[PATCH 10/10] kexec: update kexec_file_load syscall to call ima_kexec_post_load

[Tushar Sugandhi <tusharsu@linux.microsoft.com>]

The kexec_file_load syscall is used to load a new kernel for kexec.
The syscall needs to update its function to call ima_kexec_post_load, which
was implemented in a previous patch.  ima_kexec_post_load takes care of
mapping the measurement list for the next kernel and registering a reboot
notifier if it's not already registered.

Modify the kexec_file_load syscall to call ima_kexec_post_load after the
image has been loaded and prepared for kexec.  This ensures that the IMA
measurement list will be available to the next kernel after a kexec reboot.
This also ensures the measurements taken in the window between kexec load
and execute are captured and passed to the next kernel. 

Declare the kimage_file_post_load function in the kernel/kexec_internal.h, 
so it can be properly used in the syscall.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
---
 kernel/kexec_file.c     | 7 +++++++
 kernel/kexec_internal.h | 1 +
 2 files changed, 8 insertions(+)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f989f5f1933b..efe28e77280c 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -184,6 +184,11 @@ kimage_validate_signature(struct kimage *image)
 }
 #endif
 
+void kimage_file_post_load(struct kimage *image)
+{
+	ima_kexec_post_load(image);
+}
+
 /*
  * In file mode list of segments is prepared by kernel. Copy relevant
  * data from user space, do error checking, prepare segment list
@@ -399,6 +404,8 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
 
 	kimage_terminate(image);
 
+	kimage_file_post_load(image);
+
 	ret = machine_kexec_post_load(image);
 	if (ret)
 		goto out;
diff --git a/kernel/kexec_internal.h b/kernel/kexec_internal.h
index 74da1409cd14..98dd5fcafaf0 100644
--- a/kernel/kexec_internal.h
+++ b/kernel/kexec_internal.h
@@ -30,6 +30,7 @@ static inline void kexec_unlock(void)
 
 #ifdef CONFIG_KEXEC_FILE
 #include <linux/purgatory.h>
+void kimage_file_post_load(struct kimage *image);
 void kimage_file_post_load_cleanup(struct kimage *image);
 extern char kexec_purgatory[];
 extern size_t kexec_purgatory_size;
-- 
2.25.1