linux-user: Fix the computation of the requested heap size
There were several remaining bugs in the previous implementation of
do_brk():
1. the value of "new_alloc_size" was one page too large when the
requested brk was aligned on a host page boundary.
2. no new pages should be (re-)allocated when the requested brk is
in the range of the pages that were already allocated
previsouly (for the same purpose). Technically these pages are
never unmapped in the current implementation.
The problem/fix can be reproduced/validated with the test-suite above:
/* Preparation for the test "Re-allocated heap is initialized". */
old_brk = current_brk - HOST_PAGE_SIZE;
memset(old_brk, 0xFF, HOST_PAGE_SIZE);
test_title("Don't allocate the same \"brk\" page twice");
test_brk(-HOST_PAGE_SIZE, 1);
test_brk(HOST_PAGE_SIZE, 1);
test_result();
test_title("Re-allocated \"brk\" pages are initialized");
for (i = 0; i < HOST_PAGE_SIZE; i++) {
if (old_brk[i] != 0) {
printf("(index = %d, value = 0x%x) ", i, old_brk[i]);
failure = 1;
break;
}
}
test_result();