sh: Enable shared page fault handler for _32/_64.

This moves the now generic _32 page fault handling code to a shared place
and adapts the _64 implementation to make use of it.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 264 insertions, 0 deletions

diff --git a/arch/sh/mm/tlbex_64.c b/arch/sh/mm/tlbex_64.c
new file mode 100644
index 000000000000..d15b99466508
--- /dev/null
+++ b/arch/sh/mm/tlbex_64.c
@@ -0,0 +1,264 @@
+/*
+ * The SH64 TLB miss.
+ *
+ * Original code from fault.c
+ * Copyright (C) 2000, 2001  Paolo Alberelli
+ *
+ * Fast PTE->TLB refill path
+ * Copyright (C) 2003 Richard.Curnow@superh.com
+ *
+ * IMPORTANT NOTES :
+ * The do_fast_page_fault function is called from a context in entry.S
+ * where very few registers have been saved.  In particular, the code in
+ * this file must be compiled not to use ANY caller-save registers that
+ * are not part of the restricted save set.  Also, it means that code in
+ * this file must not make calls to functions elsewhere in the kernel, or
+ * else the excepting context will see corruption in its caller-save
+ * registers.  Plus, the entry.S save area is non-reentrant, so this code
+ * has to run with SR.BL==1, i.e. no interrupts taken inside it and panic
+ * on any exception.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#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/smp.h>
+#include <linux/interrupt.h>
+#include <asm/tlb.h>
+#include <asm/io.h>
+#include <asm/uaccess.h>
+#include <asm/pgalloc.h>
+#include <asm/mmu_context.h>
+#include <cpu/registers.h>
+
+/* Callable from fault.c, so not static */
+inline void __do_tlb_refill(unsigned long address,
+                            unsigned long long is_text_not_data, pte_t *pte)
+{
+        unsigned long long ptel;
+        unsigned long long pteh=0;
+        struct tlb_info *tlbp;
+        unsigned long long next;
+
+        /* Get PTEL first */
+        ptel = pte_val(*pte);
+
+        /*
+         * Set PTEH register
+         */
+        pteh = neff_sign_extend(address & MMU_VPN_MASK);
+
+        /* Set the ASID. */
+        pteh |= get_asid() << PTEH_ASID_SHIFT;
+        pteh |= PTEH_VALID;
+
+        /* Set PTEL register, set_pte has performed the sign extension */
+        ptel &= _PAGE_FLAGS_HARDWARE_MASK; /* drop software flags */
+
+        tlbp = is_text_not_data ? &(cpu_data->itlb) : &(cpu_data->dtlb);
+        next = tlbp->next;
+        __flush_tlb_slot(next);
+        asm volatile ("putcfg %0,1,%2\n\n\t"
+                      "putcfg %0,0,%1\n"
+                      :  : "r" (next), "r" (pteh), "r" (ptel) );
+
+        next += TLB_STEP;
+        if (next > tlbp->last) next = tlbp->first;
+        tlbp->next = next;
+
+}
+
+static int handle_vmalloc_fault(struct mm_struct *mm,
+                                unsigned long protection_flags,
+                                unsigned long long textaccess,
+                                unsigned long address)
+{
+        pgd_t *dir;
+        pud_t *pud;
+        pmd_t *pmd;
+        static pte_t *pte;
+        pte_t entry;
+
+        dir = pgd_offset_k(address);
+
+        pud = pud_offset(dir, address);
+        if (pud_none_or_clear_bad(pud))
+                return 0;
+
+        pmd = pmd_offset(pud, address);
+        if (pmd_none_or_clear_bad(pmd))
+                return 0;
+
+        pte = pte_offset_kernel(pmd, address);
+        entry = *pte;
+
+        if (pte_none(entry) || !pte_present(entry))
+                return 0;
+        if ((pte_val(entry) & protection_flags) != protection_flags)
+                return 0;
+
+        __do_tlb_refill(address, textaccess, pte);
+
+        return 1;
+}
+
+static int handle_tlbmiss(struct mm_struct *mm,
+                          unsigned long long protection_flags,
+                          unsigned long long textaccess,
+                          unsigned long address)
+{
+        pgd_t *dir;
+        pud_t *pud;
+        pmd_t *pmd;
+        pte_t *pte;
+        pte_t entry;
+
+        /* NB. The PGD currently only contains a single entry - there is no
+           page table tree stored for the top half of the address space since
+           virtual pages in that region should never be mapped in user mode.
+           (In kernel mode, the only things in that region are the 512Mb super
+           page (locked in), and vmalloc (modules) +  I/O device pages (handled
+           by handle_vmalloc_fault), so no PGD for the upper half is required
+           by kernel mode either).
+
+           See how mm->pgd is allocated and initialised in pgd_alloc to see why
+           the next test is necessary.  - RPC */
+        if (address >= (unsigned long) TASK_SIZE)
+                /* upper half - never has page table entries. */
+                return 0;
+
+        dir = pgd_offset(mm, address);
+        if (pgd_none(*dir) || !pgd_present(*dir))
+                return 0;
+        if (!pgd_present(*dir))
+                return 0;
+
+        pud = pud_offset(dir, address);
+        if (pud_none(*pud) || !pud_present(*pud))
+                return 0;
+
+        pmd = pmd_offset(pud, address);
+        if (pmd_none(*pmd) || !pmd_present(*pmd))
+                return 0;
+
+        pte = pte_offset_kernel(pmd, address);
+        entry = *pte;
+
+        if (pte_none(entry) || !pte_present(entry))
+                return 0;
+
+        /*
+         * If the page doesn't have sufficient protection bits set to
+         * service the kind of fault being handled, there's not much
+         * point doing the TLB refill.  Punt the fault to the general
+         * handler.
+         */
+        if ((pte_val(entry) & protection_flags) != protection_flags)
+                return 0;
+
+        __do_tlb_refill(address, textaccess, pte);
+
+        return 1;
+}
+
+/*
+ * Put all this information into one structure so that everything is just
+ * arithmetic relative to a single base address.  This reduces the number
+ * of movi/shori pairs needed just to load addresses of static data.
+ */
+struct expevt_lookup {
+        unsigned short protection_flags[8];
+        unsigned char  is_text_access[8];
+        unsigned char  is_write_access[8];
+};
+
+#define PRU (1<<9)
+#define PRW (1<<8)
+#define PRX (1<<7)
+#define PRR (1<<6)
+
+#define DIRTY (_PAGE_DIRTY | _PAGE_ACCESSED)
+#define YOUNG (_PAGE_ACCESSED)
+
+/* Sized as 8 rather than 4 to allow checking the PTE's PRU bit against whether
+   the fault happened in user mode or privileged mode. */
+static struct expevt_lookup expevt_lookup_table = {
+        .protection_flags = {PRX, PRX, 0, 0, PRR, PRR, PRW, PRW},
+        .is_text_access   = {1,   1,   0, 0, 0,   0,   0,   0}
+};
+
+/*
+   This routine handles page faults that can be serviced just by refilling a
+   TLB entry from an existing page table entry.  (This case represents a very
+   large majority of page faults.) Return 1 if the fault was successfully
+   handled.  Return 0 if the fault could not be handled.  (This leads into the
+   general fault handling in fault.c which deals with mapping file-backed
+   pages, stack growth, segmentation faults, swapping etc etc)
+ */
+asmlinkage int do_fast_page_fault(unsigned long long ssr_md,
+                                  unsigned long long expevt,
+                                  unsigned long address)
+{
+        struct task_struct *tsk;
+        struct mm_struct *mm;
+        unsigned long long textaccess;
+        unsigned long long protection_flags;
+        unsigned long long index;
+        unsigned long long expevt4;
+
+        /* The next few lines implement a way of hashing EXPEVT into a
+         * small array index which can be used to lookup parameters
+         * specific to the type of TLBMISS being handled.
+         *
+         * Note:
+         *      ITLBMISS has EXPEVT==0xa40
+         *      RTLBMISS has EXPEVT==0x040
+         *      WTLBMISS has EXPEVT==0x060
+         */
+        expevt4 = (expevt >> 4);
+        /* TODO : xor ssr_md into this expression too. Then we can check
+         * that PRU is set when it needs to be. */
+        index = expevt4 ^ (expevt4 >> 5);
+        index &= 7;
+        protection_flags = expevt_lookup_table.protection_flags[index];
+        textaccess       = expevt_lookup_table.is_text_access[index];
+
+        /* SIM
+         * Note this is now called with interrupts still disabled
+         * This is to cope with being called for a missing IO port
+         * address with interrupts disabled. This should be fixed as
+         * soon as we have a better 'fast path' miss handler.
+         *
+         * Plus take care how you try and debug this stuff.
+         * For example, writing debug data to a port which you
+         * have just faulted on is not going to work.
+         */
+
+        tsk = current;
+        mm = tsk->mm;
+
+        if (is_vmalloc_addr((void *)address)) {
+                if (ssr_md)
+                        /*
+                         * Process-contexts can never have this address
+                         * range mapped
+                         */
+                        if (handle_vmalloc_fault(mm, protection_flags,
+                                                 textaccess, address))
+                                return 1;
+        } else if (!in_interrupt() && mm) {
+                if (handle_tlbmiss(mm, protection_flags, textaccess, address))
+                        return 1;
+        }
+
+        return 0;
+}