linux-user:Fix align mistake when mmap guest space

In init_guest_space, we need to mmap guest space. If the return address
of first mmap is not aligned with align, which was set to MAX(SHMLBA,
qemu_host_page_size), we need unmap and a new mmap(space is larger than
first size). The new size is named real_size, which is aligned_size +
qemu_host_page_size. alugned_size is the guest space size. And add a
qemu_host_page_size to avoid memory error when we align real_start
manually (ROUND_UP(real_start, align)). But when SHMLBA >
qemu_host_page_size, the added size will smaller than the size to align,
which can make a mistake(in a mips machine, it appears). So change
real_size from aligned_size +qemu_host_page_size
to aligned_size + align will solve it.

Signed-off-by: Xinyu Li <precinct@mail.ustc.edu.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20191213022919.5934-1-precinct@mail.ustc.edu.cn>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

linux-user/elfload.c

@@ -2191,7 +2191,7 @@ unsigned long init_guest_space(unsigned long host_start,
              * to where we need to put the commpage.
              */
             munmap((void *)real_start, host_size);
-            real_size = aligned_size + qemu_host_page_size;
+            real_size = aligned_size + align;
             real_start = (unsigned long)
                 mmap((void *)real_start, real_size, PROT_NONE, flags, -1, 0);
             if (real_start == (unsigned long)-1) {