diff options
| -rw-r--r-- | linux-user/mmap.c | 79 |
1 files changed, 43 insertions, 36 deletions
diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 3d2c8b3073..6ce41677af 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -273,52 +273,59 @@ static abi_ulong mmap_next_start = 0x40000000; 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. */ +/* + * 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) { - 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; + void *ptr; + abi_ulong addr; size = HOST_PAGE_ALIGN(size); - start = start & qemu_host_page_mask; + start &= qemu_host_page_mask; + + /* If 'start' == 0, then a default start address is used. */ + if (start == 0) + start = mmap_next_start; + 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) + /* + * 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((void *)(unsigned long)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; + + /* If address fits target address space we've found what we need */ + if ((unsigned long)ptr + size - 1 <= (abi_ulong)-1) break; + + /* Unmap and try again with new page */ + munmap(ptr, size); addr += qemu_host_page_size; - /* we found nothing */ - if (addr == addr_start) + + /* ENOMEM if we check whole of target address space */ + if (addr == start) return (abi_ulong)-1; } - if (start == 0) - mmap_next_start = addr + size; - return addr; + + /* Update default start address */ + if (start == mmap_next_start) + mmap_next_start = (unsigned long)ptr + size; + + return h2g(ptr); } /* NOTE: all the constants are the HOST ones */ |