Re: [Qemu-devel] [PATCH 1/6] oslib-posix: add helpers for stack alloc and free

[Peter Lieven]

Am 01.07.2016 um 22:12 schrieb Richard Henderson:

On 06/30/2016 12:37 AM, Peter Lieven wrote:

+void *qemu_alloc_stack(size_t sz)
+{
+    /* allocate sz bytes plus one extra page for a guard
+     * page at the bottom of the stack */
+    void *ptr = mmap(NULL, sz + getpagesize(), PROT_NONE,
+                     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    if (ptr == MAP_FAILED) {
+        abort();
+    }
+    if (mmap(ptr + getpagesize(), sz, PROT_READ | PROT_WRITE,
+        MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0) == MAP_FAILED) {
+        abort();
+    }

Why two mmap instead of mmap + mprotect?


r~

I was looking at qemu_ram_mmap too much. mprotect seems the cleaner solution.

Thanks,
Peter