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, see <http://www.gnu.org/licenses/>.

 */

#include <stdlib.h>

#include <stdio.h>

#include <stdarg.h>

#include <string.h>

#include <unistd.h>

#include <errno.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <sys/mman.h>

#include <linux/mman.h>

#include <linux/unistd.h>

#include "qemu.h"

#include "qemu-common.h"

//#define DEBUG_MMAP

#if defined(CONFIG_USE_NPTL)

static pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER;

static __thread int mmap_lock_count;

void mmap_lock(void)

{

    if (mmap_lock_count++ == 0) {

        pthread_mutex_lock(&mmap_mutex);

    }

}

void mmap_unlock(void)

{

    if (--mmap_lock_count == 0) {

        pthread_mutex_unlock(&mmap_mutex);

    }

}

/* Grab lock to make sure things are in a consistent state after fork().  */

void mmap_fork_start(void)

{

    if (mmap_lock_count)

        abort();

    pthread_mutex_lock(&mmap_mutex);

}

void mmap_fork_end(int child)

{

    if (child)

        pthread_mutex_init(&mmap_mutex, NULL);

    else

        pthread_mutex_unlock(&mmap_mutex);

}

#else

/* We aren't threadsafe to start with, so no need to worry about locking.  */

void mmap_lock(void)

{

}

void mmap_unlock(void)

{

}

#endif

/* 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_ABI_FMT_lx

           "len=0x" TARGET_ABI_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;

    mmap_lock();

    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)

            goto error;

        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)

            goto error;

        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)

            goto error;

    }

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

    mmap_unlock();

    return 0;

error:

    mmap_unlock();

    return ret;

}

/* 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 -1;

        /* 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 */

        if (pread(fd, g2h(start), end - start, offset) == -1)

            return -1;

        /* 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 HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64

# define TASK_UNMAPPED_BASE  (1ul << 38)

#elif defined(__CYGWIN__)

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

# define TASK_UNMAPPED_BASE  0x18000000

#else

# define TASK_UNMAPPED_BASE  0x40000000

#endif

static abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;

unsigned long last_brk;

#ifdef CONFIG_USE_GUEST_BASE

/* Subroutine of mmap_find_vma, used when we have pre-allocated a chunk

   of guest address space.  */

static abi_ulong mmap_find_vma_reserved(abi_ulong start, abi_ulong size)

{

    abi_ulong addr;

    abi_ulong last_addr;

    int prot;

    int looped = 0;

    if (size > RESERVED_VA) {

        return (abi_ulong)-1;

    }

    last_addr = start;

    for (addr = start; last_addr + size != addr; addr += qemu_host_page_size) {

        if (last_addr + size >= RESERVED_VA

            || (abi_ulong)(last_addr + size) < last_addr) {

            if (looped) {

                return (abi_ulong)-1;

            }

            last_addr = qemu_host_page_size;

            addr = 0;

            looped = 1;

            continue;

        }

        prot = page_get_flags(addr);

        if (prot) {

            last_addr = addr + qemu_host_page_size;

        }

    }

    mmap_next_start = addr;

    return last_addr;

}

#endif

/*

 * Find and reserve a free memory area of size 'size'. The search

 * starts at 'start'.

 * It must be called with mmap_lock() held.

 * Return -1 if error.

 */

abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)

{

    void *ptr, *prev;

    abi_ulong addr;

    int wrapped, repeat;

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

    if (start == 0) {

        start = mmap_next_start;

    } else {

        start &= qemu_host_page_mask;

    }

    size = HOST_PAGE_ALIGN(size);

#ifdef CONFIG_USE_GUEST_BASE

    if (RESERVED_VA) {

        return mmap_find_vma_reserved(start, size);

    }

#endif

    addr = start;

    wrapped = repeat = 0;

    prev = 0;

    for (;; prev = ptr) {

        /*

         * Reserve needed memory area to avoid a race.

         * It should be discarded using:

         *  - mmap() with MAP_FIXED flag

         *  - mremap() with MREMAP_FIXED flag

         *  - shmat() with SHM_REMAP flag

         */

        ptr = mmap(g2h(addr), size, PROT_NONE,

                   MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);

        /* ENOMEM, if host address space has no memory */

        if (ptr == MAP_FAILED) {

            return (abi_ulong)-1;

        }

        /* Count the number of sequential returns of the same address.

           This is used to modify the search algorithm below.  */

        repeat = (ptr == prev ? repeat + 1 : 0);

        if (h2g_valid(ptr + size - 1)) {

            addr = h2g(ptr);

            if ((addr & ~TARGET_PAGE_MASK) == 0) {

                /* Success.  */

                if (start == mmap_next_start && addr >= TASK_UNMAPPED_BASE) {

                    mmap_next_start = addr + size;

                }

                return addr;

            }

            /* The address is not properly aligned for the target.  */

            switch (repeat) {

            case 0:

                /* Assume the result that the kernel gave us is the

                   first with enough free space, so start again at the

                   next higher target page.  */

                addr = TARGET_PAGE_ALIGN(addr);

                break;

            case 1:

                /* Sometimes the kernel decides to perform the allocation

                   at the top end of memory instead.  */

                addr &= TARGET_PAGE_MASK;

                break;

            case 2:

                /* Start over at low memory.  */

                addr = 0;

                break;

            default:

                /* Fail.  This unaligned block must the last.  */

                addr = -1;

                break;

            }

        } else {

            /* Since the result the kernel gave didn't fit, start

               again at low memory.  If any repetition, fail.  */

            addr = (repeat ? -1 : 0);

        }

        /* Unmap and try again.  */

        munmap(ptr, size);

        /* ENOMEM if we checked the whole of the target address space.  */

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

            return (abi_ulong)-1;

        } else if (addr == 0) {

            if (wrapped) {

                return (abi_ulong)-1;

            }

            wrapped = 1;

            /* Don't actually use 0 when wrapping, instead indicate

               that we'd truly like an allocation in low memory.  */

            addr = (mmap_min_addr > TARGET_PAGE_SIZE

                     ? TARGET_PAGE_ALIGN(mmap_min_addr)

                     : TARGET_PAGE_SIZE);

        } else if (wrapped && addr >= start) {

            return (abi_ulong)-1;

        }

    }

}

/* 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;

    mmap_lock();

#ifdef DEBUG_MMAP

    {

        printf("mmap: start=0x" TARGET_ABI_FMT_lx

               " len=0x" TARGET_ABI_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_ABI_FMT_lx "\n", fd, offset);

    }

#endif

    if (offset & ~TARGET_PAGE_MASK) {

        errno = EINVAL;

        goto fail;

    }

    len = TARGET_PAGE_ALIGN(len);

    if (len == 0)

        goto the_end;

    real_start = start & qemu_host_page_mask;

    /* When mapping files into a memory area larger than the file, accesses

       to pages beyond the file size will cause a SIGBUS. 

       For example, if mmaping a file of 100 bytes on a host with 4K pages

       emulating a target with 8K pages, the target expects to be able to

       access the first 8K. But the host will trap us on any access beyond

       4K.  

       When emulating a target with a larger page-size than the hosts, we

       may need to truncate file maps at EOF and add extra anonymous pages

       up to the targets page boundary.  */

    if ((qemu_real_host_page_size < TARGET_PAGE_SIZE)

        && !(flags & MAP_ANONYMOUS)) {

       struct stat sb;

       if (fstat (fd, &sb) == -1)

           goto fail;

       /* Are we trying to create a map beyond EOF?.  */

       if (offset + len > sb.st_size) {

           /* If so, truncate the file map at eof aligned with 

              the hosts real pagesize. Additional anonymous maps

              will be created beyond EOF.  */

           len = (sb.st_size - offset);

           len += qemu_real_host_page_size - 1;

           len &= ~(qemu_real_host_page_size - 1);

       }

    }

    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;

            goto fail;

        }

        /* 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 | MAP_ANONYMOUS, -1, 0);

        if (p == MAP_FAILED)

            goto fail;

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

        host_start = (unsigned long)p;

        if (!(flags & MAP_ANONYMOUS)) {

            p = mmap(g2h(mmap_start), len, prot, 

                     flags | MAP_FIXED, fd, host_offset);

            host_start += offset - host_offset;

        }

        start = h2g(host_start);

    } else {

        if (start & ~TARGET_PAGE_MASK) {

            errno = EINVAL;

            goto fail;

        }

        end = start + len;

        real_end = HOST_PAGE_ALIGN(end);

        /*

         * Test if requested memory area fits target address space

         * It can fail only on 64-bit host with 32-bit target.

         * On any other target/host host mmap() handles this error correctly.

         */

        if ((unsigned long)start + len - 1 > (abi_ulong) -1) {

            errno = EINVAL;

            goto fail;

        }

        /* 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;

                goto fail;

            }

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

                                  MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,

                                  -1, 0);

            if (retaddr == -1)

                goto fail;

            if (pread(fd, g2h(start), len, offset) == -1)

                goto fail;

            if (!(prot & PROT_WRITE)) {

                ret = target_mprotect(start, len, prot);

                if (ret != 0) {

                    start = ret;

                    goto the_end;

                }

            }

            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)

                    goto fail;

                goto the_end1;

            }

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

                            prot, flags, fd, offset);

            if (ret == -1)

                goto fail;

            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)

                goto fail;

            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)

                goto fail;

        }

    }

 the_end1:

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

 the_end:

#ifdef DEBUG_MMAP

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

    page_dump(stdout);

    printf("\n");

#endif

    mmap_unlock();

    return start;

fail:

    mmap_unlock();

    return -1;

}

static void mmap_reserve(abi_ulong start, abi_ulong size)

{

    abi_ulong real_start;

    abi_ulong real_end;

    abi_ulong addr;

    abi_ulong end;

    int prot;

    real_start = start & qemu_host_page_mask;

    real_end = HOST_PAGE_ALIGN(start + size);

    end = start + size;

    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;

    }

    if (real_start != real_end) {

        mmap(g2h(real_start), real_end - real_start, PROT_NONE,

                 MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE,

                 -1, 0);

    }

}

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" TARGET_ABI_FMT_lx " len=0x"

           TARGET_ABI_FMT_lx "\n",

           start, len);

#endif

    if (start & ~TARGET_PAGE_MASK)

        return -EINVAL;

    len = TARGET_PAGE_ALIGN(len);

    if (len == 0)

        return -EINVAL;

    mmap_lock();

    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;

    }

    ret = 0;

    /* unmap what we can */

    if (real_start < real_end) {

        if (RESERVED_VA) {

            mmap_reserve(real_start, real_end - real_start);

        } else {

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

        }

    }

    if (ret == 0)

        page_set_flags(start, start + len, 0);

    mmap_unlock();

    return ret;

}

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;

    void *host_addr;

    mmap_lock();

    if (flags & MREMAP_FIXED) {

        host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),

                                     old_size, new_size,

                                     flags,

                                     g2h(new_addr));

        if (RESERVED_VA && host_addr != MAP_FAILED) {

            /* If new and old addresses overlap then the above mremap will

               already have failed with EINVAL.  */

            mmap_reserve(old_addr, old_size);

        }

    } else if (flags & MREMAP_MAYMOVE) {

        abi_ulong mmap_start;

        mmap_start = mmap_find_vma(0, new_size);

        if (mmap_start == -1) {

            errno = ENOMEM;

            host_addr = MAP_FAILED;

        } else {

            host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),

                                         old_size, new_size,

                                         flags | MREMAP_FIXED,

                                         g2h(mmap_start));

            if ( RESERVED_VA ) {

                mmap_reserve(old_addr, old_size);

            }

        }

    } else {

        int prot = 0;

        if (RESERVED_VA && old_size < new_size) {

            abi_ulong addr;

            for (addr = old_addr + old_size;

                 addr < old_addr + new_size;

                 addr++) {

                prot |= page_get_flags(addr);

            }

        }

        if (prot == 0) {

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

            if (host_addr != MAP_FAILED && RESERVED_VA && old_size > new_size) {

                mmap_reserve(old_addr + old_size, new_size - old_size);

            }

        } else {

            errno = ENOMEM;

            host_addr = MAP_FAILED;

        }

        /* Check if address fits target address space */

        if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {

            /* Revert mremap() changes */

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

            errno = ENOMEM;

            host_addr = MAP_FAILED;

        }

    }

    if (host_addr == MAP_FAILED) {

        new_addr = -1;

    } else {

        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);

    }

    mmap_unlock();

    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);

}