[PATCH] powerpc: Fixups for kernel linked at 32 MB

There's a few places where we need to fix things up for the kernel to work
if it's linked at 32MB:

 - platforms/powermac/smp.c
   To start secondary cpus on pmac we patch the reset vector, which is fine.
   Except if we're above 32MB we don't have enough bits for an absolute branch,
   it needs to relative.
 - kernel/head_64.s
    - A few branches in the cpu hold code need to load the full target address
      and do a bctr.
    - after_prom_start needs to load PHYSICAL_START as the dest address, not 0.
    - The exception prolog needs to load the low word of the target adddress,
      not just the low halfword.
    - Fixup handling of the initial stab address.
 - kernel/setup_64.c
   smp_release_cpus() needs to write 1 to the spinloop flag near 0, not 32 MB.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 24 insertions, 6 deletions

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index f4194f5fd2e5..0763dd632b78 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -154,11 +154,15 @@ _GLOBAL(__secondary_hold)
         bne     100b
 
 #ifdef CONFIG_HMT
-        b       .hmt_init
+        LOADADDR(r4, .hmt_init)
+        mtctr   r4
+        bctr
 #else
 #ifdef CONFIG_SMP
+        LOADADDR(r4, .pSeries_secondary_smp_init)
+        mtctr   r4
         mr      r3,r24
-        b       .pSeries_secondary_smp_init
+        bctr
 #else
         BUG_OPCODE
 #endif
@@ -200,6 +204,20 @@ exception_marker:
 #define EX_R3           64
 #define EX_LR           72
 
+/*
+ * We're short on space and time in the exception prolog, so we can't use
+ * the normal LOADADDR macro. Normally we just need the low halfword of the
+ * address, but for Kdump we need the whole low word.
+ */
+#ifdef CONFIG_CRASH_DUMP
+#define LOAD_HANDLER(reg, label)                                        \
+        oris    reg,reg,(label)@h;      /* virt addr of handler ... */  \
+        ori     reg,reg,(label)@l;      /* .. and the rest */
+#else
+#define LOAD_HANDLER(reg, label)                                        \
+        ori     reg,reg,(label)@l;      /* virt addr of handler ... */
+#endif
+
 #define EXCEPTION_PROLOG_PSERIES(area, label)                           \
         mfspr   r13,SPRN_SPRG3;         /* get paca address into r13 */ \
         std     r9,area+EX_R9(r13);     /* save r9 - r12 */             \
@@ -212,7 +230,7 @@ exception_marker:
         clrrdi  r12,r13,32;             /* get high part of &label */   \
         mfmsr   r10;                                                    \
         mfspr   r11,SPRN_SRR0;          /* save SRR0 */                 \
-        ori     r12,r12,(label)@l;      /* virt addr of handler */      \
+        LOAD_HANDLER(r12,label)                                         \
         ori     r10,r10,MSR_IR|MSR_DR|MSR_RI;                           \
         mtspr   SPRN_SRR0,r12;                                          \
         mfspr   r12,SPRN_SRR1;          /* and SRR1 */                  \
@@ -1348,7 +1366,7 @@ _GLOBAL(do_stab_bolted)
  * fixed address (the linker can't compute (u64)&initial_stab >>
  * PAGE_SHIFT).
  */
-        . = STAB0_PHYS_ADDR     /* 0x6000 */
+        . = STAB0_OFFSET        /* 0x6000 */
         .globl initial_stab
 initial_stab:
         .space  4096
@@ -1553,7 +1571,7 @@ _STATIC(__boot_from_prom)
 _STATIC(__after_prom_start)
 
 /*
- * We need to run with __start at physical address 0.
+ * We need to run with __start 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
@@ -1568,7 +1586,7 @@ _STATIC(__after_prom_start)
         mr      r26,r3
         SET_REG_TO_CONST(r27,KERNELBASE)
 
-        li      r3,0                    /* target addr */
+        LOADADDR(r3, PHYSICAL_START)    /* target addr */
 
         // XXX FIXME: Use phys returned by OF (r30)
         add     r4,r27,r26              /* source addr                   */