[ARM] 4599/1: Preserve ATAG list for use with kexec (2.6.23)

This patch resolves a kexec boot failure that can occur because
no ATAGs are passed in to the kexec'd kernel. Currently the
newly-kexec'd kernel may fail if it requires specific ATAGs, or
it may fail because the fixed memory location at which it expects
to find the ATAGs may contain random data instead of ATAGs.

The patch ensures that any ATAGs passed to the current kernel
at boot time are copied to a static buffer, and are copied back
when kexec copies the new kernel into place. Thus the new
kernel sees the same ATAGs from kexec and the boot loader.

The boot parameters are copied without regard to type, content,
or length -- this patch's scope is limited soley to saving and
restoring a fixed-size block of memory containing the kernel's
boot parameters. Additional functionality to examine, alter, or
replace the ATAGs (using kexec, for example) can be implemented
by manipulating the static buffer containing the preserved ATAGs.

Note: the size of the buffer (1.5KB) is selected to comfortably
hold one of each ATAG type, including a maximum-length command
line and the maximum number of ATAG_MEM structures currently
supported by the kernel. Should an ATAG list exceed that limit,
the list will be silently truncated to that limit (to do other-
wise at that point in the boot process would make a simple
problem exceedingly complicated).

[Note: this is the same patch as 4579, modified to accomodate
the ATAG changes introduced in 2.6.23]

Signed-off-by: Mike Westerhof <mwester at dls.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 30 insertions, 0 deletions

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index efac7df..bf56eb3 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -24,6 +24,7 @@
 #include <linux/interrupt.h>
 #include <linux/smp.h>
 #include <linux/fs.h>
+#include <linux/kexec.h>
 
 #include <asm/cpu.h>
 #include <asm/elf.h>
@@ -783,6 +784,23 @@ static int __init customize_machine(void)
 }
 arch_initcall(customize_machine);
 
+#ifdef CONFIG_KEXEC
+
+/* Physical addr of where the boot params should be for this machine */
+extern unsigned long kexec_boot_params_address;
+
+/* Physical addr of the buffer into which the boot params are copied */
+extern unsigned long kexec_boot_params_copy;
+
+/* Pointer to the boot params buffer, for manipulation and display */
+unsigned long kexec_boot_params;
+EXPORT_SYMBOL(kexec_boot_params);
+
+/* The buffer itself - make sure it is sized correctly */
+static unsigned long kexec_boot_params_buf[(KEXEC_BOOT_PARAMS_SIZE + 3) / 4];
+
+#endif
+
 void __init setup_arch(char **cmdline_p)
 {
 	struct tag *tags = (struct tag *)&init_tags;
@@ -801,6 +819,18 @@ void __init setup_arch(char **cmdline_p)
 	else if (mdesc->boot_params)
 		tags = phys_to_virt(mdesc->boot_params);
 
+#ifdef CONFIG_KEXEC
+	kexec_boot_params_copy = virt_to_phys(kexec_boot_params_buf);
+	kexec_boot_params = (unsigned long)kexec_boot_params_buf;
+	if (__atags_pointer) {
+		kexec_boot_params_address = __atags_pointer;
+		memcpy((void *)kexec_boot_params, tags, KEXEC_BOOT_PARAMS_SIZE);
+	} else if (mdesc->boot_params) {
+		kexec_boot_params_address = mdesc->boot_params;
+		memcpy((void *)kexec_boot_params, tags, KEXEC_BOOT_PARAMS_SIZE);
+	}
+#endif
+
 	/*
 	 * If we have the old style parameters, convert them to
 	 * a tag list.