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, 7 insertions, 9 deletions

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 55445f1dba8a..fd8b4bae9b04 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -690,10 +690,6 @@ _GLOBAL(enter_rtas)
         std     r7,_DAR(r1)
         mfdsisr r8
         std     r8,_DSISR(r1)
-        mfsrr0  r9
-        std     r9,_SRR0(r1)
-        mfsrr1  r10
-        std     r10,_SRR1(r1)
 
         /* Temporary workaround to clear CR until RTAS can be modified to
          * ignore all bits.
@@ -754,6 +750,10 @@ _STATIC(rtas_return_loc)
         mfspr   r4,SPRN_SPRG3           /* Get PACA */
         clrldi  r4,r4,2                 /* convert to realmode address */
 
+        bcl     20,31,$+4
+0:      mflr    r3
+        ld      r3,(1f-0b)(r3)          /* get &.rtas_restore_regs */
+
         mfmsr   r6
         li      r0,MSR_RI
         andc    r6,r6,r0
@@ -761,7 +761,6 @@ _STATIC(rtas_return_loc)
         mtmsrd  r6
         
         ld      r1,PACAR1(r4)           /* Restore our SP */
-        LOAD_REG_IMMEDIATE(r3,.rtas_restore_regs)
         ld      r4,PACASAVEDMSR(r4)     /* Restore our MSR */
 
         mtspr   SPRN_SRR0,r3
@@ -769,6 +768,9 @@ _STATIC(rtas_return_loc)
         rfid
         b       .       /* prevent speculative execution */
 
+        .align  3
+1:      .llong  .rtas_restore_regs
+
 _STATIC(rtas_restore_regs)
         /* relocation is on at this point */
         REST_GPR(2, r1)                 /* Restore the TOC */
@@ -788,10 +790,6 @@ _STATIC(rtas_restore_regs)
         mtdar   r7
         ld      r8,_DSISR(r1)
         mtdsisr r8
-        ld      r9,_SRR0(r1)
-        mtsrr0  r9
-        ld      r10,_SRR1(r1)
-        mtsrr1  r10
 
         addi    r1,r1,RTAS_FRAME_SIZE   /* Unstack our frame */
         ld      r0,16(r1)               /* get return address */