/*
 * Copyright (C) 2004, 2005 MIPS Technologies, Inc.  All rights reserved.
 *
 *  This program is free software; you can distribute it and/or modify it
 *  under the terms of the GNU General Public License (Version 2) as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
 */

/*
 * VPE support module
 *
 * Provides support for loading a MIPS SP program on VPE1.
 * The SP environment is rather simple, no tlb's.  It needs to be relocatable
 * (or partially linked). You should initialise your stack in the startup
 * code. This loader looks for the symbol __start and sets up
 * execution to resume from there. The MIPS SDE kit contains suitable examples.
 *
 * To load and run, simply cat a SP 'program file' to /dev/vpe1.
 * i.e cat spapp >/dev/vpe1.
 */
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/elf.h>
#include <linux/seq_file.h>
#include <linux/syscalls.h>
#include <linux/moduleloader.h>
#include <linux/interrupt.h>
#include <linux/poll.h>
#include <linux/bootmem.h>
#include <asm/mipsregs.h>
#include <asm/mipsmtregs.h>
#include <asm/cacheflush.h>
#include <linux/atomic.h>
#include <asm/cpu.h>
#include <asm/mips_mt.h>
#include <asm/processor.h>
#include <asm/vpe.h>

typedef void *vpe_handle;

#ifndef ARCH_SHF_SMALL
#define ARCH_SHF_SMALL 0
#endif

/* If this is set, the section belongs in the init part of the module */
#define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))

/*
 * The number of TCs and VPEs physically available on the core
 */
static int hw_tcs, hw_vpes;
static char module_name[] = "vpe";
static int major;
static const int minor = 1;     /* fixed for now  */

/* grab the likely amount of memory we will need. */
#ifdef CONFIG_MIPS_VPE_LOADER_TOM
#define P_SIZE (2 * 1024 * 1024)
#else
/* add an overhead to the max kmalloc size for non-striped symbols/etc */
#define P_SIZE (256 * 1024)
#endif

extern unsigned long physical_memsize;

#define MAX_VPES 16
#define VPE_PATH_MAX 256

enum vpe_state {
        VPE_STATE_UNUSED = 0,
        VPE_STATE_INUSE,
        VPE_STATE_RUNNING
};

enum tc_state {
        TC_STATE_UNUSED = 0,
        TC_STATE_INUSE,
        TC_STATE_RUNNING,
        TC_STATE_DYNAMIC
};

struct vpe {
        enum vpe_state state;

        /* (device) minor associated with this vpe */
        int minor;

        /* elfloader stuff */
        void *load_addr;
        unsigned long len;
        char *pbuffer;
        unsigned long plen;
        unsigned int uid, gid;
        char cwd[VPE_PATH_MAX];

        unsigned long __start;

        /* tc's associated with this vpe */
        struct list_head tc;

        /* The list of vpe's */
        struct list_head list;

        /* shared symbol address */
        void *shared_ptr;

        /* the list of who wants to know when something major happens */
        struct list_head notify;

        unsigned int ntcs;
};

struct tc {
        enum tc_state state;
        int index;

        struct vpe *pvpe;       /* parent VPE */
        struct list_head tc;    /* The list of TC's with this VPE */
        struct list_head list;  /* The global list of tc's */
};

struct {
        spinlock_t vpe_list_lock;
        struct list_head vpe_list;      /* Virtual processing elements */
        spinlock_t tc_list_lock;
        struct list_head tc_list;       /* Thread contexts */
} vpecontrol = {
        .vpe_list_lock  = __SPIN_LOCK_UNLOCKED(vpe_list_lock),
        .vpe_list       = LIST_HEAD_INIT(vpecontrol.vpe_list),
        .tc_list_lock   = __SPIN_LOCK_UNLOCKED(tc_list_lock),
        .tc_list        = LIST_HEAD_INIT(vpecontrol.tc_list)
};

static void release_progmem(void *ptr);

/* get the vpe associated with this minor */
static struct vpe *get_vpe(int minor)
{
        struct vpe *res, *v;

        if (!cpu_has_mipsmt)
                return NULL;

        res = NULL;
        spin_lock(&vpecontrol.vpe_list_lock);
        list_for_each_entry(v, &vpecontrol.vpe_list, list) {
                if (v->minor == minor) {
                        res = v;
                        break;
                }
        }
        spin_unlock(&vpecontrol.vpe_list_lock);

        return res;
}

/* get the vpe associated with this minor */
static struct tc *get_tc(int index)
{
        struct tc *res, *t;

        res = NULL;
        spin_lock(&vpecontrol.tc_list_lock);
        list_for_each_entry(t, &vpecontrol.tc_list, list) {
                if (t->index == index) {
                        res = t;
                        break;
                }
        }
        spin_unlock(&vpecontrol.tc_list_lock);

        return res;
}

/* allocate a vpe and associate it with this minor (or index) */
static struct vpe *alloc_vpe(int minor)
{
        struct vpe *v;

        if ((v = kzalloc(sizeof(struct vpe), GFP_KERNEL)) == NULL)
                return NULL;

        INIT_LIST_HEAD(&v->tc);
        spin_lock(&vpecontrol.vpe_list_lock);
        list_add_tail(&v->list, &vpecontrol.vpe_list);
        spin_unlock(&vpecontrol.vpe_list_lock);

        INIT_LIST_HEAD(&v->notify);
        v->minor = minor;

        return v;
}

/* allocate a tc. At startup only tc0 is running, all other can be halted. */
static struct tc *alloc_tc(int index)
{
        struct tc *tc;

        if ((tc = kzalloc(sizeof(struct tc), GFP_KERNEL)) == NULL)
                goto out;

        INIT_LIST_HEAD(&tc->tc);
        tc->index = index;

        spin_lock(&vpecontrol.tc_list_lock);
        list_add_tail(&tc->list, &vpecontrol.tc_list);
        spin_unlock(&vpecontrol.tc_list_lock);

out:
        return tc;
}

/* clean up and free everything */
static void release_vpe(struct vpe *v)
{
        list_del(&v->list);
        if (v->load_addr)
                release_progmem(v);
        kfree(v);
}

static void __maybe_unused dump_mtregs(void)
{
        unsigned long val;

        val = read_c0_config3();
        printk("config3 0x%lx MT %ld\n", val,
               (val & CONFIG3_MT) >> CONFIG3_MT_SHIFT);

        val = read_c0_mvpcontrol();
        printk("MVPControl 0x%lx, STLB %ld VPC %ld EVP %ld\n", val,
               (val & MVPCONTROL_STLB) >> MVPCONTROL_STLB_SHIFT,
               (val & MVPCONTROL_VPC) >> MVPCONTROL_VPC_SHIFT,
               (val & MVPCONTROL_EVP));

        val = read_c0_mvpconf0();
        printk("mvpconf0 0x%lx, PVPE %ld PTC %ld M %ld\n", val,
               (val & MVPCONF0_PVPE) >> MVPCONF0_PVPE_SHIFT,
               val & MVPCONF0_PTC, (val & MVPCONF0_M) >> MVPCONF0_M_SHIFT);
}

/* Find some VPE program space  */
static void *alloc_progmem(unsigned long len)
{
        void *addr;

#ifdef CONFIG_MIPS_VPE_LOADER_TOM
        /*
         * This means you must tell Linux to use less memory than you
         * physically have, for example by passing a mem= boot argument.
         */
        addr = pfn_to_kaddr(max_low_pfn);
        memset(addr, 0, len);
#else
        /* simple grab some mem for now */
        addr = kzalloc(len, GFP_KERNEL);
#endif

        return addr;
}

static void release_progmem(void *ptr)
{
#ifndef CONFIG_MIPS_VPE_LOADER_TOM
        kfree(ptr);
#endif
}

/* Update size with this section: return offset. */
static long get_offset(unsigned long *size, Elf_Shdr * sechdr)
{
        long ret;

        ret = ALIGN(*size, sechdr->sh_addralign ? : 1);
        *size = ret + sechdr->sh_size;
        return ret;
}

/* Lay out the SHF_ALLOC sections in a way not dissimilar to how ld
   might -- code, read-only data, read-write data, small data.  Tally
   sizes, and place the offsets into sh_entsize fields: high bit means it
   belongs in init. */
static void layout_sections(struct module *mod, const Elf_Ehdr * hdr,
                            Elf_Shdr * sechdrs, const char *secstrings)
{
        static unsigned long const masks[][2] = {
                /* NOTE: all executable code must be the first section
                 * in this array; otherwise modify the text_size
                 * finder in the two loops below */
                {SHF_EXECINSTR | SHF_ALLOC, ARCH_SHF_SMALL},
                {SHF_ALLOC, SHF_WRITE | ARCH_SHF_SMALL},
                {SHF_WRITE | SHF_ALLOC, ARCH_SHF_SMALL},
                {ARCH_SHF_SMALL | SHF_ALLOC, 0}
        };
        unsigned int m, i;

        for (i = 0; i < hdr->e_shnum; i++)
                sechdrs[i].sh_entsize = ~0UL;

        for (m = 0; m < ARRAY_SIZE(masks); ++m) {
                for (i = 0; i < hdr->e_shnum; ++i) {
                        Elf_Shdr *s = &sechdrs[i];

                        //  || strncmp(secstrings + s->sh_name, ".init", 5) == 0)
                        if ((s->sh_flags & masks[m][0]) != masks[m][0]
                            || (s->sh_flags & masks[m][1])
                            || s->sh_entsize != ~0UL)
                                continue;
                        s->sh_entsize =
                                get_offset((unsigned long *)&mod->core_size, s);
                }

                if (m == 0)
                        mod->core_text_size = mod->core_size;

        }
}


/* from module-elf32.c, but subverted a little */

struct mips_hi16 {
        struct mips_hi16 *next;
        Elf32_Addr *addr;
        Elf32_Addr value;
};

static struct mips_hi16 *mips_hi16_list;
static unsigned int gp_offs, gp_addr;

static int apply_r_mips_none(struct module *me, uint32_t *location,
                             Elf32_Addr v)
{
        return 0;
}

static int apply_r_mips_gprel16(struct module *me, uint32_t *location,
                                Elf32_Addr v)
{
        int rel;

        if( !(*location & 0xffff) ) {
                rel = (int)v - gp_addr;
        }
        else {
                /* .sbss + gp(relative) + offset */
                /* kludge! */
                rel =  (int)(short)((int)v + gp_offs +
                                    (int)(short)(*location & 0xffff) - gp_addr);
        }

        if( (rel > 32768) || (rel < -32768) ) {
                printk(KERN_DEBUG "VPE loader: apply_r_mips_gprel16: "
                       "relative address 0x%x out of range of gp register\n",
                       rel);
                return -ENOEXEC;
        }

        *location = (*location & 0xffff0000) | (rel & 0xffff);

        return 0;
}

static int apply_r_mips_pc16(struct module *me, uint32_t *location,
                             Elf32_Addr v)
{
        int rel;
        rel = (((unsigned int)v - (unsigned int)location));
        rel >>= 2;              // because the offset is in _instructions_ not bytes.
        rel -= 1;               // and one instruction less due to the branch delay slot.

        if( (rel > 32768) || (rel < -32768) ) {
                printk(KERN_DEBUG "VPE loader: "
                       "apply_r_mips_pc16: relative address out of range 0x%x\n", rel);
                return -ENOEXEC;
        }

        *location = (*location & 0xffff0000) | (rel & 0xffff);

        return 0;
}

static int apply_r_mips_32(struct module *me, uint32_t *location,
                           Elf32_Addr v)
{
        *location += v;

        return 0;
}

static int apply_r_mips_26(struct module *me, uint32_t *location,
                           Elf32_Addr v)
{
        if (v % 4) {
                printk(KERN_DEBUG "VPE loader: apply_r_mips_26 "
                       " unaligned relocation\n");
                return -ENOEXEC;
        }

/*
 * Not desperately convinced this is a good check of an overflow condition
 * anyway. But it gets in the way of handling undefined weak symbols which
 * we want to set to zero.
 * if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
 * printk(KERN_ERR
 * "module %s: relocation overflow\n",
 * me->name);
 * return -ENOEXEC;
 * }
 */

        *location = (*location & ~0x03ffffff) |
                ((*location + (v >> 2)) & 0x03ffffff);
        return 0;
}

static int apply_r_mips_hi16(struct module *me, uint32_t *location,
                             Elf32_Addr v)
{
        struct mips_hi16 *n;

        /*
         * We cannot relocate this one now because we don't know the value of
         * the carry we need to add.  Save the information, and let LO16 do the
         * actual relocation.
         */
        n = kmalloc(sizeof *n, GFP_KERNEL);
        if (!n)
                return -ENOMEM;

        n->addr = location;
        n->value = v;
        n->next = mips_hi16_list;
        mips_hi16_list = n;

        return 0;
}

static int apply_r_mips_lo16(struct module *me, uint32_t *location,
                             Elf32_Addr v)
{
        unsigned long insnlo = *location;
        Elf32_Addr val, vallo;
        struct mips_hi16 *l, *next;

        /* Sign extend the addend we extract from the lo insn.  */
        vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;

        if (mips_hi16_list != NULL) {

                l = mips_hi16_list;
                while (l != NULL) {
                        unsigned long insn;

                        /*
                         * The value for the HI16 had best be the same.
                         */
                        if (v != l->value) {
                                printk(KERN_DEBUG "VPE loader: "
                                       "apply_r_mips_lo16/hi16: \t"
                                       "inconsistent value information\n");
                                goto out_free;
                        }

                        /*
                         * Do the HI16 relocation.  Note that we actually don't
                         * need to know anything about the LO16 itself, except
                         * where to find the low 16 bits of the addend needed
                         * by the LO16.
                         */
                        insn = *l->addr;
                        val = ((insn & 0xffff) << 16) + vallo;
                        val += v;

                        /*
                         * Account for the sign extension that will happen in
                         * the low bits.
                         */
                        val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;

                        insn = (insn & ~0xffff) | val;
                        *l->addr = insn;

                        next = l->next;
                        kfree(l);
                        l = next;
                }

                mips_hi16_list = NULL;
        }

        /*
         * Ok, we're done with the HI16 relocs.  Now deal with the LO16.
         */
        val = v + vallo;
        insnlo = (insnlo & ~0xffff) | (val & 0xffff);
        *location = insnlo;

        return 0;

out_free:
        while (l != NULL) {
                next = l->next;
                kfree(l);
                l = next;
        }
        mips_hi16_list = NULL;

        return -ENOEXEC;
}

static int (*reloc_handlers[]) (struct module *me, uint32_t *location,
                                Elf32_Addr v) = {
        [R_MIPS_NONE]   = apply_r_mips_none,
        [R_MIPS_32]     = apply_r_mips_32,
        [R_MIPS_26]     = apply_r_mips_26,
        [R_MIPS_HI16]   = apply_r_mips_hi16,
        [R_MIPS_LO16]   = apply_r_mips_lo16,
        [R_MIPS_GPREL16] = apply_r_mips_gprel16,
        [R_MIPS_PC16] = apply_r_mips_pc16
};

static char *rstrs[] = {
        [R_MIPS_NONE]   = "MIPS_NONE",
        [R_MIPS_32]     = "MIPS_32",
        [R_MIPS_26]     = "MIPS_26",
        [R_MIPS_HI16]   = "MIPS_HI16",
        [R_MIPS_LO16]   = "MIPS_LO16",
        [R_MIPS_GPREL16] = "MIPS_GPREL16",
        [R_MIPS_PC16] = "MIPS_PC16"
};

static int apply_relocations(Elf32_Shdr *sechdrs,
                      const char *strtab,
                      unsigned int symindex,
                      unsigned int relsec,
                      struct module *me)
{
        Elf32_Rel *rel = (void *) sechdrs[relsec].sh_addr;
        Elf32_Sym *sym;
        uint32_t *location;
        unsigned int i;
        Elf32_Addr v;
        int res;

        for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
                Elf32_Word r_info = rel[i].r_info;

                /* This is where to make the change */
                location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
                        + rel[i].r_offset;
                /* This is the symbol it is referring to */
                sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
                        + ELF32_R_SYM(r_info);

                if (!sym->st_value) {
                        printk(KERN_DEBUG "%s: undefined weak symbol %s\n",
                               me->name, strtab + sym->st_name);
                        /* just print the warning, dont barf */
                }

                v = sym->st_value;

                res = reloc_handlers[ELF32_R_TYPE(r_info)](me, location, v);
                if( res ) {
                        char *r = rstrs[ELF32_R_TYPE(r_info)];
                        printk(KERN_WARNING "VPE loader: .text+0x%x "
                               "relocation type %s for symbol \"%s\" failed\n",
                               rel[i].r_offset, r ? r : "UNKNOWN",
                               strtab + sym->st_name);
                        return res;
                }
        }

        return 0;
}

static inline void save_gp_address(unsigned int secbase, unsigned int rel)
{
        gp_addr = secbase + rel;
        gp_offs = gp_addr - (secbase & 0xffff0000);
}
/* end module-elf32.c */



/* Change all symbols so that sh_value encodes the pointer directly. */
static void simplify_symbols(Elf_Shdr * sechdrs,
                            unsigned int symindex,
                            const char *strtab,
                            const char *secstrings,
                            unsigned int nsecs, struct module *mod)
{
        Elf_Sym *sym = (void *)sechdrs[symindex].sh_addr;
        unsigned long secbase, bssbase = 0;
        unsigned int i, n = sechdrs[symindex].sh_size / sizeof(Elf_Sym);
        int size;

        /* find the .bss section for COMMON symbols */
        for (i = 0; i < nsecs; i++) {
                if (strncmp(secstrings + sechdrs[i].sh_name, ".bss", 4) == 0) {
                        bssbase = sechdrs[i].sh_addr;
                        break;
                }
        }

        for (i = 1; i < n; i++) {
                switch (sym[i].st_shndx) {
                case SHN_COMMON:
                        /* Allocate space for the symbol in the .bss section.
                           st_value is currently size.
                           We want it to have the address of the symbol. */

                        size = sym[i].st_value;
                        sym[i].st_value = bssbase;

                        bssbase += size;
                        break;

                case SHN_ABS:
                        /* Don't need to do anything */
                        break;

                case SHN_UNDEF:
                        /* ret = -ENOENT; */
                        break;

                case SHN_MIPS_SCOMMON:
                        printk(KERN_DEBUG "simplify_symbols: ignoring SHN_MIPS_SCOMMON "
                               "symbol <%s> st_shndx %d\n", strtab + sym[i].st_name,
                               sym[i].st_shndx);
                        // .sbss section
                        break;

                default:
                        secbase = sechdrs[sym[i].st_shndx].sh_addr;

                        if (strncmp(strtab + sym[i].st_name, "_gp", 3) == 0) {
                                save_gp_address(secbase, sym[i].st_value);
                        }

                        sym[i].st_value += secbase;
                        break;
                }
        }
}

#ifdef DEBUG_ELFLOADER
static void dump_elfsymbols(Elf_Shdr * sechdrs, unsigned int symindex,
                            const char *strtab, struct module *mod)
{
        Elf_Sym *sym = (void *)sechdrs[symindex].sh_addr;
        unsigned int i, n = sechdrs[symindex].sh_size / sizeof(Elf_Sym);

        printk(KERN_DEBUG "dump_elfsymbols: n %d\n", n);
        for (i = 1; i < n; i++) {
                printk(KERN_DEBUG " i %d name <%s> 0x%x\n", i,
                       strtab + sym[i].st_name, sym[i].st_value);
        }
}
#endif

/* We are prepared so configure and start the VPE... */
static int vpe_run(struct vpe * v)
{
        unsigned long flags, val, dmt_flag;
        struct vpe_notifications *n;
        unsigned int vpeflags;
        struct tc *t;

        /* check we are the Master VPE */
        local_irq_save(flags);
        val = read_c0_vpeconf0();
        if (!(val & VPECONF0_MVP)) {
                printk(KERN_WARNING
                       "VPE loader: only Master VPE's are allowed to configure MT\n");
                local_irq_restore(flags);

                return -1;
        }

        dmt_flag = dmt();
        vpeflags = dvpe();

        if (!list_empty(&v->tc)) {
                if ((t = list_entry(v->tc.next, struct tc, tc)) == NULL) {
                        evpe(vpeflags);
                        emt(dmt_flag);
                        local_irq_restore(flags);

                        printk(KERN_WARNING
                               "VPE loader: TC %d is already in use.\n",
                               t->index);
                        return -ENOEXEC;
                }
        } else {
                evpe(vpeflags);
                emt(dmt_flag);
                local_irq_restore(flags);

                printk(KERN_WARNING
                       "VPE loader: No TC's associated with VPE %d\n",
                       v->minor);

                return -ENOEXEC;
        }

        /* Put MVPE's into 'configuration state' */
        set_c0_mvpcontrol(MVPCONTROL_VPC);

        settc(t->index);

        /* should check it is halted, and not activated */
        if ((read_tc_c0_tcstatus() & TCSTATUS_A) || !(read_tc_c0_tchalt() & TCHALT_H)) {
                evpe(vpeflags);
                emt(dmt_flag);
                local_irq_restore(flags);

                printk(KERN_WARNING "VPE loader: TC %d is already active!\n",
                       t->index);

                return -ENOEXEC;
        }

        /* Write the address we want it to start running from in the TCPC register. */
        write_tc_c0_tcrestart((unsigned long)v->__start);
        write_tc_c0_tccontext((unsigned long)0);

        /*
         * Mark the TC as activated, not interrupt exempt and not dynamically
         * allocatable
         */
        val = read_tc_c0_tcstatus();
        val = (val & ~(TCSTATUS_DA | TCSTATUS_IXMT)) | TCSTATUS_A;
        write_tc_c0_tcstatus(val);

        write_tc_c0_tchalt(read_tc_c0_tchalt() & ~TCHALT_H);

        /*
         * The sde-kit passes 'memsize' to __start in $a3, so set something
         * here...  Or set $a3 to zero and define DFLT_STACK_SIZE and
         * DFLT_HEAP_SIZE when you compile your program
         */
        mttgpr(6, v->ntcs);
        mttgpr(7, physical_memsize);

        /* set up VPE1 */
        /*
         * bind the TC to VPE 1 as late as possible so we only have the final
         * VPE registers to set up, and so an EJTAG probe can trigger on it
         */
        write_tc_c0_tcbind((read_tc_c0_tcbind() & ~TCBIND_CURVPE) | 1);

        write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() & ~(VPECONF0_VPA));

        back_to_back_c0_hazard();

        /* Set up the XTC bit in vpeconf0 to point at our tc */
        write_vpe_c0_vpeconf0( (read_vpe_c0_vpeconf0() & ~(VPECONF0_XTC))
                              | (t->index << VPECONF0_XTC_SHIFT));

        back_to_back_c0_hazard();

        /* enable this VPE */
        write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() | VPECONF0_VPA);

        /* clear out any left overs from a previous program */
        write_vpe_c0_status(0);
        write_vpe_c0_cause(0);

        /* take system out of configuration state */
        clear_c0_mvpcontrol(MVPCONTROL_VPC);

        /*
         * SMTC/SMVP kernels manage VPE enable independently,
         * but uniprocessor kernels need to turn it on, even
         * if that wasn't the pre-dvpe() state.
         */
#ifdef CONFIG_SMP
        evpe(vpeflags);
#else
        evpe(EVPE_ENABLE);
#endif
        emt(dmt_flag);
        local_irq_restore(flags);

        list_for_each_entry(n, &v->notify, list)
                n->start(minor);

        return 0;
}

static int find_vpe_symbols(struct vpe * v, Elf_Shdr * sechdrs,
                                      unsigned int symindex, const char *strtab,
                                      struct module *mod)
{
        Elf_Sym *sym = (void *)sechdrs[symindex].sh_addr;
        unsigned int i, n = sechdrs[symindex].sh_size / sizeof(Elf_Sym);

        for (i = 1; i < n; i++) {
                if (strcmp(strtab + sym[i].st_name, "__start") == 0) {
                        v->__start = sym[i].st_value;
                }

                if (strcmp(strtab + sym[i].st_name, "vpe_shared") == 0) {
                        v->shared_ptr = (void *)sym[i].st_value;
                }
        }

        if ( (v->__start == 0) || (v->shared_ptr == NULL))
                return -1;

        return 0;
}

/*
 * Allocates a VPE with some program code space(the load address), copies the
 * contents of the program (p)buffer performing relocatations/etc, free's it
 * when finished.
 */
static int vpe_elfload(struct vpe * v)
{
        Elf_Ehdr *hdr;
        Elf_Shdr *sechdrs;
        long err = 0;
        char *secstrings, *strtab = NULL;
        unsigned int len, i, symindex = 0, strindex = 0, relocate = 0;
        struct module mod;      // so we can re-use the relocations code

        memset(&mod, 0, sizeof(struct module));
        strcpy(mod.name, "VPE loader");

        hdr = (Elf_Ehdr *) v->pbuffer;
        len = v->plen;

        /* Sanity checks against insmoding binaries or wrong arch,
           weird elf version */
        if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0
            || (hdr->e_type != ET_REL && hdr->e_type != ET_EXEC)
            || !elf_check_arch(hdr)
            || hdr->e_shentsize != sizeof(*sechdrs)) {
                printk(KERN_WARNING
                       "VPE loader: program wrong arch or weird elf version\n");

                return -ENOEXEC;
        }

        if (hdr->e_type == ET_REL)
                relocate = 1;

        if (len < hdr->e_shoff + hdr->e_shnum * sizeof(Elf_Shdr)) {
                printk(KERN_ERR "VPE loader: program length %u truncated\n",
                       len);

                return -ENOEXEC;
        }

        /* Convenience variables */
        sechdrs = (void *)hdr + hdr->e_shoff;
        secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
        sechdrs[0].sh_addr = 0;

        /* And these should exist, but gcc whinges if we don't init them */
        symindex = strindex = 0;

        if (relocate) {
                for (i = 1; i < hdr->e_shnum; i++) {
                        if (sechdrs[i].sh_type != SHT_NOBITS
                            && len < sechdrs[i].sh_offset + sechdrs[i].sh_size) {
                                printk(KERN_ERR "VPE program length %u truncated\n",
                                       len);
                                return -ENOEXEC;
                        }

                        /* Mark all sections sh_addr with their address in the
                           temporary image. */
                        sechdrs[i].sh_addr = (size_t) hdr + sechdrs[i].sh_offset;

                        /* Internal symbols and strings. */
                        if (sechdrs[i].sh_type == SHT_SYMTAB) {
                                symindex = i;
                                strindex = sechdrs[i].sh_link;
                                strtab = (char *)hdr + sechdrs[strindex].sh_offset;
                        }
                }
                layout_sections(&mod, hdr, sechdrs, secstrings);
        }

        v->load_addr = alloc_progmem(mod.core_size);
        if (!v->load_addr)
                return -ENOMEM;

        pr_info("VPE loader: loading to %p\n", v->load_addr);

        if (relocate) {
                for (i = 0; i < hdr->e_shnum; i++) {
                        void *dest;

                        if (!(sechdrs[i].sh_flags & SHF_ALLOC))
                                continue;

                        dest = v->load_addr + sechdrs[i].sh_entsize;

                        if (sechdrs[i].sh_type != SHT_NOBITS)
                                memcpy(dest, (void *)sechdrs[i].sh_addr,
                                       sechdrs[i].sh_size);
                        /* Update sh_addr to point to copy in image. */
                        sechdrs[i].sh_addr = (unsigned long)dest;

                        printk(KERN_DEBUG " section sh_name %s sh_addr 0x%x\n",
                               secstrings + sechdrs[i].sh_name, sechdrs[i].sh_addr);
                }

                /* Fix up syms, so that st_value is a pointer to location. */
                simplify_symbols(sechdrs, symindex, strtab, secstrings,
                                 hdr->e_shnum, &mod);

                /* Now do relocations. */
                for (i = 1; i < hdr->e_shnum; i++) {
                        const char *strtab = (char *)sechdrs[strindex].sh_addr;
                        unsigned int info = sechdrs[i].sh_info;

                        /* Not a valid relocation section? */
                        if (info >= hdr->e_shnum)
                                continue;

                        /* Don't bother with non-allocated sections */
                        if (!(sechdrs[info].sh_flags & SHF_ALLOC))
                                continue;

                        if (sechdrs[i].sh_type == SHT_REL)
                                err = apply_relocations(sechdrs, strtab, symindex, i,
                                                        &mod);
                        else if (sechdrs[i].sh_type == SHT_RELA)
                                err = apply_relocate_add(sechdrs, strtab, symindex, i,
                                                         &mod);
                        if (err < 0)
                                return err;

                }
        } else {
                struct elf_phdr *phdr = (struct elf_phdr *) ((char *)hdr + hdr->e_phoff);

                for (i = 0; i < hdr->e_phnum; i++) {
                        if (phdr->p_type == PT_LOAD) {
                                memcpy((void *)phdr->p_paddr,
                                       (char *)hdr + phdr->p_offset,
                                       phdr->p_filesz);
                                memset((void *)phdr->p_paddr + phdr->p_filesz,
                                       0, phdr->p_memsz - phdr->p_filesz);
                    }
                    phdr++;
                }

                for (i = 0; i < hdr->e_shnum; i++) {
                        /* Internal symbols and strings. */
                        if (sechdrs[i].sh_type == SHT_SYMTAB) {
                                symindex = i;
                                strindex = sechdrs[i].sh_link;
                                strtab = (char *)hdr + sechdrs[strindex].sh_offset;

                                /* mark the symtab's address for when we try to find the
                                   magic symbols */
                                sechdrs[i].sh_addr = (size_t) hdr + sechdrs[i].sh_offset;
                        }
                }
        }

        /* make sure it's physically written out */
        flush_icache_range((unsigned long)v->load_addr,
                           (unsigned long)v->load_addr + v->len);

        if ((find_vpe_symbols(v, sechdrs, symindex, strtab, &mod)) < 0) {
                if (v->__start == 0) {
                        printk(KERN_WARNING "VPE loader: program does not contain "
                               "a __start symbol\n");
                        return -ENOEXEC;
                }

                if (v->shared_ptr == NULL)
                        printk(KERN_WARNING "VPE loader: "
                               "program does not contain vpe_shared symbol.\n"
                               " Unable to use AMVP (AP/SP) facilities.\n");
        }

        printk(" elf loaded\n");
        return 0;
}

static void cleanup_tc(struct tc *tc)
{
        unsigned long flags;
        unsigned int mtflags, vpflags;
        int tmp;

        local_irq_save(flags);
        mtflags = dmt();
        vpflags = dvpe();
        /* Put MVPE's into 'configuration state' */
        set_c0_mvpcontrol(MVPCONTROL_VPC);

        settc(tc->index);
        tmp = read_tc_c0_tcstatus();

        /* mark not allocated and not dynamically allocatable */
        tmp &= ~(TCSTATUS_A | TCSTATUS_DA);
        tmp |= TCSTATUS_IXMT;   /* interrupt exempt */
        write_tc_c0_tcstatus(tmp);

        write_tc_c0_tchalt(TCHALT_H);
        mips_ihb();

        /* bind it to anything other than VPE1 */
//      write_tc_c0_tcbind(read_tc_c0_tcbind() & ~TCBIND_CURVPE); // | TCBIND_CURVPE

        clear_c0_mvpcontrol(MVPCONTROL_VPC);
        evpe(vpflags);
        emt(mtflags);
        local_irq_restore(flags);
}

static int getcwd(char *buff, int size)
{
        mm_segment_t old_fs;
        int ret;

        old_fs = get_fs();
        set_fs(KERNEL_DS);

        ret = sys_getcwd(buff, size);

        set_fs(old_fs);

        return ret;
}

/* checks VPE is unused and gets ready to load program  */
static int vpe_open(struct inode *inode, struct file *filp)
{
        enum vpe_state state;
        struct vpe_notifications *not;
        struct vpe *v;
        int ret;

        if (minor != iminor(inode)) {
                /* assume only 1 device at the moment. */
                pr_warning("VPE loader: only vpe1 is supported\n");

                return -ENODEV;
        }

        if ((v = get_vpe(tclimit)) == NULL) {
                pr_warning("VPE loader: unable to get vpe\n");

                return -ENODEV;
        }

        state = xchg(&v->state, VPE_STATE_INUSE);
        if (state != VPE_STATE_UNUSED) {
                printk(KERN_DEBUG "VPE loader: tc in use dumping regs\n");

                list_for_each_entry(not, &v->notify, list) {
                        not->stop(tclimit);
                }

                release_progmem(v->load_addr);
                cleanup_tc(get_tc(tclimit));
        }

        /* this of-course trashes what was there before... */
        v->pbuffer = vmalloc(P_SIZE);
        if (!v->pbuffer) {
                pr_warning("VPE loader: unable to allocate memory\n");
                return -ENOMEM;
        }
        v->plen = P_SIZE;
        v->load_addr = NULL;
        v->len = 0;

        v->uid = filp->f_cred->fsuid;
        v->gid = filp->f_cred->fsgid;

        v->cwd[0] = 0;
        ret = getcwd(v->cwd, VPE_PATH_MAX);
        if (ret < 0)
                printk(KERN_WARNING "VPE loader: open, getcwd returned %d\n", ret);

        v->shared_ptr = NULL;
        v->__start = 0;

        return 0;
}

static int vpe_release(struct inode *inode, struct file *filp)
{
        struct vpe *v;
        Elf_Ehdr *hdr;
        int ret = 0;

        v = get_vpe(tclimit);
        if (v == NULL)
                return -ENODEV;

        hdr = (Elf_Ehdr *) v->pbuffer;
        if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) == 0) {
                if (vpe_elfload(v) >= 0) {
                        vpe_run(v);
                } else {
                        printk(KERN_WARNING "VPE loader: ELF load failed.\n");
                        ret = -ENOEXEC;
                }
        } else {
                printk(KERN_WARNING "VPE loader: only elf files are supported\n");
                ret = -ENOEXEC;
        }

        /* It's good to be able to run the SP and if it chokes have a look at
           the /dev/rt?. But if we reset the pointer to the shared struct we
           lose what has happened. So perhaps if garbage is sent to the vpe
           device, use it as a trigger for the reset. Hopefully a nice
           executable will be along shortly. */
        if (ret < 0)
                v->shared_ptr = NULL;

        vfree(v->pbuffer);
        v->plen = 0;

        return ret;
}

static ssize_t vpe_write(struct file *file, const char __user * buffer,
                         size_t count, loff_t * ppos)
{
        size_t ret = count;
        struct vpe *v;

        if (iminor(file->f_path.dentry->d_inode) != minor)
                return -ENODEV;

        v = get_vpe(tclimit);
        if (v == NULL)
                return -ENODEV;

        if ((count + v->len) > v->plen) {
                printk(KERN_WARNING
                       "VPE loader: elf size too big. Perhaps strip uneeded symbols\n");
                return -ENOMEM;
        }

        count -= copy_from_user(v->pbuffer + v->len, buffer, count);
        if (!count)
                return -EFAULT;

        v->len += count;
        return ret;
}

static const struct file_operations vpe_fops = {
        .owner = THIS_MODULE,
        .open = vpe_open,
        .release = vpe_release,
        .write = vpe_write,
        .llseek = noop_llseek,
};

/* module wrapper entry points */
/* give me a vpe */
vpe_handle vpe_alloc(void)
{
        int i;
        struct vpe *v;

        /* find a vpe */
        for (i = 1; i < MAX_VPES; i++) {
                if ((v = get_vpe(i)) != NULL) {
                        v->state = VPE_STATE_INUSE;
                        return v;
                }
        }
        return NULL;
}

EXPORT_SYMBOL(vpe_alloc);

/* start running from here */
int vpe_start(vpe_handle vpe, unsigned long start)
{
        struct vpe *v = vpe;

        v->__start = start;
        return vpe_run(v);
}

EXPORT_SYMBOL(vpe_start);

/* halt it for now */
int vpe_stop(vpe_handle vpe)
{
        struct vpe *v = vpe;
        struct tc *t;
        unsigned int evpe_flags;

        evpe_flags = dvpe();

        if ((t = list_entry(v->tc.next, struct tc, tc)) != NULL) {

                settc(t->index);
                write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() & ~VPECONF0_VPA);
        }

        evpe(evpe_flags);

        return 0;
}

EXPORT_SYMBOL(vpe_stop);

/* I've done with it thank you */
int vpe_free(vpe_handle vpe)
{
        struct vpe *v = vpe;
        struct tc *t;
        unsigned int evpe_flags;

        if ((t = list_entry(v->tc.next, struct tc, tc)) == NULL) {
                return -ENOEXEC;
        }

        evpe_flags = dvpe();

        /* Put MVPE's into 'configuration state' */
        set_c0_mvpcontrol(MVPCONTROL_VPC);

        settc(t->index);
        write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() & ~VPECONF0_VPA);

        /* halt the TC */
        write_tc_c0_tchalt(TCHALT_H);
        mips_ihb();

        /* mark the TC unallocated */
        write_tc_c0_tcstatus(read_tc_c0_tcstatus() & ~TCSTATUS_A);

        v->state = VPE_STATE_UNUSED;

        clear_c0_mvpcontrol(MVPCONTROL_VPC);
        evpe(evpe_flags);

        return 0;
}

EXPORT_SYMBOL(vpe_free);

void *vpe_get_shared(int index)
{
        struct vpe *v;

        if ((v = get_vpe(index)) == NULL)
                return NULL;

        return v->shared_ptr;
}

EXPORT_SYMBOL(vpe_get_shared);

int vpe_getuid(int index)
{
        struct vpe *v;

        if ((v = get_vpe(index)) == NULL)
                return -1;

        return v->uid;
}

EXPORT_SYMBOL(vpe_getuid);

int vpe_getgid(int index)
{
        struct vpe *v;

        if ((v = get_vpe(index)) == NULL)
                return -1;

        return v->gid;
}

EXPORT_SYMBOL(vpe_getgid);

int vpe_notify(int index, struct vpe_notifications *notify)
{
        struct vpe *v;

        if ((v = get_vpe(index)) == NULL)
                return -1;

        list_add(&notify->list, &v->notify);
        return 0;
}

EXPORT_SYMBOL(vpe_notify);

char *vpe_getcwd(int index)
{
        struct vpe *v;

        if ((v = get_vpe(index)) == NULL)
                return NULL;

        return v->cwd;
}

EXPORT_SYMBOL(vpe_getcwd);

static ssize_t store_kill(struct device *dev, struct device_attribute *attr,
                          const char *buf, size_t len)
{
        struct vpe *vpe = get_vpe(tclimit);
        struct vpe_notifications *not;

        list_for_each_entry(not, &vpe->notify, list) {
                not->stop(tclimit);
        }

        release_progmem(vpe->load_addr);
        cleanup_tc(get_tc(tclimit));
        vpe_stop(vpe);
        vpe_free(vpe);

        return len;
}

static ssize_t show_ntcs(struct device *cd, struct device_attribute *attr,
                         char *buf)
{
        struct vpe *vpe = get_vpe(tclimit);

        return sprintf(buf, "%d\n", vpe->ntcs);
}

static ssize_t store_ntcs(struct device *dev, struct device_attribute *attr,
                          const char *buf, size_t len)
{
        struct vpe *vpe = get_vpe(tclimit);
        unsigned long new;
        char *endp;

        new = simple_strtoul(buf, &endp, 0);
        if (endp == buf)
                goto out_einval;

        if (new == 0 || new > (hw_tcs - tclimit))
                goto out_einval;

        vpe->ntcs = new;

        return len;

out_einval:
        return -EINVAL;
}

static struct device_attribute vpe_class_attributes[] = {
        __ATTR(kill, S_IWUSR, NULL, store_kill),
        __ATTR(ntcs, S_IRUGO | S_IWUSR, show_ntcs, store_ntcs),
        {}
};

static void vpe_device_release(struct device *cd)
{
        kfree(cd);
}

struct class vpe_class = {
        .name = "vpe",
        .owner = THIS_MODULE,
        .dev_release = vpe_device_release,
        .dev_attrs = vpe_class_attributes,
};

struct device vpe_device;

static int __init vpe_module_init(void)
{
        unsigned int mtflags, vpflags;
        unsigned long flags, val;
        struct vpe *v = NULL;
        struct tc *t;
        int tc, err;

        if (!cpu_has_mipsmt) {
                printk("VPE loader: not a MIPS MT capable processor\n");
                return -ENODEV;
        }

        if (vpelimit == 0) {
                printk(KERN_WARNING "No VPEs reserved for AP/SP, not "
                       "initializing VPE loader.\nPass maxvpes=<n> argument as "
                       "kernel argument\n");

                return -ENODEV;
        }

        if (tclimit == 0) {
                printk(KERN_WARNING "No TCs reserved for AP/SP, not "
                       "initializing VPE loader.\nPass maxtcs=<n> argument as "
                       "kernel argument\n");

                return -ENODEV;
        }

        major = register_chrdev(0, module_name, &vpe_fops);
        if (major < 0) {
                printk("VPE loader: unable to register character device\n");
                return major;
        }

        err = class_register(&vpe_class);
        if (err) {
                printk(KERN_ERR "vpe_class registration failed\n");
                goto out_chrdev;
        }

        device_initialize(&vpe_device);
        vpe_device.class        = &vpe_class,
        vpe_device.parent       = NULL,
        dev_set_name(&vpe_device, "vpe1");
        vpe_device.devt = MKDEV(major, minor);
        err = device_add(&vpe_device);
        if (err) {
                printk(KERN_ERR "Adding vpe_device failed\n");
                goto out_class;
        }

        local_irq_save(flags);
        mtflags = dmt();
        vpflags = dvpe();

        /* Put MVPE's into 'configuration state' */
        set_c0_mvpcontrol(MVPCONTROL_VPC);

        /* dump_mtregs(); */

        val = read_c0_mvpconf0();
        hw_tcs = (val & MVPCONF0_PTC) + 1;
        hw_vpes = ((val & MVPCONF0_PVPE) >> MVPCONF0_PVPE_SHIFT) + 1;

        for (tc = tclimit; tc < hw_tcs; tc++) {
                /*
                 * Must re-enable multithreading temporarily or in case we
                 * reschedule send IPIs or similar we might hang.
                 */
                clear_c0_mvpcontrol(MVPCONTROL_VPC);
                evpe(vpflags);
                emt(mtflags);
                local_irq_restore(flags);
                t = alloc_tc(tc);
                if (!t) {
                        err = -ENOMEM;
                        goto out;
                }

                local_irq_save(flags);
                mtflags = dmt();
                vpflags = dvpe();
                set_c0_mvpcontrol(MVPCONTROL_VPC);

                /* VPE's */
                if (tc < hw_tcs) {
                        settc(tc);

                        if ((v = alloc_vpe(tc)) == NULL) {
                                printk(KERN_WARNING "VPE: unable to allocate VPE\n");

                                goto out_reenable;
                        }

                        v->ntcs = hw_tcs - tclimit;

                        /* add the tc to the list of this vpe's tc's. */
                        list_add(&t->tc, &v->tc);

                        /* deactivate all but vpe0 */
                        if (tc >= tclimit) {
                                unsigned long tmp = read_vpe_c0_vpeconf0();

                                tmp &= ~VPECONF0_VPA;

                                /* master VPE */
                                tmp |= VPECONF0_MVP;
                                write_vpe_c0_vpeconf0(tmp);
                        }

                        /* disable multi-threading with TC's */
                        write_vpe_c0_vpecontrol(read_vpe_c0_vpecontrol() & ~VPECONTROL_TE);

                        if (tc >= vpelimit) {
                                /*
                                 * Set config to be the same as vpe0,
                                 * particularly kseg0 coherency alg
                                 */
                                write_vpe_c0_config(read_c0_config());
                        }
                }

                /* TC's */
                t->pvpe = v;    /* set the parent vpe */

                if (tc >= tclimit) {
                        unsigned long tmp;

                        settc(tc);

                        /* Any TC that is bound to VPE0 gets left as is - in case
                           we are running SMTC on VPE0. A TC that is bound to any
                           other VPE gets bound to VPE0, ideally I'd like to make
                           it homeless but it doesn't appear to let me bind a TC
                           to a non-existent VPE. Which is perfectly reasonable.

                           The (un)bound state is visible to an EJTAG probe so may
                           notify GDB...
                        */

                        if (((tmp = read_tc_c0_tcbind()) & TCBIND_CURVPE)) {
                                /* tc is bound >vpe0 */
                                write_tc_c0_tcbind(tmp & ~TCBIND_CURVPE);

                                t->pvpe = get_vpe(0);   /* set the parent vpe */
                        }

                        /* halt the TC */
                        write_tc_c0_tchalt(TCHALT_H);
                        mips_ihb();

                        tmp = read_tc_c0_tcstatus();

                        /* mark not activated and not dynamically allocatable */
                        tmp &= ~(TCSTATUS_A | TCSTATUS_DA);
                        tmp |= TCSTATUS_IXMT;   /* interrupt exempt */
                        write_tc_c0_tcstatus(tmp);
                }
        }

out_reenable:
        /* release config state */
        clear_c0_mvpcontrol(MVPCONTROL_VPC);

        evpe(vpflags);
        emt(mtflags);
        local_irq_restore(flags);

        return 0;

out_class:
        class_unregister(&vpe_class);
out_chrdev:
        unregister_chrdev(major, module_name);

out:
        return err;
}

static void __exit vpe_module_exit(void)
{
        struct vpe *v, *n;

        device_del(&vpe_device);
        unregister_chrdev(major, module_name);

        /* No locking needed here */
        list_for_each_entry_safe(v, n, &vpecontrol.vpe_list, list) {
                if (v->state != VPE_STATE_UNUSED)
                        release_vpe(v);
        }
}

module_init(vpe_module_init);
module_exit(vpe_module_exit);
MODULE_DESCRIPTION("MIPS VPE Loader");
MODULE_AUTHOR("Elizabeth Oldham, MIPS Technologies, Inc.");
MODULE_LICENSE("GPL");