[src/trunk]: src/lib/libc/sys Improve/fix doc of PT_SETSTEP and PT_CLEARSTEP.

[mgorny <mgorny%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/2e6d0bfed595
branches:  trunk
changeset: 457660:2e6d0bfed595
user:      mgorny <mgorny%NetBSD.org@localhost>
date:      Wed Jul 10 19:51:14 2019 +0000

description:
Improve/fix doc of PT_SETSTEP and PT_CLEARSTEP.

Reviewed by kamil.

diffstat:

 lib/libc/sys/ptrace.2 |  21 +++++++++++++++++----
 1 files changed, 17 insertions(+), 4 deletions(-)

diffs (38 lines):

diff -r 67d3dce84f44 -r 2e6d0bfed595 lib/libc/sys/ptrace.2
--- a/lib/libc/sys/ptrace.2     Wed Jul 10 19:03:47 2019 +0000
+++ b/lib/libc/sys/ptrace.2     Wed Jul 10 19:51:14 2019 +0000
@@ -1,7 +1,7 @@
-.\"    $NetBSD: ptrace.2,v 1.77 2019/07/10 19:03:47 mgorny Exp $
+.\"    $NetBSD: ptrace.2,v 1.78 2019/07/10 19:51:14 mgorny Exp $
 .\"
 .\" This file is in the public domain.
-.Dd June 26, 2019
+.Dd July 10, 2019
 .Dt PTRACE 2
 .Os
 .Sh NAME
@@ -632,9 +632,22 @@
 argument is less than zero, it contains the negative of the LWP ID of
 the thread to be stepped, and only that thread executes.
 .It Dv PT_SETSTEP
-This request will turn on single stepping of the specified process.
+This request will turn on single stepping of the specified thread.
+.Fa addr
+is unused.
+.Fa data
+specifies the LWP ID of the thread to be stepped.
+The execution does not continue until
+.Dv PT_CONTINUE
+is issued.
+This request permits combining single-stepping with sending syscalls and
+.Dv PT_SYSCALL .
 .It Dv PT_CLEARSTEP
-This request will turn off single stepping of the specified process.
+This request will turn off single stepping of the specified thread.
+.Fa addr
+is unused.
+.Fa data
+specifies the LWP ID of the thread to disable single-stepping.
 .It Dv PT_GETREGS
 This request reads the traced process' machine registers into the
 .Vt struct reg