Re: What can a signal handler do with SIGSTKSZ?

[Szabolcs Nagy <Szabolcs dot Nagy at arm dot com>]

On 11/01/2019 17:44, Carlos O'Donell wrote:
> In the continuing series of "What can X do with Y?" [1]
> 
> I would like to get consensus on what a signal handler can do with
> SIGSTKSZ amount of space.
> 
> I propose the following:
> ~~~
> The implementation only guarantees that a signal handler can
> manipulate a reasonable amount of local variables (no more than
> 2 KiB worth), and can read and write to memory, carry out atomic
> operations, and call simple C library functions that do similar
> memory and simple string operations e.g. memcpy, memset, strcmp,
> strcpy. The amount of signal stack allocated for SIGSTKSZ is not
> sufficient to call complex signal-safe functions e.g. fork, _exit,
> abort, nor any that can be canceled (requires enough stack for
> cancellation). Any other operations or function calls in the
> signal handler should be evaluated for runtime stack usage and
> additional stack beyond SIGSTKSZ should be allocated.
> ~~~
> 
> Thoughts?

instead of "local variables" i'd say: user
code may use X bytes stack space and the
rest is for the runtime (which is guaranteed
to be enough for simple libc calls,...).

X can be 2048.

runtime stack usage vs user stack usage can
be accounted based on stack usage of libc code
vs user code.