[RFC Patch 1/2] kexec: show memory info in /proc/iomem

[Amerigo Wang <amwang@redhat.com>]

This patch implements showing kexec memory area via /proc/iomem.
For example, with this patch we can see:

# cat /proc/iomem
...
00100000-7ffeffff : System RAM
  01000000-012e1424 : Kernel code
  012e1425-015f1aff : Kernel data
  0166b000-01b4b88f : Kernel bss
  02000000-083fffff : Crash kernel
    02000000-028fffff : Used
    02900000-083fffff : Unused
...

So that user can know how much memory the kernel uses for crash kernel.

Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Neil Horman <nhorman@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andi Kleen <andi@firstfloor.org>


---
diff --git a/kernel/kexec.c b/kernel/kexec.c
index f336e21..01673ad 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -931,6 +931,8 @@ static int kimage_load_segment(struct kimage *image,
  */
 struct kimage *kexec_image;
 struct kimage *kexec_crash_image;
+struct resource *kexec_res = NULL;
+struct resource *kexec_free_res = NULL;
 
 static DEFINE_MUTEX(kexec_mutex);
 
@@ -939,6 +941,8 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 {
 	struct kimage **dest_image, *image;
 	int result;
+	unsigned long kexec_start = crashk_res.start;
+	unsigned long kexec_end = kexec_start;
 
 	/* We only trust the superuser with rebooting the system. */
 	if (!capable(CAP_SYS_BOOT))
@@ -994,6 +998,7 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 			kimage_free(xchg(&kexec_crash_image, NULL));
 			result = kimage_crash_alloc(&image, entry,
 						     nr_segments, segments);
+			kexec_end += KEXEC_CONTROL_PAGE_SIZE;
 		}
 		if (result)
 			goto out;
@@ -1008,6 +1013,42 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 			result = kimage_load_segment(image, &image->segment[i]);
 			if (result)
 				goto out;
+			if (flags & KEXEC_ON_CRASH)
+				kexec_end += image->segment[i].memsz;
+		}
+		if (flags & KEXEC_ON_CRASH) {
+			if (kexec_res) {
+				release_resource(kexec_res);
+				release_resource(kexec_free_res);
+				kfree(kexec_res);
+				kfree(kexec_free_res);
+			}
+			kexec_res = kzalloc(sizeof(*kexec_res), GFP_KERNEL);
+			if (!kexec_res) {
+				result = -ENOMEM;
+				goto out;
+			}
+			kexec_free_res = kzalloc(sizeof(*kexec_free_res), GFP_KERNEL);
+			if (!kexec_free_res) {
+				result = -ENOMEM;
+				goto out_free;
+			}
+			kexec_res->name = "Used";
+			kexec_res->start = kexec_start;
+			kexec_res->end = roundup(kexec_end, 1<<20) - 1;
+			kexec_res->flags = IORESOURCE_BUSY | IORESOURCE_MEM;
+			if (insert_resource(&crashk_res, kexec_res)) {
+				result = -EBUSY;
+				goto out_free;
+			}
+			kexec_free_res->name = "Unused";
+			kexec_free_res->start = kexec_res->end + 1;
+			kexec_free_res->end = crashk_res.end;
+			kexec_free_res->flags = IORESOURCE_BUSY | IORESOURCE_MEM;
+			if (insert_resource(&crashk_res, kexec_free_res)) {
+				result = -EBUSY;
+				goto out_release;
+			}
 		}
 		kimage_terminate(image);
 	}
@@ -1019,6 +1060,13 @@ out:
 	kimage_free(image);
 
 	return result;
+
+out_free:
+	kfree(kexec_free_res);
+	kfree(kexec_res);
+out_release:
+	release_resource(kexec_res);
+	goto out;
 }
 
 #ifdef CONFIG_COMPAT