powerpc: Use LOAD_REG_IMMEDIATE only for constants on 64-bit

Using LOAD_REG_IMMEDIATE to get the address of kernel symbols
generates 5 instructions where LOAD_REG_ADDR can do it in one,
and will generate R_PPC64_ADDR16_* relocations in the output when
we get to making the kernel as a position-independent executable,
which we'd rather not have to handle.  This changes various bits
of assembly code to use LOAD_REG_ADDR when we need to get the
address of a symbol, or to use suitable position-independent code
for cases where we can't access the TOC for various reasons, or
if we're not running at the address we were linked at.

It also cleans up a few minor things; there's no reason to save and
restore SRR0/1 around RTAS calls, __mmu_off can get the return
address from LR more conveniently than the caller can supply it in
R4 (and we already assume elsewhere that EA == RA if the MMU is on
in early boot), and enable_64b_mode was using 5 instructions where
2 would do.

Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S
index 85cb6f340846..2d29752cbe16 100644
--- a/arch/powerpc/kernel/misc.S
+++ b/arch/powerpc/kernel/misc.S
@@ -31,11 +31,14 @@ _GLOBAL(reloc_offset)
         mflr    r0
         bl      1f
 1:      mflr    r3
-        LOAD_REG_IMMEDIATE(r4,1b)
+        PPC_LL  r4,(2f-1b)(r3)
         subf    r3,r4,r3
         mtlr    r0
         blr
 
+        .align  3
+2:      PPC_LONG 1b
+
 /*
  * add_reloc_offset(x) returns x + reloc_offset().
  */
@@ -43,12 +46,15 @@ _GLOBAL(add_reloc_offset)
         mflr    r0
         bl      1f
 1:      mflr    r5
-        LOAD_REG_IMMEDIATE(r4,1b)
+        PPC_LL  r4,(2f-1b)(r5)
         subf    r5,r4,r5
         add     r3,r3,r5
         mtlr    r0
         blr
 
+        .align  3
+2:      PPC_LONG 1b
+
 _GLOBAL(kernel_execve)
         li      r0,__NR_execve
         sc