[PATCH] Relocatable kdump kernel support in kexec-tools

[Mohan Kumar M <mohan@in.ibm.com>]

Relocatable kdump kernel support in kexec-tools

This patch adds relocatable kernel support for kdump in the kexec-tools
code. A signature (0xfeed1234) is passed in r6 from panic code to the
purgatory code through kexec_sequence function. The signature is used to
differentiate between relocatable kdump kernel and non-kdump kernels.

The purgatory code compares the signature and sets the __kdump_flag in
head_64.S by using the offset with respect to next kernel load address.
During the boot up, kernel code checks __kdump_flag and if it is set, the
kernel will behave as relocatable kdump kernel.

Signed-off-by: Mohan Kumar M <mohan@in.ibm.com>
---
diff --git a/purgatory/arch/ppc64/v2wrap.S b/purgatory/arch/ppc64/v2wrap.S
index b3563de..f69dad2 100644
--- a/purgatory/arch/ppc64/v2wrap.S
+++ b/purgatory/arch/ppc64/v2wrap.S
@@ -45,6 +45,7 @@
 	oris    rn,rn,name##@h;         \
 	ori     rn,rn,name##@l
 
+#define KDUMP_SIGNATURE 0xfeed1234
 
 	.machine ppc64
 	.globl purgatory_start
@@ -64,6 +65,7 @@ master:
 	isync
 	mr      17,3            # save cpu id to r17
 	mr      15,4            # save physical address in reg15
+	mr      18,6            # save kdump flag in reg18
 
 	LOADADDR(6,my_toc)
 	ld      2,0(6)          #setup toc
@@ -94,6 +96,12 @@ master:
 	mtctr	4		# prepare branch too
 	mr      3,16            # restore dt address
 
+	LOADADDR(6,KDUMP_SIGNATURE)
+	cmpd	18,6
+	bne	regular
+	li	7,1
+	std	7,24(4)		# mark kdump flag at kernel
+regular:
 	lwz	7,0(4)		# get the first instruction that we stole
 	stw	7,0(0)		# and put it in the slave loop at 0
 				# skip cache flush, do we care?