[PATCH] uml: add skas0 command-line option

This adds the "skas0" parameter to force skas0 operation on SKAS3 host and
shows which operating mode has been selected.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: 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

@@ -212,12 +212,26 @@ static int stop_ptraced_child(int pid, int exitcode, int mustexit)
 
 static int force_sysemu_disabled = 0;
 
+int ptrace_faultinfo = 1;
+int proc_mm = 1;
+
+static int __init skas0_cmd_param(char *str, int* add)
+{
+	ptrace_faultinfo = proc_mm = 0;
+	return 0;
+}
+
 static int __init nosysemu_cmd_param(char *str, int* add)
 {
 	force_sysemu_disabled = 1;
 	return 0;
 }
 
+__uml_setup("skas0", skas0_cmd_param,
+		"skas0\n"
+		"    Disables SKAS3 usage, so that SKAS0 is used, unless you \n"
+		"    specify mode=tt.\n\n");
+
 __uml_setup("nosysemu", nosysemu_cmd_param,
 		"nosysemu\n"
 		"    Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
@@ -359,12 +373,10 @@ void forward_pending_sigio(int target)
 		kill(target, SIGIO);
 }
 
-int ptrace_faultinfo = 0;
-int proc_mm = 1;
-
 extern void *__syscall_stub_start, __syscall_stub_end;
 
 #ifdef UML_CONFIG_MODE_SKAS
+
 static inline void check_skas3_ptrace_support(void)
 {
 	struct ptrace_faultinfo fi;
@@ -375,15 +387,18 @@ static inline void check_skas3_ptrace_support(void)
 
 	n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
 	if (n < 0) {
+		ptrace_faultinfo = 0;
 		if(errno == EIO)
 			printf("not found\n");
 		else {
 			perror("not found");
 		}
 	}
 	else {
-		ptrace_faultinfo = 1;
-		printf("found\n");
+		if (!ptrace_faultinfo)
+			printf("found but disabled on command line\n");
+		else
+			printf("found\n");
 	}
 
 	init_registers(pid);
@@ -396,13 +411,13 @@ int can_do_skas(void)
 	if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
 		proc_mm = 0;
 		printf("not found\n");
-		goto out;
-	}
-	else {
-		printf("found\n");
+	} else {
+		if (!proc_mm)
+			printf("found but disabled on command line\n");
+		else
+			printf("found\n");
 	}
 
-out:
 	check_skas3_ptrace_support();
 	return 1;
 }

arch/um/kernel/um_arch.c

@@ -38,6 +38,9 @@
 #include "choose-mode.h"
 #include "mode_kern.h"
 #include "mode.h"
+#ifdef UML_CONFIG_MODE_SKAS
+#include "skas.h"
+#endif
 
 #define DEFAULT_COMMAND_LINE "root=98:0"
 
@@ -318,6 +321,7 @@ int linux_main(int argc, char **argv)
 	unsigned long avail, diff;
 	unsigned long virtmem_size, max_physmem;
 	unsigned int i, add;
+	char * mode;
 
 	for (i = 1; i < argc; i++){
 		if((i == 1) && (argv[i][0] == ' ')) continue;
@@ -338,6 +342,21 @@ int linux_main(int argc, char **argv)
 		exit(1);
 	}
 #endif
+
+#ifndef CONFIG_MODE_SKAS
+	mode = "TT";
+#else
+	/* Show to the user the result of selection */
+	if (mode_tt)
+		mode = "TT";
+	else if (proc_mm && ptrace_faultinfo)
+		mode = "SKAS3";
+	else
+		mode = "SKAS0";
+#endif
+
+	printf("UML running in %s mode\n", mode);
+
 	uml_start = CHOOSE_MODE_PROC(set_task_sizes_tt, set_task_sizes_skas, 0,
 				     &host_task_size, &task_size);