x86, realmode: Replace open-coded ljmpw with a macro

We cannot code an ljmpw to the real-mode segment directly, because gas
refuses to assemble an ljmp with a symbolic segment.  Instead of
open-coding it everywhere, define a macro and use it for this case.

This is specifically an ljmpw from a 16-bit segment.  This is okay, as
one should never enter real mode from a 32-bit segment: if one do, the
CPU ends up in a bizarre (and useless) mode sometimes called "unreal
mode" where segments behave like real mode but the default address and
operand sizes is 32 bits.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1336501366-28617-15-git-send-email-jarkko.sakkinen@intel.com

5 files changed, 25 insertions, 16 deletions

diff --git a/arch/x86/realmode/rm/realmode.h b/arch/x86/realmode/rm/realmode.h
new file mode 100644
index 00000000000..15ab6335f84
--- /dev/null
+++ b/arch/x86/realmode/rm/realmode.h
@@ -0,0 +1,16 @@
+#ifndef ARCH_X86_REALMODE_RM_REALMODE_H
+#define ARCH_X86_REALMODE_RM_REALMODE_H
+
+#ifdef __ASSEMBLY__
+
+/*
+ * 16-bit ljmpw to the real_mode_seg
+ *
+ * This must be open-coded since gas will choke on using a
+ * relocatable symbol for the segment portion.
+ */
+#define LJMPW_RM(to)    .byte 0xea ; .word (to), real_mode_seg
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* ARCH_X86_REALMODE_RM_REALMODE_H */
diff --git a/arch/x86/realmode/rm/reboot_32.S b/arch/x86/realmode/rm/reboot_32.S
index 83803c222b4..e90f8c4bbae 100644
--- a/arch/x86/realmode/rm/reboot_32.S
+++ b/arch/x86/realmode/rm/reboot_32.S
@@ -2,6 +2,7 @@
 #include <linux/init.h>
 #include <asm/segment.h>
 #include <asm/page_types.h>
+#include "realmode.h"
 
 /*
  * The following code and data reboots the machine by switching to real
@@ -82,10 +83,7 @@ machine_real_restart_asm16:
 2:
         andb    $0x10, %dl
         movl    %edx, %cr0
-        .byte   0xea                    /* ljmpw */
-        .word   3f                      /* Offset */
-        .word   real_mode_seg           /* Segment */
-
+        LJMPW_RM(3f)
 3:
         testb   $0, %al
         jz      bios
diff --git a/arch/x86/realmode/rm/trampoline_32.S b/arch/x86/realmode/rm/trampoline_32.S
index 1315ef48dbf..279f82ef7a9 100644
--- a/arch/x86/realmode/rm/trampoline_32.S
+++ b/arch/x86/realmode/rm/trampoline_32.S
@@ -29,6 +29,7 @@
 #include <linux/init.h>
 #include <asm/segment.h>
 #include <asm/page_types.h>
+#include "realmode.h"
 
         .text
         .code16
@@ -38,9 +39,7 @@
 trampoline_data:
         wbinvd                  # Needed for NUMA-Q should be harmless for others
 
-        .byte   0xea            # ljmpw
-        .word   1f              # Offset
-        .word   real_mode_seg   # Segment
+        LJMPW_RM(1f)
 1:
         mov     %cs, %ax        # Code and data in the same place
         mov     %ax, %ds
diff --git a/arch/x86/realmode/rm/trampoline_64.S b/arch/x86/realmode/rm/trampoline_64.S
index 77b72b45d70..7459c52f0c2 100644
--- a/arch/x86/realmode/rm/trampoline_64.S
+++ b/arch/x86/realmode/rm/trampoline_64.S
@@ -31,6 +31,7 @@
 #include <asm/msr.h>
 #include <asm/segment.h>
 #include <asm/processor-flags.h>
+#include "realmode.h"
 
         .text
         .balign PAGE_SIZE
@@ -40,9 +41,7 @@ ENTRY(trampoline_data)
         cli                     # We should be safe anyway
         wbinvd
 
-        .byte   0xea            # ljmpw
-        .word   1f              # Offset
-        .word   real_mode_seg   # Segment
+        LJMPW_RM(1f)
 1:
         mov     %cs, %ax        # Code and data in the same place
         mov     %ax, %ds
diff --git a/arch/x86/realmode/rm/wakeup/wakeup_asm.S b/arch/x86/realmode/rm/wakeup/wakeup_asm.S
index 4c5c5f2bfbe..8064e1c3591 100644
--- a/arch/x86/realmode/rm/wakeup/wakeup_asm.S
+++ b/arch/x86/realmode/rm/wakeup/wakeup_asm.S
@@ -6,6 +6,7 @@
 #include <asm/page_types.h>
 #include <asm/pgtable_types.h>
 #include <asm/processor-flags.h>
+#include "../realmode.h"
 #include "wakeup.h"
 
                 .code16
@@ -36,9 +37,7 @@ wakeup_start:
         cli
         cld
 
-        .byte   0xea            /* ljmpw */
-        .word   3f
-        .word   real_mode_seg
+        LJMPW_RM(3f)
 3:
         /* Apparently some dimwit BIOS programmers don't know how to
            program a PM to RM transition, and we might end up here with
@@ -59,9 +58,7 @@ wakeup_start:
 
         andb    $~X86_CR0_PE, %al
         movl    %eax, %cr0
-        .byte   0xea            /* ljmpw */
-        .word   3f
-        .word   real_mode_seg
+        LJMPW_RM(3f)
 3:
         /* Set up segments */
         movw    %cs, %ax