Hi, things are getting too complicated and we need some advice how to deal with this frame_pointer issue. On Mon, Dec 10, 2018 at 10:26:50PM +0800, kbuild test robot wrote: > Hi Elvira, > > Thank you for the patch! Yet something to improve: > > [auto build test ERROR on linus/master] > [also build test ERROR on v4.20-rc6] > [cannot apply to next-20181207] > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] > > url: https://github.com/0day-ci/linux/commits/Dmitry-V-Levin/ptrace-add-PTRACE_GET_SYSCALL_INFO-request/20181210-174745 > config: mips-malta_kvm_defconfig (attached as .config) > compiler: mipsel-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0 > reproduce: > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross > chmod +x ~/bin/make.cross > # save the attached .config to linux build tree > GCC_VERSION=7.2.0 make.cross ARCH=mips > > All errors (new ones prefixed by >>): > > kernel/ptrace.c: In function 'ptrace_get_syscall_info': > >> kernel/ptrace.c:942:20: error: implicit declaration of function 'frame_pointer'; did you mean 'trace_printk'? [-Werror=implicit-function-declaration] > .frame_pointer = frame_pointer(regs) > ^~~~~~~~~~~~~ > trace_printk > cc1: some warnings being treated as errors > > vim +942 kernel/ptrace.c > > 931 > 932 static int > 933 ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size, > 934 void __user *datavp) > 935 { > 936 struct pt_regs *regs = task_pt_regs(child); > 937 struct ptrace_syscall_info info = { > 938 .op = PTRACE_SYSCALL_INFO_NONE, > 939 .arch = syscall_get_arch(child), > 940 .instruction_pointer = instruction_pointer(regs), > 941 .stack_pointer = user_stack_pointer(regs), > > 942 .frame_pointer = frame_pointer(regs) > 943 }; > 944 unsigned long actual_size = offsetof(struct ptrace_syscall_info, entry); > 945 unsigned long write_size; > 946 > 947 /* > 948 * This does not need lock_task_sighand() to access > 949 * child->last_siginfo because ptrace_freeze_traced() > 950 * called earlier by ptrace_check_attach() ensures that > 951 * the tracee cannot go away and clear its last_siginfo. > 952 */ > 953 switch (child->last_siginfo ? child->last_siginfo->si_code : 0) { > 954 case SIGTRAP | 0x80: > 955 switch (child->ptrace_message) { > 956 case PTRACE_EVENTMSG_SYSCALL_ENTRY: > 957 actual_size = ptrace_get_syscall_info_entry(child, regs, > 958 &info); > 959 break; > 960 case PTRACE_EVENTMSG_SYSCALL_EXIT: > 961 actual_size = ptrace_get_syscall_info_exit(child, regs, > 962 &info); > 963 break; > 964 } > 965 break; > 966 case SIGTRAP | (PTRACE_EVENT_SECCOMP << 8): > 967 actual_size = ptrace_get_syscall_info_seccomp(child, regs, > 968 &info); > 969 break; > 970 } > 971 > 972 write_size = min(actual_size, user_size); > 973 return copy_to_user(datavp, &info, write_size) ? -EFAULT : actual_size; > 974 } > 975 We decided to add .frame_pointer to struct ptrace_syscall_info just for consistency with .instruction_pointer and .stack_pointer; I must have been misled by comments in asm-generic/ptrace.h into thinking that frame_pointer() is universally available across architectures. Unlike .instruction_pointer and .stack_pointer that are actually needed in strace, .frame_pointer is not used, so from strace PoV we don't really need it. So the question is, does anybody need a struct ptrace_syscall_info.frame_pointer? If yes, how can frame_pointer() be defined on MIPS? Or should we just forget about making sense of frame_pointer() and remove struct ptrace_syscall_info.frame_pointer from the proposed API? -- ldv
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