Commit 6e4c890e authored by Cao jin's avatar Cao jin Committed by Michael Tokarev
Browse files

util/mmap-alloc: refactor a little bit for readability 



1st mmap returns *ptr* which aligns to host page size,

    |             size + align               |
    ------------------------------------------
 ptr

input param *align* could be 1M, or 2M, or host page size. After
QEMU_ALIGN_UP, offset will >= 0

2nd mmap use flag MAP_FIXED, then it return ptr+offset, or else fail.
If it success, then we will have something like:

    | offset |          size             |
    --------------------------------------
 ptr      ptr1

*ptr1* is what we really want to return, it equals ptr+offset.

Signed-off-by: default avatarCao jin <caoj.fnst@cn.fujitsu.com>
Signed-off-by: default avatarMichael Tokarev <mjt@tls.msk.ru>
parent 4a3ecf20

util/mmap-alloc.c

+4 −6
Original line number Diff line number Diff line
@@ -84,22 +84,20 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) 
        return MAP_FAILED;

    }



    ptr += offset;

    total -= offset;



    if (offset > 0) {

        munmap(ptr - offset, offset);

        munmap(ptr, offset);

    }



    /*

     * Leave a single PROT_NONE page allocated after the RAM block, to serve as

     * a guard page guarding against potential buffer overflows.

     */

    total -= offset;

    if (total > size + getpagesize()) {

        munmap(ptr + size + getpagesize(), total - size - getpagesize());

        munmap(ptr1 + size + getpagesize(), total - size - getpagesize());

    }



    return ptr;

    return ptr1;

}



void qemu_ram_munmap(void *ptr, size_t size)