Jan Engelhardt <[email protected]> wrote:
>>> +#define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
>
> There seems to be a slight problem with doing that. Running
> `ldd /bin/bash` prints out
>
> linux-gate.so.1 => (0xffffe000)
>
> and the topmost address a kernel function can return is 0xFFFFf000 when
> MAX_ERRNO=4095, but that is going to be tight with the vdso mapped at
> 0xffffE000.
http://www.trilithium.com/johan/2005/08/linux-gate/
"... an x86 box where processes live in plain old 32-bit address spaces
divided into pages of 4096 bytes, making ffffe000 the penultimate page.
The very last page is reserved to catch accesses through invalid pointers,
e.g. dereferencing a decremented NULL pointer or a MAP_FAILED pointer
returned from mmap."
Therefore, MAX_ERRNO < PAGE_SIZE is safe.
--
Ich danke GMX dafür, die Verwendung meiner Adressen mittels per SPF
verbreiteten Lügen zu sabotieren.
http://david.woodhou.se/why-not-spf.html
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