powerpc/64s/hash: convert SLB miss handlers to C

This patch moves SLB miss handlers completely to C, using the standard exception handler macros to set up the stack and branch to C.

This can be done because the segment containing the kernel stack is always bolted, so accessing it with relocation on will not cause an SLB exception.

Arbitrary kernel memory may not be accessed when handling kernel space SLB misses, so care should be taken there. However user SLB misses can access any kernel memory, which can be used to move some fields out of the paca (in later patches).

User SLB misses could quite easily reconcile IRQs and set up a first class kernel environment and exit via ret_from_except, however that doesn't seem to be necessary at the moment, so we only do that if a bad fault is encountered.

[ Credit to Aneesh for bug fixes, error checks, and improvements to bad
address handling, etc. ]

Since RFC:
- Added MSR[RI] handling
- Fixed up a register loss bug exposed by irq tracing (Aneesh)
- Reject misses outside the defined kernel regions (Aneesh)
- Added several more sanity checks and error handling (Aneesh), we may look at consolidating these tests and tightenig up the code but for a first pass we decided it's better to check carefully.

Since v1:
- Fixed SLB cache corruption (Aneesh)
- Fixed untidy SLBE allocation "leak" in get_vsid error case
- Now survives some stress testing on real hardware

---
 arch/powerpc/include/asm/asm-prototypes.h |   2 +
 arch/powerpc/kernel/exceptions-64s.S      | 202 +++----------
 arch/powerpc/mm/Makefile                  |   2 +-
 arch/powerpc/mm/slb.c                     | 271 +++++++++--------
 arch/powerpc/mm/slb_low.S                 | 335 ----------------------
 5 files changed, 196 insertions(+), 616 deletions(-)
 delete mode 100644 arch/powerpc/mm/slb_low.S

index 1f4691ce4126..78ed3c3f879a 100644
@@ -78,6 +78,8 @@ void kernel_bad_stack(struct pt_regs *regs);
 void system_reset_exception(struct pt_regs *regs);
 void machine_check_exception(struct pt_regs *regs);
 void emulation_assist_interrupt(struct pt_regs *regs);
+long do_slb_fault(struct pt_regs *regs, unsigned long ea);
+void do_bad_slb_fault(struct pt_regs *regs, unsigned long ea, long err);
 
 /* signals, syscalls and interrupts */
 long sys_swapcontext(struct ucontext __user *old_ctx,

index cdf6a9960046..892d4e061d62 100644
@@ -15,7 +15,7 @@ obj-$(CONFIG_PPC_MMU_NOHASH)	+= mmu_context_nohash.o tlb_nohash.o \
 obj-$(CONFIG_PPC_BOOK3E)	+= tlb_low_$(BITS)e.o
 hash64-$(CONFIG_PPC_NATIVE)	:= hash_native_64.o
 obj-$(CONFIG_PPC_BOOK3E_64)   += pgtable-book3e.o
-obj-$(CONFIG_PPC_BOOK3S_64)	+= pgtable-hash64.o hash_utils_64.o slb_low.o slb.o $(hash64-y) mmu_context_book3s64.o pgtable-book3s64.o
+obj-$(CONFIG_PPC_BOOK3S_64)	+= pgtable-hash64.o hash_utils_64.o slb.o $(hash64-y) mmu_context_book3s64.o pgtable-book3s64.o
 obj-$(CONFIG_PPC_RADIX_MMU)	+= pgtable-radix.o tlb-radix.o
 obj-$(CONFIG_PPC_STD_MMU_32)	+= ppc_mmu_32.o hash_low_32.o mmu_context_hash32.o
 obj-$(CONFIG_PPC_STD_MMU)	+= tlb_hash$(BITS).o

2.17.0