Re: [PATCH -v3 2/2] x86: more early console output from compressed/misc.c

["H. Peter Anvin" <hpa@zytor.com>]

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On 08/02/2010 01:59 PM, H. Peter Anvin wrote:
> On 08/02/2010 12:35 PM, Yinghai Lu wrote:
>>
>> it seems I can not global variables in arch/x86/boot/compressed/misc.c
>>
> 
> I just looked at it, it's the fact that we don't relocate the GOT that
> is causing problems.  It's relatively easy to fix: here is a patch, but
> in grand Linus tradition it is completely untested.
> 

Untested indeed... here is one which doesn't clobber live registers.

	-hpa


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diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index f543b70..58a8fb5 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -124,6 +124,19 @@ relocated:
 	rep	stosl
 
 /*
+ * Adjust our own GOT
+ */
+	leal	_got(%ebx), %edx
+	leal	_egot(%ebx), %ecx
+1:
+	cmpl	%edx, %ecx
+	jae	2f
+	addl	%ebx, (%edx)
+	addl	$4, %edx
+	jmp	1b
+2:
+
+/*
  * Do the decompression, and jump to the new kernel..
  */
 	leal	z_extract_offset_negative(%ebx), %ebp
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index faff0dc..892db2d 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -280,6 +280,19 @@ relocated:
 	rep	stosq
 
 /*
+ * Adjust our own GOT
+ */
+	leaq	_got(%rip), %rdx
+	leaq	_egot(%rip), %rcx
+1:
+	cmpq	%rdx, %rcx
+	jae	2f
+	addq	%rbx, (%rdx)
+	addq	$8, %rdx
+	jmp	1b
+2:
+	
+/*
  * Do the decompression, and jump to the new kernel..
  */
 	pushq	%rsi			/* Save the real mode argument */
diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
index 5ddabce..34d047c 100644
--- a/arch/x86/boot/compressed/vmlinux.lds.S
+++ b/arch/x86/boot/compressed/vmlinux.lds.S
@@ -41,6 +41,12 @@ SECTIONS
 		*(.rodata.*)
 		_erodata = . ;
 	}
+	.got : {
+		_got = .;
+		KEEP(*(.got.plt))
+		KEEP(*(.got))
+		_egot = .;
+	}
 	.data :	{
 		_data = . ;
 		*(.data)