Re-introduction of sigcontext.

struct sigcontext and ucontext_t/mcontext_t are defined in such
a way that both (ie struct sigcontext and ucontext_t) can be
passed on to sigreturn. The signal handler is still given a
ucontext_t for maximum flexibility.

For backward compatibility sigreturn restores the state for the
alternate signal stack from sigcontext.sc_onstack and not from
ucontext_t.uc_stack. A good way to determine which value the
application has set and thus which value to use, is still open
for discussion.

NOTE: This change should only affect those binaries that use
      sigcontext and/or ucontext_t. In the source tree itself
      this is only doscmd. Recompilation is required for those
      applications.

This commit also fixes a lot of style bugs without hopefully
adding new ones.

NOTE: struct sigaltstack.ss_size now has type size_t again. For
      some reason I changed that into unsigned int.

Parts submitted by: bde
sigaltstack bug found by: bde

1 files changed, 14 insertions, 7 deletions

diff --git a/sys/i386/include/ucontext.h b/sys/i386/include/ucontext.h
index bdf2e1d..0d72716 100644
--- a/sys/i386/include/ucontext.h
+++ b/sys/i386/include/ucontext.h
@@ -29,15 +29,22 @@
  */
 
 #ifndef _MACHINE_UCONTEXT_H_
-#define _MACHINE_UCONTEXT_H_ 1
+#define	_MACHINE_UCONTEXT_H_
 
 #include <machine/frame.h>
 
-typedef struct {
-	int		mc_gs;		/* %gs */
-	struct trapframe mc_tf;		/* trapframe */
-	int		mc_fpregs[28];	/* env87 + fpacc87 + u_long */
-	int		__spare__[17];
+typedef struct __mcontext {
+	/*
+	 * The first 3 fields must match the definition of
+	 * sigcontext. So that we can support sigcontext
+	 * and ucontext_t at the same time.
+	 */
+	int	mc_onstack;		/* XXX - sigcontext compat. */
+	int	mc_gs;
+	struct	trapframe mc_tf;
+
+	int	mc_fpregs[28];		/* env87 + fpacc87 + u_long */
+	int	__spare__[17];
 } mcontext_t;
 
-#endif /* _MACHINE_UCONTEXT_H_ */
+#endif /* !_MACHINE_UCONTEXT_H_ */