Archipelago » qemu

/*

 *  mmap support for qemu

 *

 *  Copyright (c) 2003 Fabrice Bellard

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; either version 2 of the License, or

 *  (at your option) any later version.

 *

 *  This program is distributed in the hope that 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., 675 Mass Ave, Cambridge, MA 02139, USA.

 */

#include <stdlib.h>

#include <stdio.h>

#include <stdarg.h>

#include <string.h>

#include <unistd.h>

#include <errno.h>

#include <sys/mman.h>

#include "qemu.h"

//#define DEBUG_MMAP

/* NOTE: all the constants are the HOST ones, but addresses are target. */

int target_mprotect(abi_ulong start, abi_ulong len, int prot)

{

    abi_ulong end, host_start, host_end, addr;

    int prot1, ret;

#ifdef DEBUG_MMAP

    printf("mprotect: start=0x" TARGET_FMT_lx

           "len=0x" TARGET_FMT_lx " prot=%c%c%c\n", start, len,

           prot & PROT_READ ? 'r' : '-',

           prot & PROT_WRITE ? 'w' : '-',

           prot & PROT_EXEC ? 'x' : '-');

#endif

    if ((start & ~TARGET_PAGE_MASK) != 0)

        return -EINVAL;

    len = TARGET_PAGE_ALIGN(len);

    end = start + len;

    if (end < start)

        return -EINVAL;

    prot &= PROT_READ | PROT_WRITE | PROT_EXEC;

    if (len == 0)

        return 0;

    host_start = start & qemu_host_page_mask;

    host_end = HOST_PAGE_ALIGN(end);

    if (start > host_start) {

        /* handle host page containing start */

        prot1 = prot;

        for(addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {

            prot1 |= page_get_flags(addr);

        }

        if (host_end == host_start + qemu_host_page_size) {

            for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {

                prot1 |= page_get_flags(addr);

            }

            end = host_end;

        }

        ret = mprotect(g2h(host_start), qemu_host_page_size, prot1 & PAGE_BITS);

        if (ret != 0)

            return ret;

        host_start += qemu_host_page_size;

    }

    if (end < host_end) {

        prot1 = prot;

        for(addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {

            prot1 |= page_get_flags(addr);

        }

        ret = mprotect(g2h(host_end - qemu_host_page_size), qemu_host_page_size,

                       prot1 & PAGE_BITS);

        if (ret != 0)

            return ret;

        host_end -= qemu_host_page_size;

    }

    /* handle the pages in the middle */

    if (host_start < host_end) {

        ret = mprotect(g2h(host_start), host_end - host_start, prot);

        if (ret != 0)

            return ret;

    }

    page_set_flags(start, start + len, prot | PAGE_VALID);

    return 0;

}

/* map an incomplete host page */

static int mmap_frag(abi_ulong real_start,

                     abi_ulong start, abi_ulong end,

                     int prot, int flags, int fd, abi_ulong offset)

{

    abi_ulong real_end, addr;

    void *host_start;

    int prot1, prot_new;

    real_end = real_start + qemu_host_page_size;

    host_start = g2h(real_start);

    /* get the protection of the target pages outside the mapping */

    prot1 = 0;

    for(addr = real_start; addr < real_end; addr++) {

        if (addr < start || addr >= end)

            prot1 |= page_get_flags(addr);

    }

    if (prot1 == 0) {

        /* no page was there, so we allocate one */

        void *p = mmap(host_start, qemu_host_page_size, prot,

                       flags | MAP_ANONYMOUS, -1, 0);

        if (p == MAP_FAILED)

            return -1;

        prot1 = prot;

    }

    prot1 &= PAGE_BITS;

    prot_new = prot | prot1;

    if (!(flags & MAP_ANONYMOUS)) {

        /* msync() won't work here, so we return an error if write is

           possible while it is a shared mapping */

        if ((flags & MAP_TYPE) == MAP_SHARED &&

            (prot & PROT_WRITE))

            return -EINVAL;

        /* adjust protection to be able to read */

        if (!(prot1 & PROT_WRITE))

            mprotect(host_start, qemu_host_page_size, prot1 | PROT_WRITE);

        /* read the corresponding file data */

        pread(fd, g2h(start), end - start, offset);

        /* put final protection */

        if (prot_new != (prot1 | PROT_WRITE))

            mprotect(host_start, qemu_host_page_size, prot_new);

    } else {

        /* just update the protection */

        if (prot_new != prot1) {

            mprotect(host_start, qemu_host_page_size, prot_new);

        }

    }

    return 0;

}

#if defined(__CYGWIN__)

/* Cygwin doesn't have a whole lot of address space.  */

static abi_ulong mmap_next_start = 0x18000000;

#else

static abi_ulong mmap_next_start = 0x40000000;

#endif

unsigned long last_brk;

/* find a free memory area of size 'size'. The search starts at

   'start'. If 'start' == 0, then a default start address is used.

   Return -1 if error.

*/

/* page_init() marks pages used by the host as reserved to be sure not

   to use them. */

static abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)

{

    abi_ulong addr, addr1, addr_start;

    int prot;

    unsigned long new_brk;

    new_brk = (unsigned long)sbrk(0);

    if (last_brk && last_brk < new_brk && last_brk == (target_ulong)last_brk) {

        /* This is a hack to catch the host allocating memory with brk().

           If it uses mmap then we loose.

           FIXME: We really want to avoid the host allocating memory in

           the first place, and maybe leave some slack to avoid switching

           to mmap.  */

        page_set_flags(last_brk & TARGET_PAGE_MASK,

                       TARGET_PAGE_ALIGN(new_brk),

                       PAGE_RESERVED); 

    }

    last_brk = new_brk;

    size = HOST_PAGE_ALIGN(size);

    start = start & qemu_host_page_mask;

    addr = start;

    if (addr == 0)

        addr = mmap_next_start;

    addr_start = addr;

    for(;;) {

        prot = 0;

        for(addr1 = addr; addr1 < (addr + size); addr1 += TARGET_PAGE_SIZE) {

            prot |= page_get_flags(addr1);

        }

        if (prot == 0)

            break;

        addr += qemu_host_page_size;

        /* we found nothing */

        if (addr == addr_start)

            return (abi_ulong)-1;

    }

    if (start == 0)

        mmap_next_start = addr + size;

    return addr;

}

/* NOTE: all the constants are the HOST ones */

abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,

                     int flags, int fd, abi_ulong offset)

{

    abi_ulong ret, end, real_start, real_end, retaddr, host_offset, host_len;

    unsigned long host_start;

#ifdef DEBUG_MMAP

    {

        printf("mmap: start=0x" TARGET_FMT_lx

               " len=0x" TARGET_FMT_lx " prot=%c%c%c flags=",

               start, len,

               prot & PROT_READ ? 'r' : '-',

               prot & PROT_WRITE ? 'w' : '-',

               prot & PROT_EXEC ? 'x' : '-');

        if (flags & MAP_FIXED)

            printf("MAP_FIXED ");

        if (flags & MAP_ANONYMOUS)

            printf("MAP_ANON ");

        switch(flags & MAP_TYPE) {

        case MAP_PRIVATE:

            printf("MAP_PRIVATE ");

            break;

        case MAP_SHARED:

            printf("MAP_SHARED ");

            break;

        default:

            printf("[MAP_TYPE=0x%x] ", flags & MAP_TYPE);

            break;

        }

        printf("fd=%d offset=" TARGET_FMT_lx "\n", fd, offset);

    }

#endif

    if (offset & ~TARGET_PAGE_MASK) {

        errno = EINVAL;

        return -1;

    }

    len = TARGET_PAGE_ALIGN(len);

    if (len == 0)

        return start;

    real_start = start & qemu_host_page_mask;

    if (!(flags & MAP_FIXED)) {

        abi_ulong mmap_start;

        void *p;

        host_offset = offset & qemu_host_page_mask;

        host_len = len + offset - host_offset;

        host_len = HOST_PAGE_ALIGN(host_len);

        mmap_start = mmap_find_vma(real_start, host_len);

        if (mmap_start == (abi_ulong)-1) {

            errno = ENOMEM;

            return -1;

        }

        /* Note: we prefer to control the mapping address. It is

           especially important if qemu_host_page_size >

           qemu_real_host_page_size */

        p = mmap(g2h(mmap_start),

                 host_len, prot, flags | MAP_FIXED, fd, host_offset);

        if (p == MAP_FAILED)

            return -1;

        /* update start so that it points to the file position at 'offset' */

        host_start = (unsigned long)p;

        if (!(flags & MAP_ANONYMOUS))

            host_start += offset - host_offset;

        start = h2g(host_start);

    } else {

        int flg;

        target_ulong addr;

        if (start & ~TARGET_PAGE_MASK) {

            errno = EINVAL;

            return -1;

        }

        end = start + len;

        real_end = HOST_PAGE_ALIGN(end);

        for(addr = real_start; addr < real_end; addr += TARGET_PAGE_SIZE) {

            flg = page_get_flags(addr);

            if (flg & PAGE_RESERVED) {

                errno = ENXIO;

                return -1;

            }

        }

        /* worst case: we cannot map the file because the offset is not

           aligned, so we read it */

        if (!(flags & MAP_ANONYMOUS) &&

            (offset & ~qemu_host_page_mask) != (start & ~qemu_host_page_mask)) {

            /* msync() won't work here, so we return an error if write is

               possible while it is a shared mapping */

            if ((flags & MAP_TYPE) == MAP_SHARED &&

                (prot & PROT_WRITE)) {

                errno = EINVAL;

                return -1;

            }

            retaddr = target_mmap(start, len, prot | PROT_WRITE,

                                  MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,

                                  -1, 0);

            if (retaddr == -1)

                return -1;

            pread(fd, g2h(start), len, offset);

            if (!(prot & PROT_WRITE)) {

                ret = target_mprotect(start, len, prot);

                if (ret != 0)

                    return ret;

            }

            goto the_end;

        }

        /* handle the start of the mapping */

        if (start > real_start) {

            if (real_end == real_start + qemu_host_page_size) {

                /* one single host page */

                ret = mmap_frag(real_start, start, end,

                                prot, flags, fd, offset);

                if (ret == -1)

                    return ret;

                goto the_end1;

            }

            ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,

                            prot, flags, fd, offset);

            if (ret == -1)

                return ret;

            real_start += qemu_host_page_size;

        }

        /* handle the end of the mapping */

        if (end < real_end) {

            ret = mmap_frag(real_end - qemu_host_page_size,

                            real_end - qemu_host_page_size, real_end,

                            prot, flags, fd,

                            offset + real_end - qemu_host_page_size - start);

            if (ret == -1)

                return -1;

            real_end -= qemu_host_page_size;

        }

        /* map the middle (easier) */

        if (real_start < real_end) {

            void *p;

            unsigned long offset1;

            if (flags & MAP_ANONYMOUS)

                offset1 = 0;

            else

                offset1 = offset + real_start - start;

            p = mmap(g2h(real_start), real_end - real_start,

                     prot, flags, fd, offset1);

            if (p == MAP_FAILED)

                return -1;

        }

    }

 the_end1:

    page_set_flags(start, start + len, prot | PAGE_VALID);

 the_end:

#ifdef DEBUG_MMAP

    printf("ret=0x" TARGET_FMT_lx "\n", start);

    page_dump(stdout);

    printf("\n");

#endif

    return start;

}

int target_munmap(abi_ulong start, abi_ulong len)

{

    abi_ulong end, real_start, real_end, addr;

    int prot, ret;

#ifdef DEBUG_MMAP

    printf("munmap: start=0x%lx len=0x%lx\n", start, len);

#endif

    if (start & ~TARGET_PAGE_MASK)

        return -EINVAL;

    len = TARGET_PAGE_ALIGN(len);

    if (len == 0)

        return -EINVAL;

    end = start + len;

    real_start = start & qemu_host_page_mask;

    real_end = HOST_PAGE_ALIGN(end);

    if (start > real_start) {

        /* handle host page containing start */

        prot = 0;

        for(addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {

            prot |= page_get_flags(addr);

        }

        if (real_end == real_start + qemu_host_page_size) {

            for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {

                prot |= page_get_flags(addr);

            }

            end = real_end;

        }

        if (prot != 0)

            real_start += qemu_host_page_size;

    }

    if (end < real_end) {

        prot = 0;

        for(addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {

            prot |= page_get_flags(addr);

        }

        if (prot != 0)

            real_end -= qemu_host_page_size;

    }

    /* unmap what we can */

    if (real_start < real_end) {

        ret = munmap(g2h(real_start), real_end - real_start);

        if (ret != 0)

            return ret;

    }

    page_set_flags(start, start + len, 0);

    return 0;

}

/* XXX: currently, we only handle MAP_ANONYMOUS and not MAP_FIXED

   blocks which have been allocated starting on a host page */

abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,

                       abi_ulong new_size, unsigned long flags,

                       abi_ulong new_addr)

{

    int prot;

    unsigned long host_addr;

    /* XXX: use 5 args syscall */

    host_addr = (long)mremap(g2h(old_addr), old_size, new_size, flags);

    if (host_addr == -1)

        return -1;

    new_addr = h2g(host_addr);

    prot = page_get_flags(old_addr);

    page_set_flags(old_addr, old_addr + old_size, 0);

    page_set_flags(new_addr, new_addr + new_size, prot | PAGE_VALID);

    return new_addr;

}

int target_msync(abi_ulong start, abi_ulong len, int flags)

{

    abi_ulong end;

    if (start & ~TARGET_PAGE_MASK)

        return -EINVAL;

    len = TARGET_PAGE_ALIGN(len);

    end = start + len;

    if (end < start)

        return -EINVAL;

    if (end == start)

        return 0;

    start &= qemu_host_page_mask;

    return msync(g2h(start), end - start, flags);

}