60 lines
2.0 KiB
C
60 lines
2.0 KiB
C
|
#include <stdint.h>
|
||
|
|
#include <stdlib.h>
|
||
|
|
#include <math.h>
|
||
|
|
|
||
|
|
#include "encoding.h"
|
||
|
|
|
||
|
|
#define EBREAK_OPCODE 0x00100073
|
||
|
|
#define EBREAK_MCAUSE 0x00000003
|
||
|
|
|
||
|
|
#define SLLI_X0_X0_0X1F_OPCODE 0x01f01013
|
||
|
|
#define SRAI_X0_X0_0X07_OPCODE 0x40705013
|
||
|
|
|
||
|
|
int sh_missing_host = 0;
|
||
|
|
|
||
|
|
void trap()
|
||
|
|
{
|
||
|
|
uint32_t mepc = read_csr(0x341); // Address of trap
|
||
|
|
uint32_t mtval = read_csr(0x343); // Instruction value of trap
|
||
|
|
uint32_t mcause = read_csr(0x342); // Reason for the trap
|
||
|
|
|
||
|
|
if (mcause == EBREAK_MCAUSE && mtval == EBREAK_OPCODE){
|
||
|
|
// This trap was caused by an EBREAK...
|
||
|
|
|
||
|
|
int aligned = ((mepc-4) & 0x0f) == 0;
|
||
|
|
if (aligned
|
||
|
|
&& *(uint32_t *)mepc == EBREAK_OPCODE
|
||
|
|
&& *(uint32_t *)(mepc-4) == SLLI_X0_X0_0X1F_OPCODE
|
||
|
|
&& *(uint32_t *)(mepc+4) == SRAI_X0_X0_0X07_OPCODE)
|
||
|
|
{
|
||
|
|
// The EBREAK was part of the semihosting call. (See semihosting.c)
|
||
|
|
//
|
||
|
|
// If a debugger were connected, this would have resulted in a CPU halt,
|
||
|
|
// and the debugger would have serviced the the semihosting call.
|
||
|
|
//
|
||
|
|
// However, the semihosting function was called without a debugger being
|
||
|
|
// attached. The best course of action is to simply return from the trap
|
||
|
|
// and let the semihosting function continue after the call to EBREAK to
|
||
|
|
// prevent the CPU from hanging in the trap handler.
|
||
|
|
write_csr(mepc, mepc+4);
|
||
|
|
|
||
|
|
// Set a global variable to tell the semihosting code the the semihosting
|
||
|
|
// call
|
||
|
|
// didn't execute on the host.
|
||
|
|
sh_missing_host = 1;
|
||
|
|
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
// EBREAK was not part of a semihosting call. This should not have happened.
|
||
|
|
// Hang forever.
|
||
|
|
while(1)
|
||
|
|
;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Trap was issued for another reason than an EBREAK.
|
||
|
|
// Replace the code below with whatever trap handler you'd normally use. (e.g. interrupt
|
||
|
|
// processing.)
|
||
|
|
while(1)
|
||
|
|
;
|
||
|
|
}
|