Re: prctl(PR_SET_MM)

[u3557@miso.sublimeip.com (Amnon Shiloh)]

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Cyrill Gorcunov wrote:

>> Another possibility is to have a dual #if:
>>
>> #if defined(CONFIG_CHECKPOINT_RESTORE) || defined(CONFIG_MM_FIELDS_SETTING)
>
> Thus this approach looks preferred. And MM_FIELDS_SETTING will be y by default.
> Mind to cook a patch and lets see if community accept it? Don't forget to
> CC Andrew Morton.

Very well, patch attached.

Amnon.

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diff -Naur before/init/Kconfig after/init/Kconfig
--- before/init/Kconfig	2013-02-19 10:28:34.000000000 +1030
+++ after/init/Kconfig	2013-02-21 18:03:48.000000000 +1030
@@ -999,6 +999,22 @@
 
 	  If unsure, say N here.
 
+config MM_FIELDS_SETTING
+	bool "Allow modifying per-process memory-region fields"
+	default y
+	help
+	   Support "prctl(PR_SET_MM)" which allows applications to modify
+	   the following in their "mm_struct":
+
+	      start_code, end_code, start_data, end_data, start_brk, brk,
+	      start_stack, arg_start, arg_end, env_start, env_end.
+
+	    Also to modify their executable file ("/proc/self/exe").
+
+	    This option is needed for reconstructing processes (such as when
+	    restoring a process from a checkpoint; duplicating a process;
+	    or migrating it to another computer).
+
 menuconfig NAMESPACES
 	bool "Namespaces support" if EXPERT
 	default !EXPERT
diff -Naur before/kernel/sys.c after/kernel/sys.c
--- before/kernel/sys.c	2013-02-19 10:28:34.000000000 +1030
+++ after/kernel/sys.c	2013-02-21 17:19:10.000000000 +1030
@@ -1788,7 +1788,7 @@
 	return mask;
 }
 
-#ifdef CONFIG_CHECKPOINT_RESTORE
+#if defined(CONFIG_CHECKPOINT_RESTORE) || defined(CONFIG_MM_FIELDS_SETTING)
 static int prctl_set_mm_exe_file(struct mm_struct *mm, unsigned int fd)
 {
 	struct fd exe;
@@ -1981,18 +1981,22 @@
 	up_read(&mm->mmap_sem);
 	return error;
 }
+#else /* CONFIG_CHECKPOINT_RESTORE || CONFIG_MM_FIELDS_SETTING */
 
-static int prctl_get_tid_address(struct task_struct *me, int __user **tid_addr)
-{
-	return put_user(me->clear_child_tid, tid_addr);
-}
-
-#else /* CONFIG_CHECKPOINT_RESTORE */
 static int prctl_set_mm(int opt, unsigned long addr,
 			unsigned long arg4, unsigned long arg5)
 {
 	return -EINVAL;
 }
+#endif
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static int prctl_get_tid_address(struct task_struct *me, int __user **tid_addr)
+{
+	return put_user(me->clear_child_tid, tid_addr);
+}
+
+#else
 static int prctl_get_tid_address(struct task_struct *me, int __user **tid_addr)
 {
 	return -EINVAL;