Use osigreturn(2) instead of sigreturn(2) plus broken magic for returning

from old signal handlers.  This is simpler and faster, and fixes (new)
sigreturn(2) when %eip in the new signal context happens to match the
magic value (0x1d516).  0x1d516 is below the default ELF text section,
so this probably never broken anything in practice.

locore.s:
In addition, don't build the signal trampoline for old signal handlers
when it is not used.

alpha:
Not fixed, but seems to be even less broken in practice due to more
advanced magic. A false match occurs for register #32 in mc_regs[].
Since there is no hardware register #32, a false match is only possible
for direct calls to sigreturn(2) that happen to have the magic number
in the spare mc_regs[32] field.

7 files changed, 18 insertions, 42 deletions

diff --git a/sys/amd64/amd64/locore.S b/sys/amd64/amd64/locore.S
index ab3dad5..4fff220 100644
--- a/sys/amd64/amd64/locore.S
+++ b/sys/amd64/amd64/locore.S
@@ -44,6 +44,7 @@
  */
 
 #include "opt_bootp.h"
+#include "opt_compat.h"
 #include "opt_nfsroot.h"
 
 #include <sys/syscall.h>
@@ -416,6 +417,7 @@ NON_GPROF_ENTRY(sigcode)
 	int	$0x80				/* enter kernel with args */
 0:	jmp	0b
 
+#ifdef COMPAT_43
 	ALIGN_TEXT
 osigcode:
 	call	*SIGF_HANDLER(%esp)		/* call signal handler */
@@ -425,11 +427,11 @@ osigcode:
 	jne	9f
 	movl	SC_GS(%eax),%gs			/* restore %gs */
 9:
-	movl	$0x01d516,SC_TRAPNO(%eax)	/* magic: 0ldSiG */
-	movl	$SYS_sigreturn,%eax
+	movl	$SYS_osigreturn,%eax
 	pushl	%eax				/* junk to fake return addr. */
 	int	$0x80				/* enter kernel with args */
 0:	jmp	0b
+#endif /* COMPAT_43 */
 
 	ALIGN_TEXT
 esigcode:
@@ -438,8 +440,10 @@ esigcode:
 	.globl	szsigcode, szosigcode
 szsigcode:
 	.long	esigcode-sigcode
+#ifdef COMPAT_43
 szosigcode:
 	.long	esigcode-osigcode
+#endif
 	.text
 
 /**********************************************************************
diff --git a/sys/amd64/amd64/locore.s b/sys/amd64/amd64/locore.s
index ab3dad5..4fff220 100644
--- a/sys/amd64/amd64/locore.s
+++ b/sys/amd64/amd64/locore.s
@@ -44,6 +44,7 @@
  */
 
 #include "opt_bootp.h"
+#include "opt_compat.h"
 #include "opt_nfsroot.h"
 
 #include <sys/syscall.h>
@@ -416,6 +417,7 @@ NON_GPROF_ENTRY(sigcode)
 	int	$0x80				/* enter kernel with args */
 0:	jmp	0b
 
+#ifdef COMPAT_43
 	ALIGN_TEXT
 osigcode:
 	call	*SIGF_HANDLER(%esp)		/* call signal handler */
@@ -425,11 +427,11 @@ osigcode:
 	jne	9f
 	movl	SC_GS(%eax),%gs			/* restore %gs */
 9:
-	movl	$0x01d516,SC_TRAPNO(%eax)	/* magic: 0ldSiG */
-	movl	$SYS_sigreturn,%eax
+	movl	$SYS_osigreturn,%eax
 	pushl	%eax				/* junk to fake return addr. */
 	int	$0x80				/* enter kernel with args */
 0:	jmp	0b
+#endif /* COMPAT_43 */
 
 	ALIGN_TEXT
 esigcode:
@@ -438,8 +440,10 @@ esigcode:
 	.globl	szsigcode, szosigcode
 szsigcode:
 	.long	esigcode-sigcode
+#ifdef COMPAT_43
 szosigcode:
 	.long	esigcode-osigcode
+#endif
 	.text
 
 /**********************************************************************
diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 308d319..13e8b0a 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -710,19 +710,10 @@ sigreturn(td, uap)
 	} */ *uap;
 {
 	struct proc *p = td->td_proc;
-	struct osigcontext *oscp;
-	struct osigreturn_args *ouap;
 	struct trapframe *regs;
 	ucontext_t *ucp;
 	int cs, eflags;
 
-#ifdef COMPAT_43
-	ouap = (struct osigreturn_args *)uap;
-	oscp = ouap->sigcntxp;
-	if (fuword(&oscp->sc_trapno) == 0x01d516)
-		return (osigreturn(td, ouap));
-#endif
-
 	ucp = uap->sigcntxp;
 	if (!useracc((caddr_t)ucp, sizeof(*ucp), VM_PROT_READ))
 		return (EFAULT);
diff --git a/sys/i386/i386/locore.s b/sys/i386/i386/locore.s
index ab3dad5..4fff220 100644
--- a/sys/i386/i386/locore.s
+++ b/sys/i386/i386/locore.s
@@ -44,6 +44,7 @@
  */
 
 #include "opt_bootp.h"
+#include "opt_compat.h"
 #include "opt_nfsroot.h"
 
 #include <sys/syscall.h>
@@ -416,6 +417,7 @@ NON_GPROF_ENTRY(sigcode)
 	int	$0x80				/* enter kernel with args */
 0:	jmp	0b
 
+#ifdef COMPAT_43
 	ALIGN_TEXT
 osigcode:
 	call	*SIGF_HANDLER(%esp)		/* call signal handler */
@@ -425,11 +427,11 @@ osigcode:
 	jne	9f
 	movl	SC_GS(%eax),%gs			/* restore %gs */
 9:
-	movl	$0x01d516,SC_TRAPNO(%eax)	/* magic: 0ldSiG */
-	movl	$SYS_sigreturn,%eax
+	movl	$SYS_osigreturn,%eax
 	pushl	%eax				/* junk to fake return addr. */
 	int	$0x80				/* enter kernel with args */
 0:	jmp	0b
+#endif /* COMPAT_43 */
 
 	ALIGN_TEXT
 esigcode:
@@ -438,8 +440,10 @@ esigcode:
 	.globl	szsigcode, szosigcode
 szsigcode:
 	.long	esigcode-sigcode
+#ifdef COMPAT_43
 szosigcode:
 	.long	esigcode-osigcode
+#endif
 	.text
 
 /**********************************************************************
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 308d319..13e8b0a 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -710,19 +710,10 @@ sigreturn(td, uap)
 	} */ *uap;
 {
 	struct proc *p = td->td_proc;
-	struct osigcontext *oscp;
-	struct osigreturn_args *ouap;
 	struct trapframe *regs;
 	ucontext_t *ucp;
 	int cs, eflags;
 
-#ifdef COMPAT_43
-	ouap = (struct osigreturn_args *)uap;
-	oscp = ouap->sigcntxp;
-	if (fuword(&oscp->sc_trapno) == 0x01d516)
-		return (osigreturn(td, ouap));
-#endif
-
 	ucp = uap->sigcntxp;
 	if (!useracc((caddr_t)ucp, sizeof(*ucp), VM_PROT_READ))
 		return (EFAULT);
diff --git a/sys/pc98/i386/machdep.c b/sys/pc98/i386/machdep.c
index 0c0243d..71d2098 100644
--- a/sys/pc98/i386/machdep.c
+++ b/sys/pc98/i386/machdep.c
@@ -723,19 +723,10 @@ sigreturn(td, uap)
 	} */ *uap;
 {
 	struct proc *p = td->td_proc;
-	struct osigcontext *oscp;
-	struct osigreturn_args *ouap;
 	struct trapframe *regs;
 	ucontext_t *ucp;
 	int cs, eflags;
 
-#ifdef COMPAT_43
-	ouap = (struct osigreturn_args *)uap;
-	oscp = ouap->sigcntxp;
-	if (fuword(&oscp->sc_trapno) == 0x01d516)
-		return (osigreturn(td, ouap));
-#endif
-
 	ucp = uap->sigcntxp;
 	if (!useracc((caddr_t)ucp, sizeof(*ucp), VM_PROT_READ))
 		return (EFAULT);
diff --git a/sys/pc98/pc98/machdep.c b/sys/pc98/pc98/machdep.c
index 0c0243d..71d2098 100644
--- a/sys/pc98/pc98/machdep.c
+++ b/sys/pc98/pc98/machdep.c
@@ -723,19 +723,10 @@ sigreturn(td, uap)
 	} */ *uap;
 {
 	struct proc *p = td->td_proc;
-	struct osigcontext *oscp;
-	struct osigreturn_args *ouap;
 	struct trapframe *regs;
 	ucontext_t *ucp;
 	int cs, eflags;
 
-#ifdef COMPAT_43
-	ouap = (struct osigreturn_args *)uap;
-	oscp = ouap->sigcntxp;
-	if (fuword(&oscp->sc_trapno) == 0x01d516)
-		return (osigreturn(td, ouap));
-#endif
-
 	ucp = uap->sigcntxp;
 	if (!useracc((caddr_t)ucp, sizeof(*ucp), VM_PROT_READ))
 		return (EFAULT);