stm32 semihosting with printf and hexdump.c

/***********************
  SEMIHOSTING
************************/

#define SEMIHOSTING
#ifdef SEMIHOSTING
#include <stdarg.h>
#include <ctype.h> //isprint
/*
  Note: This semihost printing utility functions is targeted towards STM32 based chips
*/
void arm_semihosting_print_string(char* str)
{
  int len = 0;

  /* Check if debugger is attached */
  if (!((CoreDebug->DHCSR & 1) == 1 ))
    return;

  /* Calculate String Length */
  for (len = 0; str[len]; (len)++);

  /* Call Semihost */
  int args[3] = {2 /*stderr*/, (int) str, (int)len};
  asm volatile (
    " mov r0, %[reason]  \n"
    " mov r1, %[arg]  \n"
    " bkpt %[swi] \n"
    : /* Output */
    : [reason] "r" (0x05), [arg] "r" (args), [swi] "i" (0xAB) /* Inputs */
    : "r0", "r1", "r2", "r3", "ip", "lr", "memory", "cc"
  );
}

void arm_semihosting_printf(char* format, ...)
{
  char buff[400] = {0};
  size_t buff_size = sizeof(buff);

  /* Check if debugger is attached */
  if (!((CoreDebug->DHCSR & 1) == 1 ))
  {
    return;
  }

  /* Format String */
  va_list argptr;
  va_start(argptr, format);
  vasnprintf(buff, &buff_size, format, argptr);
  va_end(argptr);

  /* Print */
  arm_semihosting_print_string(buff);
}

void arm_semihosting_hex_dump( const void *addr, const uint32_t nBytes)
{
  const uint8_t byte_per_row = 16;
  const uint8_t *addr_ptr = addr;

  uint32_t offset = 0;
  while (offset < nBytes)
  {
    char buff[400] = {0}; // Line Buff
    char *buff_ptr = buff;
    const char *buff_end = buff + sizeof(buff) - 1;

    buff_ptr += snprintf(buff_ptr, buff_end-buff_ptr, " %4u | ", (unsigned) offset);

    for (uint8_t i = 0 ; i < byte_per_row ; i++)
    { /* Hex */
      if ((offset + i) >= nBytes)
        break;
      buff_ptr += snprintf(buff_ptr, buff_end-buff_ptr, " %02x", addr_ptr[offset+i]);
    }

    buff_ptr += snprintf(buff_ptr, buff_end-buff_ptr, "  :  ");

    for (uint8_t i = 0 ; i < byte_per_row ; i++)
    { /* Printables */
      if ((offset + i) >= nBytes) break;
      char c = isprint(addr_ptr[offset+i]) ? addr_ptr[offset+i] : '.';
      buff_ptr += snprintf(buff_ptr, buff_end-buff_ptr, "%c", c);
    }

    offset += byte_per_row;

    arm_semihosting_print_string(buff);
    arm_semihosting_print_string("\r\n");
  }

  arm_semihosting_print_string("\r\n");
}
#else
#define arm_semihosting_print_string(...)
#define arm_semihosting_printf(...)
#define arm_semihosting_hex_dump(...)
#endif

Example output

payload integrity fail (8020000,  255 bytes) (0 != ff)
    0 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
   16 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
   32 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
   48 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
   64 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
   80 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
   96 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
  112 |  00 00 00 00 00 00 00 00 00 00 00 00 7f 00 00 00  :  ................
  128 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
  144 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
  160 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
  176 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
  192 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
  208 |  00 00 00 00 7f 00 00 00 00 00 00 00 00 00 00 00  :  ................
  224 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................
  240 |  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  :  ................

Useful for bootloader dev and other development where you don't have access to the serial console.