From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

Patch 2/3 to implement usage of PTRACE_O_TRACESYSGOOD
This is necessary, to fix UMLs bad behavior when a process does
a systemcall with syscall-number less than 0.

This patch makes SKAS-mode use PTRACE_O_TRACESYSGOOD and fixes
the problems in SKAS.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/arch/um/kernel/skas/process.c	2004-10-21 10:50:27.770336304 +0200
+++ b/arch/um/kernel/skas/process.c	2004-10-21 11:34:50.764261057 +0200
@@ -11,6 +11,7 @@
 #include <sched.h>
 #include <sys/wait.h>
 #include <sys/ptrace.h>
+#include <linux/ptrace.h>
 #include <sys/mman.h>
 #include <sys/user.h>
 #include <asm/unistd.h>
@@ -54,14 +55,9 @@
 /*To use the same value of using_sysemu as the caller, ask it that value (in local_using_sysemu)*/
 static void handle_trap(int pid, union uml_pt_regs *regs, int local_using_sysemu)
 {
-	int err, syscall_nr, status;
+	int err, status;
 
-	syscall_nr = PT_SYSCALL_NR(regs->skas.regs);
-	UPT_SYSCALL_NR(regs) = syscall_nr;
-	if(syscall_nr < 0){
-		relay_signal(SIGTRAP, regs);
-		return;
-	}
+	UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->skas.regs);
 
 	if (!local_using_sysemu)
 	{
@@ -76,7 +72,7 @@
 			      "errno = %d\n", errno);
 
 		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
-		if((err < 0) || !WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
+		if((err < 0) || !WIFSTOPPED(status) || (WSTOPSIG(status) != (SIGTRAP + 0x80)))
 			panic("handle_trap - failed to wait at end of syscall, "
 			      "errno = %d, status = %d\n", errno, status);
 	}
@@ -124,6 +120,10 @@
 		panic("start_userspace : expected SIGSTOP, got status = %d",
 		      status);
 
+	if (ptrace(PTRACE_SETOPTIONS, pid, NULL, (void *)PTRACE_O_TRACESYSGOOD) < 0)
+		panic("start_userspace : PTRACE_SETOPTIONS failed, errno=%d\n", 
+		      errno);
+
 	if(munmap(stack, PAGE_SIZE) < 0)
 		panic("start_userspace : munmap failed, errno = %d\n", errno);
 
@@ -160,9 +160,13 @@
 			case SIGSEGV:
 				handle_segv(pid);
 				break;
-			case SIGTRAP:
+			case SIGTRAP + 0x80:
 			        handle_trap(pid, regs, local_using_sysemu);
 				break;
+			case SIGTRAP:
+				UPT_SYSCALL_NR(regs) = -1;
+				relay_signal(SIGTRAP, regs);
+				break;
 			case SIGIO:
 			case SIGVTALRM:
 			case SIGILL: