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

[Peter Lieven <pl@kamp.de>]

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