Linux/x86-64 makecontext implementation.

sysdeps/unix/sysv/linux/x86_64/makecontext.c

@@ -0,0 +1,113 @@
+/* Create new context.
+   Copyright (C) 2002 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Andreas Jaeger <aj@suse.de>, 2002.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <sysdep.h>
+#include <stdarg.h>
+#include <ucontext.h>
+
+#include "ucontext_i.h"
+
+/* This implementation can handle any ARGC value but only
+   normal integer parameters.
+   makecontext sets up a stack and the registers for the
+   user context. The stack looks like this:
+               +-----------------------+
+               | next context          |
+               +-----------------------+
+               | parameter 7-n         |
+	       +-----------------------+
+	       | trampoline address    |
+    %rsp ->    +-----------------------+
+
+   The registers are set up like this:
+     %rdi,%rsi,%rdx,%rcx,%r8,%r9: parameter 1 to 6
+     %rbx   : address of next context
+     %rsp   : stack pointer.
+*/
+
+/* XXX: This implementation currently only handles integer arguments.
+   To handle long int and pointer arguments the va_arg arguments needs
+   to be changed to long and also the stdlib/tst-setcontext.c file needs
+   to be changed to pass long arguments to makecontext.  */
+
+
+void
+__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
+{
+  extern void __start_context (void);
+  unsigned long *sp, idx_uc_link;
+  va_list ap;
+  int i;
+
+  /* Generate room on stack for parameter if needed and uc_link.  */
+  sp = (long *) ((long) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
+  sp -= (argc > 6 ? argc : 0) + 1;
+  /* Align stack.  */
+  sp = (long *) (((long) sp) & -16L);
+  /* Make space for trampoline address.  */
+  sp -= 8;
+
+  idx_uc_link = (argc > 6 ? argc : 0) + 1;
+
+  /* Setup context ucp.  */
+  /* Address to jump to.  */
+  ucp->uc_mcontext.gregs[REG_RIP] = (long) func;
+  /* Setup rbx.*/
+  ucp->uc_mcontext.gregs[REG_RBX] = (long) &sp[idx_uc_link];
+  ucp->uc_mcontext.gregs[REG_RSP] = (long) sp;
+
+  /* Setup stack.  */
+  sp[0] = (long) &__start_context;
+  sp[idx_uc_link] = (long) ucp->uc_link;
+
+  va_start (ap, argc);
+  /* Handle arguments.  */
+  for (i = 0; i < argc; ++i)
+    switch (i)
+      {
+      case 0:
+	ucp->uc_mcontext.gregs [REG_RDI] = va_arg (ap, int);
+	break;
+      case 1:
+	ucp->uc_mcontext.gregs [REG_RSI] = va_arg (ap, int);
+	break;
+      case 2:
+	ucp->uc_mcontext.gregs [REG_RDX] = va_arg (ap, int);
+	break;
+      case 3:
+	ucp->uc_mcontext.gregs [REG_RCX] = va_arg (ap, int);
+	break;
+      case 4:
+	ucp->uc_mcontext.gregs [REG_R8] = va_arg (ap, int);
+	break;
+      case 5:
+	ucp->uc_mcontext.gregs [REG_R9] = va_arg (ap, int);
+	break;
+      default:
+	/* Put value on stack.  */
+	sp[8 + (i - 5)] = va_arg (ap, int);
+	break;
+      }
+  va_end (ap);
+
+}
+
+
+weak_alias(__makecontext, makecontext)