On 11/27, Elvira Khabirova wrote: > > On Mon, 26 Nov 2018 15:35:24 +0100 > Oleg Nesterov <oleg@xxxxxxxxxx> wrote: > > > On 11/25, Elvira Khabirova wrote: > > > > > > Extend PTRACE_GET_SYSCALL_INFO to support PTRACE_EVENT_SECCOMP stops. > > > The information returned is the same as for syscall-enter-stops. > > > > Oh, this is not nice ;) there must be a better option, I hope... Plus > > > > > > Can't ptrace_get_syscall() check > > > > child->exit_code == (PTRACE_EVENT_SECCOMP << 8) | SIGTRAP; > > > > to detect the PTRACE_EVENT_SECCOMP case? > > Nope; looks like exit_code is zeroed after wait(). Yes, thanks for correcting me, but we can use child->last_siginfo->si_code. Just like ptrace_request(PTRACE_LISTEN) does but you can do this lockless (no need to lock_task_sighand()). And if we require that the user of ptrace_get_syscall() should also use TRACESYSGOOD then ptrace_get_syscall() can probably do something like int entry; if (!child->last_siginfo) return -EINVAL; else if (child->last_siginfo->si_code == (PTRACE_EVENT_SECCOMP << 8) | SIGTRAP) entry = 1; else if (child->last_siginfo->si_code == SIGTRAP | 0x80) entry = child->ptrace_message == PTRACE_EVENTMSG_SYSCALL_ENTRY; else return -EINVAL; and this way PTRACE_EVENTMSG_SYSCALL_ENTRY/EXIT can't confict with seccomp or anything else. No? Of course, debugger can do PTRACE_SETSIGINFO and confuse itself but probably we do not care? Oleg.
