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Re: [RFC] Prevent tailcall optimizations of libdl functions

On 01/25/2017 04:41 PM, Szabolcs Nagy wrote:

On 25/01/17 15:40, Florian Weimer wrote:

On 01/25/2017 04:38 PM, Szabolcs Nagy wrote:

On 25/01/17 15:32, Yuri Gribov wrote:

FWIW it sounds like GCC attribute would be the most natural solution
(and probably also useful in other contexts). I'll try to cook a patch
for GCC if there are no objections.


note that even if dlsym is marked notailcall, with

p = dlsym;
...
return p();

if the type of p does not carry the attributes of
dlsym then this can be a tailcall.


Yes, but dlsym would still see the address of the function containing the dlsym call, which is what we need to
determine the relevant object.


how?
At worst, the return address points to the code which jumps to the address p. This code is still in the object which calls dlsym. 

Florian
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