OpenRISC: Memory management

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

1 files changed, 338 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;
+        }
+}