1 files changed, 55 insertions, 8 deletions

diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c
index 0da59b42843c..340980203b09 100644
--- a/arch/i386/kernel/ptrace.c
+++ b/arch/i386/kernel/ptrace.c
@@ -271,6 +271,8 @@ static void clear_singlestep(struct task_struct *child)
 void ptrace_disable(struct task_struct *child)
 { 
 	clear_singlestep(child);
+	clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+	clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 }
 
 /*
@@ -509,15 +511,20 @@ asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
 		  }
 		  break;
 
+	case PTRACE_SYSEMU: /* continue and stop at next syscall, which will not be executed */
 	case PTRACE_SYSCALL:	/* continue and stop at next (return from) syscall */
 	case PTRACE_CONT:	/* restart after signal. */
 		ret = -EIO;
 		if (!valid_signal(data))
 			break;
-		if (request == PTRACE_SYSCALL) {
+		if (request == PTRACE_SYSEMU) {
+			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+		} 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;
@@ -542,10 +549,17 @@ asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
 		wake_up_process(child);
 		break;
 
+	case PTRACE_SYSEMU_SINGLESTEP: /* Same as SYSEMU, but singlestep if not syscall */
 	case PTRACE_SINGLESTEP:	/* set the trap flag. */
 		ret = -EIO;
 		if (!valid_signal(data))
 			break;
+
+		if (request == PTRACE_SYSEMU_SINGLESTEP)
+			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+		else
+			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+
 		clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		set_singlestep(child);
 		child->exit_code = data;
@@ -678,26 +692,52 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
  * - triggered by current->work.syscall_trace
  */
 __attribute__((regparm(3)))
-void do_syscall_trace(struct pt_regs *regs, int entryexit)
+int do_syscall_trace(struct pt_regs *regs, int entryexit)
 {
+	int is_sysemu = test_thread_flag(TIF_SYSCALL_EMU), ret = 0;
+	/* With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP for syscall
+	 * interception. */
+	int is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP);
+
 	/* do the secure computing check first */
 	secure_computing(regs->orig_eax);
 
-	if (unlikely(current->audit_context) && entryexit)
-		audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
+	if (unlikely(current->audit_context)) {
+		if (entryexit)
+			audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
+		/* Debug traps, when using PTRACE_SINGLESTEP, must be sent only
+		 * on the syscall exit path. Normally, when TIF_SYSCALL_AUDIT is
+		 * not used, entry.S will call us only on syscall exit, not
+		 * entry; so when TIF_SYSCALL_AUDIT is used we must avoid
+		 * calling send_sigtrap() on syscall entry.
+		 *
+		 * Note that when PTRACE_SYSEMU_SINGLESTEP is used,
+		 * is_singlestep is false, despite his name, so we will still do
+		 * the correct thing.
+		 */
+		else if (is_singlestep)
+			goto out;
+	}
 
 	if (!(current->ptrace & PT_PTRACED))
 		goto out;
 
+	/* If a process stops on the 1st tracepoint with SYSCALL_TRACE
+	 * and then is resumed with SYSEMU_SINGLESTEP, it will come in
+	 * here. We have to check this and return */
+	if (is_sysemu && entryexit)
+		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))
+ 	if (!test_thread_flag(TIF_SYSCALL_TRACE) && !is_sysemu)
 		goto out;
 
 	/* the 0x80 provides a way for the tracing parent to distinguish
 	   between a syscall stop and SIGTRAP delivery */
+	/* Note that the debugger could change the result of test_thread_flag!*/
 	ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
 
 	/*
@@ -709,9 +749,16 @@ void do_syscall_trace(struct pt_regs *regs, int entryexit)
 		send_sig(current->exit_code, current, 1);
 		current->exit_code = 0;
 	}
+	ret = is_sysemu;
  out:
 	if (unlikely(current->audit_context) && !entryexit)
 		audit_syscall_entry(current, AUDIT_ARCH_I386, regs->orig_eax,
 				    regs->ebx, regs->ecx, regs->edx, regs->esi);
+	if (ret == 0)
+		return 0;
 
+	regs->orig_eax = -1; /* force skip of syscall restarting */
+	if (unlikely(current->audit_context))
+		audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
+	return 1;
 }