c in cpuidle_enter (drv=0xc000000002b8f558
<pseries_idle_driver>, dev=0xc0000001ff5910c0, index=<optimized out>) at
drivers/cpuidle/cpuidle.c:388
#7 0xc0000000001ce2bc in call_cpuidle (drv=<optimized out>,
drv@entry=0xc000000002b8f558 <pseries_idle_driver>, dev=<optimized out>,
dev@entry=0xc0000001ff5910c0, next_state=<optimized out>) at
kernel/sched/idle.c:134
#8 0xc0000000001d5d68 in cpuidle_idle_call () at kernel/sched/idle.c:215
#9 0xc0000000001d5f58 in do_idle () at kernel/sched/idle.c:282
#10 0xc0000000001d6298 in cpu_startup_entry (state=<optimized out>) at
kernel/sched/idle.c:380
#11 0xc000000000011030 in rest_init () at init/main.c:730
#12 0xc000000002004c80 in arch_call_rest_init () at init/main.c:827
#13 0xc0000000020051ec in start_kernel () at init/main.c:1072
#14 0xc00000000000e788 in start_here_common () at
arch/powerpc/kernel/head_64.S:1039
gdb> info threads
Id Target Id Frame
* 1 CPU 0 plpar_hcall_norets_notrace () at
arch/powerpc/platforms/pseries/hvCall.S:114
2 CPU 1 plpar_hcall_norets_notrace () at
arch/powerpc/platforms/pseries/hvCall.S:114
3 CPU 2 plpar_hcall_norets_notrace () at
arch/powerpc/platforms/pseries/hvCall.S:114
4 CPU 3 plpar_hcall_norets_notrace () at
arch/powerpc/platforms/pseries/hvCall.S:114
5 CPU 4 plpar_hcall_norets_notrace () at
arch/powerpc/platforms/pseries/hvCall.S:114
6 CPU 5 0xc00000000028b5e8 in crash_setup_regs
(oldregs=<optimized out>, newregs=0xc00000005d3e7958) at
./arch/powerpc/include/asm/kexec.h:69
7 CPU 6 plpar_hcall_norets_notrace () at
arch/powerpc/platforms/pseries/hvCall.S:114
8 CPU 7 plpar_hcall_norets_notrace () at
arch/powerpc/platforms/pseries/hvCall.S:114
gdb: page excluded: kernel virtual address: c000000002004c80 type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c000000002004c7c type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c000000002004c78 type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c000000002004c80 type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c000000002004c7c type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c000000002004c78 type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c0000000020051ec type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c0000000020051e8 type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c0000000020051e4 type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c0000000020051ec type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c0000000020051e8 type:
"gdb_readmem_callback"
gdb: page excluded: kernel virtual address: c0000000020051e4 type:
"gdb_readmem_callback"
<...>
Could you please check it again? Or am I missing anything? I did the test
based on upstream kernel 6.7.0-rc7(commit:8735c7c84d1b).
I am looking at it. As of now, I found these 'page excluded' error come up when
gdb tries to access some addresses while trying 'tramp_frame_sniffer' unwinder.
afaik most unwinders are expected to fail to unwind, as gdb tries all unwinders
to see which one can unwind the previous frame correctly, will see how to handle
this case.
BTW: I did not see the similar issues after applying the v4 patch set.
A bug got introduced in V5, where the initial gdb thread is thread 1,
irrespective of crashing thread. Found a fix for that, but still pending for
'page excluded' errors.
Thanks,
Aditya Gupta
>
> Thanks
>
> Lianbo
>
> >
> > 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:
> > ==========
> >
> > 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(-)
> >
>