powerpc/kdump: Override crash_free_reserved_phys_range to avoid freeing RTAS

The crashkernel region will almost always overlap RTAS. If we free the
crashkernel region via "echo 0 > /sys/kernel/kexec_crash_size" then we will
free RTAS and the machine will crash in confusing and exciting ways.

Override crash_free_reserved_phys_range and check for overlap with RTAS.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index 8e05c16344e4..0a2af50243cb 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -19,6 +19,7 @@
 #include <asm/prom.h>
 #include <asm/firmware.h>
 #include <asm/uaccess.h>
+#include <asm/rtas.h>
 
 #ifdef DEBUG
 #include <asm/udbg.h>
@@ -141,3 +142,35 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 
         return csize;
 }
+
+#ifdef CONFIG_PPC_RTAS
+/*
+ * The crashkernel region will almost always overlap the RTAS region, so
+ * we have to be careful when shrinking the crashkernel region.
+ */
+void crash_free_reserved_phys_range(unsigned long begin, unsigned long end)
+{
+        unsigned long addr;
+        const u32 *basep, *sizep;
+        unsigned int rtas_start = 0, rtas_end = 0;
+
+        basep = of_get_property(rtas.dev, "linux,rtas-base", NULL);
+        sizep = of_get_property(rtas.dev, "rtas-size", NULL);
+
+        if (basep && sizep) {
+                rtas_start = *basep;
+                rtas_end = *basep + *sizep;
+        }
+
+        for (addr = begin; addr < end; addr += PAGE_SIZE) {
+                /* Does this page overlap with the RTAS region? */
+                if (addr <= rtas_end && ((addr + PAGE_SIZE) > rtas_start))
+                        continue;
+
+                ClearPageReserved(pfn_to_page(addr >> PAGE_SHIFT));
+                init_page_count(pfn_to_page(addr >> PAGE_SHIFT));
+                free_page((unsigned long)__va(addr));
+                totalram_pages++;
+        }
+}
+#endif