OpenRISC: Memory management

Signed-off-by: Jonas Bonn <jonas@southpole.se>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

4 files changed, 951 insertions, 0 deletions

diff --git a/arch/openrisc/mm/fault.c b/arch/openrisc/mm/fault.c
new file mode 100644
index 000000000000..a5dce82f864b
--- /dev/null
+++ b/arch/openrisc/mm/fault.c
@@ -0,0 +1,338 @@
+/*
+ * OpenRISC fault.c
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
+ *
+ *      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/mm.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+
+#include <asm/uaccess.h>
+#include <asm/siginfo.h>
+#include <asm/signal.h>
+
+#define NUM_TLB_ENTRIES 64
+#define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1))
+
+unsigned long pte_misses;       /* updated by do_page_fault() */
+unsigned long pte_errors;       /* updated by do_page_fault() */
+
+/* __PHX__ :: - check the vmalloc_fault in do_page_fault()
+ *            - also look into include/asm-or32/mmu_context.h
+ */
+volatile pgd_t *current_pgd;
+
+extern void die(char *, struct pt_regs *, long);
+
+/*
+ * This routine handles page faults.  It determines the address,
+ * and the problem, and then passes it off to one of the appropriate
+ * routines.
+ *
+ * If this routine detects a bad access, it returns 1, otherwise it
+ * returns 0.
+ */
+
+asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
+                              unsigned long vector, int write_acc)
+{
+        struct task_struct *tsk;
+        struct mm_struct *mm;
+        struct vm_area_struct *vma;
+        siginfo_t info;
+        int fault;
+
+        tsk = current;
+
+        /*
+         * We fault-in kernel-space virtual memory on-demand. The
+         * 'reference' page table is init_mm.pgd.
+         *
+         * NOTE! We MUST NOT take any locks for this case. We may
+         * be in an interrupt or a critical region, and should
+         * only copy the information from the master page table,
+         * nothing more.
+         *
+         * NOTE2: This is done so that, when updating the vmalloc
+         * mappings we don't have to walk all processes pgdirs and
+         * add the high mappings all at once. Instead we do it as they
+         * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
+         * bit set so sometimes the TLB can use a lingering entry.
+         *
+         * This verifies that the fault happens in kernel space
+         * and that the fault was not a protection error.
+         */
+
+        if (address >= VMALLOC_START &&
+            (vector != 0x300 && vector != 0x400) &&
+            !user_mode(regs))
+                goto vmalloc_fault;
+
+        /* If exceptions were enabled, we can reenable them here */
+        if (user_mode(regs)) {
+                /* Exception was in userspace: reenable interrupts */
+                local_irq_enable();
+        } else {
+                /* If exception was in a syscall, then IRQ's may have
+                 * been enabled or disabled.  If they were enabled,
+                 * reenable them.
+                 */
+                if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE))
+                        local_irq_enable();
+        }
+
+        mm = tsk->mm;
+        info.si_code = SEGV_MAPERR;
+
+        /*
+         * If we're in an interrupt or have no user
+         * context, we must not take the fault..
+         */
+
+        if (in_interrupt() || !mm)
+                goto no_context;
+
+        down_read(&mm->mmap_sem);
+        vma = find_vma(mm, address);
+
+        if (!vma)
+                goto bad_area;
+
+        if (vma->vm_start <= address)
+                goto good_area;
+
+        if (!(vma->vm_flags & VM_GROWSDOWN))
+                goto bad_area;
+
+        if (user_mode(regs)) {
+                /*
+                 * accessing the stack below usp is always a bug.
+                 * we get page-aligned addresses so we can only check
+                 * if we're within a page from usp, but that might be
+                 * enough to catch brutal errors at least.
+                 */
+                if (address + PAGE_SIZE < regs->sp)
+                        goto bad_area;
+        }
+        if (expand_stack(vma, address))
+                goto bad_area;
+
+        /*
+         * Ok, we have a good vm_area for this memory access, so
+         * we can handle it..
+         */
+
+good_area:
+        info.si_code = SEGV_ACCERR;
+
+        /* first do some preliminary protection checks */
+
+        if (write_acc) {
+                if (!(vma->vm_flags & VM_WRITE))
+                        goto bad_area;
+        } else {
+                /* not present */
+                if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
+                        goto bad_area;
+        }
+
+        /* are we trying to execute nonexecutable area */
+        if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC))
+                goto bad_area;
+
+        /*
+         * If for any reason at all we couldn't handle the fault,
+         * make sure we exit gracefully rather than endlessly redo
+         * the fault.
+         */
+
+        fault = handle_mm_fault(mm, vma, address, write_acc);
+        if (unlikely(fault & VM_FAULT_ERROR)) {
+                if (fault & VM_FAULT_OOM)
+                        goto out_of_memory;
+                else if (fault & VM_FAULT_SIGBUS)
+                        goto do_sigbus;
+                BUG();
+        }
+        /*RGD modeled on Cris */
+        if (fault & VM_FAULT_MAJOR)
+                tsk->maj_flt++;
+        else
+                tsk->min_flt++;
+
+        up_read(&mm->mmap_sem);
+        return;
+
+        /*
+         * Something tried to access memory that isn't in our memory map..
+         * Fix it, but check if it's kernel or user first..
+         */
+
+bad_area:
+        up_read(&mm->mmap_sem);
+
+bad_area_nosemaphore:
+
+        /* User mode accesses just cause a SIGSEGV */
+
+        if (user_mode(regs)) {
+                info.si_signo = SIGSEGV;
+                info.si_errno = 0;
+                /* info.si_code has been set above */
+                info.si_addr = (void *)address;
+                force_sig_info(SIGSEGV, &info, tsk);
+                return;
+        }
+
+no_context:
+
+        /* Are we prepared to handle this kernel fault?
+         *
+         * (The kernel has valid exception-points in the source
+         *  when it acesses user-memory. When it fails in one
+         *  of those points, we find it in a table and do a jump
+         *  to some fixup code that loads an appropriate error
+         *  code)
+         */
+
+        {
+                const struct exception_table_entry *entry;
+
+                __asm__ __volatile__("l.nop 42");
+
+                if ((entry = search_exception_tables(regs->pc)) != NULL) {
+                        /* Adjust the instruction pointer in the stackframe */
+                        regs->pc = entry->fixup;
+                        return;
+                }
+        }
+
+        /*
+         * Oops. The kernel tried to access some bad page. We'll have to
+         * terminate things with extreme prejudice.
+         */
+
+        if ((unsigned long)(address) < PAGE_SIZE)
+                printk(KERN_ALERT
+                       "Unable to handle kernel NULL pointer dereference");
+        else
+                printk(KERN_ALERT "Unable to handle kernel access");
+        printk(" at virtual address 0x%08lx\n", address);
+
+        die("Oops", regs, write_acc);
+
+        do_exit(SIGKILL);
+
+        /*
+         * We ran out of memory, or some other thing happened to us that made
+         * us unable to handle the page fault gracefully.
+         */
+
+out_of_memory:
+        __asm__ __volatile__("l.nop 42");
+        __asm__ __volatile__("l.nop 1");
+
+        up_read(&mm->mmap_sem);
+        printk("VM: killing process %s\n", tsk->comm);
+        if (user_mode(regs))
+                do_exit(SIGKILL);
+        goto no_context;
+
+do_sigbus:
+        up_read(&mm->mmap_sem);
+
+        /*
+         * Send a sigbus, regardless of whether we were in kernel
+         * or user mode.
+         */
+        info.si_signo = SIGBUS;
+        info.si_errno = 0;
+        info.si_code = BUS_ADRERR;
+        info.si_addr = (void *)address;
+        force_sig_info(SIGBUS, &info, tsk);
+
+        /* Kernel mode? Handle exceptions or die */
+        if (!user_mode(regs))
+                goto no_context;
+        return;
+
+vmalloc_fault:
+        {
+                /*
+                 * Synchronize this task's top level page-table
+                 * with the 'reference' page table.
+                 *
+                 * Use current_pgd instead of tsk->active_mm->pgd
+                 * since the latter might be unavailable if this
+                 * code is executed in a misfortunately run irq
+                 * (like inside schedule() between switch_mm and
+                 *  switch_to...).
+                 */
+
+                int offset = pgd_index(address);
+                pgd_t *pgd, *pgd_k;
+                pud_t *pud, *pud_k;
+                pmd_t *pmd, *pmd_k;
+                pte_t *pte_k;
+
+/*
+                phx_warn("do_page_fault(): vmalloc_fault will not work, "
+                         "since current_pgd assign a proper value somewhere\n"
+                         "anyhow we don't need this at the moment\n");
+
+                phx_mmu("vmalloc_fault");
+*/
+                pgd = (pgd_t *)current_pgd + offset;
+                pgd_k = init_mm.pgd + offset;
+
+                /* Since we're two-level, we don't need to do both
+                 * set_pgd and set_pmd (they do the same thing). If
+                 * we go three-level at some point, do the right thing
+                 * with pgd_present and set_pgd here.
+                 *
+                 * Also, since the vmalloc area is global, we don't
+                 * need to copy individual PTE's, it is enough to
+                 * copy the pgd pointer into the pte page of the
+                 * root task. If that is there, we'll find our pte if
+                 * it exists.
+                 */
+
+                pud = pud_offset(pgd, address);
+                pud_k = pud_offset(pgd_k, address);
+                if (!pud_present(*pud_k))
+                        goto no_context;
+
+                pmd = pmd_offset(pud, address);
+                pmd_k = pmd_offset(pud_k, address);
+
+                if (!pmd_present(*pmd_k))
+                        goto bad_area_nosemaphore;
+
+                set_pmd(pmd, *pmd_k);
+
+                /* Make sure the actual PTE exists as well to
+                 * catch kernel vmalloc-area accesses to non-mapped
+                 * addresses. If we don't do this, this will just
+                 * silently loop forever.
+                 */
+
+                pte_k = pte_offset_kernel(pmd_k, address);
+                if (!pte_present(*pte_k))
+                        goto no_context;
+
+                return;
+        }
+}
diff --git a/arch/openrisc/mm/init.c b/arch/openrisc/mm/init.c
new file mode 100644
index 000000000000..359dcb20fe85
--- /dev/null
+++ b/arch/openrisc/mm/init.c
@@ -0,0 +1,283 @@
+/*
+ * OpenRISC idle.c
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
+ *
+ *      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/signal.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/smp.h>
+#include <linux/bootmem.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/blkdev.h>       /* for initrd_* */
+#include <linux/pagemap.h>
+#include <linux/memblock.h>
+
+#include <asm/system.h>
+#include <asm/segment.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <asm/dma.h>
+#include <asm/io.h>
+#include <asm/tlb.h>
+#include <asm/mmu_context.h>
+#include <asm/kmap_types.h>
+#include <asm/fixmap.h>
+#include <asm/tlbflush.h>
+
+int mem_init_done;
+
+DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
+
+static void __init zone_sizes_init(void)
+{
+        unsigned long zones_size[MAX_NR_ZONES];
+
+        /* Clear the zone sizes */
+        memset(zones_size, 0, sizeof(zones_size));
+
+        /*
+         * We use only ZONE_NORMAL
+         */
+        zones_size[ZONE_NORMAL] = max_low_pfn;
+
+        free_area_init(zones_size);
+}
+
+extern const char _s_kernel_ro[], _e_kernel_ro[];
+
+/*
+ * Map all physical memory into kernel's address space.
+ *
+ * This is explicitly coded for two-level page tables, so if you need
+ * something else then this needs to change.
+ */
+static void __init map_ram(void)
+{
+        unsigned long v, p, e;
+        pgprot_t prot;
+        pgd_t *pge;
+        pud_t *pue;
+        pmd_t *pme;
+        pte_t *pte;
+        /* These mark extents of read-only kernel pages...
+         * ...from vmlinux.lds.S
+         */
+        struct memblock_region *region;
+
+        v = PAGE_OFFSET;
+
+        for_each_memblock(memory, region) {
+                p = (u32) region->base & PAGE_MASK;
+                e = p + (u32) region->size;
+
+                v = (u32) __va(p);
+                pge = pgd_offset_k(v);
+
+                while (p < e) {
+                        int j;
+                        pue = pud_offset(pge, v);
+                        pme = pmd_offset(pue, v);
+
+                        if ((u32) pue != (u32) pge || (u32) pme != (u32) pge) {
+                                panic("%s: OR1K kernel hardcoded for "
+                                      "two-level page tables",
+                                     __func__);
+                        }
+
+                        /* Alloc one page for holding PTE's... */
+                        pte = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
+                        set_pmd(pme, __pmd(_KERNPG_TABLE + __pa(pte)));
+
+                        /* Fill the newly allocated page with PTE'S */
+                        for (j = 0; p < e && j < PTRS_PER_PGD;
+                             v += PAGE_SIZE, p += PAGE_SIZE, j++, pte++) {
+                                if (v >= (u32) _e_kernel_ro ||
+                                    v < (u32) _s_kernel_ro)
+                                        prot = PAGE_KERNEL;
+                                else
+                                        prot = PAGE_KERNEL_RO;
+
+                                set_pte(pte, mk_pte_phys(p, prot));
+                        }
+
+                        pge++;
+                }
+
+                printk(KERN_INFO "%s: Memory: 0x%x-0x%x\n", __func__,
+                       region->base, region->base + region->size);
+        }
+}
+
+void __init paging_init(void)
+{
+        extern void tlb_init(void);
+
+        unsigned long end;
+        int i;
+
+        printk(KERN_INFO "Setting up paging and PTEs.\n");
+
+        /* clear out the init_mm.pgd that will contain the kernel's mappings */
+
+        for (i = 0; i < PTRS_PER_PGD; i++)
+                swapper_pg_dir[i] = __pgd(0);
+
+        /* make sure the current pgd table points to something sane
+         * (even if it is most probably not used until the next
+         *  switch_mm)
+         */
+        current_pgd = init_mm.pgd;
+
+        end = (unsigned long)__va(max_low_pfn * PAGE_SIZE);
+
+        map_ram();
+
+        zone_sizes_init();
+
+        /* self modifying code ;) */
+        /* Since the old TLB miss handler has been running up until now,
+         * the kernel pages are still all RW, so we can still modify the
+         * text directly... after this change and a TLB flush, the kernel
+         * pages will become RO.
+         */
+        {
+                extern unsigned long dtlb_miss_handler;
+                extern unsigned long itlb_miss_handler;
+
+                unsigned long *dtlb_vector = __va(0x900);
+                unsigned long *itlb_vector = __va(0xa00);
+
+                printk(KERN_INFO "dtlb_miss_handler %p\n", &dtlb_miss_handler);
+                *dtlb_vector = ((unsigned long)&dtlb_miss_handler -
+                                (unsigned long)dtlb_vector) >> 2;
+
+                printk(KERN_INFO "itlb_miss_handler %p\n", &itlb_miss_handler);
+                *itlb_vector = ((unsigned long)&itlb_miss_handler -
+                                (unsigned long)itlb_vector) >> 2;
+        }
+
+        /* Invalidate instruction caches after code modification */
+        mtspr(SPR_ICBIR, 0x900);
+        mtspr(SPR_ICBIR, 0xa00);
+
+        /* New TLB miss handlers and kernel page tables are in now place.
+         * Make sure that page flags get updated for all pages in TLB by
+         * flushing the TLB and forcing all TLB entries to be recreated
+         * from their page table flags.
+         */
+        flush_tlb_all();
+}
+
+/* References to section boundaries */
+
+extern char _stext, _etext, _edata, __bss_start, _end;
+extern char __init_begin, __init_end;
+
+static int __init free_pages_init(void)
+{
+        int reservedpages, pfn;
+
+        /* this will put all low memory onto the freelists */
+        totalram_pages = free_all_bootmem();
+
+        reservedpages = 0;
+        for (pfn = 0; pfn < max_low_pfn; pfn++) {
+                /*
+                 * Only count reserved RAM pages
+                 */
+                if (PageReserved(mem_map + pfn))
+                        reservedpages++;
+        }
+
+        return reservedpages;
+}
+
+static void __init set_max_mapnr_init(void)
+{
+        max_mapnr = num_physpages = max_low_pfn;
+}
+
+void __init mem_init(void)
+{
+        int codesize, reservedpages, datasize, initsize;
+
+        if (!mem_map)
+                BUG();
+
+        set_max_mapnr_init();
+
+        high_memory = (void *)__va(max_low_pfn * PAGE_SIZE);
+
+        /* clear the zero-page */
+        memset((void *)empty_zero_page, 0, PAGE_SIZE);
+
+        reservedpages = free_pages_init();
+
+        codesize = (unsigned long)&_etext - (unsigned long)&_stext;
+        datasize = (unsigned long)&_edata - (unsigned long)&_etext;
+        initsize = (unsigned long)&__init_end - (unsigned long)&__init_begin;
+
+        printk(KERN_INFO
+               "Memory: %luk/%luk available (%dk kernel code, %dk reserved, %dk data, %dk init, %ldk highmem)\n",
+               (unsigned long)nr_free_pages() << (PAGE_SHIFT - 10),
+               max_mapnr << (PAGE_SHIFT - 10), codesize >> 10,
+               reservedpages << (PAGE_SHIFT - 10), datasize >> 10,
+               initsize >> 10, (unsigned long)(0 << (PAGE_SHIFT - 10))
+            );
+
+        printk("mem_init_done ...........................................\n");
+        mem_init_done = 1;
+        return;
+}
+
+#ifdef CONFIG_BLK_DEV_INITRD
+void free_initrd_mem(unsigned long start, unsigned long end)
+{
+        printk(KERN_INFO "Freeing initrd memory: %ldk freed\n",
+               (end - start) >> 10);
+
+        for (; start < end; start += PAGE_SIZE) {
+                ClearPageReserved(virt_to_page(start));
+                init_page_count(virt_to_page(start));
+                free_page(start);
+                totalram_pages++;
+        }
+}
+#endif
+
+void free_initmem(void)
+{
+        unsigned long addr;
+
+        addr = (unsigned long)(&__init_begin);
+        for (; addr < (unsigned long)(&__init_end); addr += PAGE_SIZE) {
+                ClearPageReserved(virt_to_page(addr));
+                init_page_count(virt_to_page(addr));
+                free_page(addr);
+                totalram_pages++;
+        }
+        printk(KERN_INFO "Freeing unused kernel memory: %luk freed\n",
+               ((unsigned long)&__init_end -
+                (unsigned long)&__init_begin) >> 10);
+}
diff --git a/arch/openrisc/mm/ioremap.c b/arch/openrisc/mm/ioremap.c
new file mode 100644
index 000000000000..62b08ef392be
--- /dev/null
+++ b/arch/openrisc/mm/ioremap.c
@@ -0,0 +1,137 @@
+/*
+ * OpenRISC ioremap.c
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
+ *
+ *      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/vmalloc.h>
+#include <linux/io.h>
+#include <asm/pgalloc.h>
+#include <asm/kmap_types.h>
+#include <asm/fixmap.h>
+#include <asm/bug.h>
+#include <asm/pgtable.h>
+#include <linux/sched.h>
+#include <asm/tlbflush.h>
+
+extern int mem_init_done;
+
+static unsigned int fixmaps_used __initdata;
+
+/*
+ * Remap an arbitrary physical address space into the kernel virtual
+ * address space. Needed when the kernel wants to access high addresses
+ * directly.
+ *
+ * NOTE! We need to allow non-page-aligned mappings too: we will obviously
+ * have to convert them into an offset in a page-aligned mapping, but the
+ * caller shouldn't need to know that small detail.
+ */
+void __iomem *__init_refok
+__ioremap(phys_addr_t addr, unsigned long size, pgprot_t prot)
+{
+        phys_addr_t p;
+        unsigned long v;
+        unsigned long offset, last_addr;
+        struct vm_struct *area = NULL;
+
+        /* Don't allow wraparound or zero size */
+        last_addr = addr + size - 1;
+        if (!size || last_addr < addr)
+                return NULL;
+
+        /*
+         * Mappings have to be page-aligned
+         */
+        offset = addr & ~PAGE_MASK;
+        p = addr & PAGE_MASK;
+        size = PAGE_ALIGN(last_addr + 1) - p;
+
+        if (likely(mem_init_done)) {
+                area = get_vm_area(size, VM_IOREMAP);
+                if (!area)
+                        return NULL;
+                v = (unsigned long)area->addr;
+        } else {
+                if ((fixmaps_used + (size >> PAGE_SHIFT)) > FIX_N_IOREMAPS)
+                        return NULL;
+                v = fix_to_virt(FIX_IOREMAP_BEGIN + fixmaps_used);
+                fixmaps_used += (size >> PAGE_SHIFT);
+        }
+
+        if (ioremap_page_range(v, v + size, p, prot)) {
+                if (likely(mem_init_done))
+                        vfree(area->addr);
+                else
+                        fixmaps_used -= (size >> PAGE_SHIFT);
+                return NULL;
+        }
+
+        return (void __iomem *)(offset + (char *)v);
+}
+
+void iounmap(void *addr)
+{
+        /* If the page is from the fixmap pool then we just clear out
+         * the fixmap mapping.
+         */
+        if (unlikely((unsigned long)addr > FIXADDR_START)) {
+                /* This is a bit broken... we don't really know
+                 * how big the area is so it's difficult to know
+                 * how many fixed pages to invalidate...
+                 * just flush tlb and hope for the best...
+                 * consider this a FIXME
+                 *
+                 * Really we should be clearing out one or more page
+                 * table entries for these virtual addresses so that
+                 * future references cause a page fault... for now, we
+                 * rely on two things:
+                 *   i)  this code never gets called on known boards
+                 *   ii) invalid accesses to the freed areas aren't made
+                 */
+                flush_tlb_all();
+                return;
+        }
+
+        return vfree((void *)(PAGE_MASK & (unsigned long)addr));
+}
+
+/**
+ * OK, this one's a bit tricky... ioremap can get called before memory is
+ * initialized (early serial console does this) and will want to alloc a page
+ * for its mapping.  No userspace pages will ever get allocated before memory
+ * is initialized so this applies only to kernel pages.  In the event that
+ * this is called before memory is initialized we allocate the page using
+ * the memblock infrastructure.
+ */
+
+pte_t __init_refok *pte_alloc_one_kernel(struct mm_struct *mm,
+                                         unsigned long address)
+{
+        pte_t *pte;
+
+        if (likely(mem_init_done)) {
+                pte = (pte_t *) __get_free_page(GFP_KERNEL | __GFP_REPEAT);
+        } else {
+                pte = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
+#if 0
+                /* FIXME: use memblock... */
+                pte = (pte_t *) __va(memblock_alloc(PAGE_SIZE, PAGE_SIZE));
+#endif
+        }
+
+        if (pte)
+                clear_page(pte);
+        return pte;
+}
diff --git a/arch/openrisc/mm/tlb.c b/arch/openrisc/mm/tlb.c
new file mode 100644
index 000000000000..56b0b89624af
--- /dev/null
+++ b/arch/openrisc/mm/tlb.c
@@ -0,0 +1,193 @@
+/*
+ * OpenRISC tlb.c
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
+ * Copyright (C) 2010-2011 Julius Baxter <julius.baxter@orsoc.se>
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
+ *
+ *      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/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/init.h>
+
+#include <asm/system.h>
+#include <asm/segment.h>
+#include <asm/tlbflush.h>
+#include <asm/pgtable.h>
+#include <asm/mmu_context.h>
+#include <asm/spr_defs.h>
+
+#define NO_CONTEXT -1
+
+#define NUM_DTLB_SETS (1 << ((mfspr(SPR_IMMUCFGR) & SPR_IMMUCFGR_NTS) >> \
+                            SPR_DMMUCFGR_NTS_OFF))
+#define NUM_ITLB_SETS (1 << ((mfspr(SPR_IMMUCFGR) & SPR_IMMUCFGR_NTS) >> \
+                            SPR_IMMUCFGR_NTS_OFF))
+#define DTLB_OFFSET(addr) (((addr) >> PAGE_SHIFT) & (NUM_DTLB_SETS-1))
+#define ITLB_OFFSET(addr) (((addr) >> PAGE_SHIFT) & (NUM_ITLB_SETS-1))
+/*
+ * Invalidate all TLB entries.
+ *
+ * This comes down to setting the 'valid' bit for all xTLBMR registers to 0.
+ * Easiest way to accomplish this is to just zero out the xTLBMR register
+ * completely.
+ *
+ */
+
+void flush_tlb_all(void)
+{
+        int i;
+        unsigned long num_tlb_sets;
+
+        /* Determine number of sets for IMMU. */
+        /* FIXME: Assumption is I & D nsets equal. */
+        num_tlb_sets = NUM_ITLB_SETS;
+
+        for (i = 0; i < num_tlb_sets; i++) {
+                mtspr_off(SPR_DTLBMR_BASE(0), i, 0);
+                mtspr_off(SPR_ITLBMR_BASE(0), i, 0);
+        }
+}
+
+#define have_dtlbeir (mfspr(SPR_DMMUCFGR) & SPR_DMMUCFGR_TEIRI)
+#define have_itlbeir (mfspr(SPR_IMMUCFGR) & SPR_IMMUCFGR_TEIRI)
+
+/*
+ * Invalidate a single page.  This is what the xTLBEIR register is for.
+ *
+ * There's no point in checking the vma for PAGE_EXEC to determine whether it's
+ * the data or instruction TLB that should be flushed... that would take more
+ * than the few instructions that the following compiles down to!
+ *
+ * The case where we don't have the xTLBEIR register really only works for
+ * MMU's with a single way and is hard-coded that way.
+ */
+
+#define flush_dtlb_page_eir(addr) mtspr(SPR_DTLBEIR, addr)
+#define flush_dtlb_page_no_eir(addr) \
+        mtspr_off(SPR_DTLBMR_BASE(0), DTLB_OFFSET(addr), 0);
+
+#define flush_itlb_page_eir(addr) mtspr(SPR_ITLBEIR, addr)
+#define flush_itlb_page_no_eir(addr) \
+        mtspr_off(SPR_ITLBMR_BASE(0), ITLB_OFFSET(addr), 0);
+
+void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
+{
+        if (have_dtlbeir)
+                flush_dtlb_page_eir(addr);
+        else
+                flush_dtlb_page_no_eir(addr);
+
+        if (have_itlbeir)
+                flush_itlb_page_eir(addr);
+        else
+                flush_itlb_page_no_eir(addr);
+}
+
+void flush_tlb_range(struct vm_area_struct *vma,
+                     unsigned long start, unsigned long end)
+{
+        int addr;
+        bool dtlbeir;
+        bool itlbeir;
+
+        dtlbeir = have_dtlbeir;
+        itlbeir = have_itlbeir;
+
+        for (addr = start; addr < end; addr += PAGE_SIZE) {
+                if (dtlbeir)
+                        flush_dtlb_page_eir(addr);
+                else
+                        flush_dtlb_page_no_eir(addr);
+
+                if (itlbeir)
+                        flush_itlb_page_eir(addr);
+                else
+                        flush_itlb_page_no_eir(addr);
+        }
+}
+
+/*
+ * Invalidate the selected mm context only.
+ *
+ * FIXME: Due to some bug here, we're flushing everything for now.
+ * This should be changed to loop over over mm and call flush_tlb_range.
+ */
+
+void flush_tlb_mm(struct mm_struct *mm)
+{
+
+        /* Was seeing bugs with the mm struct passed to us. Scrapped most of
+           this function. */
+        /* Several architctures do this */
+        flush_tlb_all();
+}
+
+/* called in schedule() just before actually doing the switch_to */
+
+void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+               struct task_struct *next_tsk)
+{
+        /* remember the pgd for the fault handlers
+         * this is similar to the pgd register in some other CPU's.
+         * we need our own copy of it because current and active_mm
+         * might be invalid at points where we still need to derefer
+         * the pgd.
+         */
+        current_pgd = next->pgd;
+
+        /* We don't have context support implemented, so flush all
+         * entries belonging to previous map
+         */
+
+        if (prev != next)
+                flush_tlb_mm(prev);
+
+}
+
+/*
+ * Initialize the context related info for a new mm_struct
+ * instance.
+ */
+
+int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+        mm->context = NO_CONTEXT;
+        return 0;
+}
+
+/* called by __exit_mm to destroy the used MMU context if any before
+ * destroying the mm itself. this is only called when the last user of the mm
+ * drops it.
+ */
+
+void destroy_context(struct mm_struct *mm)
+{
+        flush_tlb_mm(mm);
+
+}
+
+/* called once during VM initialization, from init.c */
+
+void __init tlb_init(void)
+{
+        /* Do nothing... */
+        /* invalidate the entire TLB */
+        /* flush_tlb_all(); */
+}