fix

Author: olsajiri

arch/x86/kernel/uprobes.c

@@ -635,7 +635,7 @@ static bool is_reachable_by_call(unsigned long vtramp, unsigned long vaddr)
 	return delta >= INT_MIN && delta <= INT_MAX;
 }
 
-#define MASK_4GB	((1UL << 32) - 1)
+#define MASK_4GB	~((1UL << 32) - 1)
 
 static unsigned long find_nearest_page(unsigned long vaddr)
 {
@@ -644,37 +644,66 @@ static unsigned long find_nearest_page(unsigned long vaddr)
 		.align_mask = ~PAGE_MASK,
 	};
 	unsigned long low_limit = PAGE_SIZE, high_limit = TASK_SIZE;
-	unsigned long limit, tramp_low_4GB, tramp_high_4GB;
-	unsigned long call_end = vaddr + 5, tramp1, tramp2;
+        unsigned long tramp1 = ~0UL, tramp2 = ~0UL;
+	unsigned long limit, low_4GB, high_4GB;
+	unsigned long call_end = vaddr + 5;
 
 	if (!check_add_overflow(call_end, INT_MIN, &limit))
 		low_limit = limit;
 	if (!check_add_overflow(call_end, INT_MAX, &limit))
 		high_limit = limit;
 
-	tramp_low_4GB = call_end & MASK_4GB;
-	tramp_high_4GB = tramp_low_4GB + (1UL << 32);
+	printk("find_nearest_page1 low_limit %lx high_limit %lx\n", low_limit, high_limit);
 
-	if (low_limit > tramp_low_4GB) {
-		info.low_limit = tramp_high_4GB;
+	low_4GB = call_end & MASK_4GB;
+	high_4GB = low_4GB + (1UL << 32);
+
+	if (low_limit == PAGE_SIZE)
+		low_4GB = low_limit;
+
+	printk("find_nearest_page2 low_4GB %lx high_4GB %lx\n", low_4GB, high_4GB);
+
+#if 0
+        0               4               8   
+        |               |               |
+           '-------^-------'
+     '-------^-------'
+                   '-------^-------'
+#endif
+
+	if (low_limit <= low_4GB) {
+		info.low_limit = low_4GB;
 		info.high_limit = high_limit;
 	} else {
-		info.low_limit = tramp_low_4GB;
-		info.high_limit = high_limit;;
+		info.low_limit = high_4GB;
+		info.high_limit = high_limit;
 	}
 
 	tramp1 = vm_unmapped_area(&info);
+	printk("find_nearest_page3 tramp1 %lx low_limit %lx high_limit %lx\n", tramp1, info.low_limit, info.high_limit);
 
-	if (low_limit > tramp_low_4GB) {
+	if (low_limit <= low_4GB) {
 		info.low_limit = low_limit;
-		info.high_limit = tramp_high_4GB;
+		info.high_limit = low_4GB;
 	} else {
 		info.low_limit = low_limit;
-		info.high_limit = tramp_low_4GB;
+		info.high_limit = high_4GB;
 	}
 
 	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 	tramp2 = vm_unmapped_area(&info);
+	printk("find_nearest_page4 tramp2 %lx low_limit %lx high_limit %lx\n", tramp2, info.low_limit, info.high_limit);
+
+	tramp1 = IS_ERR_VALUE(tramp1) ? ~0UL : tramp1;
+	tramp2 = IS_ERR_VALUE(tramp2) ? ~0UL : tramp2;
+
+	printk("find_nearest_page5 tramp1 %lx tramp2 %lx\n", tramp1, tramp2);
+
+	printk("find_nearest_page6 mask %lx tramp1 %lx tramp2 %lx min %lx\n",
+			MASK_4GB,
+			tramp1 & ~MASK_4GB,
+			tramp2 & ~MASK_4GB,
+			min(tramp1 & ~MASK_4GB, tramp2 & ~MASK_4GB));
 
 	return min(tramp1 & ~MASK_4GB, tramp2 & ~MASK_4GB);
 }