12 files changed, 243 insertions, 160 deletions

diff --git a/arch/tile/kernel/entry.S b/arch/tile/kernel/entry.S
index 431e9ae60488..ec91568df880 100644
--- a/arch/tile/kernel/entry.S
+++ b/arch/tile/kernel/entry.S
@@ -85,6 +85,7 @@ STD_ENTRY(cpu_idle_on_new_stack)
 /* Loop forever on a nap during SMP boot. */
 STD_ENTRY(smp_nap)
         nap
+        nop       /* avoid provoking the icache prefetch with a jump */
         j smp_nap /* we are not architecturally guaranteed not to exit nap */
         jrp lr    /* clue in the backtracer */
         STD_ENDPROC(smp_nap)
@@ -105,5 +106,6 @@ STD_ENTRY(_cpu_idle)
         .global _cpu_idle_nap
 _cpu_idle_nap:
         nap
+        nop       /* avoid provoking the icache prefetch with a jump */
         jrp lr
         STD_ENDPROC(_cpu_idle)
diff --git a/arch/tile/kernel/intvec_32.S b/arch/tile/kernel/intvec_32.S
index aecc8ed5f39b..5d56a1ef5ba5 100644
--- a/arch/tile/kernel/intvec_32.S
+++ b/arch/tile/kernel/intvec_32.S
@@ -799,6 +799,10 @@ handle_interrupt:
  * This routine takes a boolean in r30 indicating if this is an NMI.
  * If so, we also expect a boolean in r31 indicating whether to
  * re-enable the oprofile interrupts.
+ *
+ * Note that .Lresume_userspace is jumped to directly in several
+ * places, and we need to make sure r30 is set correctly in those
+ * callers as well.
  */
 STD_ENTRY(interrupt_return)
         /* If we're resuming to kernel space, don't check thread flags. */
@@ -1237,7 +1241,10 @@ handle_syscall:
         bzt     r30, 1f
         jal     do_syscall_trace
         FEEDBACK_REENTER(handle_syscall)
-1:      j       .Lresume_userspace   /* jump into middle of interrupt_return */
+1:      {
+         movei  r30, 0               /* not an NMI */
+         j      .Lresume_userspace   /* jump into middle of interrupt_return */
+        }
 
 .Linvalid_syscall:
         /* Report an invalid syscall back to the user program */
@@ -1246,7 +1253,10 @@ handle_syscall:
          movei  r28, -ENOSYS
         }
         sw      r29, r28
-        j       .Lresume_userspace   /* jump into middle of interrupt_return */
+        {
+         movei  r30, 0               /* not an NMI */
+         j      .Lresume_userspace   /* jump into middle of interrupt_return */
+        }
         STD_ENDPROC(handle_syscall)
 
         /* Return the address for oprofile to suppress in backtraces. */
@@ -1262,7 +1272,10 @@ STD_ENTRY(ret_from_fork)
         jal     sim_notify_fork
         jal     schedule_tail
         FEEDBACK_REENTER(ret_from_fork)
-        j       .Lresume_userspace   /* jump into middle of interrupt_return */
+        {
+         movei  r30, 0               /* not an NMI */
+         j      .Lresume_userspace   /* jump into middle of interrupt_return */
+        }
         STD_ENDPROC(ret_from_fork)
 
         /*
@@ -1376,7 +1389,10 @@ handle_ill:
 
         jal     send_sigtrap    /* issue a SIGTRAP */
         FEEDBACK_REENTER(handle_ill)
-        j       .Lresume_userspace   /* jump into middle of interrupt_return */
+        {
+         movei  r30, 0               /* not an NMI */
+         j      .Lresume_userspace   /* jump into middle of interrupt_return */
+        }
 
 .Ldispatch_normal_ill:
         {
diff --git a/arch/tile/kernel/intvec_64.S b/arch/tile/kernel/intvec_64.S
index 79c93e10ba27..49d9d6621682 100644
--- a/arch/tile/kernel/intvec_64.S
+++ b/arch/tile/kernel/intvec_64.S
@@ -22,6 +22,7 @@
 #include <asm/irqflags.h>
 #include <asm/asm-offsets.h>
 #include <asm/types.h>
+#include <asm/signal.h>
 #include <hv/hypervisor.h>
 #include <arch/abi.h>
 #include <arch/interrupts.h>
@@ -605,6 +606,10 @@ handle_interrupt:
  * This routine takes a boolean in r30 indicating if this is an NMI.
  * If so, we also expect a boolean in r31 indicating whether to
  * re-enable the oprofile interrupts.
+ *
+ * Note that .Lresume_userspace is jumped to directly in several
+ * places, and we need to make sure r30 is set correctly in those
+ * callers as well.
  */
 STD_ENTRY(interrupt_return)
         /* If we're resuming to kernel space, don't check thread flags. */
@@ -1039,11 +1044,28 @@ handle_syscall:
 
         /* Do syscall trace again, if requested. */
         ld      r30, r31
-        andi    r30, r30, _TIF_SYSCALL_TRACE
-        beqzt   r30, 1f
+        andi    r0, r30, _TIF_SYSCALL_TRACE
+        {
+         andi    r0, r30, _TIF_SINGLESTEP
+         beqzt   r0, 1f
+        }
         jal     do_syscall_trace
         FEEDBACK_REENTER(handle_syscall)
-1:      j       .Lresume_userspace   /* jump into middle of interrupt_return */
+        andi    r0, r30, _TIF_SINGLESTEP
+
+1:      beqzt   r0, 2f
+
+        /* Single stepping -- notify ptrace. */
+        {
+         movei   r0, SIGTRAP
+         jal     ptrace_notify
+        }
+        FEEDBACK_REENTER(handle_syscall)
+
+2:      {
+         movei  r30, 0               /* not an NMI */
+         j      .Lresume_userspace   /* jump into middle of interrupt_return */
+        }
 
 .Lcompat_syscall:
         /*
@@ -1077,7 +1099,10 @@ handle_syscall:
          movei  r28, -ENOSYS
         }
         st      r29, r28
-        j       .Lresume_userspace   /* jump into middle of interrupt_return */
+        {
+         movei  r30, 0               /* not an NMI */
+         j      .Lresume_userspace   /* jump into middle of interrupt_return */
+        }
         STD_ENDPROC(handle_syscall)
 
         /* Return the address for oprofile to suppress in backtraces. */
@@ -1093,7 +1118,10 @@ STD_ENTRY(ret_from_fork)
         jal     sim_notify_fork
         jal     schedule_tail
         FEEDBACK_REENTER(ret_from_fork)
-        j       .Lresume_userspace
+        {
+         movei  r30, 0               /* not an NMI */
+         j      .Lresume_userspace   /* jump into middle of interrupt_return */
+        }
         STD_ENDPROC(ret_from_fork)
 
 /* Various stub interrupt handlers and syscall handlers */
@@ -1156,6 +1184,18 @@ int_unalign:
         push_extra_callee_saves r0
         j       do_trap
 
+/* Fill the return address stack with nonzero entries. */
+STD_ENTRY(fill_ra_stack)
+        {
+         move   r0, lr
+         jal    1f
+        }
+1:      jal     2f
+2:      jal     3f
+3:      jal     4f
+4:      jrp     r0
+        STD_ENDPROC(fill_ra_stack)
+
 /* Include .intrpt1 array of interrupt vectors */
         .section ".intrpt1", "ax"
 
@@ -1166,7 +1206,7 @@ int_unalign:
 #define do_hardwall_trap bad_intr
 #endif
 
-        int_hand     INT_MEM_ERROR, MEM_ERROR, bad_intr
+        int_hand     INT_MEM_ERROR, MEM_ERROR, do_trap
         int_hand     INT_SINGLE_STEP_3, SINGLE_STEP_3, bad_intr
 #if CONFIG_KERNEL_PL == 2
         int_hand     INT_SINGLE_STEP_2, SINGLE_STEP_2, gx_singlestep_handle
diff --git a/arch/tile/kernel/module.c b/arch/tile/kernel/module.c
index b90ab9925674..98d476920106 100644
--- a/arch/tile/kernel/module.c
+++ b/arch/tile/kernel/module.c
@@ -67,6 +67,8 @@ void *module_alloc(unsigned long size)
         area = __get_vm_area(size, VM_ALLOC, MEM_MODULE_START, MEM_MODULE_END);
         if (!area)
                 goto error;
+        area->nr_pages = npages;
+        area->pages = pages;
 
         if (map_vm_area(area, prot_rwx, &pages)) {
                 vunmap(area->addr);
diff --git a/arch/tile/kernel/proc.c b/arch/tile/kernel/proc.c
index 7a9327046404..446a7f52cc11 100644
--- a/arch/tile/kernel/proc.c
+++ b/arch/tile/kernel/proc.c
@@ -146,7 +146,6 @@ static ctl_table unaligned_table[] = {
         },
         {}
 };
-#endif
 
 static struct ctl_path tile_path[] = {
         { .procname = "tile" },
@@ -155,10 +154,9 @@ static struct ctl_path tile_path[] = {
 
 static int __init proc_sys_tile_init(void)
 {
-#ifndef __tilegx__  /* FIXME: GX: no support for unaligned access yet */
         register_sysctl_paths(tile_path, unaligned_table);
-#endif
         return 0;
 }
 
 arch_initcall(proc_sys_tile_init);
+#endif
diff --git a/arch/tile/kernel/process.c b/arch/tile/kernel/process.c
index 30caecac94dc..2d5ef617bb39 100644
--- a/arch/tile/kernel/process.c
+++ b/arch/tile/kernel/process.c
@@ -28,6 +28,7 @@
 #include <linux/tracehook.h>
 #include <linux/signal.h>
 #include <asm/stack.h>
+#include <asm/switch_to.h>
 #include <asm/homecache.h>
 #include <asm/syscalls.h>
 #include <asm/traps.h>
@@ -285,7 +286,7 @@ struct task_struct *validate_current(void)
         static struct task_struct corrupt = { .comm = "<corrupt>" };
         struct task_struct *tsk = current;
         if (unlikely((unsigned long)tsk < PAGE_OFFSET ||
-                     (void *)tsk > high_memory ||
+                     (high_memory && (void *)tsk > high_memory) ||
                      ((unsigned long)tsk & (__alignof__(*tsk) - 1)) != 0)) {
                 pr_err("Corrupt 'current' %p (sp %#lx)\n", tsk, stack_pointer);
                 tsk = &corrupt;
diff --git a/arch/tile/kernel/setup.c b/arch/tile/kernel/setup.c
index 92a94f4920ad..bff23f476110 100644
--- a/arch/tile/kernel/setup.c
+++ b/arch/tile/kernel/setup.c
@@ -103,13 +103,11 @@ unsigned long __initdata pci_reserve_end_pfn = -1U;
 
 static int __init setup_maxmem(char *str)
 {
-        long maxmem_mb;
-        if (str == NULL || strict_strtol(str, 0, &maxmem_mb) != 0 ||
-            maxmem_mb == 0)
+        unsigned long long maxmem;
+        if (str == NULL || (maxmem = memparse(str, NULL)) == 0)
                 return -EINVAL;
 
-        maxmem_pfn = (maxmem_mb >> (HPAGE_SHIFT - 20)) <<
-                (HPAGE_SHIFT - PAGE_SHIFT);
+        maxmem_pfn = (maxmem >> HPAGE_SHIFT) << (HPAGE_SHIFT - PAGE_SHIFT);
         pr_info("Forcing RAM used to no more than %dMB\n",
                maxmem_pfn >> (20 - PAGE_SHIFT));
         return 0;
@@ -119,14 +117,15 @@ early_param("maxmem", setup_maxmem);
 static int __init setup_maxnodemem(char *str)
 {
         char *endp;
-        long maxnodemem_mb, node;
+        unsigned long long maxnodemem;
+        long node;
 
         node = str ? simple_strtoul(str, &endp, 0) : INT_MAX;
-        if (node >= MAX_NUMNODES || *endp != ':' ||
-            strict_strtol(endp+1, 0, &maxnodemem_mb) != 0)
+        if (node >= MAX_NUMNODES || *endp != ':')
                 return -EINVAL;
 
-        maxnodemem_pfn[node] = (maxnodemem_mb >> (HPAGE_SHIFT - 20)) <<
+        maxnodemem = memparse(endp+1, NULL);
+        maxnodemem_pfn[node] = (maxnodemem >> HPAGE_SHIFT) <<
                 (HPAGE_SHIFT - PAGE_SHIFT);
         pr_info("Forcing RAM used on node %ld to no more than %dMB\n",
                node, maxnodemem_pfn[node] >> (20 - PAGE_SHIFT));
@@ -913,6 +912,13 @@ void __cpuinit setup_cpu(int boot)
 
 #ifdef CONFIG_BLK_DEV_INITRD
 
+/*
+ * Note that the kernel can potentially support other compression
+ * techniques than gz, though we don't do so by default.  If we ever
+ * decide to do so we can either look for other filename extensions,
+ * or just allow a file with this name to be compressed with an
+ * arbitrary compressor (somewhat counterintuitively).
+ */
 static int __initdata set_initramfs_file;
 static char __initdata initramfs_file[128] = "initramfs.cpio.gz";
 
@@ -928,9 +934,9 @@ static int __init setup_initramfs_file(char *str)
 early_param("initramfs_file", setup_initramfs_file);
 
 /*
- * We look for an additional "initramfs.cpio.gz" file in the hvfs.
+ * We look for an "initramfs.cpio.gz" file in the hvfs.
  * If there is one, we allocate some memory for it and it will be
- * unpacked to the initramfs after any built-in initramfs_data.
+ * unpacked to the initramfs.
  */
 static void __init load_hv_initrd(void)
 {
diff --git a/arch/tile/kernel/single_step.c b/arch/tile/kernel/single_step.c
index bc1eb586e24d..9efbc1391b3c 100644
--- a/arch/tile/kernel/single_step.c
+++ b/arch/tile/kernel/single_step.c
@@ -153,6 +153,25 @@ static tile_bundle_bits rewrite_load_store_unaligned(
         if (((unsigned long)addr % size) == 0)
                 return bundle;
 
+        /*
+         * Return SIGBUS with the unaligned address, if requested.
+         * Note that we return SIGBUS even for completely invalid addresses
+         * as long as they are in fact unaligned; this matches what the
+         * tilepro hardware would be doing, if it could provide us with the
+         * actual bad address in an SPR, which it doesn't.
+         */
+        if (unaligned_fixup == 0) {
+                siginfo_t info = {
+                        .si_signo = SIGBUS,
+                        .si_code = BUS_ADRALN,
+                        .si_addr = addr
+                };
+                trace_unhandled_signal("unaligned trap", regs,
+                                       (unsigned long)addr, SIGBUS);
+                force_sig_info(info.si_signo, &info, current);
+                return (tilepro_bundle_bits) 0;
+        }
+
 #ifndef __LITTLE_ENDIAN
 # error We assume little-endian representation with copy_xx_user size 2 here
 #endif
@@ -192,18 +211,6 @@ static tile_bundle_bits rewrite_load_store_unaligned(
                 return (tile_bundle_bits) 0;
         }
 
-        if (unaligned_fixup == 0) {
-                siginfo_t info = {
-                        .si_signo = SIGBUS,
-                        .si_code = BUS_ADRALN,
-                        .si_addr = addr
-                };
-                trace_unhandled_signal("unaligned trap", regs,
-                                       (unsigned long)addr, SIGBUS);
-                force_sig_info(info.si_signo, &info, current);
-                return (tile_bundle_bits) 0;
-        }
-
         if (unaligned_printk || unaligned_fixup_count == 0) {
                 pr_info("Process %d/%s: PC %#lx: Fixup of"
                         " unaligned %s at %#lx.\n",
diff --git a/arch/tile/kernel/smp.c b/arch/tile/kernel/smp.c
index a44e103c5a63..91da0f721958 100644
--- a/arch/tile/kernel/smp.c
+++ b/arch/tile/kernel/smp.c
@@ -103,7 +103,7 @@ static void smp_stop_cpu_interrupt(void)
         set_cpu_online(smp_processor_id(), 0);
         arch_local_irq_disable_all();
         for (;;)
-                asm("nap");
+                asm("nap; nop");
 }
 
 /* This function calls the 'stop' function on all other CPUs in the system. */
@@ -113,6 +113,12 @@ void smp_send_stop(void)
         send_IPI_allbutself(MSG_TAG_STOP_CPU);
 }
 
+/* On panic, just wait; we may get an smp_send_stop() later on. */
+void panic_smp_self_stop(void)
+{
+        while (1)
+                asm("nap; nop");
+}
 
 /*
  * Dispatch code called from hv_message_intr() for HV_MSG_TILE hv messages.
diff --git a/arch/tile/kernel/smpboot.c b/arch/tile/kernel/smpboot.c
index b949edcec200..172aef7d3159 100644
--- a/arch/tile/kernel/smpboot.c
+++ b/arch/tile/kernel/smpboot.c
@@ -196,6 +196,8 @@ void __cpuinit online_secondary(void)
         /* This must be done before setting cpu_online_mask */
         wmb();
 
+        notify_cpu_starting(smp_processor_id());
+
         /*
          * We need to hold call_lock, so there is no inconsistency
          * between the time smp_call_function() determines number of
diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index 37ee4d037e0b..b2f44c28dda6 100644
--- a/arch/tile/kernel/stack.c
+++ b/arch/tile/kernel/stack.c
@@ -21,10 +21,12 @@
 #include <linux/stacktrace.h>
 #include <linux/uaccess.h>
 #include <linux/mmzone.h>
+#include <linux/dcache.h>
+#include <linux/fs.h>
 #include <asm/backtrace.h>
 #include <asm/page.h>
-#include <asm/tlbflush.h>
 #include <asm/ucontext.h>
+#include <asm/switch_to.h>
 #include <asm/sigframe.h>
 #include <asm/stack.h>
 #include <arch/abi.h>
@@ -44,72 +46,23 @@ static int in_kernel_stack(struct KBacktraceIterator *kbt, unsigned long sp)
         return sp >= kstack_base && sp < kstack_base + THREAD_SIZE;
 }
 
-/* Is address valid for reading? */
-static int valid_address(struct KBacktraceIterator *kbt, unsigned long address)
-{
-        HV_PTE *l1_pgtable = kbt->pgtable;
-        HV_PTE *l2_pgtable;
-        unsigned long pfn;
-        HV_PTE pte;
-        struct page *page;
-
-        if (l1_pgtable == NULL)
-                return 0;       /* can't read user space in other tasks */
-
-#ifdef CONFIG_64BIT
-        /* Find the real l1_pgtable by looking in the l0_pgtable. */
-        pte = l1_pgtable[HV_L0_INDEX(address)];
-        if (!hv_pte_get_present(pte))
-                return 0;
-        pfn = hv_pte_get_pfn(pte);
-        if (pte_huge(pte)) {
-                if (!pfn_valid(pfn)) {
-                        pr_err("L0 huge page has bad pfn %#lx\n", pfn);
-                        return 0;
-                }
-                return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
-        }
-        page = pfn_to_page(pfn);
-        BUG_ON(PageHighMem(page));  /* No HIGHMEM on 64-bit. */
-        l1_pgtable = (HV_PTE *)pfn_to_kaddr(pfn);
-#endif
-        pte = l1_pgtable[HV_L1_INDEX(address)];
-        if (!hv_pte_get_present(pte))
-                return 0;
-        pfn = hv_pte_get_pfn(pte);
-        if (pte_huge(pte)) {
-                if (!pfn_valid(pfn)) {
-                        pr_err("huge page has bad pfn %#lx\n", pfn);
-                        return 0;
-                }
-                return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
-        }
-
-        page = pfn_to_page(pfn);
-        if (PageHighMem(page)) {
-                pr_err("L2 page table not in LOWMEM (%#llx)\n",
-                       HV_PFN_TO_CPA(pfn));
-                return 0;
-        }
-        l2_pgtable = (HV_PTE *)pfn_to_kaddr(pfn);
-        pte = l2_pgtable[HV_L2_INDEX(address)];
-        return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
-}
-
 /* Callback for backtracer; basically a glorified memcpy */
 static bool read_memory_func(void *result, unsigned long address,
                              unsigned int size, void *vkbt)
 {
         int retval;
         struct KBacktraceIterator *kbt = (struct KBacktraceIterator *)vkbt;
+
+        if (address == 0)
+                return 0;
         if (__kernel_text_address(address)) {
                 /* OK to read kernel code. */
         } else if (address >= PAGE_OFFSET) {
                 /* We only tolerate kernel-space reads of this task's stack */
                 if (!in_kernel_stack(kbt, address))
                         return 0;
-        } else if (!valid_address(kbt, address)) {
-                return 0;       /* invalid user-space address */
+        } else if (!kbt->is_current) {
+                return 0;       /* can't read from other user address spaces */
         }
         pagefault_disable();
         retval = __copy_from_user_inatomic(result,
@@ -127,6 +80,8 @@ static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
         unsigned long sp = kbt->it.sp;
         struct pt_regs *p;
 
+        if (sp % sizeof(long) != 0)
+                return NULL;
         if (!in_kernel_stack(kbt, sp))
                 return NULL;
         if (!in_kernel_stack(kbt, sp + C_ABI_SAVE_AREA_SIZE + PTREGS_SIZE-1))
@@ -169,27 +124,27 @@ static int is_sigreturn(unsigned long pc)
 }
 
 /* Return a pt_regs pointer for a valid signal handler frame */
-static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt)
+static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt,
+                                      struct rt_sigframe* kframe)
 {
         BacktraceIterator *b = &kbt->it;
 
-        if (b->pc == VDSO_BASE) {
-                struct rt_sigframe *frame;
-                unsigned long sigframe_top =
-                        b->sp + sizeof(struct rt_sigframe) - 1;
-                if (!valid_address(kbt, b->sp) ||
-                    !valid_address(kbt, sigframe_top)) {
-                        if (kbt->verbose)
-                                pr_err("  (odd signal: sp %#lx?)\n",
-                                       (unsigned long)(b->sp));
+        if (b->pc == VDSO_BASE && b->sp < PAGE_OFFSET &&
+            b->sp % sizeof(long) == 0) {
+                int retval;
+                pagefault_disable();
+                retval = __copy_from_user_inatomic(
+                        kframe, (void __user __force *)b->sp,
+                        sizeof(*kframe));
+                pagefault_enable();
+                if (retval != 0 ||
+                    (unsigned int)(kframe->info.si_signo) >= _NSIG)
                         return NULL;
-                }
-                frame = (struct rt_sigframe *)b->sp;
                 if (kbt->verbose) {
                         pr_err("  <received signal %d>\n",
-                               frame->info.si_signo);
+                               kframe->info.si_signo);
                 }
-                return (struct pt_regs *)&frame->uc.uc_mcontext;
+                return (struct pt_regs *)&kframe->uc.uc_mcontext;
         }
         return NULL;
 }
@@ -202,10 +157,11 @@ static int KBacktraceIterator_is_sigreturn(struct KBacktraceIterator *kbt)
 static int KBacktraceIterator_restart(struct KBacktraceIterator *kbt)
 {
         struct pt_regs *p;
+        struct rt_sigframe kframe;
 
         p = valid_fault_handler(kbt);
         if (p == NULL)
-                p = valid_sigframe(kbt);
+                p = valid_sigframe(kbt, &kframe);
         if (p == NULL)
                 return 0;
         backtrace_init(&kbt->it, read_memory_func, kbt,
@@ -265,41 +221,19 @@ void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
 
         /*
          * Set up callback information.  We grab the kernel stack base
-         * so we will allow reads of that address range, and if we're
-         * asking about the current process we grab the page table
-         * so we can check user accesses before trying to read them.
-         * We flush the TLB to avoid any weird skew issues.
+         * so we will allow reads of that address range.
          */
-        is_current = (t == NULL);
+        is_current = (t == NULL || t == current);
         kbt->is_current = is_current;
         if (is_current)
                 t = validate_current();
         kbt->task = t;
-        kbt->pgtable = NULL;
         kbt->verbose = 0;   /* override in caller if desired */
         kbt->profile = 0;   /* override in caller if desired */
         kbt->end = KBT_ONGOING;
-        kbt->new_context = 0;
-        if (is_current) {
-                HV_PhysAddr pgdir_pa = hv_inquire_context().page_table;
-                if (pgdir_pa == (unsigned long)swapper_pg_dir - PAGE_OFFSET) {
-                        /*
-                         * Not just an optimization: this also allows
-                         * this to work at all before va/pa mappings
-                         * are set up.
-                         */
-                        kbt->pgtable = swapper_pg_dir;
-                } else {
-                        struct page *page = pfn_to_page(PFN_DOWN(pgdir_pa));
-                        if (!PageHighMem(page))
-                                kbt->pgtable = __va(pgdir_pa);
-                        else
-                                pr_err("page table not in LOWMEM"
-                                       " (%#llx)\n", pgdir_pa);
-                }
-                local_flush_tlb_all();
+        kbt->new_context = 1;
+        if (is_current)
                 validate_stack(regs);
-        }
 
         if (regs == NULL) {
                 if (is_current || t->state == TASK_RUNNING) {
@@ -345,6 +279,78 @@ void KBacktraceIterator_next(struct KBacktraceIterator *kbt)
 }
 EXPORT_SYMBOL(KBacktraceIterator_next);
 
+static void describe_addr(struct KBacktraceIterator *kbt,
+                          unsigned long address,
+                          int have_mmap_sem, char *buf, size_t bufsize)
+{
+        struct vm_area_struct *vma;
+        size_t namelen, remaining;
+        unsigned long size, offset, adjust;
+        char *p, *modname;
+        const char *name;
+        int rc;
+
+        /*
+         * Look one byte back for every caller frame (i.e. those that
+         * aren't a new context) so we look up symbol data for the
+         * call itself, not the following instruction, which may be on
+         * a different line (or in a different function).
+         */
+        adjust = !kbt->new_context;
+        address -= adjust;
+
+        if (address >= PAGE_OFFSET) {
+                /* Handle kernel symbols. */
+                BUG_ON(bufsize < KSYM_NAME_LEN);
+                name = kallsyms_lookup(address, &size, &offset,
+                                       &modname, buf);
+                if (name == NULL) {
+                        buf[0] = '\0';
+                        return;
+                }
+                namelen = strlen(buf);
+                remaining = (bufsize - 1) - namelen;
+                p = buf + namelen;
+                rc = snprintf(p, remaining, "+%#lx/%#lx ",
+                              offset + adjust, size);
+                if (modname && rc < remaining)
+                        snprintf(p + rc, remaining - rc, "[%s] ", modname);
+                buf[bufsize-1] = '\0';
+                return;
+        }
+
+        /* If we don't have the mmap_sem, we can't show any more info. */
+        buf[0] = '\0';
+        if (!have_mmap_sem)
+                return;
+
+        /* Find vma info. */
+        vma = find_vma(kbt->task->mm, address);
+        if (vma == NULL || address < vma->vm_start) {
+                snprintf(buf, bufsize, "[unmapped address] ");
+                return;
+        }
+
+        if (vma->vm_file) {
+                char *s;
+                p = d_path(&vma->vm_file->f_path, buf, bufsize);
+                if (IS_ERR(p))
+                        p = "?";
+                s = strrchr(p, '/');
+                if (s)
+                        p = s+1;
+        } else {
+                p = "anon";
+        }
+
+        /* Generate a string description of the vma info. */
+        namelen = strlen(p);
+        remaining = (bufsize - 1) - namelen;
+        memmove(buf, p, namelen);
+        snprintf(buf + namelen, remaining, "[%lx+%lx] ",
+                 vma->vm_start, vma->vm_end - vma->vm_start);
+}
+
 /*
  * This method wraps the backtracer's more generic support.
  * It is only invoked from the architecture-specific code; show_stack()
@@ -353,6 +359,7 @@ EXPORT_SYMBOL(KBacktraceIterator_next);
 void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
 {
         int i;
+        int have_mmap_sem = 0;
 
         if (headers) {
                 /*
@@ -369,31 +376,16 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
         kbt->verbose = 1;
         i = 0;
         for (; !KBacktraceIterator_end(kbt); KBacktraceIterator_next(kbt)) {
-                char *modname;
-                const char *name;
-                unsigned long address = kbt->it.pc;
-                unsigned long offset, size;
                 char namebuf[KSYM_NAME_LEN+100];
+                unsigned long address = kbt->it.pc;
 
-                if (address >= PAGE_OFFSET)
-                        name = kallsyms_lookup(address, &size, &offset,
-                                               &modname, namebuf);
-                else
-                        name = NULL;
-
-                if (!name)
-                        namebuf[0] = '\0';
-                else {
-                        size_t namelen = strlen(namebuf);
-                        size_t remaining = (sizeof(namebuf) - 1) - namelen;
-                        char *p = namebuf + namelen;
-                        int rc = snprintf(p, remaining, "+%#lx/%#lx ",
-                                          offset, size);
-                        if (modname && rc < remaining)
-                                snprintf(p + rc, remaining - rc,
-                                         "[%s] ", modname);
-                        namebuf[sizeof(namebuf)-1] = '\0';
-                }
+                /* Try to acquire the mmap_sem as we pass into userspace. */
+                if (address < PAGE_OFFSET && !have_mmap_sem && kbt->task->mm)
+                        have_mmap_sem =
+                                down_read_trylock(&kbt->task->mm->mmap_sem);
+
+                describe_addr(kbt, address, have_mmap_sem,
+                              namebuf, sizeof(namebuf));
 
                 pr_err("  frame %d: 0x%lx %s(sp 0x%lx)\n",
                        i++, address, namebuf, (unsigned long)(kbt->it.sp));
@@ -408,6 +400,8 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
                 pr_err("Stack dump stopped; next frame identical to this one\n");
         if (headers)
                 pr_err("Stack dump complete\n");
+        if (have_mmap_sem)
+                up_read(&kbt->task->mm->mmap_sem);
 }
 EXPORT_SYMBOL(tile_show_stack);
 
diff --git a/arch/tile/kernel/traps.c b/arch/tile/kernel/traps.c
index 2bb6602a1ee7..73cff814ac57 100644
--- a/arch/tile/kernel/traps.c
+++ b/arch/tile/kernel/traps.c
@@ -200,7 +200,7 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
 {
         siginfo_t info = { 0 };
         int signo, code;
-        unsigned long address;
+        unsigned long address = 0;
         bundle_bits instr;
 
         /* Re-enable interrupts. */
@@ -223,6 +223,10 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
         }
 
         switch (fault_num) {
+        case INT_MEM_ERROR:
+                signo = SIGBUS;
+                code = BUS_OBJERR;
+                break;
         case INT_ILL:
                 if (copy_from_user(&instr, (void __user *)regs->pc,
                                    sizeof(instr))) {
@@ -289,7 +293,10 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
                 address = regs->pc;
                 break;
 #ifdef __tilegx__
-        case INT_ILL_TRANS:
+        case INT_ILL_TRANS: {
+                /* Avoid a hardware erratum with the return address stack. */
+                fill_ra_stack();
+
                 signo = SIGSEGV;
                 code = SEGV_MAPERR;
                 if (reason & SPR_ILL_TRANS_REASON__I_STREAM_VA_RMASK)
@@ -297,6 +304,7 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
                 else
                         address = 0;  /* FIXME: GX: single-step for address */
                 break;
+        }
 #endif
         default:
                 panic("Unexpected do_trap interrupt number %d", fault_num);
@@ -308,7 +316,8 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num,
         info.si_addr = (void __user *)address;
         if (signo == SIGILL)
                 info.si_trapno = fault_num;
-        trace_unhandled_signal("trap", regs, address, signo);
+        if (signo != SIGTRAP)
+                trace_unhandled_signal("trap", regs, address, signo);
         force_sig_info(signo, &info, current);
 }