3 files changed, 82 insertions, 0 deletions

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index adc34f2c6eff..c356b6914ffd 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -206,6 +206,8 @@ extern size_t vmcoreinfo_max_size;
 
 int __init parse_crashkernel(char *cmdline, unsigned long long system_ram,
                 unsigned long long *crash_size, unsigned long long *crash_base);
+int crash_shrink_memory(unsigned long new_size);
+size_t crash_get_memory_size(void);
 
 #else /* !CONFIG_KEXEC */
 struct pt_regs;
diff --git a/kernel/kexec.c b/kernel/kexec.c
index f336e2107f98..433e9fcc1fc5 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -31,6 +31,7 @@
 #include <linux/cpu.h>
 #include <linux/console.h>
 #include <linux/vmalloc.h>
+#include <linux/swap.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
@@ -1082,6 +1083,64 @@ void crash_kexec(struct pt_regs *regs)
         }
 }
 
+size_t crash_get_memory_size(void)
+{
+        size_t size;
+        mutex_lock(&kexec_mutex);
+        size = crashk_res.end - crashk_res.start + 1;
+        mutex_unlock(&kexec_mutex);
+        return size;
+}
+
+static void free_reserved_phys_range(unsigned long begin, unsigned long end)
+{
+        unsigned long addr;
+
+        for (addr = begin; addr < end; addr += PAGE_SIZE) {
+                ClearPageReserved(pfn_to_page(addr >> PAGE_SHIFT));
+                init_page_count(pfn_to_page(addr >> PAGE_SHIFT));
+                free_page((unsigned long)__va(addr));
+                totalram_pages++;
+        }
+}
+
+int crash_shrink_memory(unsigned long new_size)
+{
+        int ret = 0;
+        unsigned long start, end;
+
+        mutex_lock(&kexec_mutex);
+
+        if (kexec_crash_image) {
+                ret = -ENOENT;
+                goto unlock;
+        }
+        start = crashk_res.start;
+        end = crashk_res.end;
+
+        if (new_size >= end - start + 1) {
+                ret = -EINVAL;
+                if (new_size == end - start + 1)
+                        ret = 0;
+                goto unlock;
+        }
+
+        start = roundup(start, PAGE_SIZE);
+        end = roundup(start + new_size, PAGE_SIZE);
+
+        free_reserved_phys_range(end, crashk_res.end);
+
+        if (start == end) {
+                crashk_res.end = end;
+                release_resource(&crashk_res);
+        } else
+                crashk_res.end = end - 1;
+
+unlock:
+        mutex_unlock(&kexec_mutex);
+        return ret;
+}
+
 static u32 *append_elf_note(u32 *buf, char *name, unsigned type, void *data,
                             size_t data_len)
 {
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index 528dd78e7e7e..3feaf5a74514 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -100,6 +100,26 @@ static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
 }
 KERNEL_ATTR_RO(kexec_crash_loaded);
 
+static ssize_t kexec_crash_size_show(struct kobject *kobj,
+                                       struct kobj_attribute *attr, char *buf)
+{
+        return sprintf(buf, "%zu\n", crash_get_memory_size());
+}
+static ssize_t kexec_crash_size_store(struct kobject *kobj,
+                                   struct kobj_attribute *attr,
+                                   const char *buf, size_t count)
+{
+        unsigned long cnt;
+        int ret;
+
+        if (strict_strtoul(buf, 0, &cnt))
+                return -EINVAL;
+
+        ret = crash_shrink_memory(cnt);
+        return ret < 0 ? ret : count;
+}
+KERNEL_ATTR_RW(kexec_crash_size);
+
 static ssize_t vmcoreinfo_show(struct kobject *kobj,
                                struct kobj_attribute *attr, char *buf)
 {
@@ -147,6 +167,7 @@ static struct attribute * kernel_attrs[] = {
 #ifdef CONFIG_KEXEC
         &kexec_loaded_attr.attr,
         &kexec_crash_loaded_attr.attr,
+        &kexec_crash_size_attr.attr,
         &vmcoreinfo_attr.attr,
 #endif
         NULL