Hi Lianbo, On Fri, Jan 05, 2024 at 01:53:53PM +0800, Lianbo Jiang wrote: > > > > ...<snip>... > > > > Q. Is it harmless ? > > > > Yes, all unwinders which were tried before chosing the correct one, are expected > > to fail. > > > > About address being unavailable, that also is harmless because: > > 1. The functions instructions were freed by the kernel, so the data at those > > address being missing is expected > > 2. Even GDB is okay with a read failing, in this case, tramp_frame_sniffer > > simply returns if it's unable to get an address. > > > > ------------ > > > > Btw, this only happens with CPU0 WHEN it has idle task. Since unlike other CPUs > > idle tasks, CPU 0's idle task is called during this initialisation sequence, > > thus it's backtrace having very early init functions. > It's true. > > Since this is expected and harmless (gdb handles such cases), I am thinking to > > ignore this warning when called by gdb, what do you suggest ? > > If this does happen and it's rare, it might be good to have a warning for > users. > > At least it reflects the actual situation, although the warning output looks > not very friendly. So I would suggest still leaving it there for the time > being. > Yes, the warning is not very friendly but it does tell that the page is excluded. > > > i) Add flag "IGNORE_PAGE_EXCLUDED" to 'readmem' call when done by gdb, and > > only print the error if this is true: > > if ((error_handle & IGNORE_PAGE_EXCLUDED) && (CRASHDEBUG(0)) > > ... > > This way, it will still be visible with -d 1 and above debug levels. > > ii) Append 'quiet' to the 'error_handle': > > This way we don't have to introduce a flag, but it might skip showing other > > warnings/errors which might be of interest > > > > Other than this, there was a bug introduced in V5, where default thread is still > > thread 1 (CPU 0) at initialisation, which has been fixed, and will also fix the > Sounds good. So for now there's no change needed to the 'page excluded' warnings ? > > 'unavailable' frame being shown. Though it's funny that bug helped in a way to > > uncover these warnings, this would have hit in earlier versions also. > > Indeed, it can be triggered conditionally. > > I have no other issues, thank you for the great job, Aditya. Thanks, Aditya Gupta > > > Thanks > > Lianbo > > > > > Thanks, > > Aditya Gupta > > > > > crash> gdb frame > > > #0 <unavailable> in ?? () > > > 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" > > > > > > gdb> thread 1 > > > [Switching to thread 1 (CPU 0)] > > > #0 plpar_hcall_norets_notrace () at > > > arch/powerpc/platforms/pseries/hvCall.S:114 > > > 114 li r4,0 > > > gdb> bt > > > #0 plpar_hcall_norets_notrace () at > > > arch/powerpc/platforms/pseries/hvCall.S:114 > > > #1 0xc000000001004dd8 in cede_processor () at > > > ./arch/powerpc/include/asm/plpar_wrappers.h:37 > > > #2 check_and_cede_processor () at drivers/cpuidle/cpuidle-pseries.c:83 > > > #3 0xc000000001005000 in shared_cede_loop (dev=<optimized out>, > > > drv=<optimized out>, index=<optimized out>) at > > > drivers/cpuidle/cpuidle-pseries.c:256 > > > #4 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 > > > #5 0xc000000000c0eb4c in cpuidle_enter (drv=0xc000000002b8f558 > > > <pseries_idle_driver>, dev=0xc0000001ff5910c0, index=<optimized out>) at > > > drivers/cpuidle/cpuidle.c:388 > > > #6 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 > > > #7 0xc0000000001d5d68 in cpuidle_idle_call () at kernel/sched/idle.c:215 > > > #8 0xc0000000001d5f58 in do_idle () at kernel/sched/idle.c:282 > > > #9 0xc0000000001d6298 in cpu_startup_entry (state=<optimized out>) at > > > kernel/sched/idle.c:380 > > > #10 0xc000000000011030 in rest_init () at init/main.c:730 > > > 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" > > > #11 0xc000000002004c80 in arch_call_rest_init () at init/main.c:827 > > > 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" > > > #12 0xc0000000020051ec in start_kernel () at init/main.c:1072 > > > #13 0xc00000000000e788 in start_here_common () at > > > arch/powerpc/kernel/head_64.S:1039 > > > gdb> thread 3 > > > [Switching to thread 3 (CPU 2)] > > > #0 plpar_hcall_norets_notrace () at > > > arch/powerpc/platforms/pseries/hvCall.S:114 > > > 114 li r4,0 > > > gdb> bt > > > #0 plpar_hcall_norets_notrace () at > > > arch/powerpc/platforms/pseries/hvCall.S:114 > > > #1 0xc000000001004dd8 in cede_processor () at > > > ./arch/powerpc/include/asm/plpar_wrappers.h:37 > > > #2 check_and_cede_processor () at drivers/cpuidle/cpuidle-pseries.c:83 > > > #3 0xc000000001005000 in shared_cede_loop (dev=<optimized out>, > > > drv=<optimized out>, index=<optimized out>) at > > > drivers/cpuidle/cpuidle-pseries.c:256 > > > #4 0xc000000001004498 in cpuidle_enter_state > > > (dev=dev@entry=0xc0000001ff7910c0, drv=drv@entry=0xc000000002b8f558 > > > <pseries_idle_driver>, index=index@entry=1) at drivers/cpuidle/cpuidle.c:267 > > > #5 0xc000000000c0eb4c in cpuidle_enter (drv=0xc000000002b8f558 > > > <pseries_idle_driver>, dev=0xc0000001ff7910c0, index=<optimized out>) at > > > drivers/cpuidle/cpuidle.c:388 > > > #6 0xc0000000001ce2bc in call_cpuidle (drv=<optimized out>, > > > drv@entry=0xc000000002b8f558 <pseries_idle_driver>, dev=<optimized out>, > > > dev@entry=0xc0000001ff7910c0, next_state=<optimized out>) at > > > kernel/sched/idle.c:134 > > > #7 0xc0000000001d5d68 in cpuidle_idle_call () at kernel/sched/idle.c:215 > > > #8 0xc0000000001d5f58 in do_idle () at kernel/sched/idle.c:282 > > > #9 0xc0000000001d6298 in cpu_startup_entry (state=<optimized out>) at > > > kernel/sched/idle.c:380 > > > #10 0xc00000000005f048 in start_secondary (unused=<optimized out>) at > > > arch/powerpc/kernel/smp.c:1680 > > > #11 0xc00000000000e058 in start_secondary_prolog () at > > > arch/powerpc/kernel/head_64.S:885 > > > gdb> > > > > > > > > > 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). > > > > > > BTW: I did not see the similar issues after applying the v4 patch set. > > > > > > > > > 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/b684c09f09e7a6af3794d4233ef785819e72db79 > > > > > > > > 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(-) > > > > > -- Crash-utility mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxxxxxx https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki
