kexec: introduce a protection mechanism for the crashkernel reserved memory
For the cases that some kernel (module) path stamps the crash reserved
memory(already mapped by the kernel) where has been loaded the second
kernel data, the kdump kernel will probably fail to boot when panic
happens (or even not happens) leaving the culprit at large, this is
unacceptable.
The patch introduces a mechanism for detecting such cases:
1) After each crash kexec loading, it simply marks the reserved memory
regions readonly since we no longer access it after that. When someone
stamps the region, the first kernel will panic and trigger the kdump.
The weak arch_kexec_protect_crashkres() is introduced to do the actual
protection.
2) To allow multiple loading, once 1) was done we also need to remark
the reserved memory to readwrite each time a system call related to
kdump is made. The weak arch_kexec_unprotect_crashkres() is introduced
to do the actual protection.
The architecture can make its specific implementation by overriding
arch_kexec_protect_crashkres() and arch_kexec_unprotect_crashkres().
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/kernel/kexec.c b/kernel/kexec.c
index ee70aef..b44cb3f 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -167,8 +167,12 @@
return -EBUSY;
dest_image = &kexec_image;
- if (flags & KEXEC_ON_CRASH)
+ if (flags & KEXEC_ON_CRASH) {
dest_image = &kexec_crash_image;
+ if (kexec_crash_image)
+ arch_kexec_unprotect_crashkres();
+ }
+
if (nr_segments > 0) {
unsigned long i;
@@ -211,6 +215,9 @@
image = xchg(dest_image, image);
out:
+ if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
+ arch_kexec_protect_crashkres();
+
mutex_unlock(&kexec_mutex);
kimage_free(image);