Setting stack before jumping to kernel code makes it randomly crash (e.g. invalid opcode)

VisualDevelopment · November 16, 2021, 5:03pm

See here

Firework-OS/FWLauncher/blob/master/src/main.rs#L77

    
      
              .1
          {
              if let Some(ent) = helpers::kaboom::mem_type_from_desc(desc) {
                  memory_map_entries.push(ent)
              }
          }
          
          
tags.push(kaboom::tags::TagType::MemoryMap(memory_map_entries.leak()));
          explosion.tags = tags.leak();
          
          
unsafe {
              asm!(
                  "cli",
                  // "mov rsp, {}",
                  "call {}",
                  // in(reg) stack,
                  in(reg) kernel_main,
                  in("rdi") Box::leak(explosion),
                  options(noreturn)
              )
          }

if I uncomment the commented lines in that asm statement, the kernel behaves weirdly
e.g. throws invalid opcode errors or page faults.
The kernel allocates 4KiB of memory for the stack; see here:

github.com

Firework-OS/Fuse/blob/master/src/main.rs#L28

    
      
          
          
extern crate alloc;
          
          
use alloc::boxed::Box;
          
          
use log::info;
          
          
mod sys;
          mod utils;
          
          
static STACK: [u8; 4096] = [0; 4096];
          
          
#[link_section = ".kaboom"]
          #[used]
          static EXPLOSION_FUEL: kaboom::ExplosionFuel = kaboom::ExplosionFuel::new(&STACK[4095]);
          
          
#[no_mangle]
          pub extern "sysv64" fn kernel_main(explosion: &'static kaboom::ExplosionResult) -> ! {
              sys::io::serial::SERIAL.lock().init();
          
          
    assert_eq!(explosion.revision, kaboom::CURRENT_REVISION);

VisualDevelopment · November 16, 2021, 7:29pm

Turns out, the issue was the stack being too small. I guess 4KiB is not enough for rust, set it to 2MiB and now everything works properly.
This thread shall be closed

system · February 14, 2022, 7:29pm

This topic was automatically closed 90 days after the last reply. We invite you to open a new topic if you have further questions or comments.