The /proc/PID/stack file on procfs-enabled systems contains information about the stack of the specified process (PID)
% sudo cat /proc/self/stack [<0>] proc_pid_stack+0xab/0x120 [<0>] proc_single_show+0x4d/0xb0 [<0>] seq_read_iter+0x11f/0x450 [<0>] seq_read+0xd0/0x100 [<0>] vfs_read+0xa2/0x310 [<0>] ksys_read+0x6b/0xf0 [<0>] do_syscall_64+0x55/0xb0 [<0>] entry_SYSCALL_64_after_hwframe+0x6e/0xd8