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powerpc: Use LOAD_REG_IMMEDIATE only for constants on 64-bit

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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>
This commit is contained in:
Paul Mackerras
2008-08-30 11:41:12 +10:00
parent 1f6a93e4c3
commit e31aa453bb
6 changed files with 111 additions and 127 deletions
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16
arch/powerpc/kernel/entry_64.S
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@ -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 */