2 files changed, 32 insertions, 10 deletions

diff --git a/Documentation/kdump/kdump.txt b/Documentation/kdump/kdump.txt
index bc4bd5a44b88..88ff63d5fde3 100644
--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -263,12 +263,6 @@ The syntax is:
     crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
     range=start-[end]
 
-Please note, on arm, the offset is required.
-    crashkernel=<range1>:<size1>[,<range2>:<size2>,...]@offset
-    range=start-[end]
-
-    'start' is inclusive and 'end' is exclusive.
-
 For example:
 
     crashkernel=512M-2G:64M,2G-:128M
@@ -307,10 +301,9 @@ Boot into System Kernel
    on the memory consumption of the kdump system. In general this is not
    dependent on the memory size of the production system.
 
-   On arm, use "crashkernel=Y@X". Note that the start address of the kernel
-   will be aligned to 128MiB (0x08000000), so if the start address is not then
-   any space below the alignment point may be overwritten by the dump-capture kernel,
-   which means it is possible that the vmcore is not that precise as expected.
+   On arm, the use of "crashkernel=Y@X" is no longer necessary; the
+   kernel will automatically locate the crash kernel image within the
+   first 512MB of RAM if X is not given.
 
 
 Load the Dump-capture Kernel
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 139791ed473d..77b54c461c52 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -938,6 +938,13 @@ static int __init init_machine_late(void)
 late_initcall(init_machine_late);
 
 #ifdef CONFIG_KEXEC
+/*
+ * The crash region must be aligned to 128MB to avoid
+ * zImage relocating below the reserved region.
+ */
+#define CRASH_ALIGN     (128 << 20)
+#define CRASH_ADDR_MAX  (PHYS_OFFSET + (512 << 20))
+
 static inline unsigned long long get_total_mem(void)
 {
         unsigned long total;
@@ -965,6 +972,28 @@ static void __init reserve_crashkernel(void)
         if (ret)
                 return;
 
+        if (crash_base <= 0) {
+                unsigned long long crash_max = CRASH_ADDR_MAX;
+                if (crash_max > (u32)~0)
+                        crash_max = (u32)~0;
+                crash_base = memblock_find_in_range(CRASH_ALIGN, crash_max,
+                                                    crash_size, CRASH_ALIGN);
+                if (!crash_base) {
+                        pr_err("crashkernel reservation failed - No suitable area found.\n");
+                        return;
+                }
+        } else {
+                unsigned long long start;
+
+                start = memblock_find_in_range(crash_base,
+                                               crash_base + crash_size,
+                                               crash_size, SECTION_SIZE);
+                if (start != crash_base) {
+                        pr_err("crashkernel reservation failed - memory is in use.\n");
+                        return;
+                }
+        }
+
         ret = memblock_reserve(crash_base, crash_size);
         if (ret < 0) {
                 pr_warn("crashkernel reservation failed - memory is in use (0x%lx)\n",