powerpc/mm: Mark get_slice_psize() & slice_addr_is_low() as notrace

These slice routines are called from the SLB miss handler, which can
lead to warnings from the IRQ code, because we have not reconciled the
IRQ state properly:

  WARNING: CPU: 72 PID: 30150 at arch/powerpc/kernel/irq.c:258 arch_local_irq_restore.part.0+0xcc/0x100
  Modules linked in:
  CPU: 72 PID: 30150 Comm: ftracetest Not tainted 5.5.0-rc2-gcc9x-g7e0165b2 #1
  NIP:  c00000000001d83c LR: c00000000029ab90 CTR: c00000000026cf90
  REGS: c0000007eee3b960 TRAP: 0700   Not tainted  (5.5.0-rc2-gcc9x-g7e0165b2)
  MSR:  8000000000021033 <SF,ME,IR,DR,RI,LE>  CR: 22242844  XER: 20000000
  CFAR: c00000000001d780 IRQMASK: 0
  ...
  NIP arch_local_irq_restore.part.0+0xcc/0x100
  LR  trace_graph_entry+0x270/0x340
  Call Trace:
    trace_graph_entry+0x254/0x340 (unreliable)
    function_graph_enter+0xe4/0x1a0
    prepare_ftrace_return+0xa0/0x130
    ftrace_graph_caller+0x44/0x94	# (get_slice_psize())
    slb_allocate_user+0x7c/0x100
    do_slb_fault+0xf8/0x300
    instruction_access_slb_common+0x140/0x180

Fixes: 48e7b769 ("powerpc/64s/hash: Convert SLB miss handlers to C")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191221121337.4894-1-mpe@ellerman.id.au

arch/powerpc/mm/slice.c

@@ -50,7 +50,7 @@ static void slice_print_mask(const char *label, const struct slice_mask *mask) {
 
 #endif
 
-static inline bool slice_addr_is_low(unsigned long addr)
+static inline notrace bool slice_addr_is_low(unsigned long addr)
 {
 	u64 tmp = (u64)addr;
 
@@ -659,7 +659,7 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 				       mm_ctx_user_psize(&current->mm->context), 1);
 }
 
-unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
+unsigned int notrace get_slice_psize(struct mm_struct *mm, unsigned long addr)
 {
 	unsigned char *psizes;
 	int index, mask_index;