Syscall ABI

User code calls the kernel with ecall.

a7 = syscall number
a0 = arg0
a1 = arg1
a2 = arg2

Number	Name	Arguments	Return
1	SYS_EXIT	none	does not return
2	SYS_SLEEP	a0 = milliseconds	returns after sleep
3	SYS_YIELD	none	returns when scheduled again
10	SYS_EP_CREATE	none	a0 = endpoint ID
11	SYS_EP_SEND	a0 = endpoint, a1/a2 = message	a0 = 0 after delivery
12	SYS_EP_RECV	a0 = endpoint	a0/a1 = message
100	SYS_PUTCHAR	a0 = byte	none

The capability chapter changes endpoint arguments from raw endpoint IDs to capability slots.