[S390] nss: disable kexec.

nss and kexec don't work together since kexec wants to write to the
read-only text section of the shared kernel image.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 7 insertions, 0 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index d9425f59be91..0f293aa7b0fa 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -376,6 +376,8 @@ config SHARED_KERNEL
           Select this option, if you want to share the text segment of the
           Linux kernel between different VM guests. This reduces memory
           usage with lots of guests but greatly increases kernel size.
+          Also if a kernel was IPL'ed from a shared segment the kexec system
+          call will not work.
           You should only select this option if you know what you are
           doing and want to exploit this feature.
 
diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
index 52f57af252b4..3c77dd36994c 100644
--- a/arch/s390/kernel/machine_kexec.c
+++ b/arch/s390/kernel/machine_kexec.c
@@ -19,6 +19,7 @@
 #include <asm/system.h>
 #include <asm/smp.h>
 #include <asm/reset.h>
+#include <asm/ipl.h>
 
 typedef void (*relocate_kernel_t)(kimage_entry_t *, unsigned long);
 
@@ -29,6 +30,10 @@ int machine_kexec_prepare(struct kimage *image)
 {
         void *reboot_code_buffer;
 
+        /* Can't replace kernel image since it is read-only. */
+        if (ipl_flags & IPL_NSS_VALID)
+                return -ENOSYS;
+
         /* We don't support anything but the default image type for now. */
         if (image->type != KEXEC_TYPE_DEFAULT)
                 return -EINVAL;