[src/trunk]: src/lib/libpthread/arch/i386 Avoid getcontext() as it triggers c...

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

details:   https://anonhg.NetBSD.org/src/rev/ff668a4d5779
branches:  trunk
changeset: 777749:ff668a4d5779
user:      joerg <joerg%NetBSD.org@localhost>
date:      Fri Mar 02 23:19:47 2012 +0000

description:
Avoid getcontext() as it triggers clobbering warnings. Use inline
assembler to get the fields directly. Saves a system call as side
effect.

diffstat:

 lib/libpthread/arch/i386/pthread_md.h |  42 +++++++++++-----------------------
 1 files changed, 14 insertions(+), 28 deletions(-)

diffs (56 lines):

diff -r 0018a9a69d6d -r ff668a4d5779 lib/libpthread/arch/i386/pthread_md.h
--- a/lib/libpthread/arch/i386/pthread_md.h     Fri Mar 02 23:13:55 2012 +0000
+++ b/lib/libpthread/arch/i386/pthread_md.h     Fri Mar 02 23:19:47 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pthread_md.h,v 1.19 2011/02/24 04:28:43 joerg Exp $    */
+/*     $NetBSD: pthread_md.h,v 1.20 2012/03/02 23:19:47 joerg Exp $    */
 
 /*-
  * Copyright (c) 2001, 2007, 2008 The NetBSD Foundation, Inc.
@@ -46,33 +46,19 @@
 
 #define pthread__uc_sp(ucp) ((ucp)->uc_mcontext.__gregs[_REG_UESP])
 
-/*
- * Set initial, sane values for registers whose values aren't just
- * "don't care".
- *
- * We use the current context instead of a guessed one because we cannot
- * assume how the GDT entries are ordered:  what is true on i386 is not
- * true anymore on amd64.
- */
-#define _INITCONTEXT_U_MD(ucp)                                         \
-       do {                                                            \
-               ucontext_t ucur;                                        \
-               (void)getcontext(&ucur);                                \
-               (ucp)->uc_mcontext.__gregs[_REG_GS] =                   \
-                   ucur.uc_mcontext.__gregs[_REG_GS],                  \
-               (ucp)->uc_mcontext.__gregs[_REG_FS] =                   \
-                   ucur.uc_mcontext.__gregs[_REG_FS],                  \
-               (ucp)->uc_mcontext.__gregs[_REG_ES] =                   \
-                   ucur.uc_mcontext.__gregs[_REG_ES],                  \
-               (ucp)->uc_mcontext.__gregs[_REG_DS] =                   \
-                   ucur.uc_mcontext.__gregs[_REG_DS],                  \
-               (ucp)->uc_mcontext.__gregs[_REG_CS] =                   \
-                   ucur.uc_mcontext.__gregs[_REG_CS],                  \
-               (ucp)->uc_mcontext.__gregs[_REG_SS] =                   \
-                   ucur.uc_mcontext.__gregs[_REG_SS],                  \
-               (ucp)->uc_mcontext.__gregs[_REG_EFL] =                  \
-                   ucur.uc_mcontext.__gregs[_REG_EFL];                 \
-       } while (/*CONSTCOND*/0);
+static inline void
+_initcontext_u_md(ucontext_t *ucp)
+{
+       __asm ("pushfl; popl %0" : "=a" (ucp->uc_mcontext.__gregs[_REG_EFL]));
+       __asm ("pushl %%cs; popl %0" : "=a" (ucp->uc_mcontext.__gregs[_REG_CS]));
+       __asm ("movl %%ds, %0" : "=a" (ucp->uc_mcontext.__gregs[_REG_DS]));
+       __asm ("movl %%es, %0" : "=a" (ucp->uc_mcontext.__gregs[_REG_ES]));
+       __asm ("movl %%fs, %0" : "=a" (ucp->uc_mcontext.__gregs[_REG_FS]));
+       __asm ("movl %%gs, %0" : "=a" (ucp->uc_mcontext.__gregs[_REG_GS]));
+       __asm ("movl %%ss, %0" : "=a" (ucp->uc_mcontext.__gregs[_REG_SS]));
+}
+
+#define        _INITCONTEXT_U_MD(ucp)  _initcontext_u_md(ucp);
 
 #define        pthread__smt_pause()    __asm __volatile("rep; nop" ::: "memory")