[PATCH] uml: Fix for sysemu patches

- Correct some silly errors (dereferencing a pointer before checking if it's
  != NULL when creating /proc/sysemu, some error messages)

- separate using_sysemu from sysemu_supported (so to refuse to activate
  sysemu if it is not supported, avoiding panics)

- not probe sysemu if in tt mode.

Signed-off-by: <blaisorblade_spam@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/kernel/process.c

@@ -212,6 +212,49 @@ __uml_setup("nosysemu", nosysemu_cmd_param,
 		"    To make it working, you need a kernel patch for your host, too.\n"
 		"    See http://perso.wanadoo.fr/laurent.vivier/UML/ for further information.\n");
 
+static void __init check_sysemu(void)
+{
+	void *stack;
+	int pid, n, status;
+
+	if (mode_tt)
+		return;
+
+	printk("Checking syscall emulation patch for ptrace...");
+	sysemu_supported = 0;
+	pid = start_ptraced_child(&stack);
+	if(ptrace(PTRACE_SYSEMU, pid, 0, 0) >= 0) {
+		struct user_regs_struct regs;
+
+		if (waitpid(pid, &status, WUNTRACED) < 0)
+			panic("check_ptrace : wait failed, errno = %d", errno);
+		if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
+			panic("check_ptrace : expected SIGTRAP, "
+			      "got status = %d", status);
+
+		if (ptrace(PTRACE_GETREGS, pid, 0, &regs) < 0)
+			panic("check_ptrace : failed to read child "
+			      "registers, errno = %d", errno);
+		regs.orig_eax = pid;
+		if (ptrace(PTRACE_SETREGS, pid, 0, &regs) < 0)
+			panic("check_ptrace : failed to modify child "
+			      "registers, errno = %d", errno);
+
+		stop_ptraced_child(pid, stack, 0);
+
+		sysemu_supported = 1;
+		printk("found\n");
+	}
+	else
+	{
+		stop_ptraced_child(pid, stack, 1);
+		sysemu_supported = 0;
+		printk("missing\n");
+	}
+
+	set_using_sysemu(!force_sysemu_disabled);
+}
+
 void __init check_ptrace(void)
 {
 	void *stack;
@@ -244,42 +287,7 @@ void __init check_ptrace(void)
 	}
 	stop_ptraced_child(pid, stack, 0);
 	printk("OK\n");
-
-	printk("Checking syscall emulation patch for ptrace...");
-	set_using_sysemu(0);
-	pid = start_ptraced_child(&stack);
-	if(ptrace(PTRACE_SYSEMU, pid, 0, 0) >= 0) {
-		struct user_regs_struct regs;
-
-		if (waitpid(pid, &status, WUNTRACED) < 0)
-			panic("check_ptrace : wait failed, errno = %d", errno);
-		if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
-			panic("check_ptrace : expected SIGTRAP, "
-			      "got status = %d", status);
-
-		if (ptrace(PTRACE_GETREGS, pid, 0, &regs) < 0)
-			panic("check_ptrace : failed to read child "
-			      "registers, errno = %d", errno);
-		regs.orig_eax = pid;
-		if (ptrace(PTRACE_SETREGS, pid, 0, &regs) < 0)
-			panic("check_ptrace : failed to modify child "
-			      "registers, errno = %d", errno);
-
-		stop_ptraced_child(pid, stack, 0);
-
-		if (!force_sysemu_disabled) {
-			printk("found\n");
-			set_using_sysemu(1);
-		} else {
-			printk("found but disabled\n");
-		}
-	}
-	else
-	{
-		printk("missing\n");
-		stop_ptraced_child(pid, stack, 1);
-	}
-
+	check_sysemu();
 }
 
 int run_kernel_thread(int (*fn)(void *), void *arg, void **jmp_ptr)

arch/um/kernel/skas/include/ptrace-skas.h

@@ -18,6 +18,7 @@
 
 void set_using_sysemu(int value);
 int get_using_sysemu(void);
+extern int sysemu_supported;
 
 #include "skas_ptregs.h"
 

arch/um/kernel/skas/process.c

@@ -151,8 +151,8 @@ void userspace(union uml_pt_regs *regs)
 	else
 		err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
 	if(err)
-		panic("userspace - PTRACE_SYSCALL failed, errno = %d\n", 
-		       errno);
+		panic("userspace - PTRACE_%s failed, errno = %d\n",
+		       local_using_sysemu ? "SYSEMU" : "SYSCALL", errno);
 	while(1){
 		err = waitpid(pid, &status, WUNTRACED);
 		if(err < 0)
@@ -199,8 +199,9 @@ void userspace(union uml_pt_regs *regs)
 
 		err = ptrace(op, pid, 0, 0);
 		if(err)
-			panic("userspace - PTRACE_SYSCALL failed, "
-			      "errno = %d\n", errno);
+			panic("userspace - PTRACE_%s failed, "
+			      "errno = %d\n",
+			      local_using_sysemu ? "SYSEMU" : "SYSCALL", errno);
 	}
 }
 

arch/um/kernel/skas/process_kern.c

@@ -23,13 +23,12 @@
 #include "kern.h"
 #include "mode.h"
 
-#ifdef PTRACE_SYSEMU
 static atomic_t using_sysemu;
-#endif
+int sysemu_supported;
 
 void set_using_sysemu(int value)
 {
-	atomic_set(&using_sysemu, value);
+	atomic_set(&using_sysemu, sysemu_supported && value);
 }
 
 int get_using_sysemu(void)
@@ -60,10 +59,10 @@ int proc_write_sysemu(struct file *file,const char *buf, unsigned long count,voi
 int __init make_proc_sysemu(void)
 {
 	struct proc_dir_entry *ent;
+	if (mode_tt || !sysemu_supported)
+		return 0;
 
-	ent = create_proc_entry("sysemu", 00600, &proc_root);
-	ent->read_proc  = proc_read_sysemu;
-	ent->write_proc = proc_write_sysemu;
+	ent = create_proc_entry("sysemu", 0600, &proc_root);
 
 	if (ent == NULL)
 	{
@@ -71,6 +70,9 @@ int __init make_proc_sysemu(void)
 		return(0);
 	}
 
+	ent->read_proc  = proc_read_sysemu;
+	ent->write_proc = proc_write_sysemu;
+
 	return 0;
 }