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

This patch is based on 2.6.9-vanilla + host-skas3-2.6.9-v7.patch
It reorganizes the code without changing the behavior of the
host kernel. This is done to free TIF_SYSCALL_EMU from double
use as a preparation for SYSEMU_SINGLESTEP extension.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
---

 clean-linux-2.6.11-paolo/arch/i386/kernel/entry.S  |    8 +++
 clean-linux-2.6.11-paolo/arch/i386/kernel/ptrace.c |   43 +++++++--------------
 2 files changed, 22 insertions(+), 29 deletions(-)

diff -puN arch/i386/kernel/entry.S~sysemu-reorganize arch/i386/kernel/entry.S
--- clean-linux-2.6.11/arch/i386/kernel/entry.S~sysemu-reorganize	2005-07-10 16:55:37.000000000 +0200
+++ clean-linux-2.6.11-paolo/arch/i386/kernel/entry.S	2005-07-10 16:57:35.000000000 +0200
@@ -305,12 +305,18 @@ syscall_trace_entry:
 	xorl %edx,%edx
 	call do_syscall_trace
 	cmpl $0, %eax
-	jne syscall_exit		# ret != 0 -> running under PTRACE_SYSEMU,
+	jne syscall_skip		# ret != 0 -> running under PTRACE_SYSEMU,
 					# so must skip actual syscall
 	movl ORIG_EAX(%esp), %eax
 	cmpl $(nr_syscalls), %eax
 	jnae syscall_call
 	jmp syscall_exit
+syscall_skip:
+	cli				# make sure we don't miss an interrupt
+					# setting need_resched or sigpending
+					# between sampling and the iret
+	movl TI_flags(%ebp), %ecx
+	jmp work_pending
 
 	# perform syscall exit tracing
 	ALIGN
diff -puN arch/i386/kernel/ptrace.c~sysemu-reorganize arch/i386/kernel/ptrace.c
--- clean-linux-2.6.11/arch/i386/kernel/ptrace.c~sysemu-reorganize	2005-07-10 16:55:37.000000000 +0200
+++ clean-linux-2.6.11-paolo/arch/i386/kernel/ptrace.c	2005-07-10 16:57:37.000000000 +0200
@@ -514,21 +514,16 @@ asmlinkage int sys_ptrace(long request, 
 		ret = -EIO;
 		if ((unsigned long) data > _NSIG)
 			break;
-		/* If we came here with PTRACE_SYSEMU and now continue with
-		 * PTRACE_SYSCALL, entry.S used to intercept the syscall return.
-		 * But it shouldn't!
-		 * So we don't clear TIF_SYSCALL_EMU, which is always unused in
-		 * this special case, to remember, we came from SYSEMU. That
-		 * flag will be cleared by do_syscall_trace().
-		 */
 		if (request == PTRACE_SYSEMU) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
-		} else if (request == PTRACE_CONT) {
-			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		}
-		if (request == PTRACE_SYSCALL) {
+		else if (request == PTRACE_SYSCALL) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
-		} else {
+			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+		}
+		else {
+			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		}
 		child->exit_code = data;
@@ -557,8 +552,7 @@ asmlinkage int sys_ptrace(long request, 
 		ret = -EIO;
 		if ((unsigned long) data > _NSIG)
 			break;
-		/*See do_syscall_trace to know why we don't clear
-		 * TIF_SYSCALL_EMU.*/
+		clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 		clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		set_singlestep(child);
 		child->exit_code = data;
@@ -745,7 +739,7 @@ void send_sigtrap(struct task_struct *ts
 __attribute__((regparm(3)))
 int do_syscall_trace(struct pt_regs *regs, int entryexit)
 {
-	int is_sysemu, is_systrace, is_singlestep;
+	int is_sysemu, is_singlestep;
 	if (unlikely(current->audit_context)) {
 		if (!entryexit)
 			audit_syscall_entry(current, regs->orig_eax,
@@ -758,22 +752,10 @@ int do_syscall_trace(struct pt_regs *reg
 		return 0;
 
 	is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
-	is_systrace = test_thread_flag(TIF_SYSCALL_TRACE);
 	is_singlestep = test_thread_flag(TIF_SINGLESTEP);
 
-	/* We can detect the case of coming from PTRACE_SYSEMU and now running
-	 * with PTRACE_SYSCALL or PTRACE_SINGLESTEP, by TIF_SYSCALL_EMU being
-	 * set additionally.
-	 * If so let's reset the flag and return without action (no singlestep
-	 * nor syscall tracing, since no actual step has been executed).
-	 */
-	if (is_sysemu && (is_systrace || is_singlestep)) {
-		clear_thread_flag(TIF_SYSCALL_EMU);
-		return 0;
-	}
-
 	/* Fake a debug trap */
-	if (test_thread_flag(TIF_SINGLESTEP))
+	if (is_singlestep)
 		send_sigtrap(current, regs, 0);
 
 	if (!test_thread_flag(TIF_SYSCALL_TRACE))
@@ -794,5 +776,10 @@ int do_syscall_trace(struct pt_regs *reg
 		current->exit_code = 0;
 	}
 	/* != 0 if nullifying the syscall, 0 if running it normally */
-	return is_sysemu;
+	if ( !is_sysemu )
+		return 0;
+
+	if (unlikely(current->audit_context))
+		audit_syscall_exit(current, regs->eax);
+	return 1;
 }
_