Merge commit 'paulus-perf/master' into next

7 files changed, 588 insertions, 16 deletions

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index eb17da781128..2a5da069714e 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -104,8 +104,8 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
         else
                 pte_update(ptep, ~_PAGE_HASHPTE, pte_val(pte));
 
-#elif defined(CONFIG_PPC32) && defined(CONFIG_PTE_64BIT) && defined(CONFIG_SMP)
-        /* Second case is 32-bit with 64-bit PTE in SMP mode. In this case, we
+#elif defined(CONFIG_PPC32) && defined(CONFIG_PTE_64BIT)
+        /* Second case is 32-bit with 64-bit PTE.  In this case, we
          * can just store as long as we do the two halves in the right order
          * with a barrier in between. This is possible because we take care,
          * in the hash code, to pre-invalidate if the PTE was already hashed,
@@ -140,7 +140,7 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 
 #else
         /* Anything else just stores the PTE normally. That covers all 64-bit
-         * cases, and 32-bit non-hash with 64-bit PTEs in UP mode
+         * cases, and 32-bit non-hash with 32-bit PTEs.
          */
         *ptep = pte;
 #endif
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 720e8c3b8e94..7c83edbc2155 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -97,7 +97,7 @@ obj64-$(CONFIG_AUDIT)		+= compat_audit.o
 
 obj-$(CONFIG_DYNAMIC_FTRACE)    += ftrace.o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER)     += ftrace.o
-obj-$(CONFIG_PPC_PERF_CTRS)     += perf_counter.o
+obj-$(CONFIG_PPC_PERF_CTRS)     += perf_counter.o perf_callchain.o
 obj64-$(CONFIG_PPC_PERF_CTRS)   += power4-pmu.o ppc970-pmu.o power5-pmu.o \
                                    power5+-pmu.o power6-pmu.o power7-pmu.o
 obj32-$(CONFIG_PPC_PERF_CTRS)   += mpc7450-pmu.o
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index b9e010d0fc91..f0df285f0f87 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -69,6 +69,8 @@ int main(void)
         DEFINE(MMCONTEXTID, offsetof(struct mm_struct, context.id));
 #ifdef CONFIG_PPC64
         DEFINE(AUDITCONTEXT, offsetof(struct task_struct, audit_context));
+        DEFINE(SIGSEGV, SIGSEGV);
+        DEFINE(NMI_MASK, NMI_MASK);
 #else
         DEFINE(THREAD_INFO, offsetof(struct task_struct, stack));
 #endif /* CONFIG_PPC64 */
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 50f2ad36ed09..1808876edcc9 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -731,6 +731,11 @@ BEGIN_FTR_SECTION
         bne-    do_ste_alloc            /* If so handle it */
 END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
 
+        clrrdi  r11,r1,THREAD_SHIFT
+        lwz     r0,TI_PREEMPT(r11)      /* If we're in an "NMI" */
+        andis.  r0,r0,NMI_MASK@h        /* (i.e. an irq when soft-disabled) */
+        bne     77f                     /* then don't call hash_page now */
+
         /*
          * On iSeries, we soft-disable interrupts here, then
          * hard-enable interrupts so that the hash_page code can spin on
@@ -835,6 +840,20 @@ handle_page_fault:
         bl      .low_hash_fault
         b       .ret_from_except
 
+/*
+ * We come here as a result of a DSI at a point where we don't want
+ * to call hash_page, such as when we are accessing memory (possibly
+ * user memory) inside a PMU interrupt that occurred while interrupts
+ * were soft-disabled.  We want to invoke the exception handler for
+ * the access, or panic if there isn't a handler.
+ */
+77:     bl      .save_nvgprs
+        mr      r4,r3
+        addi    r3,r1,STACK_FRAME_OVERHEAD
+        li      r5,SIGSEGV
+        bl      .bad_page_fault
+        b       .ret_from_except
+
         /* here we have a segment miss */
 do_ste_alloc:
         bl      .ste_allocate           /* try to insert stab entry */
diff --git a/arch/powerpc/kernel/perf_callchain.c b/arch/powerpc/kernel/perf_callchain.c
new file mode 100644
index 000000000000..f74b62c67511
--- /dev/null
+++ b/arch/powerpc/kernel/perf_callchain.c
@@ -0,0 +1,527 @@
+/*
+ * Performance counter callchain support - powerpc architecture code
+ *
+ * Copyright © 2009 Paul Mackerras, IBM Corporation.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/perf_counter.h>
+#include <linux/percpu.h>
+#include <linux/uaccess.h>
+#include <linux/mm.h>
+#include <asm/ptrace.h>
+#include <asm/pgtable.h>
+#include <asm/sigcontext.h>
+#include <asm/ucontext.h>
+#include <asm/vdso.h>
+#ifdef CONFIG_PPC64
+#include "ppc32.h"
+#endif
+
+/*
+ * Store another value in a callchain_entry.
+ */
+static inline void callchain_store(struct perf_callchain_entry *entry, u64 ip)
+{
+        unsigned int nr = entry->nr;
+
+        if (nr < PERF_MAX_STACK_DEPTH) {
+                entry->ip[nr] = ip;
+                entry->nr = nr + 1;
+        }
+}
+
+/*
+ * Is sp valid as the address of the next kernel stack frame after prev_sp?
+ * The next frame may be in a different stack area but should not go
+ * back down in the same stack area.
+ */
+static int valid_next_sp(unsigned long sp, unsigned long prev_sp)
+{
+        if (sp & 0xf)
+                return 0;               /* must be 16-byte aligned */
+        if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
+                return 0;
+        if (sp >= prev_sp + STACK_FRAME_OVERHEAD)
+                return 1;
+        /*
+         * sp could decrease when we jump off an interrupt stack
+         * back to the regular process stack.
+         */
+        if ((sp & ~(THREAD_SIZE - 1)) != (prev_sp & ~(THREAD_SIZE - 1)))
+                return 1;
+        return 0;
+}
+
+static void perf_callchain_kernel(struct pt_regs *regs,
+                                  struct perf_callchain_entry *entry)
+{
+        unsigned long sp, next_sp;
+        unsigned long next_ip;
+        unsigned long lr;
+        long level = 0;
+        unsigned long *fp;
+
+        lr = regs->link;
+        sp = regs->gpr[1];
+        callchain_store(entry, PERF_CONTEXT_KERNEL);
+        callchain_store(entry, regs->nip);
+
+        if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
+                return;
+
+        for (;;) {
+                fp = (unsigned long *) sp;
+                next_sp = fp[0];
+
+                if (next_sp == sp + STACK_INT_FRAME_SIZE &&
+                    fp[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
+                        /*
+                         * This looks like an interrupt frame for an
+                         * interrupt that occurred in the kernel
+                         */
+                        regs = (struct pt_regs *)(sp + STACK_FRAME_OVERHEAD);
+                        next_ip = regs->nip;
+                        lr = regs->link;
+                        level = 0;
+                        callchain_store(entry, PERF_CONTEXT_KERNEL);
+
+                } else {
+                        if (level == 0)
+                                next_ip = lr;
+                        else
+                                next_ip = fp[STACK_FRAME_LR_SAVE];
+
+                        /*
+                         * We can't tell which of the first two addresses
+                         * we get are valid, but we can filter out the
+                         * obviously bogus ones here.  We replace them
+                         * with 0 rather than removing them entirely so
+                         * that userspace can tell which is which.
+                         */
+                        if ((level == 1 && next_ip == lr) ||
+                            (level <= 1 && !kernel_text_address(next_ip)))
+                                next_ip = 0;
+
+                        ++level;
+                }
+
+                callchain_store(entry, next_ip);
+                if (!valid_next_sp(next_sp, sp))
+                        return;
+                sp = next_sp;
+        }
+}
+
+#ifdef CONFIG_PPC64
+
+#ifdef CONFIG_HUGETLB_PAGE
+#define is_huge_psize(pagesize) (HPAGE_SHIFT && mmu_huge_psizes[pagesize])
+#else
+#define is_huge_psize(pagesize) 0
+#endif
+
+/*
+ * On 64-bit we don't want to invoke hash_page on user addresses from
+ * interrupt context, so if the access faults, we read the page tables
+ * to find which page (if any) is mapped and access it directly.
+ */
+static int read_user_stack_slow(void __user *ptr, void *ret, int nb)
+{
+        pgd_t *pgdir;
+        pte_t *ptep, pte;
+        int pagesize;
+        unsigned long addr = (unsigned long) ptr;
+        unsigned long offset;
+        unsigned long pfn;
+        void *kaddr;
+
+        pgdir = current->mm->pgd;
+        if (!pgdir)
+                return -EFAULT;
+
+        pagesize = get_slice_psize(current->mm, addr);
+
+        /* align address to page boundary */
+        offset = addr & ((1ul << mmu_psize_defs[pagesize].shift) - 1);
+        addr -= offset;
+
+        if (is_huge_psize(pagesize))
+                ptep = huge_pte_offset(current->mm, addr);
+        else
+                ptep = find_linux_pte(pgdir, addr);
+
+        if (ptep == NULL)
+                return -EFAULT;
+        pte = *ptep;
+        if (!pte_present(pte) || !(pte_val(pte) & _PAGE_USER))
+                return -EFAULT;
+        pfn = pte_pfn(pte);
+        if (!page_is_ram(pfn))
+                return -EFAULT;
+
+        /* no highmem to worry about here */
+        kaddr = pfn_to_kaddr(pfn);
+        memcpy(ret, kaddr + offset, nb);
+        return 0;
+}
+
+static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
+{
+        if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
+            ((unsigned long)ptr & 7))
+                return -EFAULT;
+
+        if (!__get_user_inatomic(*ret, ptr))
+                return 0;
+
+        return read_user_stack_slow(ptr, ret, 8);
+}
+
+static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
+{
+        if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
+            ((unsigned long)ptr & 3))
+                return -EFAULT;
+
+        if (!__get_user_inatomic(*ret, ptr))
+                return 0;
+
+        return read_user_stack_slow(ptr, ret, 4);
+}
+
+static inline int valid_user_sp(unsigned long sp, int is_64)
+{
+        if (!sp || (sp & 7) || sp > (is_64 ? TASK_SIZE : 0x100000000UL) - 32)
+                return 0;
+        return 1;
+}
+
+/*
+ * 64-bit user processes use the same stack frame for RT and non-RT signals.
+ */
+struct signal_frame_64 {
+        char            dummy[__SIGNAL_FRAMESIZE];
+        struct ucontext uc;
+        unsigned long   unused[2];
+        unsigned int    tramp[6];
+        struct siginfo  *pinfo;
+        void            *puc;
+        struct siginfo  info;
+        char            abigap[288];
+};
+
+static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
+{
+        if (nip == fp + offsetof(struct signal_frame_64, tramp))
+                return 1;
+        if (vdso64_rt_sigtramp && current->mm->context.vdso_base &&
+            nip == current->mm->context.vdso_base + vdso64_rt_sigtramp)
+                return 1;
+        return 0;
+}
+
+/*
+ * Do some sanity checking on the signal frame pointed to by sp.
+ * We check the pinfo and puc pointers in the frame.
+ */
+static int sane_signal_64_frame(unsigned long sp)
+{
+        struct signal_frame_64 __user *sf;
+        unsigned long pinfo, puc;
+
+        sf = (struct signal_frame_64 __user *) sp;
+        if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
+            read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
+                return 0;
+        return pinfo == (unsigned long) &sf->info &&
+                puc == (unsigned long) &sf->uc;
+}
+
+static void perf_callchain_user_64(struct pt_regs *regs,
+                                   struct perf_callchain_entry *entry)
+{
+        unsigned long sp, next_sp;
+        unsigned long next_ip;
+        unsigned long lr;
+        long level = 0;
+        struct signal_frame_64 __user *sigframe;
+        unsigned long __user *fp, *uregs;
+
+        next_ip = regs->nip;
+        lr = regs->link;
+        sp = regs->gpr[1];
+        callchain_store(entry, PERF_CONTEXT_USER);
+        callchain_store(entry, next_ip);
+
+        for (;;) {
+                fp = (unsigned long __user *) sp;
+                if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
+                        return;
+                if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
+                        return;
+
+                /*
+                 * Note: the next_sp - sp >= signal frame size check
+                 * is true when next_sp < sp, which can happen when
+                 * transitioning from an alternate signal stack to the
+                 * normal stack.
+                 */
+                if (next_sp - sp >= sizeof(struct signal_frame_64) &&
+                    (is_sigreturn_64_address(next_ip, sp) ||
+                     (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
+                    sane_signal_64_frame(sp)) {
+                        /*
+                         * This looks like an signal frame
+                         */
+                        sigframe = (struct signal_frame_64 __user *) sp;
+                        uregs = sigframe->uc.uc_mcontext.gp_regs;
+                        if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
+                            read_user_stack_64(&uregs[PT_LNK], &lr) ||
+                            read_user_stack_64(&uregs[PT_R1], &sp))
+                                return;
+                        level = 0;
+                        callchain_store(entry, PERF_CONTEXT_USER);
+                        callchain_store(entry, next_ip);
+                        continue;
+                }
+
+                if (level == 0)
+                        next_ip = lr;
+                callchain_store(entry, next_ip);
+                ++level;
+                sp = next_sp;
+        }
+}
+
+static inline int current_is_64bit(void)
+{
+        /*
+         * We can't use test_thread_flag() here because we may be on an
+         * interrupt stack, and the thread flags don't get copied over
+         * from the thread_info on the main stack to the interrupt stack.
+         */
+        return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
+}
+
+#else  /* CONFIG_PPC64 */
+/*
+ * On 32-bit we just access the address and let hash_page create a
+ * HPTE if necessary, so there is no need to fall back to reading
+ * the page tables.  Since this is called at interrupt level,
+ * do_page_fault() won't treat a DSI as a page fault.
+ */
+static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
+{
+        if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
+            ((unsigned long)ptr & 3))
+                return -EFAULT;
+
+        return __get_user_inatomic(*ret, ptr);
+}
+
+static inline void perf_callchain_user_64(struct pt_regs *regs,
+                                          struct perf_callchain_entry *entry)
+{
+}
+
+static inline int current_is_64bit(void)
+{
+        return 0;
+}
+
+static inline int valid_user_sp(unsigned long sp, int is_64)
+{
+        if (!sp || (sp & 7) || sp > TASK_SIZE - 32)
+                return 0;
+        return 1;
+}
+
+#define __SIGNAL_FRAMESIZE32    __SIGNAL_FRAMESIZE
+#define sigcontext32            sigcontext
+#define mcontext32              mcontext
+#define ucontext32              ucontext
+#define compat_siginfo_t        struct siginfo
+
+#endif /* CONFIG_PPC64 */
+
+/*
+ * Layout for non-RT signal frames
+ */
+struct signal_frame_32 {
+        char                    dummy[__SIGNAL_FRAMESIZE32];
+        struct sigcontext32     sctx;
+        struct mcontext32       mctx;
+        int                     abigap[56];
+};
+
+/*
+ * Layout for RT signal frames
+ */
+struct rt_signal_frame_32 {
+        char                    dummy[__SIGNAL_FRAMESIZE32 + 16];
+        compat_siginfo_t        info;
+        struct ucontext32       uc;
+        int                     abigap[56];
+};
+
+static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
+{
+        if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
+                return 1;
+        if (vdso32_sigtramp && current->mm->context.vdso_base &&
+            nip == current->mm->context.vdso_base + vdso32_sigtramp)
+                return 1;
+        return 0;
+}
+
+static int is_rt_sigreturn_32_address(unsigned int nip, unsigned int fp)
+{
+        if (nip == fp + offsetof(struct rt_signal_frame_32,
+                                 uc.uc_mcontext.mc_pad))
+                return 1;
+        if (vdso32_rt_sigtramp && current->mm->context.vdso_base &&
+            nip == current->mm->context.vdso_base + vdso32_rt_sigtramp)
+                return 1;
+        return 0;
+}
+
+static int sane_signal_32_frame(unsigned int sp)
+{
+        struct signal_frame_32 __user *sf;
+        unsigned int regs;
+
+        sf = (struct signal_frame_32 __user *) (unsigned long) sp;
+        if (read_user_stack_32((unsigned int __user *) &sf->sctx.regs, &regs))
+                return 0;
+        return regs == (unsigned long) &sf->mctx;
+}
+
+static int sane_rt_signal_32_frame(unsigned int sp)
+{
+        struct rt_signal_frame_32 __user *sf;
+        unsigned int regs;
+
+        sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
+        if (read_user_stack_32((unsigned int __user *) &sf->uc.uc_regs, &regs))
+                return 0;
+        return regs == (unsigned long) &sf->uc.uc_mcontext;
+}
+
+static unsigned int __user *signal_frame_32_regs(unsigned int sp,
+                                unsigned int next_sp, unsigned int next_ip)
+{
+        struct mcontext32 __user *mctx = NULL;
+        struct signal_frame_32 __user *sf;
+        struct rt_signal_frame_32 __user *rt_sf;
+
+        /*
+         * Note: the next_sp - sp >= signal frame size check
+         * is true when next_sp < sp, for example, when
+         * transitioning from an alternate signal stack to the
+         * normal stack.
+         */
+        if (next_sp - sp >= sizeof(struct signal_frame_32) &&
+            is_sigreturn_32_address(next_ip, sp) &&
+            sane_signal_32_frame(sp)) {
+                sf = (struct signal_frame_32 __user *) (unsigned long) sp;
+                mctx = &sf->mctx;
+        }
+
+        if (!mctx && next_sp - sp >= sizeof(struct rt_signal_frame_32) &&
+            is_rt_sigreturn_32_address(next_ip, sp) &&
+            sane_rt_signal_32_frame(sp)) {
+                rt_sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
+                mctx = &rt_sf->uc.uc_mcontext;
+        }
+
+        if (!mctx)
+                return NULL;
+        return mctx->mc_gregs;
+}
+
+static void perf_callchain_user_32(struct pt_regs *regs,
+                                   struct perf_callchain_entry *entry)
+{
+        unsigned int sp, next_sp;
+        unsigned int next_ip;
+        unsigned int lr;
+        long level = 0;
+        unsigned int __user *fp, *uregs;
+
+        next_ip = regs->nip;
+        lr = regs->link;
+        sp = regs->gpr[1];
+        callchain_store(entry, PERF_CONTEXT_USER);
+        callchain_store(entry, next_ip);
+
+        while (entry->nr < PERF_MAX_STACK_DEPTH) {
+                fp = (unsigned int __user *) (unsigned long) sp;
+                if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
+                        return;
+                if (level > 0 && read_user_stack_32(&fp[1], &next_ip))
+                        return;
+
+                uregs = signal_frame_32_regs(sp, next_sp, next_ip);
+                if (!uregs && level <= 1)
+                        uregs = signal_frame_32_regs(sp, next_sp, lr);
+                if (uregs) {
+                        /*
+                         * This looks like an signal frame, so restart
+                         * the stack trace with the values in it.
+                         */
+                        if (read_user_stack_32(&uregs[PT_NIP], &next_ip) ||
+                            read_user_stack_32(&uregs[PT_LNK], &lr) ||
+                            read_user_stack_32(&uregs[PT_R1], &sp))
+                                return;
+                        level = 0;
+                        callchain_store(entry, PERF_CONTEXT_USER);
+                        callchain_store(entry, next_ip);
+                        continue;
+                }
+
+                if (level == 0)
+                        next_ip = lr;
+                callchain_store(entry, next_ip);
+                ++level;
+                sp = next_sp;
+        }
+}
+
+/*
+ * Since we can't get PMU interrupts inside a PMU interrupt handler,
+ * we don't need separate irq and nmi entries here.
+ */
+static DEFINE_PER_CPU(struct perf_callchain_entry, callchain);
+
+struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
+{
+        struct perf_callchain_entry *entry = &__get_cpu_var(callchain);
+
+        entry->nr = 0;
+
+        if (current->pid == 0)          /* idle task? */
+                return entry;
+
+        if (!user_mode(regs)) {
+                perf_callchain_kernel(regs, entry);
+                if (current->mm)
+                        regs = task_pt_regs(current);
+                else
+                        regs = NULL;
+        }
+
+        if (regs) {
+                if (current_is_64bit())
+                        perf_callchain_user_64(regs, entry);
+                else
+                        perf_callchain_user_32(regs, entry);
+        }
+
+        return entry;
+}
diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index 6bc8b4aeba5c..07961c5c169e 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c
@@ -92,15 +92,13 @@ static inline void create_shadowed_slbe(unsigned long ea, int ssize,
                      : "memory" );
 }
 
-void slb_flush_and_rebolt(void)
+static void __slb_flush_and_rebolt(void)
 {
         /* If you change this make sure you change SLB_NUM_BOLTED
          * appropriately too. */
         unsigned long linear_llp, vmalloc_llp, lflags, vflags;
         unsigned long ksp_esid_data, ksp_vsid_data;
 
-        WARN_ON(!irqs_disabled());
-
         linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
         vmalloc_llp = mmu_psize_defs[mmu_vmalloc_psize].sllp;
         lflags = SLB_VSID_KERNEL | linear_llp;
@@ -117,12 +115,6 @@ void slb_flush_and_rebolt(void)
                 ksp_vsid_data = get_slb_shadow()->save_area[2].vsid;
         }
 
-        /*
-         * We can't take a PMU exception in the following code, so hard
-         * disable interrupts.
-         */
-        hard_irq_disable();
-
         /* We need to do this all in asm, so we're sure we don't touch
          * the stack between the slbia and rebolting it. */
         asm volatile("isync\n"
@@ -139,6 +131,21 @@ void slb_flush_and_rebolt(void)
                      : "memory");
 }
 
+void slb_flush_and_rebolt(void)
+{
+
+        WARN_ON(!irqs_disabled());
+
+        /*
+         * We can't take a PMU exception in the following code, so hard
+         * disable interrupts.
+         */
+        hard_irq_disable();
+
+        __slb_flush_and_rebolt();
+        get_paca()->slb_cache_ptr = 0;
+}
+
 void slb_vmalloc_update(void)
 {
         unsigned long vflags;
@@ -180,12 +187,20 @@ static inline int esids_match(unsigned long addr1, unsigned long addr2)
 /* Flush all user entries from the segment table of the current processor. */
 void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
 {
-        unsigned long offset = get_paca()->slb_cache_ptr;
+        unsigned long offset;
         unsigned long slbie_data = 0;
         unsigned long pc = KSTK_EIP(tsk);
         unsigned long stack = KSTK_ESP(tsk);
         unsigned long exec_base;
 
+        /*
+         * We need interrupts hard-disabled here, not just soft-disabled,
+         * so that a PMU interrupt can't occur, which might try to access
+         * user memory (to get a stack trace) and possible cause an SLB miss
+         * which would update the slb_cache/slb_cache_ptr fields in the PACA.
+         */
+        hard_irq_disable();
+        offset = get_paca()->slb_cache_ptr;
         if (!cpu_has_feature(CPU_FTR_NO_SLBIE_B) &&
             offset <= SLB_CACHE_ENTRIES) {
                 int i;
@@ -200,7 +215,7 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
                 }
                 asm volatile("isync" : : : "memory");
         } else {
-                slb_flush_and_rebolt();
+                __slb_flush_and_rebolt();
         }
 
         /* Workaround POWER5 < DD2.1 issue */
diff --git a/arch/powerpc/mm/stab.c b/arch/powerpc/mm/stab.c
index 98cd1dc2ae75..ab5fb48b3e90 100644
--- a/arch/powerpc/mm/stab.c
+++ b/arch/powerpc/mm/stab.c
@@ -164,7 +164,7 @@ void switch_stab(struct task_struct *tsk, struct mm_struct *mm)
 {
         struct stab_entry *stab = (struct stab_entry *) get_paca()->stab_addr;
         struct stab_entry *ste;
-        unsigned long offset = __get_cpu_var(stab_cache_ptr);
+        unsigned long offset;
         unsigned long pc = KSTK_EIP(tsk);
         unsigned long stack = KSTK_ESP(tsk);
         unsigned long unmapped_base;
@@ -172,6 +172,15 @@ void switch_stab(struct task_struct *tsk, struct mm_struct *mm)
         /* Force previous translations to complete. DRENG */
         asm volatile("isync" : : : "memory");
 
+        /*
+         * We need interrupts hard-disabled here, not just soft-disabled,
+         * so that a PMU interrupt can't occur, which might try to access
+         * user memory (to get a stack trace) and possible cause an STAB miss
+         * which would update the stab_cache/stab_cache_ptr per-cpu variables.
+         */
+        hard_irq_disable();
+
+        offset = __get_cpu_var(stab_cache_ptr);
         if (offset <= NR_STAB_CACHE_ENTRIES) {
                 int i;