x86, setup: Allow global variables and functions in the decompressor

In order for global variables and functions to work in the
decompressor, we need to fix up the GOT in assembly code.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
LKML-Reference: <4C57382E.8050501@zytor.com>

3 files changed, 32 insertions, 0 deletions

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index f543b70ffae2..67a655a39ce4 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    %ecx, %edx
+        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 faff0dc9c06a..52f85a196fa0 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    %rcx, %rdx
+        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 5ddabceee124..34d047c98284 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)