kernel_5.10 no rt

hc

2023-12-11 6778948f9de86c3cfaf36725a7c87dcff9ba247f

 kernel/arch/mips/kernel/crash_dump.c
..
..
@@ -5,6 +5,8 @@
5
5
 #include <linux/uaccess.h>
6
6
 #include <linux/slab.h>
7
7
 
8
+static void *kdump_buf_page;
9
+
8
10
 /**
9
11
  * copy_oldmem_page - copy one page from "oldmem"
10
12
  * @pfn: page frame number to be copied
..
..
@@ -15,25 +17,51 @@
15
17
  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
16
18
  *	otherwise @buf is in kernel address space, use memcpy().
17
19
  *
18
- * Copy a page from "oldmem". For this page, there might be no pte mapped
20
+ * Copy a page from "oldmem". For this page, there is no pte mapped
19
21
  * in the current kernel.
22
+ *
23
+ * Calling copy_to_user() in atomic context is not desirable. Hence first
24
+ * copying the data to a pre-allocated kernel page and then copying to user
25
+ * space in non-atomic context.
20
26
  */
21
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
22
-			 unsigned long offset, int userbuf)
27
+ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
28
+			 size_t csize, unsigned long offset, int userbuf)
23
29
 {
24
30
 	void  *vaddr;
25
31
 
26
32
 	if (!csize)
27
33
 		return 0;
28
34
 
29
-	vaddr = kmap_local_pfn(pfn);
35
+	vaddr = kmap_atomic_pfn(pfn);
30
36
 
31
37
 	if (!userbuf) {
32
-		memcpy(buf, vaddr + offset, csize);
38
+		memcpy(buf, (vaddr + offset), csize);
39
+		kunmap_atomic(vaddr);
33
40
 	} else {
34
-		if (copy_to_user(buf, vaddr + offset, csize))
35
-			csize = -EFAULT;
41
+		if (!kdump_buf_page) {
42
+			pr_warn("Kdump: Kdump buffer page not allocated\n");
43
+
44
+			return -EFAULT;
45
+		}
46
+		copy_page(kdump_buf_page, vaddr);
47
+		kunmap_atomic(vaddr);
48
+		if (copy_to_user(buf, (kdump_buf_page + offset), csize))
49
+			return -EFAULT;
36
50
 	}
37
51
 
38
52
 	return csize;
39
53
 }
54
+
55
+static int __init kdump_buf_page_init(void)
56
+{
57
+	int ret = 0;
58
+
59
+	kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
60
+	if (!kdump_buf_page) {
61
+		pr_warn("Kdump: Failed to allocate kdump buffer page\n");
62
+		ret = -ENOMEM;
63
+	}
64
+
65
+	return ret;
66
+}
67
+arch_initcall(kdump_buf_page_init);