From 9d7ff3e89e65c15fb8788a38a0f140100f740244 Mon Sep 17 00:00:00 2001 From: jhb Date: Wed, 16 Sep 2015 20:55:00 +0000 Subject: Always clear TDB_USERWR before fetching system call arguments. The TDB_USERWR flag may still be set after a debugger detaches from a process via PT_DETACH. Previously the flag would never be cleared forcing a double fetch of the system call arguments for each system call. Note that the flag cannot be cleared at PT_DETACH time in case one of the threads in the process is currently stopped in syscallenter() and the debugger has modified the arguments for that pending system call before detaching. Reviewed by: kib MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D3678 --- sys/kern/subr_syscall.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c index 6d12b61..af09613 100644 --- a/sys/kern/subr_syscall.c +++ b/sys/kern/subr_syscall.c @@ -63,14 +63,14 @@ syscallenter(struct thread *td, struct syscall_args *sa) td->td_pticks = 0; if (td->td_cowgen != p->p_cowgen) thread_cow_update(td); - if (p->p_flag & P_TRACED) { - traced = 1; + traced = (p->p_flag & P_TRACED) != 0; + if (traced || td->td_dbgflags & TDB_USERWR) { PROC_LOCK(p); td->td_dbgflags &= ~TDB_USERWR; - td->td_dbgflags |= TDB_SCE; + if (traced) + td->td_dbgflags |= TDB_SCE; PROC_UNLOCK(p); - } else - traced = 0; + } error = (p->p_sysent->sv_fetch_syscall_args)(td, sa); #ifdef KTRACE if (KTRPOINT(td, KTR_SYSCALL)) -- cgit v1.1