Re: Fwd: What can a signal handler do with SIGSTKSZ?

[Szabolcs Nagy <Szabolcs.Nagy@arm.com>]

On 14/01/2019 16:22, Carlos O'Donell wrote:
> On 1/14/19 11:18 AM, Florian Weimer wrote:
>> * Szabolcs Nagy:
>>
>>> i think proposing sysconf(_SC_{MIN}SIGSTKSZ) for posix is the
>>> right solution with the kernel providing an upper bound of the
>>> stack frame in AT_MINSIGSTKSZ (as it already does on aarch64).
>>
>> It's still a bit nasty for process migration, but at least it should for
>> VM migration.  I think that would be a reasonable compromise.
>>
>> Of course, we'd still need a way to determine how much we should add on
>> top of AT_MINSIGSTKSZ for the application developer's benefit. 8-)
> 
> The value of SIGSTKSZ seems to be a "culturally relevant detail" that will
> probably be impossible to pin down to a real value.
> 
> If *I* were a developer I might expect as Zach pointed out, that I can call
> every function on the list of callable AS-safe functions, at least once,
> without recursion, and expect them to operate correctly.
> 
> A test case for this would therefore be a main, that register a handler
> that exercises *all* functions in the AS-safe list, and then looks for
> stack corruption at each execution.
> 
> The test could also be used to set the value to some accepted value for
> all machines.
> 
> Can we do this in practice?

e.g. exec functions that need to copy their
arguments to an on stack argv array may fail
depending on how many args are passed.