On 2023/02/22 19:19, lijiang wrote: > On Mon, Feb 20, 2023 at 9:29 AM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx> > wrote: > >> On kernels configured with CONFIG_RANDOMIZE_KSTACK_OFFSET=y and >> random_kstack_offset=on, a random offset is added to the stack with >> __kstack_alloca() at the beginning of do_syscall_64() and other syscall >> entry functions. This function has the following instruction. >> >> <do_syscall_64+32>: sub %rax,%rsp > > On the other hand, crash uses only a part of data for ORC unwinder to >> unwind stacks and if an ip value doesn't have a usable ORC data, it >> caluculates the frame size with parsing the assembly of the function. >> >> However, crash cannot calculate the frame size correctly with the >> instruction above, and prints stale return addresses like this: >> >> crash> bt 1 >> PID: 1 TASK: ffff9c250023b880 CPU: 0 COMMAND: "systemd" >> #0 [ffffb7e5c001fc80] __schedule at ffffffff91ae2b16 >> #1 [ffffb7e5c001fd00] schedule at ffffffff91ae2ed3 >> #2 [ffffb7e5c001fd18] schedule_hrtimeout_range_clock at >> ffffffff91ae7ed8 >> #3 [ffffb7e5c001fda8] ep_poll at ffffffff913ef828 >> #4 [ffffb7e5c001fe48] do_epoll_wait at ffffffff913ef943 >> #5 [ffffb7e5c001fe80] __x64_sys_epoll_wait at ffffffff913f0130 >> #6 [ffffb7e5c001fed0] do_syscall_64 at ffffffff91ad7169 >> #7 [ffffb7e5c001fef0] do_syscall_64 at ffffffff91ad7179 << >> #8 [ffffb7e5c001ff10] syscall_exit_to_user_mode at ffffffff91adaab2 << >> stale entries >> #9 [ffffb7e5c001ff20] do_syscall_64 at ffffffff91ad7179 << >> #10 [ffffb7e5c001ff50] entry_SYSCALL_64_after_hwframe at >> ffffffff91c0009b >> RIP: 00007f258d9427ae RSP: 00007fffda631d60 RFLAGS: 00000293 >> ... >> >> To fix this, enhance the usage of ORC data. The ORC unwinder often uses >> %rbp value, so keep it from exception frames and inactive task stacks. >> > > Good understanding, Kazu. > > The patch looks good to me. So: Ack. Thank you for the review, applied. https://github.com/crash-utility/crash/commit/daa43fa5324f2dd232ad72df2c6554646868f3b2 Thanks, Kazu -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/crash-utility Contribution Guidelines: https://github.com/crash-utility/crash/wiki
