arch/mips/kernel/vpe.c

root/arch/mips/kernel/vpe.c
/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2004, 2005 MIPS Technologies, Inc.  All rights reserved.
 * Copyright (C) 2013 Imagination Technologies Ltd.
 *
 * VPE support module for loading a MIPS SP program into VPE1. The SP
 * environment is rather simple since there are no TLBs. It needs
 * to be relocatable (or partially linked). Initialize your stack in
 * the startup-code. The loader looks for the symbol __start and sets
 * up the execution to resume from there. To load and run, simply do
 * a cat SP 'binary' to the /dev/vpe1 device.
 */
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/elf.h>
#include <linux/seq_file.h>
#include <linux/string.h>
#include <linux/syscalls.h>
#include <linux/moduleloader.h>
#include <linux/interrupt.h>
#include <linux/poll.h>
#include <linux/memblock.h>
#include <asm/mipsregs.h>
#include <asm/mipsmtregs.h>
#include <asm/cacheflush.h>
#include <linux/atomic.h>
#include <asm/mips_mt.h>
#include <asm/processor.h>
#include <asm/vpe.h>

#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))

struct vpe_control 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)
};

/* get the vpe associated with this minor */
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 == VPE_MODULE_MINOR) {
                        res = v;
                        break;
                }
        }
        spin_unlock(&vpecontrol.vpe_list_lock);

        return res;
}

/* get the vpe associated with this minor */
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) */
struct vpe *alloc_vpe(int minor)
{
        struct vpe *v;

        v = kzalloc_obj(struct vpe);
        if (v == NULL)
                goto out;

        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 = VPE_MODULE_MINOR;

out:
        return v;
}

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

        tc = kzalloc_obj(struct tc);
        if (tc == 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 */
void release_vpe(struct vpe *v)
{
        list_del(&v->list);
        if (v->load_addr)
                release_progmem(v->load_addr);
        kfree(v);
}

/* Find some VPE program space */
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;
}

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];
                        struct module_memory *mod_mem;

                        mod_mem = &mod->mem[MOD_TEXT];

                        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_mem->size, s);
                }
        }
}

/* 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)) {
                pr_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)) {
                pr_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) {
                pr_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_obj(*n);
        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) {
                                pr_debug("VPE loader: apply_r_mips_lo16/hi16: 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) {
                        pr_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)];
                        pr_warn("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:
                        pr_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);

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

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));
        strscpy(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)) {
                pr_warn("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)) {
                pr_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)) {
                                pr_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.mem[MOD_TEXT].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;

                        pr_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 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) {
                        pr_warn("VPE loader: program does not contain a __start symbol\n");
                        return -ENOEXEC;
                }

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

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

/* 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 *notifier;
        struct vpe *v;

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

                return -ENODEV;
        }

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

                return -ENODEV;
        }

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

                list_for_each_entry(notifier, &v->notify, list)
                        notifier->stop(aprp_cpu_index());

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

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

        return 0;
}

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

        v = get_vpe(aprp_cpu_index());
        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 {
                        pr_warn("VPE loader: ELF load failed.\n");
                        ret = -ENOEXEC;
                }
        } else {
                pr_warn("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;
#else
        pr_warn("VPE loader: ELF load failed.\n");
        return -ENOEXEC;
#endif
}

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_inode(file)) != VPE_MODULE_MINOR)
                return -ENODEV;

        v = get_vpe(aprp_cpu_index());

        if (v == NULL)
                return -ENODEV;

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

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

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

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

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

        if (v == NULL)
                return NULL;

        return v->shared_ptr;
}
EXPORT_SYMBOL(vpe_get_shared);

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

        if (v == NULL)
                return -1;

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

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");