/*
 * PowerPC64 SLB support.
 *
 * Copyright (C) 2004 David Gibson <dwg@au.ibm.com>, IBM
 * Based on earlier code written by:
 * Dave Engebretsen and Mike Corrigan {engebret|mikejc}@us.ibm.com
 *    Copyright (c) 2001 Dave Engebretsen
 * Copyright (C) 2002 Anton Blanchard <anton@au.ibm.com>, IBM
 *
 *
 *      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 <asm/pgtable.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/paca.h>
#include <asm/cputable.h>
#include <asm/cacheflush.h>
#include <asm/smp.h>
#include <linux/compiler.h>
#include <linux/context_tracking.h>
#include <linux/mm_types.h>

#include <asm/udbg.h>
#include <asm/code-patching.h>

enum slb_index {
        LINEAR_INDEX    = 0, /* Kernel linear map  (0xc000000000000000) */
        VMALLOC_INDEX   = 1, /* Kernel virtual map (0xd000000000000000) */
        KSTACK_INDEX    = 2, /* Kernel stack map */
};

extern void slb_allocate(unsigned long ea);

#define slb_esid_mask(ssize)    \
        (((ssize) == MMU_SEGSIZE_256M)? ESID_MASK: ESID_MASK_1T)

static inline unsigned long mk_esid_data(unsigned long ea, int ssize,
                                         enum slb_index index)
{
        return (ea & slb_esid_mask(ssize)) | SLB_ESID_V | index;
}

static inline unsigned long mk_vsid_data(unsigned long ea, int ssize,
                                         unsigned long flags)
{
        return (get_kernel_vsid(ea, ssize) << slb_vsid_shift(ssize)) | flags |
                ((unsigned long) ssize << SLB_VSID_SSIZE_SHIFT);
}

static inline void slb_shadow_update(unsigned long ea, int ssize,
                                     unsigned long flags,
                                     enum slb_index index)
{
        struct slb_shadow *p = get_slb_shadow();

        /*
         * Clear the ESID first so the entry is not valid while we are
         * updating it.  No write barriers are needed here, provided
         * we only update the current CPU's SLB shadow buffer.
         */
        WRITE_ONCE(p->save_area[index].esid, 0);
        WRITE_ONCE(p->save_area[index].vsid, cpu_to_be64(mk_vsid_data(ea, ssize, flags)));
        WRITE_ONCE(p->save_area[index].esid, cpu_to_be64(mk_esid_data(ea, ssize, index)));
}

static inline void slb_shadow_clear(enum slb_index index)
{
        WRITE_ONCE(get_slb_shadow()->save_area[index].esid, cpu_to_be64(index));
}

static inline void create_shadowed_slbe(unsigned long ea, int ssize,
                                        unsigned long flags,
                                        enum slb_index index)
{
        /*
         * Updating the shadow buffer before writing the SLB ensures
         * we don't get a stale entry here if we get preempted by PHYP
         * between these two statements.
         */
        slb_shadow_update(ea, ssize, flags, index);

        asm volatile("slbmte  %0,%1" :
                     : "r" (mk_vsid_data(ea, ssize, flags)),
                       "r" (mk_esid_data(ea, ssize, index))
                     : "memory" );
}

/*
 * Insert bolted entries into SLB (which may not be empty, so don't clear
 * slb_cache_ptr).
 */
void __slb_restore_bolted_realmode(void)
{
        struct slb_shadow *p = get_slb_shadow();
        enum slb_index index;

         /* No isync needed because realmode. */
        for (index = 0; index < SLB_NUM_BOLTED; index++) {
                asm volatile("slbmte  %0,%1" :
                     : "r" (be64_to_cpu(p->save_area[index].vsid)),
                       "r" (be64_to_cpu(p->save_area[index].esid)));
        }
}

/*
 * Insert the bolted entries into an empty SLB.
 * This is not the same as rebolt because the bolted segments are not
 * changed, just loaded from the shadow area.
 */
void slb_restore_bolted_realmode(void)
{
        __slb_restore_bolted_realmode();
        get_paca()->slb_cache_ptr = 0;
}

/*
 * This flushes all SLB entries including 0, so it must be realmode.
 */
void slb_flush_all_realmode(void)
{
        /*
         * This flushes all SLB entries including 0, so it must be realmode.
         */
        asm volatile("slbmte %0,%0; slbia" : : "r" (0));
}

static void __slb_flush_and_rebolt(void)
{
        /* If you change this make sure you change SLB_NUM_BOLTED
         * and PR KVM appropriately too. */
        unsigned long linear_llp, vmalloc_llp, lflags, vflags;
        unsigned long ksp_esid_data, ksp_vsid_data;

        linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
        vmalloc_llp = mmu_psize_defs[mmu_vmalloc_psize].sllp;
        lflags = SLB_VSID_KERNEL | linear_llp;
        vflags = SLB_VSID_KERNEL | vmalloc_llp;

        ksp_esid_data = mk_esid_data(get_paca()->kstack, mmu_kernel_ssize, KSTACK_INDEX);
        if ((ksp_esid_data & ~0xfffffffUL) <= PAGE_OFFSET) {
                ksp_esid_data &= ~SLB_ESID_V;
                ksp_vsid_data = 0;
                slb_shadow_clear(KSTACK_INDEX);
        } else {
                /* Update stack entry; others don't change */
                slb_shadow_update(get_paca()->kstack, mmu_kernel_ssize, lflags, KSTACK_INDEX);
                ksp_vsid_data =
                        be64_to_cpu(get_slb_shadow()->save_area[KSTACK_INDEX].vsid);
        }

        /* 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"
                     "slbia\n"
                     /* Slot 1 - first VMALLOC segment */
                     "slbmte    %0,%1\n"
                     /* Slot 2 - kernel stack */
                     "slbmte    %2,%3\n"
                     "isync"
                     :: "r"(mk_vsid_data(VMALLOC_START, mmu_kernel_ssize, vflags)),
                        "r"(mk_esid_data(VMALLOC_START, mmu_kernel_ssize, VMALLOC_INDEX)),
                        "r"(ksp_vsid_data),
                        "r"(ksp_esid_data)
                     : "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_save_contents(struct slb_entry *slb_ptr)
{
        int i;
        unsigned long e, v;

        /* Save slb_cache_ptr value. */
        get_paca()->slb_save_cache_ptr = get_paca()->slb_cache_ptr;

        if (!slb_ptr)
                return;

        for (i = 0; i < mmu_slb_size; i++) {
                asm volatile("slbmfee  %0,%1" : "=r" (e) : "r" (i));
                asm volatile("slbmfev  %0,%1" : "=r" (v) : "r" (i));
                slb_ptr->esid = e;
                slb_ptr->vsid = v;
                slb_ptr++;
        }
}

void slb_dump_contents(struct slb_entry *slb_ptr)
{
        int i, n;
        unsigned long e, v;
        unsigned long llp;

        if (!slb_ptr)
                return;

        pr_err("SLB contents of cpu 0x%x\n", smp_processor_id());
        pr_err("Last SLB entry inserted at slot %lld\n", get_paca()->stab_rr);

        for (i = 0; i < mmu_slb_size; i++) {
                e = slb_ptr->esid;
                v = slb_ptr->vsid;
                slb_ptr++;

                if (!e && !v)
                        continue;

                pr_err("%02d %016lx %016lx\n", i, e, v);

                if (!(e & SLB_ESID_V)) {
                        pr_err("\n");
                        continue;
                }
                llp = v & SLB_VSID_LLP;
                if (v & SLB_VSID_B_1T) {
                        pr_err("  1T  ESID=%9lx  VSID=%13lx LLP:%3lx\n",
                               GET_ESID_1T(e),
                               (v & ~SLB_VSID_B) >> SLB_VSID_SHIFT_1T, llp);
                } else {
                        pr_err(" 256M ESID=%9lx  VSID=%13lx LLP:%3lx\n",
                               GET_ESID(e),
                               (v & ~SLB_VSID_B) >> SLB_VSID_SHIFT, llp);
                }
        }
        pr_err("----------------------------------\n");

        /* Dump slb cache entires as well. */
        pr_err("SLB cache ptr value = %d\n", get_paca()->slb_save_cache_ptr);
        pr_err("Valid SLB cache entries:\n");
        n = min_t(int, get_paca()->slb_save_cache_ptr, SLB_CACHE_ENTRIES);
        for (i = 0; i < n; i++)
                pr_err("%02d EA[0-35]=%9x\n", i, get_paca()->slb_cache[i]);
        pr_err("Rest of SLB cache entries:\n");
        for (i = n; i < SLB_CACHE_ENTRIES; i++)
                pr_err("%02d EA[0-35]=%9x\n", i, get_paca()->slb_cache[i]);
}

void slb_vmalloc_update(void)
{
        unsigned long vflags;

        vflags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_vmalloc_psize].sllp;
        slb_shadow_update(VMALLOC_START, mmu_kernel_ssize, vflags, VMALLOC_INDEX);
        slb_flush_and_rebolt();
}

/* Helper function to compare esids.  There are four cases to handle.
 * 1. The system is not 1T segment size capable.  Use the GET_ESID compare.
 * 2. The system is 1T capable, both addresses are < 1T, use the GET_ESID compare.
 * 3. The system is 1T capable, only one of the two addresses is > 1T.  This is not a match.
 * 4. The system is 1T capable, both addresses are > 1T, use the GET_ESID_1T macro to compare.
 */
static inline int esids_match(unsigned long addr1, unsigned long addr2)
{
        int esid_1t_count;

        /* System is not 1T segment size capable. */
        if (!mmu_has_feature(MMU_FTR_1T_SEGMENT))
                return (GET_ESID(addr1) == GET_ESID(addr2));

        esid_1t_count = (((addr1 >> SID_SHIFT_1T) != 0) +
                                ((addr2 >> SID_SHIFT_1T) != 0));

        /* both addresses are < 1T */
        if (esid_1t_count == 0)
                return (GET_ESID(addr1) == GET_ESID(addr2));

        /* One address < 1T, the other > 1T.  Not a match */
        if (esid_1t_count == 1)
                return 0;

        /* Both addresses are > 1T. */
        return (GET_ESID_1T(addr1) == GET_ESID_1T(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;
        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 (!mmu_has_feature(MMU_FTR_NO_SLBIE_B) &&
            offset <= SLB_CACHE_ENTRIES) {
                int i;
                asm volatile("isync" : : : "memory");
                for (i = 0; i < offset; i++) {
                        slbie_data = (unsigned long)get_paca()->slb_cache[i]
                                << SID_SHIFT; /* EA */
                        slbie_data |= user_segment_size(slbie_data)
                                << SLBIE_SSIZE_SHIFT;
                        slbie_data |= SLBIE_C; /* C set for user addresses */
                        asm volatile("slbie %0" : : "r" (slbie_data));
                }
                asm volatile("isync" : : : "memory");
        } else {
                __slb_flush_and_rebolt();
        }

        /* Workaround POWER5 < DD2.1 issue */
        if (offset == 1 || offset > SLB_CACHE_ENTRIES)
                asm volatile("slbie %0" : : "r" (slbie_data));

        get_paca()->slb_cache_ptr = 0;
        copy_mm_to_paca(mm);

        /*
         * preload some userspace segments into the SLB.
         * Almost all 32 and 64bit PowerPC executables are linked at
         * 0x10000000 so it makes sense to preload this segment.
         */
        exec_base = 0x10000000;

        if (is_kernel_addr(pc) || is_kernel_addr(stack) ||
            is_kernel_addr(exec_base))
                return;

        slb_allocate(pc);

        if (!esids_match(pc, stack))
                slb_allocate(stack);

        if (!esids_match(pc, exec_base) &&
            !esids_match(stack, exec_base))
                slb_allocate(exec_base);
}

static inline void patch_slb_encoding(unsigned int *insn_addr,
                                      unsigned int immed)
{

        /*
         * This function patches either an li or a cmpldi instruction with
         * a new immediate value. This relies on the fact that both li
         * (which is actually addi) and cmpldi both take a 16-bit immediate
         * value, and it is situated in the same location in the instruction,
         * ie. bits 16-31 (Big endian bit order) or the lower 16 bits.
         * The signedness of the immediate operand differs between the two
         * instructions however this code is only ever patching a small value,
         * much less than 1 << 15, so we can get away with it.
         * To patch the value we read the existing instruction, clear the
         * immediate value, and or in our new value, then write the instruction
         * back.
         */
        unsigned int insn = (*insn_addr & 0xffff0000) | immed;
        patch_instruction((struct ppc_inst *)insn_addr, ppc_inst(insn));
}

extern u32 slb_miss_kernel_load_linear[];
extern u32 slb_miss_kernel_load_io[];
extern u32 slb_compare_rr_to_size[];
extern u32 slb_miss_kernel_load_vmemmap[];

void slb_set_size(u16 size)
{
        if (mmu_slb_size == size)
                return;

        mmu_slb_size = size;
        patch_slb_encoding(slb_compare_rr_to_size, mmu_slb_size);
}

void slb_initialize(void)
{
        unsigned long linear_llp, vmalloc_llp, io_llp;
        unsigned long lflags, vflags;
        static int slb_encoding_inited;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
        unsigned long vmemmap_llp;
#endif

        /* Prepare our SLB miss handler based on our page size */
        linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
        io_llp = mmu_psize_defs[mmu_io_psize].sllp;
        vmalloc_llp = mmu_psize_defs[mmu_vmalloc_psize].sllp;
        get_paca()->vmalloc_sllp = SLB_VSID_KERNEL | vmalloc_llp;
#ifdef CONFIG_SPARSEMEM_VMEMMAP
        vmemmap_llp = mmu_psize_defs[mmu_vmemmap_psize].sllp;
#endif
        if (!slb_encoding_inited) {
                slb_encoding_inited = 1;
                patch_slb_encoding(slb_miss_kernel_load_linear,
                                   SLB_VSID_KERNEL | linear_llp);
                patch_slb_encoding(slb_miss_kernel_load_io,
                                   SLB_VSID_KERNEL | io_llp);
                patch_slb_encoding(slb_compare_rr_to_size,
                                   mmu_slb_size);

                pr_devel("SLB: linear  LLP = %04lx\n", linear_llp);
                pr_devel("SLB: io      LLP = %04lx\n", io_llp);

#ifdef CONFIG_SPARSEMEM_VMEMMAP
                patch_slb_encoding(slb_miss_kernel_load_vmemmap,
                                   SLB_VSID_KERNEL | vmemmap_llp);
                pr_devel("SLB: vmemmap LLP = %04lx\n", vmemmap_llp);
#endif
        }

        get_paca()->stab_rr = SLB_NUM_BOLTED;

        lflags = SLB_VSID_KERNEL | linear_llp;
        vflags = SLB_VSID_KERNEL | vmalloc_llp;

        /* Invalidate the entire SLB (even entry 0) & all the ERATS */
        asm volatile("isync":::"memory");
        asm volatile("slbmte  %0,%0"::"r" (0) : "memory");
        asm volatile("isync; slbia; isync":::"memory");
        create_shadowed_slbe(PAGE_OFFSET, mmu_kernel_ssize, lflags, LINEAR_INDEX);
        create_shadowed_slbe(VMALLOC_START, mmu_kernel_ssize, vflags, VMALLOC_INDEX);

        /* 
         * For the boot cpu, we're running on the stack in init_thread_union,
         * which is in the first segment of the linear mapping, and also
         * get_paca()->kstack hasn't been initialized yet.
         * For secondary cpus, we need to bolt the kernel stack entry now.
         */
        slb_shadow_clear(KSTACK_INDEX);
        if (raw_smp_processor_id() != boot_cpuid &&
            (get_paca()->kstack & slb_esid_mask(mmu_kernel_ssize)) > PAGE_OFFSET)
                create_shadowed_slbe(get_paca()->kstack,
                                     mmu_kernel_ssize, lflags, KSTACK_INDEX);

        asm volatile("isync":::"memory");
}

static void insert_slb_entry(unsigned long vsid, unsigned long ea,
                             int bpsize, int ssize)
{
        unsigned long flags, vsid_data, esid_data;
        enum slb_index index;
        int slb_cache_index;

        /*
         * We are irq disabled, hence should be safe to access PACA.
         */
        VM_WARN_ON(!irqs_disabled());

        /*
         * We can't take a PMU exception in the following code, so hard
         * disable interrupts.
         */
        hard_irq_disable();

        index = get_paca()->stab_rr;

        /*
         * simple round-robin replacement of slb starting at SLB_NUM_BOLTED.
         */
        if (index < (mmu_slb_size - 1))
                index++;
        else
                index = SLB_NUM_BOLTED;

        get_paca()->stab_rr = index;

        flags = SLB_VSID_USER | mmu_psize_defs[bpsize].sllp;
        vsid_data = (vsid << slb_vsid_shift(ssize)) | flags |
                    ((unsigned long) ssize << SLB_VSID_SSIZE_SHIFT);
        esid_data = mk_esid_data(ea, ssize, index);

        /*
         * No need for an isync before or after this slbmte. The exception
         * we enter with and the rfid we exit with are context synchronizing.
         * Also we only handle user segments here.
         */
        asm volatile("slbmte %0, %1" : : "r" (vsid_data), "r" (esid_data)
                     : "memory");

        /*
         * Now update slb cache entries
         */
        slb_cache_index = get_paca()->slb_cache_ptr;
        if (slb_cache_index < SLB_CACHE_ENTRIES) {
                /*
                 * We have space in slb cache for optimized switch_slb().
                 * Top 36 bits from esid_data as per ISA
                 */
                get_paca()->slb_cache[slb_cache_index++] = esid_data >> 28;
                get_paca()->slb_cache_ptr++;
        } else {
                /*
                 * Our cache is full and the current cache content strictly
                 * doesn't indicate the active SLB conents. Bump the ptr
                 * so that switch_slb() will ignore the cache.
                 */
                get_paca()->slb_cache_ptr = SLB_CACHE_ENTRIES + 1;
        }
}

static void handle_multi_context_slb_miss(int context_id, unsigned long ea)
{
        struct mm_struct *mm = current->mm;
        unsigned long vsid;
        int bpsize;

        /*
         * We are always above 1TB, hence use high user segment size.
         */
        vsid = get_vsid(context_id, ea, mmu_highuser_ssize);
        bpsize = get_slice_psize(mm, ea);
        insert_slb_entry(vsid, ea, bpsize, mmu_highuser_ssize);
}

void slb_miss_large_addr(struct pt_regs *regs)
{
        enum ctx_state prev_state = exception_enter();
        unsigned long ea = regs->dar;
        int context;

        if (REGION_ID(ea) != USER_REGION_ID)
                goto slb_bad_addr;

        /*
         * Are we beyound what the page table layout supports ?
         */
        if ((ea & ~REGION_MASK) >= H_PGTABLE_RANGE)
                goto slb_bad_addr;

        /* Lower address should have been handled by asm code */
        if (ea < (1UL << MAX_EA_BITS_PER_CONTEXT))
                goto slb_bad_addr;

        /*
         * consider this as bad access if we take a SLB miss
         * on an address above addr limit.
         */
        if (ea >= current->mm->context.slb_addr_limit)
                goto slb_bad_addr;

        context = get_ea_context(&current->mm->context, ea);
        if (!context)
                goto slb_bad_addr;

        handle_multi_context_slb_miss(context, ea);
        exception_exit(prev_state);
        return;

slb_bad_addr:
        if (user_mode(regs))
                _exception(SIGSEGV, regs, SEGV_BNDERR, ea);
        else
                bad_page_fault(regs, ea, SIGSEGV);
        exception_exit(prev_state);
}