[Xen-changelog] [linux-2.6.18-xen] Imported patch allow-i386-crash-kernels-to-handle-x86_64-dumps.patch from xen-unstable.hg 15200:bd3d6b4c52ec

["Xen patchbot-linux-2.6.18-xen" <patchbot-linux-2.6.18-xen@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxxxxx>
# Date 1180947924 -3600
# Node ID 9d24e876046f003df275e403cc012b61d43a4978
# Parent  61ed8662b69cc65aeb3371bcc6bc13d616999cd1
Imported patch allow-i386-crash-kernels-to-handle-x86_64-dumps.patch from 
xen-unstable.hg 15200:bd3d6b4c52ec

The specific case I am encountering is kdump under Xen with a 64 bit
hypervisor and 32 bit kernel/userspace.  The dump created is 64 bit due to
the hypervisor but the dump kernel is 32 bit for maximum compatibility.

It's possibly less likely to be useful in a purely native scenario but I
see no reason to disallow it.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxxxxx>
Acked-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Horms <horms@xxxxxxxxxxxx>
Cc: Magnus Damm <magnus.damm@xxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 fs/proc/vmcore.c           |    2 +-
 include/asm-i386/kexec.h   |    3 +++
 include/linux/crash_dump.h |    8 ++++++++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff -r 61ed8662b69c -r 9d24e876046f fs/proc/vmcore.c
--- a/fs/proc/vmcore.c  Mon Jun 04 10:05:24 2007 +0100
+++ b/fs/proc/vmcore.c  Mon Jun 04 10:05:24 2007 +0100
@@ -514,7 +514,7 @@ static int __init parse_crash_elf64_head
        /* Do some basic Verification. */
        if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0 ||
                (ehdr.e_type != ET_CORE) ||
-               !elf_check_arch(&ehdr) ||
+               !vmcore_elf_check_arch(&ehdr) ||
                ehdr.e_ident[EI_CLASS] != ELFCLASS64 ||
                ehdr.e_ident[EI_VERSION] != EV_CURRENT ||
                ehdr.e_version != EV_CURRENT ||
diff -r 61ed8662b69c -r 9d24e876046f include/asm-i386/kexec.h
--- a/include/asm-i386/kexec.h  Mon Jun 04 10:05:24 2007 +0100
+++ b/include/asm-i386/kexec.h  Mon Jun 04 10:05:24 2007 +0100
@@ -46,6 +46,9 @@
 
 /* The native architecture */
 #define KEXEC_ARCH KEXEC_ARCH_386
+
+/* We can also handle crash dumps from 64 bit kernel. */
+#define vmcore_elf_check_arch_cross(x) ((x)->e_machine == EM_X86_64)
 
 #define MAX_NOTE_BYTES 1024
 
diff -r 61ed8662b69c -r 9d24e876046f include/linux/crash_dump.h
--- a/include/linux/crash_dump.h        Mon Jun 04 10:05:24 2007 +0100
+++ b/include/linux/crash_dump.h        Mon Jun 04 10:05:24 2007 +0100
@@ -14,5 +14,13 @@ extern const struct file_operations proc
 extern const struct file_operations proc_vmcore_operations;
 extern struct proc_dir_entry *proc_vmcore;
 
+/* Architecture code defines this if there are other possible ELF
+ * machine types, e.g. on bi-arch capable hardware. */
+#ifndef vmcore_elf_check_arch_cross(x)
+#define vmcore_elf_check_arch_cross(x) 0
+#endif
+
+#define vmcore_elf_check_arch(x) (elf_check_arch(x) || 
vmcore_elf_check_arch_cross(x))
+
 #endif /* CONFIG_CRASH_DUMP */
 #endif /* LINUX_CRASHDUMP_H */

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