[ARM] 4736/1: Export atags to userspace and allow kexec to use customised atags

Currently, the atags used by kexec are fixed to the ones originally used
to boot the kernel. This is less than ideal as changing the commandline,
initrd and other options would be a useful feature.

This patch exports the atags used for the current kernel to userspace
through an "atags" file in procfs. The presence of the file is
controlled by its own Kconfig option and cleans up several ifdef blocks
into a separate file. The tags for the new kernel are assumed to be at
a fixed location before the kernel image itself. The location of the
tags used to boot the original kernel is unimportant and no longer
saved.

Based on a patch from Uli Luckas <u.luckas@road.de>

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Acked-by: Uli Luckas <u.luckas@road.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 863c66454f2b..db8f54a3451f 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -21,6 +21,7 @@ extern void setup_mm_for_reboot(char mode);
 extern unsigned long kexec_start_address;
 extern unsigned long kexec_indirection_page;
 extern unsigned long kexec_mach_type;
+extern unsigned long kexec_boot_atags;
 
 /*
  * Provide a dummy crash_notes definition while crash dump arrives to arm.
@@ -62,6 +63,7 @@ void machine_kexec(struct kimage *image)
         kexec_start_address = image->start;
         kexec_indirection_page = page_list;
         kexec_mach_type = machine_arch_type;
+        kexec_boot_atags = image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET;
 
         /* copy our kernel relocation code to the control code page */
         memcpy(reboot_code_buffer,