[PATCH] crashdump: x86_64: crashkernel option

This is the x86_64 implementation of the crashkernel option.  It reserves
a window of memory very early in the bootup process, so we never use
it for anything but the kernel to switch to when the running
kernel panics.

In addition to reserving this memory a resource structure is registered
so looking at /proc/iomem it is clear what happened to that memory.

ISSUES:
Is it possible to implement this in a architecture generic way?
What should be done with architectures that always use an iommu and
thus don't report their RAM memory resources in /proc/iomem?

Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/x86_64/kernel/e820.c b/arch/x86_64/kernel/e820.c
index cf4878309b04bc938a696729d9c84663b8874750..6ded3a50dfe63682174470acc3e78e2cfdbfd8b5 100644 (file)
--- a/arch/x86_64/kernel/e820.c
+++ b/arch/x86_64/kernel/e820.c
@@ -16,6 +16,7 @@
 #include <linux/bootmem.h>
 #include <linux/ioport.h>
 #include <linux/string.h>
+#include <linux/kexec.h>
 #include <asm/page.h>
 #include <asm/e820.h>
 #include <asm/proto.h>
@@ -210,6 +211,9 @@ void __init e820_reserve_resources(void)
                         */
                        request_resource(res, &code_resource);
                        request_resource(res, &data_resource);
+#ifdef CONFIG_KEXEC
+                       request_resource(res, &crashk_res);
+#endif
                }
        }
 }

diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index ca9a915a6d4ad5c0dfc57228762bd29ef85a5aa3..b02d921da4f72267cf9e7fb534fccf5a33001456 100644 (file)
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -41,6 +41,7 @@
 #include <linux/kallsyms.h>
 #include <linux/edd.h>
 #include <linux/mmzone.h>
+#include <linux/kexec.h>
 
 #include <asm/mtrr.h>
 #include <asm/uaccess.h>
@@ -367,6 +368,27 @@ static __init void parse_cmdline_early (char ** cmdline_p)
                if (!memcmp(from, "noexec=", 7))
                        nonx_setup(from + 7);
 
+#ifdef CONFIG_KEXEC
+               /* crashkernel=size@addr specifies the location to reserve for
+                * a crash kernel.  By reserving this memory we guarantee
+                * that linux never set's it up as a DMA target.
+                * Useful for holding code to do something appropriate
+                * after a kernel panic.
+                */
+               else if (!memcmp(from, "crashkernel=", 12)) {
+                       unsigned long size, base;
+                       size = memparse(from+12, &from);
+                       if (*from == '@') {
+                               base = memparse(from+1, &from);
+                               /* FIXME: Do I want a sanity check
+                                * to validate the memory range?
+                                */
+                               crashk_res.start = base;
+                               crashk_res.end   = base + size - 1;
+                       }
+               }
+#endif
+
        next_char:
                c = *(from++);
                if (!c)
@@ -625,6 +647,13 @@ void __init setup_arch(char **cmdline_p)
 #endif
 
        sparse_init();
+
+#ifdef CONFIG_KEXEC
+       if (crashk_res.start != crashk_res.end) {
+               reserve_bootmem(crashk_res.start,
+                       crashk_res.end - crashk_res.start + 1);
+       }
+#endif
        paging_init();
 
        check_ioapic();