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, 82 insertions, 99 deletions

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 97bb6e6f67b1..6cdfd44d8efe 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -128,11 +128,11 @@ __secondary_hold:
         /* Tell the master cpu we're here */
         /* Relocation is off & we are located at an address less */
         /* than 0x100, so only need to grab low order offset.    */
-        std     r24,__secondary_hold_acknowledge@l(0)
+        std     r24,__secondary_hold_acknowledge-_stext(0)
         sync
 
         /* All secondary cpus wait here until told to start. */
-100:    ld      r4,__secondary_hold_spinloop@l(0)
+100:    ld      r4,__secondary_hold_spinloop-_stext(0)
         cmpdi   0,r4,0
         beq     100b
 
@@ -1223,11 +1223,14 @@ _GLOBAL(generic_secondary_smp_init)
         /* turn on 64-bit mode */
         bl      .enable_64b_mode
 
+        /* get the TOC pointer (real address) */
+        bl      .relative_toc
+
         /* Set up a paca value for this processor. Since we have the
          * physical cpu id in r24, we need to search the pacas to find
          * which logical id maps to our physical one.
          */
-        LOAD_REG_IMMEDIATE(r13, paca)   /* Get base vaddr of paca array  */
+        LOAD_REG_ADDR(r13, paca)        /* Get base vaddr of paca array  */
         li      r5,0                    /* logical cpu id                */
 1:      lhz     r6,PACAHWCPUID(r13)     /* Load HW procid from paca      */
         cmpw    r6,r24                  /* Compare to our id             */
@@ -1256,7 +1259,7 @@ _GLOBAL(generic_secondary_smp_init)
         sync                            /* order paca.run and cur_cpu_spec */
 
         /* See if we need to call a cpu state restore handler */
-        LOAD_REG_IMMEDIATE(r23, cur_cpu_spec)
+        LOAD_REG_ADDR(r23, cur_cpu_spec)
         ld      r23,0(r23)
         ld      r23,CPU_SPEC_RESTORE(r23)
         cmpdi   0,r23,0
@@ -1272,10 +1275,15 @@ _GLOBAL(generic_secondary_smp_init)
         b       __secondary_start
 #endif
 
+/*
+ * Turn the MMU off.
+ * Assumes we're mapped EA == RA if the MMU is on.
+ */
 _STATIC(__mmu_off)
         mfmsr   r3
         andi.   r0,r3,MSR_IR|MSR_DR
         beqlr
+        mflr    r4
         andc    r3,r3,r0
         mtspr   SPRN_SRR0,r4
         mtspr   SPRN_SRR1,r3
@@ -1296,6 +1304,18 @@ _STATIC(__mmu_off)
  *
  */
 _GLOBAL(__start_initialization_multiplatform)
+        /* Make sure we are running in 64 bits mode */
+        bl      .enable_64b_mode
+
+        /* Get TOC pointer (current runtime address) */
+        bl      .relative_toc
+
+        /* find out where we are now */
+        bcl     20,31,$+4
+0:      mflr    r26                     /* r26 = runtime addr here */
+        addis   r26,r26,(_stext - 0b)@ha
+        addi    r26,r26,(_stext - 0b)@l /* current runtime base addr */
+
         /*
          * Are we booted from a PROM Of-type client-interface ?
          */
@@ -1307,9 +1327,6 @@ _GLOBAL(__start_initialization_multiplatform)
         mr      r31,r3
         mr      r30,r4
 
-        /* Make sure we are running in 64 bits mode */
-        bl      .enable_64b_mode
-
         /* Setup some critical 970 SPRs before switching MMU off */
         mfspr   r0,SPRN_PVR
         srwi    r0,r0,16
@@ -1324,9 +1341,7 @@ _GLOBAL(__start_initialization_multiplatform)
 1:      bl      .__cpu_preinit_ppc970
 2:
 
-        /* Switch off MMU if not already */
-        LOAD_REG_IMMEDIATE(r4, .__after_prom_start - KERNELBASE)
-        add     r4,r4,r30
+        /* Switch off MMU if not already off */
         bl      .__mmu_off
         b       .__after_prom_start
 
@@ -1341,23 +1356,10 @@ _INIT_STATIC(__boot_from_prom)
         /*
          * Align the stack to 16-byte boundary
          * Depending on the size and layout of the ELF sections in the initial
-         * boot binary, the stack pointer will be unalignet on PowerMac
+         * boot binary, the stack pointer may be unaligned on PowerMac
          */
         rldicr  r1,r1,0,59
 
-        /* Make sure we are running in 64 bits mode */
-        bl      .enable_64b_mode
-
-        /* put a relocation offset into r3 */
-        bl      .reloc_offset
-
-        LOAD_REG_IMMEDIATE(r2,__toc_start)
-        addi    r2,r2,0x4000
-        addi    r2,r2,0x4000
-
-        /* Relocate the TOC from a virt addr to a real addr */
-        add     r2,r2,r3
-
         /* Restore parameters */
         mr      r3,r31
         mr      r4,r30
@@ -1373,53 +1375,37 @@ _INIT_STATIC(__boot_from_prom)
 _STATIC(__after_prom_start)
 
 /*
- * We need to run with __start at physical address PHYSICAL_START.
+ * We need to run with _stext at physical address PHYSICAL_START.
  * This will leave some code in the first 256B of
  * real memory, which are reserved for software use.
- * The remainder of the first page is loaded with the fixed
- * interrupt vectors.  The next two pages are filled with
- * unknown exception placeholders.
  *
  * Note: This process overwrites the OF exception vectors.
- *      r26 == relocation offset
- *      r27 == KERNELBASE
  */
-        bl      .reloc_offset
-        mr      r26,r3
-        LOAD_REG_IMMEDIATE(r27, KERNELBASE)
-
         LOAD_REG_IMMEDIATE(r3, PHYSICAL_START)  /* target addr */
-
-        // XXX FIXME: Use phys returned by OF (r30)
-        add     r4,r27,r26              /* source addr                   */
-                                        /* current address of _start     */
-                                        /*   i.e. where we are running   */
-                                        /*      the source addr          */
-
-        cmpdi   r4,0                    /* In some cases the loader may  */
-        bne     1f
-        b       .start_here_multiplatform /* have already put us at zero */
-                                        /* so we can skip the copy.      */
-1:      LOAD_REG_IMMEDIATE(r5,copy_to_here) /* # bytes of memory to copy */
-        sub     r5,r5,r27
-
+        cmpd    r3,r26                  /* In some cases the loader may  */
+        beq     9f                      /* have already put us at zero */
+        mr      r4,r26                  /* source address */
+        lis     r5,(copy_to_here - _stext)@ha
+        addi    r5,r5,(copy_to_here - _stext)@l /* # bytes of memory to copy */
         li      r6,0x100                /* Start offset, the first 0x100 */
                                         /* bytes were copied earlier.    */
 
         bl      .copy_and_flush         /* copy the first n bytes        */
                                         /* this includes the code being  */
                                         /* executed here.                */
-
-        LOAD_REG_IMMEDIATE(r0, 4f)      /* Jump to the copy of this code */
-        mtctr   r0                      /* that we just made/relocated   */
+        addis   r8,r3,(4f - _stext)@ha  /* Jump to the copy of this code */
+        addi    r8,r8,(4f - _stext)@l   /* that we just made */
+        mtctr   r8
         bctr
 
-4:      LOAD_REG_IMMEDIATE(r5,klimit)
-        add     r5,r5,r26
-        ld      r5,0(r5)                /* get the value of klimit */
-        sub     r5,r5,r27
+4:      /* Now copy the rest of the kernel up to _end */
+        addis   r5,r26,(p_end - _stext)@ha
+        ld      r5,(p_end - _stext)@l(r5)       /* get _end */
         bl      .copy_and_flush         /* copy the rest */
-        b       .start_here_multiplatform
+
+9:      b       .start_here_multiplatform
+
+p_end:  .llong  _end - _stext
 
 /*
  * Copy routine used to copy the kernel to start at physical address 0
@@ -1484,6 +1470,9 @@ _GLOBAL(pmac_secondary_start)
         /* turn on 64-bit mode */
         bl      .enable_64b_mode
 
+        /* get TOC pointer (real address) */
+        bl      .relative_toc
+
         /* Copy some CPU settings from CPU 0 */
         bl      .__restore_cpu_ppc970
 
@@ -1493,10 +1482,10 @@ _GLOBAL(pmac_secondary_start)
         mtmsrd  r3                      /* RI on */
 
         /* Set up a paca value for this processor. */
-        LOAD_REG_IMMEDIATE(r4, paca)    /* Get base vaddr of paca array */
-        mulli   r13,r24,PACA_SIZE        /* Calculate vaddr of right paca */
+        LOAD_REG_ADDR(r4,paca)          /* Get base vaddr of paca array */
+        mulli   r13,r24,PACA_SIZE       /* Calculate vaddr of right paca */
         add     r13,r13,r4              /* for this processor.          */
-        mtspr   SPRN_SPRG3,r13           /* Save vaddr of paca in SPRG3 */
+        mtspr   SPRN_SPRG3,r13          /* Save vaddr of paca in SPRG3  */
 
         /* Create a temp kernel stack for use before relocation is on.  */
         ld      r1,PACAEMERGSP(r13)
@@ -1524,9 +1513,6 @@ __secondary_start:
         /* Set thread priority to MEDIUM */
         HMT_MEDIUM
 
-        /* Load TOC */
-        ld      r2,PACATOC(r13)
-
         /* Do early setup for that CPU (stab, slb, hash table pointer) */
         bl      .early_setup_secondary
 
@@ -1563,9 +1549,11 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
 
 /* 
  * Running with relocation on at this point.  All we want to do is
- * zero the stack back-chain pointer before going into C code.
+ * zero the stack back-chain pointer and get the TOC virtual address
+ * before going into C code.
  */
 _GLOBAL(start_secondary_prolog)
+        ld      r2,PACATOC(r13)
         li      r3,0
         std     r3,0(r1)                /* Zero the stack frame pointer */
         bl      .start_secondary
@@ -1577,34 +1565,46 @@ _GLOBAL(start_secondary_prolog)
  */
 _GLOBAL(enable_64b_mode)
         mfmsr   r11                     /* grab the current MSR */
-        li      r12,1
-        rldicr  r12,r12,MSR_SF_LG,(63-MSR_SF_LG)
-        or      r11,r11,r12
-        li      r12,1
-        rldicr  r12,r12,MSR_ISF_LG,(63-MSR_ISF_LG)
+        li      r12,(MSR_SF | MSR_ISF)@highest
+        sldi    r12,r12,48
         or      r11,r11,r12
         mtmsrd  r11
         isync
         blr
 
 /*
+ * This puts the TOC pointer into r2, offset by 0x8000 (as expected
+ * by the toolchain).  It computes the correct value for wherever we
+ * are running at the moment, using position-independent code.
+ */
+_GLOBAL(relative_toc)
+        mflr    r0
+        bcl     20,31,$+4
+0:      mflr    r9
+        ld      r2,(p_toc - 0b)(r9)
+        add     r2,r2,r9
+        mtlr    r0
+        blr
+
+p_toc:  .llong  __toc_start + 0x8000 - 0b
+
+/*
  * This is where the main kernel code starts.
  */
 _INIT_STATIC(start_here_multiplatform)
-        /* get a new offset, now that the kernel has moved. */
-        bl      .reloc_offset
-        mr      r26,r3
+        /* set up the TOC (real address) */
+        bl      .relative_toc
 
         /* Clear out the BSS. It may have been done in prom_init,
          * already but that's irrelevant since prom_init will soon
          * be detached from the kernel completely. Besides, we need
          * to clear it now for kexec-style entry.
          */
-        LOAD_REG_IMMEDIATE(r11,__bss_stop)
-        LOAD_REG_IMMEDIATE(r8,__bss_start)
+        LOAD_REG_ADDR(r11,__bss_stop)
+        LOAD_REG_ADDR(r8,__bss_start)
         sub     r11,r11,r8              /* bss size                     */
         addi    r11,r11,7               /* round up to an even double word */
-        rldicl. r11,r11,61,3            /* shift right by 3             */
+        srdi.   r11,r11,3               /* shift right by 3             */
         beq     4f
         addi    r8,r8,-8
         li      r0,0
@@ -1617,35 +1617,28 @@ _INIT_STATIC(start_here_multiplatform)
         ori     r6,r6,MSR_RI
         mtmsrd  r6                      /* RI on */
 
-        /* The following gets the stack and TOC set up with the regs */
+        /* The following gets the stack set up with the regs */
         /* pointing to the real addr of the kernel stack.  This is   */
         /* all done to support the C function call below which sets  */
         /* up the htab.  This is done because we have relocated the  */
         /* kernel but are still running in real mode. */
 
-        LOAD_REG_IMMEDIATE(r3,init_thread_union)
-        add     r3,r3,r26
+        LOAD_REG_ADDR(r3,init_thread_union)
 
-        /* set up a stack pointer (physical address) */
+        /* set up a stack pointer */
         addi    r1,r3,THREAD_SIZE
         li      r0,0
         stdu    r0,-STACK_FRAME_OVERHEAD(r1)
 
-        /* set up the TOC (physical address) */
-        LOAD_REG_IMMEDIATE(r2,__toc_start)
-        addi    r2,r2,0x4000
-        addi    r2,r2,0x4000
-        add     r2,r2,r26
-
         /* Do very early kernel initializations, including initial hash table,
          * stab and slb setup before we turn on relocation.     */
 
         /* Restore parameters passed from prom_init/kexec */
         mr      r3,r31
-        bl      .early_setup
+        bl      .early_setup            /* also sets r13 and SPRG3 */
 
-        LOAD_REG_IMMEDIATE(r3, .start_here_common)
-        LOAD_REG_IMMEDIATE(r4, MSR_KERNEL)
+        LOAD_REG_ADDR(r3, .start_here_common)
+        ld      r4,PACAKMSR(r13)
         mtspr   SPRN_SRR0,r3
         mtspr   SPRN_SRR1,r4
         rfid
@@ -1654,20 +1647,10 @@ _INIT_STATIC(start_here_multiplatform)
         /* This is where all platforms converge execution */
 _INIT_GLOBAL(start_here_common)
         /* relocation is on at this point */
+        std     r1,PACAKSAVE(r13)
 
-        /* The following code sets up the SP and TOC now that we are */
-        /* running with translation enabled. */
-
-        LOAD_REG_IMMEDIATE(r3,init_thread_union)
-
-        /* set up the stack */
-        addi    r1,r3,THREAD_SIZE
-        li      r0,0
-        stdu    r0,-STACK_FRAME_OVERHEAD(r1)
-
-        /* Load the TOC */
+        /* Load the TOC (virtual address) */
         ld      r2,PACATOC(r13)
-        std     r1,PACAKSAVE(r13)
 
         bl      .setup_system