kexec: provide arch_kexec_protect(unprotect)_crashkres()

Implement the protection method for the crash kernel memory reservation
for the 64-bit x86 kdump.

Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Minfei Huang <mhuang@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index ba7fbba9831b88e0be4c228db2fe61b298c62d64..5a294e48b18529045ae4371f4ef8dc281773aea8 100644 (file)
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -538,3 +538,48 @@ overflow:
        return -ENOEXEC;
 }
 #endif /* CONFIG_KEXEC_FILE */
+
+static int
+kexec_mark_range(unsigned long start, unsigned long end, bool protect)
+{
+       struct page *page;
+       unsigned int nr_pages;
+
+       /*
+        * For physical range: [start, end]. We must skip the unassigned
+        * crashk resource with zero-valued "end" member.
+        */
+       if (!end || start > end)
+               return 0;
+
+       page = pfn_to_page(start >> PAGE_SHIFT);
+       nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1;
+       if (protect)
+               return set_pages_ro(page, nr_pages);
+       else
+               return set_pages_rw(page, nr_pages);
+}
+
+static void kexec_mark_crashkres(bool protect)
+{
+       unsigned long control;
+
+       kexec_mark_range(crashk_low_res.start, crashk_low_res.end, protect);
+
+       /* Don't touch the control code page used in crash_kexec().*/
+       control = PFN_PHYS(page_to_pfn(kexec_crash_image->control_code_page));
+       /* Control code page is located in the 2nd page. */
+       kexec_mark_range(crashk_res.start, control + PAGE_SIZE - 1, protect);
+       control += KEXEC_CONTROL_PAGE_SIZE;
+       kexec_mark_range(control, crashk_res.end, protect);
+}
+
+void arch_kexec_protect_crashkres(void)
+{
+       kexec_mark_crashkres(true);
+}
+
+void arch_kexec_unprotect_crashkres(void)
+{
+       kexec_mark_crashkres(false);
+}