kernel/crash: handle multi-page vmcoreinfo in crash kernel copy

kimage_crash_copy_vmcoreinfo() currently assumes vmcoreinfo fits in a
single page.  This breaks if VMCOREINFO_BYTES exceeds PAGE_SIZE.

Allocate the required order of control pages and vmap all pages needed to
safely copy vmcoreinfo into the crash kernel image.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Pnina Feder <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Vivek Goyal <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Pnina Feder

kernel/crash_core.c

@@ -44,9 +44,15 @@ note_buf_t __percpu *crash_notes;
 
 int kimage_crash_copy_vmcoreinfo(struct kimage *image)
 {
-	struct page *vmcoreinfo_page;
+	struct page *vmcoreinfo_base;
+	struct page *vmcoreinfo_pages[DIV_ROUND_UP(VMCOREINFO_BYTES, PAGE_SIZE)];
+	unsigned int order, nr_pages;
+	int i;
 	void *safecopy;
 
+	nr_pages = DIV_ROUND_UP(VMCOREINFO_BYTES, PAGE_SIZE);
+	order = get_order(VMCOREINFO_BYTES);
+
 	if (!IS_ENABLED(CONFIG_CRASH_DUMP))
 		return 0;
 	if (image->type != KEXEC_TYPE_CRASH)
@@ -61,12 +67,15 @@ int kimage_crash_copy_vmcoreinfo(struct kimage *image)
 	 * happens to generate vmcoreinfo note, hereby we rely on
 	 * vmap for this purpose.
 	 */
-	vmcoreinfo_page = kimage_alloc_control_pages(image, 0);
-	if (!vmcoreinfo_page) {
+	vmcoreinfo_base = kimage_alloc_control_pages(image, order);
+	if (!vmcoreinfo_base) {
 		pr_warn("Could not allocate vmcoreinfo buffer\n");
 		return -ENOMEM;
 	}
-	safecopy = vmap(&vmcoreinfo_page, 1, VM_MAP, PAGE_KERNEL);
+	for (i = 0; i < nr_pages; i++)
+		vmcoreinfo_pages[i] = vmcoreinfo_base + i;
+
+	safecopy = vmap(vmcoreinfo_pages, nr_pages, VM_MAP, PAGE_KERNEL);
 	if (!safecopy) {
 		pr_warn("Could not vmap vmcoreinfo buffer\n");
 		return -ENOMEM;