semihosting.h

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#ifndef EFX_SEMIHOSTING_H
#define EFX_SEMIHOSTING_H
 
 
#include "bsp.h"
#include "vexriscv.h"
 
 
#define RISCV_SEMIHOSTING_CALL_NUMBER 7
enum semihosting_operation_numbers {
    /*
     * ARM semihosting operations, in lexicographic order.
     */
    SEMIHOSTING_ENTER_SVC           = 0x17, /* DEPRECATED */
 
    SEMIHOSTING_SYS_CLOSE           = 0x02,
    SEMIHOSTING_SYS_CLOCK           = 0x10,
    SEMIHOSTING_SYS_ELAPSED         = 0x30,
    SEMIHOSTING_SYS_ERRNO           = 0x13,
    SEMIHOSTING_SYS_EXIT            = 0x18,
    SEMIHOSTING_SYS_EXIT_EXTENDED   = 0x20,
    SEMIHOSTING_SYS_FLEN            = 0x0C,
    SEMIHOSTING_SYS_GET_CMDLINE     = 0x15,
    SEMIHOSTING_SYS_HEAPINFO        = 0x16,
    SEMIHOSTING_SYS_ISERROR         = 0x08,
    SEMIHOSTING_SYS_ISTTY           = 0x09,
    SEMIHOSTING_SYS_OPEN            = 0x01,
    SEMIHOSTING_SYS_READ            = 0x06,
    SEMIHOSTING_SYS_READC           = 0x07,
    SEMIHOSTING_SYS_REMOVE          = 0x0E,
    SEMIHOSTING_SYS_RENAME          = 0x0F,
    SEMIHOSTING_SYS_SEEK            = 0x0A,
    SEMIHOSTING_SYS_SYSTEM          = 0x12,
    SEMIHOSTING_SYS_TICKFREQ        = 0x31,
    SEMIHOSTING_SYS_TIME            = 0x11,
    SEMIHOSTING_SYS_TMPNAM          = 0x0D,
    SEMIHOSTING_SYS_WRITE           = 0x05,
    SEMIHOSTING_SYS_WRITEC          = 0x03,
    SEMIHOSTING_SYS_WRITE0          = 0x04,
};
 
static inline int __attribute__ ((always_inline)) call_host(int reason, void* arg) {
    register int value asm ("a0") = reason;
    register void* ptr asm ("a1") = arg;
    asm volatile (
        " .option push \n"
        // Force non-compressed RISC-V instructions
        " .option norvc \n"
        // Force 16-byte alignment to make sure that the 3 instructions fall
        // within the same virtual page.
        // Note: align 4 means, align by 2 to the power of 4!
        " .align 4 \n"
        " slli x0, x0, 0x1f \n"
        " ebreak \n"
        " srai x0, x0, %[swi] \n"
        " .option pop \n"
        " nop \n"
        : "=r" (value) /* Outputs */
        : "0" (value), "r" (ptr), [swi] "i" (RISCV_SEMIHOSTING_CALL_NUMBER) /* Inputs */
        : "memory" /* Clobbers */
    );
    return value;
}
 
static void sh_write0(char* buf)
{
    // Print zero-terminated string
    call_host(SEMIHOSTING_SYS_WRITE0, (void*) buf);
}
 
static void sh_writec(char c)
{
    // Print single character
    call_host(SEMIHOSTING_SYS_WRITEC, (void*)&c);
}
 
static char sh_readc(void)
{
    // Read character - Blocking operation!
    return call_host(SEMIHOSTING_SYS_READC, (void*)0);
}
 
 
#endif // EFX_SEMIHOSTING_H