[PATCH] uml: use PTRACE_OLDSETOPTIONS instead of PTRACE_SETOPTIONS

In linux 2.6, PTRACE_SETOPTIONS is redefined to 0x4200, while the old 2.4
value (21) is still available as PTRACE_OLDSETOPTIONS.

So, if UML uses PTRACE_SETOPTIONS, an UML-kernel built on a 2.6 won't run
on a 2.4 host.  Hence we must use PTRACE_OLDSETOPTIONS.

For cases when PTRACE_OLDSETOPTIONS does not exists (i.e.  2.4 host or
archs which miss it because they don't have a "deprecated" value), we
fallback this macro to PTRACE_SETOPTIONS.
Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/include/ptrace_user.h

@@ -26,6 +26,26 @@ extern void ptrace_pokeuser(unsigned long addr, unsigned long data);
 #define PTRACE_SYSEMU_SINGLESTEP 32
 #endif
 
+/* On architectures, that started to support PTRACE_O_TRACESYSGOOD
+ * in linux 2.4, there are two different definitions of
+ * PTRACE_SETOPTIONS: linux 2.4 uses 21 while linux 2.6 uses 0x4200.
+ * For binary compatibility, 2.6 also supports the old "21", named
+ * PTRACE_OLDSETOPTION. On these architectures, UML always must use
+ * "21", to ensure the kernel runs on 2.4 and 2.6 host without
+ * recompilation. So, we use PTRACE_OLDSETOPTIONS in UML.
+ * We also want to be able to build the kernel on 2.4, which doesn't
+ * have PTRACE_OLDSETOPTIONS. So, if it is missing, we declare
+ * PTRACE_OLDSETOPTIONS to to be the same as PTRACE_SETOPTIONS.
+ *
+ * On architectures, that start to support PTRACE_O_TRACESYSGOOD on
+ * linux 2.6, PTRACE_OLDSETOPTIONS never is defined, and also isn't
+ * supported by the host kernel. In that case, our trick lets us use
+ * the new 0x4200 with the name PTRACE_OLDSETOPTIONS.
+ */
+#ifndef PTRACE_OLDSETOPTIONS
+#define PTRACE_OLDSETOPTIONS PTRACE_SETOPTIONS
+#endif
+
 void set_using_sysemu(int value);
 int get_using_sysemu(void);
 extern int sysemu_supported;

arch/um/include/sysdep-x86_64/ptrace_user.h

@@ -49,10 +49,11 @@
 #define MAX_REG_NR ((MAX_REG_OFFSET) / sizeof(unsigned long))
 
 /* x86_64 FC3 doesn't define this in /usr/include/linux/ptrace.h even though
- * it's defined in the kernel's include/linux/ptrace.h
+ * it's defined in the kernel's include/linux/ptrace.h. Additionally, use the
+ * 2.4 name and value for 2.4 host compatibility.
  */
-#ifndef PTRACE_SETOPTIONS
-#define PTRACE_SETOPTIONS 0x4200
+#ifndef PTRACE_OLDSETOPTIONS
+#define PTRACE_OLDSETOPTIONS 21
 #endif
 
 #endif

arch/um/kernel/process.c

@@ -322,7 +322,7 @@ void __init check_ptrace(void)
 	printk("Checking that ptrace can change system call numbers...");
 	pid = start_ptraced_child(&stack);
 
-	if(ptrace(PTRACE_SETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
+	if (ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 		panic("check_ptrace: PTRACE_SETOPTIONS failed, errno = %d", errno);
 
 	while(1){

arch/um/kernel/skas/process.c

@@ -124,7 +124,7 @@ void start_userspace(int cpu)
 		panic("start_userspace : expected SIGSTOP, got status = %d",
 		      status);
 
-	if (ptrace(PTRACE_SETOPTIONS, pid, NULL, (void *)PTRACE_O_TRACESYSGOOD) < 0)
+	if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 		panic("start_userspace : PTRACE_SETOPTIONS failed, errno=%d\n",
 		      errno);
 

arch/um/kernel/tt/exec_user.c

@@ -39,7 +39,7 @@ void do_exec(int old_pid, int new_pid)
 
 	os_kill_ptraced_process(old_pid, 0);
 
-	if (ptrace(PTRACE_SETOPTIONS, new_pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
+	if (ptrace(PTRACE_OLDSETOPTIONS, new_pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 		tracer_panic("do_exec: PTRACE_SETOPTIONS failed, errno = %d", errno);
 
 	if(ptrace_setregs(new_pid, regs) < 0)

arch/um/kernel/tt/tracer.c

@@ -72,7 +72,7 @@ void attach_process(int pid)
 	   (ptrace(PTRACE_CONT, pid, 0, 0) < 0))
 		tracer_panic("OP_FORK failed to attach pid");
 	wait_for_stop(pid, SIGSTOP, PTRACE_CONT, NULL);
-	if (ptrace(PTRACE_SETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
+	if (ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 		tracer_panic("OP_FORK: PTRACE_SETOPTIONS failed, errno = %d", errno);
 	if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
 		tracer_panic("OP_FORK failed to continue process");
@@ -200,7 +200,7 @@ int tracer(int (*init_proc)(void *), void *sp)
 		printf("waitpid on idle thread failed, errno = %d\n", errno);
 		exit(1);
 	}
-	if (ptrace(PTRACE_SETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0) {
+	if (ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0) {
 		printf("Failed to PTRACE_SETOPTIONS for idle thread, errno = %d\n", errno);
 		exit(1);
 	}