35 lines
702 B
C
35 lines
702 B
C
|
#include "types.h"
|
||
|
|
#include "memlayout.h"
|
||
|
|
#include "riscv.h"
|
||
|
|
#include "defs.h"
|
||
|
|
|
||
|
|
void main();
|
||
|
|
|
||
|
|
// entry.S uses this as the initial stack.
|
||
|
|
char stack0[4096];
|
||
|
|
|
||
|
|
// entry.S jumps here in machine mode on stack0.
|
||
|
|
void
|
||
|
|
mstart()
|
||
|
|
{
|
||
|
|
// set M Previous Privilege mode to Supervisor, for mret.
|
||
|
|
unsigned long x = r_mstatus();
|
||
|
|
x &= ~MSTATUS_MPP_MASK;
|
||
|
|
x |= MSTATUS_MPP_S;
|
||
|
|
w_mstatus(x);
|
||
|
|
|
||
|
|
// set M Exception Program Counter to main, for mret.
|
||
|
|
// requires gcc -mcmodel=medany
|
||
|
|
w_mepc((uint64)main);
|
||
|
|
|
||
|
|
// disable paging for now.
|
||
|
|
w_satp(0);
|
||
|
|
|
||
|
|
// delegate all interrupts and exceptions to supervisor mode.
|
||
|
|
w_medeleg(0xffff);
|
||
|
|
w_mideleg(0xffff);
|
||
|
|
|
||
|
|
// jump to main in supervisor mode.
|
||
|
|
asm("mret");
|
||
|
|
}
|