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Update yield info

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Toby Jaffey 2025-12-10 10:48:01 +00:00
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@ -140,7 +140,6 @@ If the bytecode attempts to execute more instructions than the the passed value
* `UVM32_EVT_END` the program has ended
* `UVM32_EVT_ERR` the program has encountered an error
* `UVM32_EVT_YIELD` the program has called `yield()` signifying that it requires more instructions to be executed, but has not crashed/hung
* `UVM32_EVT_SYSCALL` the program requests some IO via the host
## Internals
@ -190,9 +189,9 @@ The [RISC-V SBI](https://github.com/riscv-non-isa/riscv-sbi-doc/blob/master/risc
## syscalls
There are two system syscalls used by uvm32, `halt()` and `yield()`.
There are two inbuilt syscalls used by uvm32, `halt()` and `yield()`.
`halt()` tells the host that the program has ended normally. `yield()` tells the host that the program requires more instructions to be executed. These are handled internally to uvm32.
`halt()` tells the host that the program has ended normally. `yield()` tells the host that the program requires more instructions to be executed. Halt is handled internally and transitions the VM to `UVM32_STATUS_ENDED`, `yield()` is handled in the VM host like other syscalls.
Syscalls are handled in the host by reading the syscall identifier, then using the provided functions to get arguments and set a return response. Direct access to the VM's memory space is not allowed, to avoid memory corruption issues.