asm/cvc_entry.S: r2 save fix

The TOC save area for the current stack frame should be used to save
r2, not the caller's frame.

Acked-by: Stewart Smith <stewart@flamingspork.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>

asm/cvc_entry.S

@@ -24,6 +24,11 @@
 
 #.include "kernel/ppcconsts.S"
 
+# Updated hostboot location is src/securerom/rom_entry.S.
+# This also has a fix for TOC save frame pointer.
+
+#include <stack.h>
+
 .section .text
 
 .global __cvc_verify_v1
@@ -33,10 +38,10 @@ __cvc_verify_v1:
 __cvc_sha512_v1:
 
 call_rom_entry:
-    std %r2, 40(%r1)
     mflr %r0
     std %r0, 16(%r1)
     stdu %r1, -128(%r1)
+    std %r2, STACK_TOC_OFFSET(%r1)
     li %r2, 0
     mtctr %r3
     mr %r3, %r4
@@ -45,8 +50,8 @@ call_rom_entry:
     mr %r6, %r7
     mr %r7, %r8
     bctrl
+    ld %r2, STACK_TOC_OFFSET(%r1)
     addi %r1, %r1, 128
-    ld %r2, 40(%r1)
     ld %r0, 16(%r1)
     mtlr %r0
     blr

include/stack.h

@@ -11,6 +11,8 @@
 #define STACK_ENTRY_RESET	0x0100	/* System reset */
 #define STACK_ENTRY_SOFTPATCH	0x1500	/* Soft patch (denorm emulation) */
 
+#define STACK_TOC_OFFSET	40
+
 /* Safety/ABI gap at top of stack */
 #define STACK_TOP_GAP		0x100