vpe.c

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/*
 * 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");