1 files changed, 43 insertions, 26 deletions

diff --git a/kernel/arch/powerpc/mm/slb.c b/kernel/arch/powerpc/mm/slb.c
index 6e450ca66..515730e49 100644
--- a/kernel/arch/powerpc/mm/slb.c
+++ b/kernel/arch/powerpc/mm/slb.c
@@ -25,6 +25,11 @@
 #include <asm/udbg.h>
 #include <asm/code-patching.h>
 
+enum slb_index {
+	LINEAR_INDEX	= 0, /* Kernel linear map  (0xc000000000000000) */
+	VMALLOC_INDEX	= 1, /* Kernel virtual map (0xd000000000000000) */
+	KSTACK_INDEX	= 2, /* Kernel stack map */
+};
 
 extern void slb_allocate_realmode(unsigned long ea);
 extern void slb_allocate_user(unsigned long ea);
@@ -41,9 +46,9 @@ static void slb_allocate(unsigned long ea)
 	(((ssize) == MMU_SEGSIZE_256M)? ESID_MASK: ESID_MASK_1T)
 
 static inline unsigned long mk_esid_data(unsigned long ea, int ssize,
-					 unsigned long slot)
+					 enum slb_index index)
 {
-	return (ea & slb_esid_mask(ssize)) | SLB_ESID_V | slot;
+	return (ea & slb_esid_mask(ssize)) | SLB_ESID_V | index;
 }
 
 static inline unsigned long mk_vsid_data(unsigned long ea, int ssize,
@@ -55,39 +60,39 @@ static inline unsigned long mk_vsid_data(unsigned long ea, int ssize,
 
 static inline void slb_shadow_update(unsigned long ea, int ssize,
 				     unsigned long flags,
-				     unsigned long entry)
+				     enum slb_index index)
 {
+	struct slb_shadow *p = get_slb_shadow();
+
 	/*
 	 * Clear the ESID first so the entry is not valid while we are
 	 * updating it.  No write barriers are needed here, provided
 	 * we only update the current CPU's SLB shadow buffer.
 	 */
-	get_slb_shadow()->save_area[entry].esid = 0;
-	get_slb_shadow()->save_area[entry].vsid =
-				cpu_to_be64(mk_vsid_data(ea, ssize, flags));
-	get_slb_shadow()->save_area[entry].esid =
-				cpu_to_be64(mk_esid_data(ea, ssize, entry));
+	p->save_area[index].esid = 0;
+	p->save_area[index].vsid = cpu_to_be64(mk_vsid_data(ea, ssize, flags));
+	p->save_area[index].esid = cpu_to_be64(mk_esid_data(ea, ssize, index));
 }
 
-static inline void slb_shadow_clear(unsigned long entry)
+static inline void slb_shadow_clear(enum slb_index index)
 {
-	get_slb_shadow()->save_area[entry].esid = 0;
+	get_slb_shadow()->save_area[index].esid = 0;
 }
 
 static inline void create_shadowed_slbe(unsigned long ea, int ssize,
 					unsigned long flags,
-					unsigned long entry)
+					enum slb_index index)
 {
 	/*
 	 * Updating the shadow buffer before writing the SLB ensures
 	 * we don't get a stale entry here if we get preempted by PHYP
 	 * between these two statements.
 	 */
-	slb_shadow_update(ea, ssize, flags, entry);
+	slb_shadow_update(ea, ssize, flags, index);
 
 	asm volatile("slbmte  %0,%1" :
 		     : "r" (mk_vsid_data(ea, ssize, flags)),
-		       "r" (mk_esid_data(ea, ssize, entry))
+		       "r" (mk_esid_data(ea, ssize, index))
 		     : "memory" );
 }
 
@@ -103,16 +108,16 @@ static void __slb_flush_and_rebolt(void)
 	lflags = SLB_VSID_KERNEL | linear_llp;
 	vflags = SLB_VSID_KERNEL | vmalloc_llp;
 
-	ksp_esid_data = mk_esid_data(get_paca()->kstack, mmu_kernel_ssize, 2);
+	ksp_esid_data = mk_esid_data(get_paca()->kstack, mmu_kernel_ssize, KSTACK_INDEX);
 	if ((ksp_esid_data & ~0xfffffffUL) <= PAGE_OFFSET) {
 		ksp_esid_data &= ~SLB_ESID_V;
 		ksp_vsid_data = 0;
-		slb_shadow_clear(2);
+		slb_shadow_clear(KSTACK_INDEX);
 	} else {
 		/* Update stack entry; others don't change */
-		slb_shadow_update(get_paca()->kstack, mmu_kernel_ssize, lflags, 2);
+		slb_shadow_update(get_paca()->kstack, mmu_kernel_ssize, lflags, KSTACK_INDEX);
 		ksp_vsid_data =
-			be64_to_cpu(get_slb_shadow()->save_area[2].vsid);
+			be64_to_cpu(get_slb_shadow()->save_area[KSTACK_INDEX].vsid);
 	}
 
 	/* We need to do this all in asm, so we're sure we don't touch
@@ -151,7 +156,7 @@ void slb_vmalloc_update(void)
 	unsigned long vflags;
 
 	vflags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_vmalloc_psize].sllp;
-	slb_shadow_update(VMALLOC_START, mmu_kernel_ssize, vflags, 1);
+	slb_shadow_update(VMALLOC_START, mmu_kernel_ssize, vflags, VMALLOC_INDEX);
 	slb_flush_and_rebolt();
 }
 
@@ -249,11 +254,24 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
 static inline void patch_slb_encoding(unsigned int *insn_addr,
 				      unsigned int immed)
 {
-	int insn = (*insn_addr & 0xffff0000) | immed;
+
+	/*
+	 * This function patches either an li or a cmpldi instruction with
+	 * a new immediate value. This relies on the fact that both li
+	 * (which is actually addi) and cmpldi both take a 16-bit immediate
+	 * value, and it is situated in the same location in the instruction,
+	 * ie. bits 16-31 (Big endian bit order) or the lower 16 bits.
+	 * The signedness of the immediate operand differs between the two
+	 * instructions however this code is only ever patching a small value,
+	 * much less than 1 << 15, so we can get away with it.
+	 * To patch the value we read the existing instruction, clear the
+	 * immediate value, and or in our new value, then write the instruction
+	 * back.
+	 */
+	unsigned int insn = (*insn_addr & 0xffff0000) | immed;
 	patch_instruction(insn_addr, insn);
 }
 
-extern u32 slb_compare_rr_to_size[];
 extern u32 slb_miss_kernel_load_linear[];
 extern u32 slb_miss_kernel_load_io[];
 extern u32 slb_compare_rr_to_size[];
@@ -309,24 +327,23 @@ void slb_initialize(void)
 	lflags = SLB_VSID_KERNEL | linear_llp;
 	vflags = SLB_VSID_KERNEL | vmalloc_llp;
 
-	/* Invalidate the entire SLB (even slot 0) & all the ERATS */
+	/* Invalidate the entire SLB (even entry 0) & all the ERATS */
 	asm volatile("isync":::"memory");
 	asm volatile("slbmte  %0,%0"::"r" (0) : "memory");
 	asm volatile("isync; slbia; isync":::"memory");
-	create_shadowed_slbe(PAGE_OFFSET, mmu_kernel_ssize, lflags, 0);
-
-	create_shadowed_slbe(VMALLOC_START, mmu_kernel_ssize, vflags, 1);
+	create_shadowed_slbe(PAGE_OFFSET, mmu_kernel_ssize, lflags, LINEAR_INDEX);
+	create_shadowed_slbe(VMALLOC_START, mmu_kernel_ssize, vflags, VMALLOC_INDEX);
 
 	/* For the boot cpu, we're running on the stack in init_thread_union,
 	 * which is in the first segment of the linear mapping, and also
 	 * get_paca()->kstack hasn't been initialized yet.
 	 * For secondary cpus, we need to bolt the kernel stack entry now.
 	 */
-	slb_shadow_clear(2);
+	slb_shadow_clear(KSTACK_INDEX);
 	if (raw_smp_processor_id() != boot_cpuid &&
 	    (get_paca()->kstack & slb_esid_mask(mmu_kernel_ssize)) > PAGE_OFFSET)
 		create_shadowed_slbe(get_paca()->kstack,
-				     mmu_kernel_ssize, lflags, 2);
+				     mmu_kernel_ssize, lflags, KSTACK_INDEX);
 
 	asm volatile("isync":::"memory");
 }