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

4 files changed, 78 insertions, 39 deletions

diff --git a/sys/amd64/amd64/genassym.c b/sys/amd64/amd64/genassym.c
index 62dbf53..8299177 100644
--- a/sys/amd64/amd64/genassym.c
+++ b/sys/amd64/amd64/genassym.c
@@ -69,11 +69,10 @@
 #include <machine/apic.h>
 #endif
 #include <machine/segments.h>
+#include <machine/sigframe.h>
 #include <machine/globaldata.h>
 #include <machine/vm86.h>
 
-#include <machine/sigframe.h>
-
 #define	OS(s, m)	((u_int)offsetof(struct s, m))
 
 int	main __P((void));
@@ -157,7 +156,8 @@ main()
 	printf("#define\tSC_FS %#x\n", OS(osigcontext, sc_fs));
 	printf("#define\tSC_GS %#x\n", OS(osigcontext, sc_gs));
 
-	printf("#define\tUC_EFLAGS %#x\n", OS(__ucontext, uc_mcontext.mc_tf.tf_eflags));
+	printf("#define\tUC_EFLAGS %#x\n",
+	    OS(__ucontext, uc_mcontext.mc_tf.tf_eflags));
 	printf("#define\tUC_GS %#x\n", OS(__ucontext, uc_mcontext.mc_gs));
 
 	printf("#define\tB_READ %#x\n", B_READ);
diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 8b6bb84..1ef6fb0 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -613,6 +613,7 @@ sendsig(catcher, sig, mask, code)
 	struct trapframe *regs;
 	struct sigacts *psp;
 	struct sigframe sf, *sfp;
+	int onstack;
 
 	p = curproc;
 
@@ -623,17 +624,18 @@ sendsig(catcher, sig, mask, code)
 
 	regs = p->p_md.md_regs;
 	psp = p->p_sigacts;
+	onstack = (psp->ps_sigstk.ss_flags & SS_ONSTACK) ? 1 : 0;
 
 	/* save user context */
 	bzero(&sf, sizeof(struct sigframe));
 	sf.sf_uc.uc_sigmask = *mask;
 	sf.sf_uc.uc_stack = psp->ps_sigstk;
+	sf.sf_uc.uc_mcontext.mc_onstack = onstack;
 	sf.sf_uc.uc_mcontext.mc_tf = *regs;
 	sf.sf_uc.uc_mcontext.mc_gs = rgs();
 
 	/* Allocate and validate space for the signal handler context. */
-        if ((psp->ps_flags & SAS_ALTSTACK) != 0 &&
-	    (psp->ps_sigstk.ss_flags & SS_ONSTACK) == 0 &&
+        if ((psp->ps_flags & SAS_ALTSTACK) != 0 && !onstack &&
 	    SIGISMEMBER(psp->ps_sigonstack, sig)) {
 		sfp = (struct sigframe *)(psp->ps_sigstk.ss_sp +
 		    psp->ps_sigstk.ss_size - sizeof(struct sigframe));
@@ -884,16 +886,13 @@ sigreturn(p, uap)
 {
 	struct trapframe *regs;
 	ucontext_t *ucp;
-	struct sigframe *sfp;
 	int cs, eflags;
 
 	regs = p->p_md.md_regs;
 	ucp = uap->sigcntxp;
-	sfp = (struct sigframe *)
-	    ((caddr_t)ucp - offsetof(struct sigframe, sf_uc));
 	eflags = ucp->uc_mcontext.mc_tf.tf_eflags;
 
-	if (useracc((caddr_t)sfp, sizeof(struct sigframe), B_WRITE) == 0)
+	if (useracc((caddr_t)ucp, sizeof(ucontext_t), B_WRITE) == 0)
 		return(EFAULT);
 
 	if (eflags & PSL_VM) {
@@ -963,7 +962,11 @@ sigreturn(p, uap)
 		*regs = ucp->uc_mcontext.mc_tf;
 	}
 
-	p->p_sigacts->ps_sigstk = ucp->uc_stack;
+	if (ucp->uc_mcontext.mc_onstack & 1)
+		p->p_sigacts->ps_sigstk.ss_flags |= SS_ONSTACK;
+	else
+		p->p_sigacts->ps_sigstk.ss_flags &= ~SS_ONSTACK;
+
 	p->p_sigmask = ucp->uc_sigmask;
 	SIG_CANTMASK(p->p_sigmask);
 	return(EJUSTRETURN);
diff --git a/sys/amd64/include/signal.h b/sys/amd64/include/signal.h
index e9f739e..f02539e 100644
--- a/sys/amd64/include/signal.h
+++ b/sys/amd64/include/signal.h
@@ -57,33 +57,62 @@ typedef int sig_atomic_t;
 typedef unsigned int osigset_t;
 
 struct	osigcontext {
-	int		sc_onstack;	/* sigstack state to restore */
-	osigset_t	sc_mask;	/* signal mask to restore */
-	int		sc_esp;		/* machine state */
-	int		sc_ebp;
-	int		sc_isp;
-	int		sc_eip;
-	int		sc_efl;
-	int		sc_es;
-	int		sc_ds;
-	int		sc_cs;
-	int		sc_ss;
-	int		sc_edi;
-	int		sc_esi;
-	int		sc_ebx;
-	int		sc_edx;
-	int		sc_ecx;
-	int		sc_eax;
-	int		sc_gs;
-	int		sc_fs;
+	int	sc_onstack;	/* sigstack state to restore */
+	osigset_t sc_mask;	/* signal mask to restore */
+	int	sc_esp;		/* machine state */
+	int	sc_ebp;
+	int	sc_isp;
+	int	sc_eip;
+	int	sc_efl;
+	int	sc_es;
+	int	sc_ds;
+	int	sc_cs;
+	int	sc_ss;
+	int	sc_edi;
+	int	sc_esi;
+	int	sc_ebx;
+	int	sc_edx;
+	int	sc_ecx;
+	int	sc_eax;
+	int	sc_gs;
+	int	sc_fs;
+	int	sc_trapno;
+	int	sc_err;
+};
+
+/*
+ * The sequence of the fields/registers in sigcontext should match
+ * those in mcontext_t.
+ */
+struct	sigcontext {
+	sigset_t sc_mask;		/* signal mask to restore */
+	int	sc_onstack;		/* sigstack state to restore */
+	int	sc_gs;
+	int	sc_fs;
+	int	sc_es;
+	int	sc_ds;
+	int	sc_edi;
+	int	sc_esi;
+	int	sc_ebp;
+	int	sc_isp;
+	int	sc_ebx;
+	int	sc_edx;
+	int	sc_ecx;
+	int	sc_eax;
+	int	sc_trapno;
+	int	sc_err;
+	int	sc_eip;
+	int	sc_cs;
+	int	sc_efl;
+	int	sc_esp;			/* machine state */
+	int	sc_ss;
+};
+
 #define sc_sp		sc_esp
 #define sc_fp		sc_ebp
 #define sc_pc		sc_eip
 #define sc_ps		sc_efl
 #define sc_eflags	sc_efl
-	int		sc_trapno;
-	int		sc_err;
-};
 
 #endif /* !_ANSI_SOURCE && !_POSIX_SOURCE */
 
diff --git a/sys/amd64/include/ucontext.h b/sys/amd64/include/ucontext.h
index bdf2e1d..0d72716 100644
--- a/sys/amd64/include/ucontext.h
+++ b/sys/amd64/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_ */