Re: riscv gcc-13 allyesconfig error the frame size of 2064 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]

[Kent Overstreet]

On Sun, May 25, 2025 at 06:47:57PM +0100, David Laight wrote:
> On Sun, 25 May 2025 13:36:16 -0400
> Kent Overstreet <kent.overstreet@xxxxxxxxx> wrote:
> 
> > +cc Steve
> ...
> > > I've a cunning plan to do a proper static analysis of stack usage.
> > > It is a 'simple' matter of getting objtool to output all calls with
> > > the stack offset.
> > > Indirect calls need the function hashes from fine-ibt, but also need
> > > clang to support 'hash seeds' to disambiguate all the void (*)(void *)
> > > functions.
> > > That'll first barf at all recursion, and then, I expect, show a massive
> > > stack use inside snprintf() in some error path.  
> > 
> > I suspect recursion will make the results you get with that approach
> > useless.
> 
> Recursion is an issue, but the kernel really doesn't support recursion.
> So you actually want to know the possible recursion loops anyway.
> I suspect (hope) most will be the 'recurses only once' type.
> If not they need some other bound.

Recursion is a fact of life when you get different subsystems
interacting in unpredictable ways.

You can be in one filesystem, and then end up in a fault handler (gup(),
or a simple copy to/from user), and then end up in a completely
different filesystem - and then you call into the block layer, or
networking if it's NFS.

Static analysis might get you some useful data within a subsystem, but
it won't tell you much about the kernel as a whole as people are
actually running it.