Date: Mon, 29 Aug 2016 19:33:07 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r305022 - head/lib/libc/sys Message-ID: <201608291933.u7TJX7gn076921@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: kib Date: Mon Aug 29 19:33:07 2016 New Revision: 305022 URL: https://svnweb.freebsd.org/changeset/base/305022 Log: Restore the requirement of setting errno to zero before calling ptrace(2). Describe the behaviour of automatically zeroing errno as historical feature. Requested by: ache, jhb Reviewed by: ache, bjk Sponsored by: The FreeBSD Foundation MFC after: 1 week Modified: head/lib/libc/sys/ptrace.2 Modified: head/lib/libc/sys/ptrace.2 ============================================================================== --- head/lib/libc/sys/ptrace.2 Mon Aug 29 19:14:52 2016 (r305021) +++ head/lib/libc/sys/ptrace.2 Mon Aug 29 19:33:07 2016 (r305022) @@ -2,7 +2,7 @@ .\" $NetBSD: ptrace.2,v 1.2 1995/02/27 12:35:37 cgd Exp $ .\" .\" This file is in the public domain. -.Dd August 28, 2016 +.Dd August 29, 2016 .Dt PTRACE 2 .Os .Sh NAME @@ -900,19 +900,29 @@ argument is ignored. .Pp Additionally, other machine-specific requests can exist. .Sh RETURN VALUES +Most requests return 0 on success and \-1 on error. Some requests can cause .Fn ptrace to return \-1 -as a non-error value; to disambiguate, +as a non-error value, among them are +.Dv PT_READ_I +and +.Dv PT_READ_D , +which return the value read from the process memory on success. +To disambiguate, .Va errno -is set to 0 in the libc wrapper for the -.Fn ptrace -system call and +can be set to 0 before the call and checked afterwards. +.Pp +The current .Fn ptrace -callers can reliably check +implementation always sets +.Va errno +to 0 before calling into the kernel, both for historic reasons and for +consistency with other operating systems. +It is recommended to assign zero to .Va errno -for non-zero value afterwards. +explicitly for forward compatibility. .Sh ERRORS The .Fn ptrace
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201608291933.u7TJX7gn076921>