Stack size? about tillitis-key1 HOT 4 CLOSED

@mchack-work
I've worked on this today. Draft PRs here #40 and tillitis/tkey-ssh-agent#18

I'm trying 8 kb stack, and it mostly works. The issue I see is that the setup of new stack doesn't seem to bite. https://github.com/tillitis/tillitis-key1-apps/pull/18/files#diff-3857988385a284fb03dc747adb79566dac6d15e071f51256f9a7e702e4208d62R84

li sp, NEW_STACK might not be enough? The second time the program puts &stack, the addr is the same as the first. Some proper relocation needed? But how?

Might there then be other issues due to not doing proper relocation? I'm not so familar with riscv addressing yet, could there be address references that needs to be relocated? But the jump to forever_ledflash() works at least...

from tillitis-key1.

We probably can't do any relocation as inline assembler. If so, we're messing with the C runtime.

In our relocation example we want to run the relocation before starting running C code. This probably means linking with another libcrt0 if people want support for relocation.

I think it's more important to allow for larger device apps (make the stack smaller) than thinking about dynamic relocation.

from tillitis-key1.

Ah yes, I tried my hand at accomplishing relocation by having a different app.lds and crt0.S. Relocating the init crt0 at 0x40002000 and the app C main at 0x40010000. Setting the stack below that in crt0.S. It almost worked, except the call main ended up executing a jump to 0x40012000 -- too high. But it feels like this could be possible, just have to get the lds script right.

I think I'll leave the example app outside scope of this issue. And also settle on 16 kb stack, 8 seems a bit too small

from tillitis-key1.

Closed with these:
tillitis/tkey-ssh-agent#18
#40

from tillitis-key1.