[PATCH 2/3] x86/boot/compressed/32: Allow adjust_got to be called repeatedly

[Arvind Sankar <nivedita@alum.mit.edu>]

Save the new relocation address so that this function can be called
safely multiple times.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
---
 arch/x86/boot/compressed/head_32.S | 42 +++++++++++++++++++++++-------
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index e43ac17cb9fb..973ac0b51af5 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -173,15 +173,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
 /*
  * Adjust our own GOT
  */
-	leal	_got(%ebx), %edx
-	leal	_egot(%ebx), %ecx
-1:
-	cmpl	%ecx, %edx
-	jae	2f
-	addl	%ebx, (%edx)
-	addl	$4, %edx
-	jmp	1b
-2:
+	call	.Ladjust_got
 
 /*
  * Do the extraction, and jump to the new kernel..
@@ -211,6 +203,38 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
 	jmp	*%eax
 SYM_FUNC_END(.Lrelocated)
 
+/*
+ * Adjust the global offset table
+ *
+ * The relocation base address is passed in EBX. If the kernel is being
+ * relocated to a new address, this function must be called after the kernel
+ * has been copied to the new location. We keep track of the relocation address
+ * so that it can be backed out if this function is called repeatedly.
+ */
+
+SYM_FUNC_START_LOCAL(.Ladjust_got)
+	/* Get the new relocation base address */
+	movl	%ebx, %eax
+	/* Backout the previous relocation address if any */
+	subl	got_relocation_base(%ebx), %eax
+	/* Store the relocation base address for future reference */
+	addl	%eax, got_relocation_base(%ebx)
+
+	leal	_got(%ebx), %edx
+	leal	_egot(%ebx), %ecx
+1:
+	cmpl	%ecx, %edx
+	jae	2f
+	addl	%eax, (%edx)
+	addl	$4, %edx
+	jmp	1b
+2:
+	ret
+SYM_FUNC_END(.Ladjust_got)
+
+	.data
+SYM_DATA_LOCAL(got_relocation_base, .long 0)
+
 /*
  * Stack and heap for uncompression
  */
-- 
2.24.1