Author: kib Date: Wed May 23 21:39:29 2018 New Revision: 334122 URL: https://svnweb.freebsd.org/changeset/base/334122
Log: x86: stop unconditionally clearing PSL_T on the trace trap. We certainly should clear PSL_T when calling the SIGTRAP signal handler, which is already done by all x86 sendsig(9) ABI code. On the other hand, there is no obvious reason why PSL_T needs to be cleared when returning from the signal handler. For instance, Linux allows userspace to set PSL_T and keep tracing enabled for the desired period. There are userspace programs which would use PSL_T if we make it possible, for instance sbcl. Remember if PSL_T was set by PT_STEP or PT_SETSTEP by mean of TDB_STEP flag, and only clear it when the flag is set. Discussed with: Ali Mashtizadeh Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D15054 Modified: head/sys/amd64/amd64/machdep.c head/sys/amd64/amd64/trap.c head/sys/i386/i386/machdep.c head/sys/i386/i386/trap.c head/sys/sys/proc.h Modified: head/sys/amd64/amd64/machdep.c ============================================================================== --- head/sys/amd64/amd64/machdep.c Wed May 23 21:26:41 2018 (r334121) +++ head/sys/amd64/amd64/machdep.c Wed May 23 21:39:29 2018 (r334122) @@ -1978,7 +1978,12 @@ ptrace_set_pc(struct thread *td, unsigned long addr) int ptrace_single_step(struct thread *td) { - td->td_frame->tf_rflags |= PSL_T; + + PROC_LOCK_ASSERT(td->td_proc, MA_OWNED); + if ((td->td_frame->tf_rflags & PSL_T) == 0) { + td->td_frame->tf_rflags |= PSL_T; + td->td_dbgflags |= TDB_STEP; + } return (0); } @@ -1986,7 +1991,9 @@ int ptrace_clear_single_step(struct thread *td) { + PROC_LOCK_ASSERT(td->td_proc, MA_OWNED); td->td_frame->tf_rflags &= ~PSL_T; + td->td_dbgflags &= ~TDB_STEP; return (0); } Modified: head/sys/amd64/amd64/trap.c ============================================================================== --- head/sys/amd64/amd64/trap.c Wed May 23 21:26:41 2018 (r334121) +++ head/sys/amd64/amd64/trap.c Wed May 23 21:39:29 2018 (r334122) @@ -285,8 +285,14 @@ trap(struct trapframe *frame) signo = SIGTRAP; ucode = TRAP_TRACE; dr6 = rdr6(); - if (dr6 & DBREG_DR6_BS) - frame->tf_rflags &= ~PSL_T; + if ((dr6 & DBREG_DR6_BS) != 0) { + PROC_LOCK(td->td_proc); + if ((td->td_dbgflags & TDB_STEP) != 0) { + td->td_frame->tf_rflags &= ~PSL_T; + td->td_dbgflags &= ~TDB_STEP; + } + PROC_UNLOCK(td->td_proc); + } break; case T_ARITHTRAP: /* arithmetic trap */ Modified: head/sys/i386/i386/machdep.c ============================================================================== --- head/sys/i386/i386/machdep.c Wed May 23 21:26:41 2018 (r334121) +++ head/sys/i386/i386/machdep.c Wed May 23 21:39:29 2018 (r334122) @@ -2764,7 +2764,12 @@ ptrace_set_pc(struct thread *td, u_long addr) int ptrace_single_step(struct thread *td) { - td->td_frame->tf_eflags |= PSL_T; + + PROC_LOCK_ASSERT(td->td_proc, MA_OWNED); + if ((td->td_frame->tf_eflags & PSL_T) == 0) { + td->td_frame->tf_eflags |= PSL_T; + td->td_dbgflags |= TDB_STEP; + } return (0); } @@ -2772,7 +2777,9 @@ int ptrace_clear_single_step(struct thread *td) { + PROC_LOCK_ASSERT(td->td_proc, MA_OWNED); td->td_frame->tf_eflags &= ~PSL_T; + td->td_dbgflags &= ~TDB_STEP; return (0); } Modified: head/sys/i386/i386/trap.c ============================================================================== --- head/sys/i386/i386/trap.c Wed May 23 21:26:41 2018 (r334121) +++ head/sys/i386/i386/trap.c Wed May 23 21:39:29 2018 (r334122) @@ -337,8 +337,14 @@ user_trctrap_out: signo = SIGTRAP; ucode = TRAP_TRACE; dr6 = rdr6(); - if (dr6 & DBREG_DR6_BS) - frame->tf_eflags &= ~PSL_T; + if ((dr6 & DBREG_DR6_BS) != 0) { + PROC_LOCK(td->td_proc); + if ((td->td_dbgflags & TDB_STEP) != 0) { + td->td_frame->tf_eflags &= ~PSL_T; + td->td_dbgflags &= ~TDB_STEP; + } + PROC_UNLOCK(td->td_proc); + } break; case T_ARITHTRAP: /* arithmetic trap */ Modified: head/sys/sys/proc.h ============================================================================== --- head/sys/sys/proc.h Wed May 23 21:26:41 2018 (r334121) +++ head/sys/sys/proc.h Wed May 23 21:39:29 2018 (r334122) @@ -465,6 +465,7 @@ do { \ #define TDB_EXIT 0x00000400 /* Exiting LWP indicator for ptrace() */ #define TDB_VFORK 0x00000800 /* vfork indicator for ptrace() */ #define TDB_FSTP 0x00001000 /* The thread is PT_ATTACH leader */ +#define TDB_STEP 0x00002000 /* (x86) PSL_T set for PT_STEP */ /* * "Private" flags kept in td_pflags: _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
