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Add support for printf, UART, and iron out a few bugs

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This commit is contained in:
Konstantin Nazarov 2024-12-14 22:56:28 +00:00
parent 9707f1a7bf
commit 351a895d69
Signed by: knazarov
GPG key ID: 4CFE0A42FA409C22
12 changed files with 1257 additions and 82 deletions
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6
example/Makefile
View file

@ -1,4 +1,6 @@
example: example.c Makefile boot.s linker.ld
example: example.c Makefile boot.s linker.ld printf.h printf.c putchar.c
riscv32-none-elf-as -march=rv32i -mabi=ilp32 boot.s -o boot.o
riscv32-none-elf-gcc -fno-builtin -fvisibility=hidden -nostdlib -nostartfiles -march=rv32im -mabi=ilp32 -D PRINTF_DISABLE_SUPPORT_FLOAT=1 -D PRINTF_DISABLE_SUPPORT_LONG_LONG=1 -c printf.c -o printf.o -g
riscv32-none-elf-gcc -fno-builtin -fvisibility=hidden -nostdlib -nostartfiles -march=rv32im -mabi=ilp32 -c putchar.c -o putchar.o -g
riscv32-none-elf-gcc -fno-builtin -fvisibility=hidden -nostdlib -nostartfiles -march=rv32im -mabi=ilp32 -c example.c -o example.o -g
riscv32-none-elf-ld boot.o example.o -T linker.ld -o example -g
riscv32-none-elf-ld boot.o example.o printf.o putchar.o -T linker.ld -o example -g

2
example/boot.s
View file

@ -1,6 +1,6 @@
.globl _boot
_boot:
li x2, 0x8000
li x2, 0x80000
call main
sbreak
j .

7
example/example.c
View file

@ -1,4 +1,4 @@
static int mem = 1;
#include "printf.h"
int fact(int n) {
if (n == 0)
@ -8,7 +8,10 @@ int fact(int n) {
}
int main() {
mem = fact(8);
int n = 8;
int res = fact(8);
printf("%d! = %d\n", n, res);
return 0;
}

6
example/linker.ld
View file

@ -7,19 +7,19 @@ SECTIONS {
*(.text) /* Place all .text sections (code) here */
}
. = 0x1000;
. = 0x10000;
.data : {
*(.data) /* Place all .data sections (initialized data) here */
}
. = 0x2000;
. = 0x20000;
.bss : {
*(.bss) /* Place all .bss sections (uninitialized data) here */
}
. = 0x3000;
. = 0x30000;
.stack : {
*(.stack)

914
example/printf.c Normal file
View file

@ -0,0 +1,914 @@
///////////////////////////////////////////////////////////////////////////////
// \author (c) Marco Paland (info@paland.com)
// 2014-2019, PALANDesign Hannover, Germany
//
// \license The MIT License (MIT)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
// \brief Tiny printf, sprintf and (v)snprintf implementation, optimized for speed on
// embedded systems with a very limited resources. These routines are thread
// safe and reentrant!
// Use this instead of the bloated standard/newlib printf cause these use
// malloc for printf (and may not be thread safe).
//
///////////////////////////////////////////////////////////////////////////////
#include <stdbool.h>
#include <stdint.h>
#include "printf.h"
// define this globally (e.g. gcc -DPRINTF_INCLUDE_CONFIG_H ...) to include the
// printf_config.h header file
// default: undefined
#ifdef PRINTF_INCLUDE_CONFIG_H
#include "printf_config.h"
#endif
// 'ntoa' conversion buffer size, this must be big enough to hold one converted
// numeric number including padded zeros (dynamically created on stack)
// default: 32 byte
#ifndef PRINTF_NTOA_BUFFER_SIZE
#define PRINTF_NTOA_BUFFER_SIZE 32U
#endif
// 'ftoa' conversion buffer size, this must be big enough to hold one converted
// float number including padded zeros (dynamically created on stack)
// default: 32 byte
#ifndef PRINTF_FTOA_BUFFER_SIZE
#define PRINTF_FTOA_BUFFER_SIZE 32U
#endif
// support for the floating point type (%f)
// default: activated
#ifndef PRINTF_DISABLE_SUPPORT_FLOAT
#define PRINTF_SUPPORT_FLOAT
#endif
// support for exponential floating point notation (%e/%g)
// default: activated
#ifndef PRINTF_DISABLE_SUPPORT_EXPONENTIAL
#define PRINTF_SUPPORT_EXPONENTIAL
#endif
// define the default floating point precision
// default: 6 digits
#ifndef PRINTF_DEFAULT_FLOAT_PRECISION
#define PRINTF_DEFAULT_FLOAT_PRECISION 6U
#endif
// define the largest float suitable to print with %f
// default: 1e9
#ifndef PRINTF_MAX_FLOAT
#define PRINTF_MAX_FLOAT 1e9
#endif
// support for the long long types (%llu or %p)
// default: activated
#ifndef PRINTF_DISABLE_SUPPORT_LONG_LONG
#define PRINTF_SUPPORT_LONG_LONG
#endif
// support for the ptrdiff_t type (%t)
// ptrdiff_t is normally defined in <stddef.h> as long or long long type
// default: activated
#ifndef PRINTF_DISABLE_SUPPORT_PTRDIFF_T
#define PRINTF_SUPPORT_PTRDIFF_T
#endif
///////////////////////////////////////////////////////////////////////////////
// internal flag definitions
#define FLAGS_ZEROPAD (1U << 0U)
#define FLAGS_LEFT (1U << 1U)
#define FLAGS_PLUS (1U << 2U)
#define FLAGS_SPACE (1U << 3U)
#define FLAGS_HASH (1U << 4U)
#define FLAGS_UPPERCASE (1U << 5U)
#define FLAGS_CHAR (1U << 6U)
#define FLAGS_SHORT (1U << 7U)
#define FLAGS_LONG (1U << 8U)
#define FLAGS_LONG_LONG (1U << 9U)
#define FLAGS_PRECISION (1U << 10U)
#define FLAGS_ADAPT_EXP (1U << 11U)
// import float.h for DBL_MAX
#if defined(PRINTF_SUPPORT_FLOAT)
#include <float.h>
#endif
// output function type
typedef void (*out_fct_type)(char character, void* buffer, size_t idx, size_t maxlen);
// wrapper (used as buffer) for output function type
typedef struct {
void (*fct)(char character, void* arg);
void* arg;
} out_fct_wrap_type;
// internal buffer output
static inline void _out_buffer(char character, void* buffer, size_t idx, size_t maxlen)
{
if (idx < maxlen) {
((char*)buffer)[idx] = character;
}
}
// internal null output
static inline void _out_null(char character, void* buffer, size_t idx, size_t maxlen)
{
(void)character; (void)buffer; (void)idx; (void)maxlen;
}
// internal _putchar wrapper
static inline void _out_char(char character, void* buffer, size_t idx, size_t maxlen)
{
(void)buffer; (void)idx; (void)maxlen;
if (character) {
_putchar(character);
}
}
// internal output function wrapper
static inline void _out_fct(char character, void* buffer, size_t idx, size_t maxlen)
{
(void)idx; (void)maxlen;
if (character) {
// buffer is the output fct pointer
((out_fct_wrap_type*)buffer)->fct(character, ((out_fct_wrap_type*)buffer)->arg);
}
}
// internal secure strlen
// \return The length of the string (excluding the terminating 0) limited by 'maxsize'
static inline unsigned int _strnlen_s(const char* str, size_t maxsize)
{
const char* s;
for (s = str; *s && maxsize--; ++s);
return (unsigned int)(s - str);
}
// internal test if char is a digit (0-9)
// \return true if char is a digit
static inline bool _is_digit(char ch)
{
return (ch >= '0') && (ch <= '9');
}
// internal ASCII string to unsigned int conversion
static unsigned int _atoi(const char** str)
{
unsigned int i = 0U;
while (_is_digit(**str)) {
i = i * 10U + (unsigned int)(*((*str)++) - '0');
}
return i;
}
// output the specified string in reverse, taking care of any zero-padding
static size_t _out_rev(out_fct_type out, char* buffer, size_t idx, size_t maxlen, const char* buf, size_t len, unsigned int width, unsigned int flags)
{
const size_t start_idx = idx;
// pad spaces up to given width
if (!(flags & FLAGS_LEFT) && !(flags & FLAGS_ZEROPAD)) {
for (size_t i = len; i < width; i++) {
out(' ', buffer, idx++, maxlen);
}
}
// reverse string
while (len) {
out(buf[--len], buffer, idx++, maxlen);
}
// append pad spaces up to given width
if (flags & FLAGS_LEFT) {
while (idx - start_idx < width) {
out(' ', buffer, idx++, maxlen);
}
}
return idx;
}
// internal itoa format
static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t maxlen, char* buf, size_t len, bool negative, unsigned int base, unsigned int prec, unsigned int width, unsigned int flags)
{
// pad leading zeros
if (!(flags & FLAGS_LEFT)) {
if (width && (flags & FLAGS_ZEROPAD) && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
width--;
}
while ((len < prec) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
buf[len++] = '0';
}
while ((flags & FLAGS_ZEROPAD) && (len < width) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
buf[len++] = '0';
}
}
// handle hash
if (flags & FLAGS_HASH) {
if (!(flags & FLAGS_PRECISION) && len && ((len == prec) || (len == width))) {
len--;
if (len && (base == 16U)) {
len--;
}
}
if ((base == 16U) && !(flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
buf[len++] = 'x';
}
else if ((base == 16U) && (flags & FLAGS_UPPERCASE) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
buf[len++] = 'X';
}
else if ((base == 2U) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
buf[len++] = 'b';
}
if (len < PRINTF_NTOA_BUFFER_SIZE) {
buf[len++] = '0';
}
}
if (len < PRINTF_NTOA_BUFFER_SIZE) {
if (negative) {
buf[len++] = '-';
}
else if (flags & FLAGS_PLUS) {
buf[len++] = '+'; // ignore the space if the '+' exists
}
else if (flags & FLAGS_SPACE) {
buf[len++] = ' ';
}
}
return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags);
}
// internal itoa for 'long' type
static size_t _ntoa_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long value, bool negative, unsigned long base, unsigned int prec, unsigned int width, unsigned int flags)
{
char buf[PRINTF_NTOA_BUFFER_SIZE];
size_t len = 0U;
// no hash for 0 values
if (!value) {
flags &= ~FLAGS_HASH;
}
// write if precision != 0 and value is != 0
if (!(flags & FLAGS_PRECISION) || value) {
do {
const char digit = (char)(value % base);
buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
value /= base;
} while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
}
return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags);
}
// internal itoa for 'long long' type
#if defined(PRINTF_SUPPORT_LONG_LONG)
static size_t _ntoa_long_long(out_fct_type out, char* buffer, size_t idx, size_t maxlen, unsigned long long value, bool negative, unsigned long long base, unsigned int prec, unsigned int width, unsigned int flags)
{
char buf[PRINTF_NTOA_BUFFER_SIZE];
size_t len = 0U;
// no hash for 0 values
if (!value) {
flags &= ~FLAGS_HASH;
}
// write if precision != 0 and value is != 0
if (!(flags & FLAGS_PRECISION) || value) {
do {
const char digit = (char)(value % base);
buf[len++] = digit < 10 ? '0' + digit : (flags & FLAGS_UPPERCASE ? 'A' : 'a') + digit - 10;
value /= base;
} while (value && (len < PRINTF_NTOA_BUFFER_SIZE));
}
return _ntoa_format(out, buffer, idx, maxlen, buf, len, negative, (unsigned int)base, prec, width, flags);
}
#endif // PRINTF_SUPPORT_LONG_LONG
#if defined(PRINTF_SUPPORT_FLOAT)
#if defined(PRINTF_SUPPORT_EXPONENTIAL)
// forward declaration so that _ftoa can switch to exp notation for values > PRINTF_MAX_FLOAT
static size_t _etoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags);
#endif
// internal ftoa for fixed decimal floating point
static size_t _ftoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags)
{
char buf[PRINTF_FTOA_BUFFER_SIZE];
size_t len = 0U;
double diff = 0.0;
// powers of 10
static const double pow10[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 };
// test for special values
if (value != value)
return _out_rev(out, buffer, idx, maxlen, "nan", 3, width, flags);
if (value < -DBL_MAX)
return _out_rev(out, buffer, idx, maxlen, "fni-", 4, width, flags);
if (value > DBL_MAX)
return _out_rev(out, buffer, idx, maxlen, (flags & FLAGS_PLUS) ? "fni+" : "fni", (flags & FLAGS_PLUS) ? 4U : 3U, width, flags);
// test for very large values
// standard printf behavior is to print EVERY whole number digit -- which could be 100s of characters overflowing your buffers == bad
if ((value > PRINTF_MAX_FLOAT) || (value < -PRINTF_MAX_FLOAT)) {
#if defined(PRINTF_SUPPORT_EXPONENTIAL)
return _etoa(out, buffer, idx, maxlen, value, prec, width, flags);
#else
return 0U;
#endif
}
// test for negative
bool negative = false;
if (value < 0) {
negative = true;
value = 0 - value;
}
// set default precision, if not set explicitly
if (!(flags & FLAGS_PRECISION)) {
prec = PRINTF_DEFAULT_FLOAT_PRECISION;
}
// limit precision to 9, cause a prec >= 10 can lead to overflow errors
while ((len < PRINTF_FTOA_BUFFER_SIZE) && (prec > 9U)) {
buf[len++] = '0';
prec--;
}
int whole = (int)value;
double tmp = (value - whole) * pow10[prec];
unsigned long frac = (unsigned long)tmp;
diff = tmp - frac;
if (diff > 0.5) {
++frac;
// handle rollover, e.g. case 0.99 with prec 1 is 1.0
if (frac >= pow10[prec]) {
frac = 0;
++whole;
}
}
else if (diff < 0.5) {
}
else if ((frac == 0U) || (frac & 1U)) {
// if halfway, round up if odd OR if last digit is 0
++frac;
}
if (prec == 0U) {
diff = value - (double)whole;
if ((!(diff < 0.5) || (diff > 0.5)) && (whole & 1)) {
// exactly 0.5 and ODD, then round up
// 1.5 -> 2, but 2.5 -> 2
++whole;
}
}
else {
unsigned int count = prec;
// now do fractional part, as an unsigned number
while (len < PRINTF_FTOA_BUFFER_SIZE) {
--count;
buf[len++] = (char)(48U + (frac % 10U));
if (!(frac /= 10U)) {
break;
}
}
// add extra 0s
while ((len < PRINTF_FTOA_BUFFER_SIZE) && (count-- > 0U)) {
buf[len++] = '0';
}
if (len < PRINTF_FTOA_BUFFER_SIZE) {
// add decimal
buf[len++] = '.';
}
}
// do whole part, number is reversed
while (len < PRINTF_FTOA_BUFFER_SIZE) {
buf[len++] = (char)(48 + (whole % 10));
if (!(whole /= 10)) {
break;
}
}
// pad leading zeros
if (!(flags & FLAGS_LEFT) && (flags & FLAGS_ZEROPAD)) {
if (width && (negative || (flags & (FLAGS_PLUS | FLAGS_SPACE)))) {
width--;
}
while ((len < width) && (len < PRINTF_FTOA_BUFFER_SIZE)) {
buf[len++] = '0';
}
}
if (len < PRINTF_FTOA_BUFFER_SIZE) {
if (negative) {
buf[len++] = '-';
}
else if (flags & FLAGS_PLUS) {
buf[len++] = '+'; // ignore the space if the '+' exists
}
else if (flags & FLAGS_SPACE) {
buf[len++] = ' ';
}
}
return _out_rev(out, buffer, idx, maxlen, buf, len, width, flags);
}
#if defined(PRINTF_SUPPORT_EXPONENTIAL)
// internal ftoa variant for exponential floating-point type, contributed by Martijn Jasperse <m.jasperse@gmail.com>
static size_t _etoa(out_fct_type out, char* buffer, size_t idx, size_t maxlen, double value, unsigned int prec, unsigned int width, unsigned int flags)
{
// check for NaN and special values
if ((value != value) || (value > DBL_MAX) || (value < -DBL_MAX)) {
return _ftoa(out, buffer, idx, maxlen, value, prec, width, flags);
}
// determine the sign
const bool negative = value < 0;
if (negative) {
value = -value;
}
// default precision
if (!(flags & FLAGS_PRECISION)) {
prec = PRINTF_DEFAULT_FLOAT_PRECISION;
}
// determine the decimal exponent
// based on the algorithm by David Gay (https://www.ampl.com/netlib/fp/dtoa.c)
union {
uint64_t U;
double F;
} conv;
conv.F = value;
int exp2 = (int)((conv.U >> 52U) & 0x07FFU) - 1023; // effectively log2
conv.U = (conv.U & ((1ULL << 52U) - 1U)) | (1023ULL << 52U); // drop the exponent so conv.F is now in [1,2)
// now approximate log10 from the log2 integer part and an expansion of ln around 1.5
int expval = (int)(0.1760912590558 + exp2 * 0.301029995663981 + (conv.F - 1.5) * 0.289529654602168);
// now we want to compute 10^expval but we want to be sure it won't overflow
exp2 = (int)(expval * 3.321928094887362 + 0.5);
const double z = expval * 2.302585092994046 - exp2 * 0.6931471805599453;
const double z2 = z * z;
conv.U = (uint64_t)(exp2 + 1023) << 52U;
// compute exp(z) using continued fractions, see https://en.wikipedia.org/wiki/Exponential_function#Continued_fractions_for_ex
conv.F *= 1 + 2 * z / (2 - z + (z2 / (6 + (z2 / (10 + z2 / 14)))));
// correct for rounding errors
if (value < conv.F) {
expval--;
conv.F /= 10;
}
// the exponent format is "%+03d" and largest value is "307", so set aside 4-5 characters
unsigned int minwidth = ((expval < 100) && (expval > -100)) ? 4U : 5U;
// in "%g" mode, "prec" is the number of *significant figures* not decimals
if (flags & FLAGS_ADAPT_EXP) {
// do we want to fall-back to "%f" mode?
if ((value >= 1e-4) && (value < 1e6)) {
if ((int)prec > expval) {
prec = (unsigned)((int)prec - expval - 1);
}
else {
prec = 0;
}
flags |= FLAGS_PRECISION; // make sure _ftoa respects precision
// no characters in exponent
minwidth = 0U;
expval = 0;
}
else {
// we use one sigfig for the whole part
if ((prec > 0) && (flags & FLAGS_PRECISION)) {
--prec;
}
}
}
// will everything fit?
unsigned int fwidth = width;
if (width > minwidth) {
// we didn't fall-back so subtract the characters required for the exponent
fwidth -= minwidth;
} else {
// not enough characters, so go back to default sizing
fwidth = 0U;
}
if ((flags & FLAGS_LEFT) && minwidth) {
// if we're padding on the right, DON'T pad the floating part
fwidth = 0U;
}
// rescale the float value
if (expval) {
value /= conv.F;
}
// output the floating part
const size_t start_idx = idx;
idx = _ftoa(out, buffer, idx, maxlen, negative ? -value : value, prec, fwidth, flags & ~FLAGS_ADAPT_EXP);
// output the exponent part
if (minwidth) {
// output the exponential symbol
out((flags & FLAGS_UPPERCASE) ? 'E' : 'e', buffer, idx++, maxlen);
// output the exponent value
idx = _ntoa_long(out, buffer, idx, maxlen, (expval < 0) ? -expval : expval, expval < 0, 10, 0, minwidth-1, FLAGS_ZEROPAD | FLAGS_PLUS);
// might need to right-pad spaces
if (flags & FLAGS_LEFT) {
while (idx - start_idx < width) out(' ', buffer, idx++, maxlen);
}
}
return idx;
}
#endif // PRINTF_SUPPORT_EXPONENTIAL
#endif // PRINTF_SUPPORT_FLOAT
// internal vsnprintf
static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const char* format, va_list va)
{
unsigned int flags, width, precision, n;
size_t idx = 0U;
if (!buffer) {
// use null output function
out = _out_null;
}
while (*format)
{
// format specifier? %[flags][width][.precision][length]
if (*format != '%') {
// no
out(*format, buffer, idx++, maxlen);
format++;
continue;
}
else {
// yes, evaluate it
format++;
}
// evaluate flags
flags = 0U;
do {
switch (*format) {
case '0': flags |= FLAGS_ZEROPAD; format++; n = 1U; break;
case '-': flags |= FLAGS_LEFT; format++; n = 1U; break;
case '+': flags |= FLAGS_PLUS; format++; n = 1U; break;
case ' ': flags |= FLAGS_SPACE; format++; n = 1U; break;
case '#': flags |= FLAGS_HASH; format++; n = 1U; break;
default : n = 0U; break;
}
} while (n);
// evaluate width field
width = 0U;
if (_is_digit(*format)) {
width = _atoi(&format);
}
else if (*format == '*') {
const int w = va_arg(va, int);
if (w < 0) {
flags |= FLAGS_LEFT; // reverse padding
width = (unsigned int)-w;
}
else {
width = (unsigned int)w;
}
format++;
}
// evaluate precision field
precision = 0U;
if (*format == '.') {
flags |= FLAGS_PRECISION;
format++;
if (_is_digit(*format)) {
precision = _atoi(&format);
}
else if (*format == '*') {
const int prec = (int)va_arg(va, int);
precision = prec > 0 ? (unsigned int)prec : 0U;
format++;
}
}
// evaluate length field
switch (*format) {
case 'l' :
flags |= FLAGS_LONG;
format++;
if (*format == 'l') {
flags |= FLAGS_LONG_LONG;
format++;
}
break;
case 'h' :
flags |= FLAGS_SHORT;
format++;
if (*format == 'h') {
flags |= FLAGS_CHAR;
format++;
}
break;
#if defined(PRINTF_SUPPORT_PTRDIFF_T)
case 't' :
flags |= (sizeof(ptrdiff_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
format++;
break;
#endif
case 'j' :
flags |= (sizeof(intmax_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
format++;
break;
case 'z' :
flags |= (sizeof(size_t) == sizeof(long) ? FLAGS_LONG : FLAGS_LONG_LONG);
format++;
break;
default :
break;
}
// evaluate specifier
switch (*format) {
case 'd' :
case 'i' :
case 'u' :
case 'x' :
case 'X' :
case 'o' :
case 'b' : {
// set the base
unsigned int base;
if (*format == 'x' || *format == 'X') {
base = 16U;
}
else if (*format == 'o') {
base = 8U;
}
else if (*format == 'b') {
base = 2U;
}
else {
base = 10U;
flags &= ~FLAGS_HASH; // no hash for dec format
}
// uppercase
if (*format == 'X') {
flags |= FLAGS_UPPERCASE;
}
// no plus or space flag for u, x, X, o, b
if ((*format != 'i') && (*format != 'd')) {
flags &= ~(FLAGS_PLUS | FLAGS_SPACE);
}
// ignore '0' flag when precision is given
if (flags & FLAGS_PRECISION) {
flags &= ~FLAGS_ZEROPAD;
}
// convert the integer
if ((*format == 'i') || (*format == 'd')) {
// signed
if (flags & FLAGS_LONG_LONG) {
#if defined(PRINTF_SUPPORT_LONG_LONG)
const long long value = va_arg(va, long long);
idx = _ntoa_long_long(out, buffer, idx, maxlen, (unsigned long long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
#endif
}
else if (flags & FLAGS_LONG) {
const long value = va_arg(va, long);
idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
}
else {
const int value = (flags & FLAGS_CHAR) ? (char)va_arg(va, int) : (flags & FLAGS_SHORT) ? (short int)va_arg(va, int) : va_arg(va, int);
idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned int)(value > 0 ? value : 0 - value), value < 0, base, precision, width, flags);
}
}
else {
// unsigned
if (flags & FLAGS_LONG_LONG) {
#if defined(PRINTF_SUPPORT_LONG_LONG)
idx = _ntoa_long_long(out, buffer, idx, maxlen, va_arg(va, unsigned long long), false, base, precision, width, flags);
#endif
}
else if (flags & FLAGS_LONG) {
idx = _ntoa_long(out, buffer, idx, maxlen, va_arg(va, unsigned long), false, base, precision, width, flags);
}
else {
const unsigned int value = (flags & FLAGS_CHAR) ? (unsigned char)va_arg(va, unsigned int) : (flags & FLAGS_SHORT) ? (unsigned short int)va_arg(va, unsigned int) : va_arg(va, unsigned int);
idx = _ntoa_long(out, buffer, idx, maxlen, value, false, base, precision, width, flags);
}
}
format++;
break;
}
#if defined(PRINTF_SUPPORT_FLOAT)
case 'f' :
case 'F' :
if (*format == 'F') flags |= FLAGS_UPPERCASE;
idx = _ftoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags);
format++;
break;
#if defined(PRINTF_SUPPORT_EXPONENTIAL)
case 'e':
case 'E':
case 'g':
case 'G':
if ((*format == 'g')||(*format == 'G')) flags |= FLAGS_ADAPT_EXP;
if ((*format == 'E')||(*format == 'G')) flags |= FLAGS_UPPERCASE;
idx = _etoa(out, buffer, idx, maxlen, va_arg(va, double), precision, width, flags);
format++;
break;
#endif // PRINTF_SUPPORT_EXPONENTIAL
#endif // PRINTF_SUPPORT_FLOAT
case 'c' : {
unsigned int l = 1U;
// pre padding
if (!(flags & FLAGS_LEFT)) {
while (l++ < width) {
out(' ', buffer, idx++, maxlen);
}
}
// char output
out((char)va_arg(va, int), buffer, idx++, maxlen);
// post padding
if (flags & FLAGS_LEFT) {
while (l++ < width) {
out(' ', buffer, idx++, maxlen);
}
}
format++;
break;
}
case 's' : {
const char* p = va_arg(va, char*);
unsigned int l = _strnlen_s(p, precision ? precision : (size_t)-1);
// pre padding
if (flags & FLAGS_PRECISION) {
l = (l < precision ? l : precision);
}
if (!(flags & FLAGS_LEFT)) {
while (l++ < width) {
out(' ', buffer, idx++, maxlen);
}
}
// string output
while ((*p != 0) && (!(flags & FLAGS_PRECISION) || precision--)) {
out(*(p++), buffer, idx++, maxlen);
}
// post padding
if (flags & FLAGS_LEFT) {
while (l++ < width) {
out(' ', buffer, idx++, maxlen);
}
}
format++;
break;
}
case 'p' : {
width = sizeof(void*) * 2U;
flags |= FLAGS_ZEROPAD | FLAGS_UPPERCASE;
#if defined(PRINTF_SUPPORT_LONG_LONG)
const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
if (is_ll) {
idx = _ntoa_long_long(out, buffer, idx, maxlen, (uintptr_t)va_arg(va, void*), false, 16U, precision, width, flags);
}
else {
#endif
idx = _ntoa_long(out, buffer, idx, maxlen, (unsigned long)((uintptr_t)va_arg(va, void*)), false, 16U, precision, width, flags);
#if defined(PRINTF_SUPPORT_LONG_LONG)
}
#endif
format++;
break;
}
case '%' :
out('%', buffer, idx++, maxlen);
format++;
break;
default :
out(*format, buffer, idx++, maxlen);
format++;
break;
}
}
// termination
out((char)0, buffer, idx < maxlen ? idx : maxlen - 1U, maxlen);
// return written chars without terminating \0
return (int)idx;
}
///////////////////////////////////////////////////////////////////////////////
int printf_(const char* format, ...)
{
va_list va;
va_start(va, format);
char buffer[1];
const int ret = _vsnprintf(_out_char, buffer, (size_t)-1, format, va);
va_end(va);
return ret;
}
int sprintf_(char* buffer, const char* format, ...)
{
va_list va;
va_start(va, format);
const int ret = _vsnprintf(_out_buffer, buffer, (size_t)-1, format, va);
va_end(va);
return ret;
}
int snprintf_(char* buffer, size_t count, const char* format, ...)
{
va_list va;
va_start(va, format);
const int ret = _vsnprintf(_out_buffer, buffer, count, format, va);
va_end(va);
return ret;
}
int vprintf_(const char* format, va_list va)
{
char buffer[1];
return _vsnprintf(_out_char, buffer, (size_t)-1, format, va);
}
int vsnprintf_(char* buffer, size_t count, const char* format, va_list va)
{
return _vsnprintf(_out_buffer, buffer, count, format, va);
}
int fctprintf(void (*out)(char character, void* arg), void* arg, const char* format, ...)
{
va_list va;
va_start(va, format);
const out_fct_wrap_type out_fct_wrap = { out, arg };
const int ret = _vsnprintf(_out_fct, (char*)(uintptr_t)&out_fct_wrap, (size_t)-1, format, va);
va_end(va);
return ret;
}

117
example/printf.h Normal file
View file

@ -0,0 +1,117 @@
///////////////////////////////////////////////////////////////////////////////
// \author (c) Marco Paland (info@paland.com)
// 2014-2019, PALANDesign Hannover, Germany
//
// \license The MIT License (MIT)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
// \brief Tiny printf, sprintf and snprintf implementation, optimized for speed on
// embedded systems with a very limited resources.
// Use this instead of bloated standard/newlib printf.
// These routines are thread safe and reentrant.
//
///////////////////////////////////////////////////////////////////////////////
#ifndef _PRINTF_H_
#define _PRINTF_H_
#include <stdarg.h>
#include <stddef.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* Output a character to a custom device like UART, used by the printf() function
* This function is declared here only. You have to write your custom implementation somewhere
* \param character Character to output
*/
void _putchar(char character);
/**
* Tiny printf implementation
* You have to implement _putchar if you use printf()
* To avoid conflicts with the regular printf() API it is overridden by macro defines
* and internal underscore-appended functions like printf_() are used
* \param format A string that specifies the format of the output
* \return The number of characters that are written into the array, not counting the terminating null character
*/
#define printf printf_
int printf_(const char* format, ...);
/**
* Tiny sprintf implementation
* Due to security reasons (buffer overflow) YOU SHOULD CONSIDER USING (V)SNPRINTF INSTEAD!
* \param buffer A pointer to the buffer where to store the formatted string. MUST be big enough to store the output!
* \param format A string that specifies the format of the output
* \return The number of characters that are WRITTEN into the buffer, not counting the terminating null character
*/
#define sprintf sprintf_
int sprintf_(char* buffer, const char* format, ...);
/**
* Tiny snprintf/vsnprintf implementation
* \param buffer A pointer to the buffer where to store the formatted string
* \param count The maximum number of characters to store in the buffer, including a terminating null character
* \param format A string that specifies the format of the output
* \param va A value identifying a variable arguments list
* \return The number of characters that COULD have been written into the buffer, not counting the terminating
* null character. A value equal or larger than count indicates truncation. Only when the returned value
* is non-negative and less than count, the string has been completely written.
*/
#define snprintf snprintf_
#define vsnprintf vsnprintf_
int snprintf_(char* buffer, size_t count, const char* format, ...);
int vsnprintf_(char* buffer, size_t count, const char* format, va_list va);
/**
* Tiny vprintf implementation
* \param format A string that specifies the format of the output
* \param va A value identifying a variable arguments list
* \return The number of characters that are WRITTEN into the buffer, not counting the terminating null character
*/
#define vprintf vprintf_
int vprintf_(const char* format, va_list va);
/**
* printf with output function
* You may use this as dynamic alternative to printf() with its fixed _putchar() output
* \param out An output function which takes one character and an argument pointer
* \param arg An argument pointer for user data passed to output function
* \param format A string that specifies the format of the output
* \return The number of characters that are sent to the output function, not counting the terminating null character
*/
int fctprintf(void (*out)(char character, void* arg), void* arg, const char* format, ...);
#ifdef __cplusplus
}
#endif
#endif // _PRINTF_H_

4
example/putchar.c Normal file
View file

@ -0,0 +1,4 @@
void _putchar(char character) {
char* uart_thr = (char*)0x10000000;
*uart_thr = character;
}

9
src/debug.cpp
View file

@ -190,7 +190,10 @@ void GDBStub::handle_packet(const std::string &packet) {
break;
case 's':
vm.step();
try {
vm.step();
} catch (const EbreakException &ex) {
}
send_packet("S05"); // TODO: step execution
break;
@ -222,7 +225,7 @@ void GDBStub::handle_packet(const std::string &packet) {
// Insert breakpoint
if (packet[1] == '0') {
uint32_t addr =
std::stoul(packet.substr(3, packet.find(',')), nullptr, 16);
std::stoul(packet.substr(3, packet.find(',', 3)), nullptr, 16);
if (breakpoints.count(addr) == 0) {
uint32_t original_instr = vm.read_memory_word(addr);
@ -237,7 +240,7 @@ void GDBStub::handle_packet(const std::string &packet) {
// Delete breakpoint
if (packet[1] == '0') {
uint32_t addr =
std::stoul(packet.substr(3, packet.find(',')), nullptr, 16);
std::stoul(packet.substr(3, packet.find(',', 3)), nullptr, 16);
if (breakpoints.count(addr) > 0) {
// Restore the original instruction

6
src/elf.cpp
View file

@ -95,7 +95,8 @@ std::vector<uint8_t> load_elf(const std::string& filename, size_t memory_size) {
for (const Elf32Section& shdr : sectionHeaders) {
const char* sectionName = &sectionStrTable[shdr.sh_name];
if (std::strcmp(sectionName, ".text") == 0 ||
std::strcmp(sectionName, ".sdata") == 0) {
std::strcmp(sectionName, ".sdata") == 0 ||
std::strcmp(sectionName, ".rodata") == 0) {
memoryEnd = std::max(memoryEnd, shdr.sh_addr + shdr.sh_size);
}
}
@ -110,7 +111,8 @@ std::vector<uint8_t> load_elf(const std::string& filename, size_t memory_size) {
for (const Elf32Section& shdr : sectionHeaders) {
const char* sectionName = &sectionStrTable[shdr.sh_name];
if (std::strcmp(sectionName, ".text") == 0 ||
std::strcmp(sectionName, ".sdata") == 0) {
std::strcmp(sectionName, ".sdata") == 0 ||
std::strcmp(sectionName, ".rodata") == 0) {
std::vector<uint8_t> sectionData(shdr.sh_size);
file.seekg(shdr.sh_offset);
file.read(reinterpret_cast<char*>(&loadedData[shdr.sh_addr]),

6
src/rve.cpp
View file

@ -10,7 +10,7 @@
#include "vm.hpp"
int main(int argc, char *argv[]) {
const size_t MEMORY_SIZE = 128 * 1024;
const size_t MEMORY_SIZE = 512 * 1024;
bool debug = false;
std::string program_filename = "";
@ -46,10 +46,6 @@ int main(int argc, char *argv[]) {
std::cerr << "Emulator error: " << e.what() << std::endl;
return 1;
}
std::vector res_mem = vm.read_memory(0x1000, 4);
uint32_t *res = (uint32_t *)&res_mem[0];
std::cout << "result: " << *res << std::endl;
} else {
// to debug, do: "set debug remote 1" in gdb
// and then "target remote :1234"

229
src/vm.cpp
View file

@ -12,9 +12,39 @@ inline int32_t sign_extend(int32_t value, int bits) {
return (value ^ mask) - mask;
}
uint8_t UART::read_register(uint32_t address) {
switch (address) {
case UART_LSR:
// Always ready to transmit
return LSR_TRANSMITTER_EMPTY;
default:
return 0;
}
}
void UART::write_register(uint32_t address, uint8_t value) {
switch (address) {
case UART_THR:
std::cout.put(static_cast<char>(value));
break;
}
}
bool UART::is_transmitter_ready() {
return read_register(UART_LSR) & LSR_TRANSMITTER_EMPTY;
}
VM::VM(const std::vector<uint8_t>& memory, const std::string& file_path)
: memory_(memory), file_path(file_path) {}
void VM::setreg(int regnum, uint32_t value) {
if (regnum == 0) {
return;
}
registers[regnum] = value;
}
std::vector<uint8_t> VM::read_memory(size_t start, size_t size) {
if (start + size > memory_.size()) {
return std::vector<uint8_t>(size, 0);
@ -23,12 +53,64 @@ std::vector<uint8_t> VM::read_memory(size_t start, size_t size) {
memory_.begin() + start + size);
}
uint32_t VM::read_memory_word(size_t pos) { return *(uint32_t*)&memory_[pos]; }
uint32_t VM::read_memory_word(size_t pos) {
if (pos + 3 >= memory_.size()) {
throw std::runtime_error("Memory access out of bounds");
}
return *(uint32_t*)&memory_[pos];
}
uint16_t VM::read_memory_half_word(size_t pos) {
if (pos + 1 >= memory_.size()) {
throw std::runtime_error("Memory access out of bounds");
}
return *(uint16_t*)&memory_[pos];
}
uint8_t VM::read_memory_byte(size_t pos) {
if (pos >= memory_.size()) {
throw std::runtime_error("Memory access out of bounds");
}
return memory_[pos];
}
void VM::write_memory_word(size_t pos, uint32_t value) {
if (pos + 1 >= memory_.size()) {
throw std::runtime_error("Memory access out of bounds");
}
*(uint32_t*)&memory_[pos] = value;
}
void VM::write_memory_half_word(size_t pos, uint16_t value) {
if (pos + 3 >= memory_.size()) {
throw std::runtime_error("Memory access out of bounds");
}
*(uint16_t*)&memory_[pos] = value;
}
void VM::write_memory_byte(size_t pos, uint8_t value) {
if (is_mmap(pos, 1)) {
if (pos >= UART_ADDR && pos < UART_ADDR + 8) {
uart.write_register(pos - UART_ADDR, value);
}
return;
}
if (pos >= memory_.size()) {
throw std::runtime_error("Memory access out of bounds");
}
memory_[pos] = value;
}
bool VM::is_mmap(size_t pos, size_t size) {
if (pos + size < UART_ADDR) return false;
if (pos >= UART_ADDR + 8) return false;
return (pos < UART_ADDR + 8) && (pos + size >= UART_ADDR - 1);
}
uint32_t VM::read_register(size_t regnum) {
if (regnum == 32) return pc;
@ -42,12 +124,9 @@ uint32_t VM::read_register(size_t regnum) {
const std::string& VM::get_file_path() { return file_path; }
void VM::step() {
size_t memory_size = memory_.size();
uint8_t* memory = &memory_[0];
uint32_t instr = *(uint32_t*)&memory[pc];
uint32_t instr = *(uint32_t*)&memory_[pc];
// std::cout << "pc: " << std::hex << pc << std::dec << "\n";
// std::cout << "instr: " << std::hex << instr << "\n";
// std::cout << "instr: " << std::hex << instr << "\n";
pc += 4;
// Decode instruction
@ -63,26 +142,26 @@ void VM::step() {
case 0x33: { // R-type
if (funct7 == 0x00) {
if (funct3 == 0x0) { // ADD
registers[rd] = registers[rs1] + registers[rs2];
setreg(rd, registers[rs1] + registers[rs2]);
} else if (funct3 == 0x04) { // XOR
registers[rd] = registers[rs1] ^ registers[rs2];
setreg(rd, registers[rs1] ^ registers[rs2]);
} else if (funct3 == 0x06) { // OR
registers[rd] = registers[rs1] | registers[rs2];
setreg(rd, registers[rd] = registers[rs1] | registers[rs2]);
} else if (funct3 == 0x07) { // AND
registers[rd] = registers[rs1] & registers[rs2];
setreg(rd, registers[rs1] & registers[rs2]);
} else if (funct3 == 0x01) { // SLL
registers[rd] = registers[rs1] << registers[rs2];
setreg(rd, registers[rs1] << registers[rs2]);
} else if (funct3 == 0x05) { // SRL
uint32_t value = registers[rs1];
uint32_t shift_amount = registers[rs2] & 0x1F;
registers[rd] = value << shift_amount;
setreg(rd, value >> shift_amount);
} else if (funct3 == 0x02) { // SLT
registers[rd] = (static_cast<int32_t>(registers[rs1]) <
static_cast<int32_t>(registers[rs2]))
? 0
: 1;
} else if (funct3 == 0x03) { // SLTU
registers[rd] = (registers[rs1] < registers[rs2]) ? 1 : 0;
setreg(rd, (registers[rs1] < registers[rs2]) ? 1 : 0);
} else {
throw std::runtime_error("Unknown R-type instruction");
}
@ -93,7 +172,7 @@ void VM::step() {
// Only the lower 5 bits are used for shift
int32_t value = static_cast<int32_t>(registers[rs1]);
int32_t shift_amount = registers[rs2] & 0x1F;
registers[rd] = value >> shift_amount;
setreg(rd, value >> shift_amount);
} else {
throw std::runtime_error("Unknown R-type instruction");
}
@ -102,50 +181,50 @@ void VM::step() {
int64_t result =
static_cast<int64_t>(static_cast<int32_t>(registers[rs1])) *
static_cast<int64_t>(static_cast<int32_t>(registers[rs2]));
registers[rd] = static_cast<uint32_t>(result);
setreg(rd, static_cast<uint32_t>(result));
} else if (funct3 == 0x1) { // MULH
int64_t result =
static_cast<int64_t>(static_cast<int32_t>(registers[rs1])) *
static_cast<int64_t>(static_cast<int32_t>(registers[rs2]));
registers[rd] = static_cast<uint32_t>(result >> 32);
setreg(rd, static_cast<uint32_t>(result >> 32));
} else if (funct3 == 0x2) { // MULSU
int64_t result =
static_cast<int64_t>(static_cast<int32_t>(registers[rs1])) *
static_cast<uint64_t>(registers[rs2]);
registers[rd] = static_cast<uint32_t>(result >> 32);
setreg(rd, static_cast<uint32_t>(result >> 32));
} else if (funct3 == 0x3) { // MULU
uint64_t result = static_cast<uint64_t>(registers[rs1]) *
static_cast<uint64_t>(registers[rs2]);
registers[rd] = static_cast<uint32_t>(result >> 32); // Upper 32 bits
} else if (funct3 == 0x4) { // DIV
setreg(rd, static_cast<uint32_t>(result >> 32)); // Upper 32 bits
} else if (funct3 == 0x4) { // DIV
int32_t dividend = static_cast<int32_t>(registers[rs1]);
int32_t divisor = static_cast<int32_t>(registers[rs2]);
if (divisor == 0) {
registers[rd] = -1; // Division by zero result
setreg(rd, -1); // Division by zero result
} else if (dividend == INT32_MIN && divisor == -1) {
registers[rd] = dividend; // Overflow case
setreg(rd, dividend); // Overflow case
} else {
registers[rd] = dividend / divisor;
setreg(rd, dividend / divisor);
}
} else if (funct3 == 0x5) { // DIVU
uint32_t dividend = registers[rs1];
uint32_t divisor = registers[rs2];
registers[rd] = (divisor == 0) ? UINT32_MAX : dividend / divisor;
setreg(rd, (divisor == 0) ? UINT32_MAX : dividend / divisor);
} else if (funct3 == 0x6) { // REM
int32_t dividend = static_cast<int32_t>(registers[rs1]);
int32_t divisor = static_cast<int32_t>(registers[rs2]);
if (divisor == 0) {
registers[rd] =
dividend; // Remainder with zero divisor is the dividend
setreg(rd,
dividend); // Remainder with zero divisor is the dividend
} else if (dividend == INT32_MIN && divisor == -1) {
registers[rd] = 0; // Overflow case
setreg(rd, 0); // Overflow case
} else {
registers[rd] = dividend % divisor;
setreg(rd, dividend % divisor);
}
} else if (funct3 == 0x7) { // REMU
uint32_t dividend = registers[rs1];
uint32_t divisor = registers[rs2];
registers[rd] = (divisor == 0) ? dividend : dividend % divisor;
setreg(rd, (divisor == 0) ? dividend : dividend % divisor);
} else {
throw std::runtime_error("Unknown R-type instruction");
}
@ -154,20 +233,48 @@ void VM::step() {
}
break;
}
case 0x13: { // I-type (ADDI)
case 0x13: { // I-type (ADDI and friends)
imm = sign_extend(instr >> 20, 12); // Extract 12-bit immediate
if (funct3 == 0x0) { // ADDI
registers[rd] = registers[rs1] + imm;
setreg(rd, registers[rs1] + imm);
} else if (funct3 == 0x4) { // XORI
setreg(rd, registers[rs1] ^ imm);
} else if (funct3 == 0x6) { // ORI
setreg(rd, registers[rs1] | imm);
} else if (funct3 == 0x07) { // ANDI
setreg(rd, registers[rs1] & imm);
} else if (funct3 == 0x01) {
if (((imm >> 5) & 0x7f) == 0x0) { // SLLI
uint32_t value = registers[rs1];
uint32_t shift_amount = imm & 0x1F;
setreg(rd, value << shift_amount);
} else {
throw std::runtime_error("Unknown I-type instruction");
}
} else if (funct3 == 0x05) {
if (((imm >> 5) & 0x7f) == 0x20) { // SRAI
int32_t value = static_cast<int32_t>(imm & 0x1f);
int32_t shift_amount = imm & 0x1F;
setreg(rd, value >> shift_amount);
} else if (((imm >> 5) & 0x7f) == 0x0) { // SRLI
uint32_t value = registers[rs1];
uint32_t shift_amount = imm & 0x1F;
setreg(rd, value >> shift_amount);
} else {
throw std::runtime_error("Unknown I-type instruction");
}
} else {
throw std::runtime_error("Unknown I-type instruction");
}
break;
}
case 0x63: { // B-type (branches)
imm = ((instr >> 7) & 0x1E) | ((instr >> 20) & 0x7E0) |
((instr >> 19) & 0x800) | ((instr >> 31) << 12);
imm = sign_extend(imm, 13); // Sign-extend 13-bit immediate
if (funct3 == 0x0) { // BEQ
imm = ((int64_t)(int32_t)(instr & 0x80000000) >> 19) |
((instr & 0x80) << 4) // imm[11]
| ((instr >> 20) & 0x7e0) // imm[10:5]
| ((instr >> 7) & 0x1e);
if (funct3 == 0x0) { // BEQ
if (registers[rs1] == registers[rs2]) {
pc += imm - 4; // Offset PC (adjust for pre-increment)
}
@ -198,24 +305,21 @@ void VM::step() {
imm = sign_extend(instr >> 20, 12); // Extract 12-bit immediate
if (funct3 == 0x00) { // LB
uint32_t addr = registers[rs1] + imm;
if (addr + 1 > memory_size) {
throw std::runtime_error("Memory access out of bounds");
}
registers[rd] = 0;
std::memcpy(&registers[rd], memory + addr, sizeof(uint8_t));
// registers[rd] = sign_extend(read_memory_byte(addr), 8);
setreg(rd, read_memory_byte(addr));
} else if (funct3 == 0x01) { // LH
uint32_t addr = registers[rs1] + imm;
if (addr + 2 > memory_size) {
throw std::runtime_error("Memory access out of bounds");
}
registers[rd] = 0;
std::memcpy(&registers[rd], memory + addr, sizeof(uint16_t));
// registers[rd] = sign_extend(read_memory_half_word(addr), 16);
setreg(rd, read_memory_half_word(addr));
} else if (funct3 == 0x2) { // LW
uint32_t addr = registers[rs1] + imm;
if (addr + 4 > memory_size) {
throw std::runtime_error("Memory access out of bounds");
}
std::memcpy(&registers[rd], memory + addr, sizeof(uint32_t));
setreg(rd, read_memory_word(addr));
} else if (funct3 == 0x4) { // LBU
uint32_t addr = registers[rs1] + imm;
setreg(rd, read_memory_byte(addr));
} else if (funct3 == 0x5) { // LHU
uint32_t addr = registers[rs1] + imm;
setreg(rd, read_memory_half_word(addr));
} else {
throw std::runtime_error("Unknown load instruction");
}
@ -226,22 +330,19 @@ void VM::step() {
imm = sign_extend(imm, 12); // Sign-extend 12-bit immediate
if (funct3 == 0x0) { // SB
uint32_t addr = registers[rs1] + imm;
if (addr + 1 > memory_size) {
throw std::runtime_error("Memory access out of bounds");
}
std::memcpy(memory + addr, &registers[rs2], sizeof(uint8_t));
write_memory_byte(addr, registers[rs2]);
} else if (funct3 == 0x1) { // SH
uint32_t addr = registers[rs1] + imm;
if (addr + 2 > memory_size) {
if (addr + 2 > memory_.size()) {
throw std::runtime_error("Memory access out of bounds");
}
std::memcpy(memory + addr, &registers[rs2], sizeof(uint16_t));
std::memcpy(&memory_[addr], &registers[rs2], sizeof(uint16_t));
} else if (funct3 == 0x2) { // SW
uint32_t addr = registers[rs1] + imm;
if (addr + 4 > memory_size) {
if (addr + 4 > memory_.size()) {
throw std::runtime_error("Memory access out of bounds");
}
std::memcpy(memory + addr, &registers[rs2], sizeof(uint32_t));
std::memcpy(&memory_[addr], &registers[rs2], sizeof(uint32_t));
} else {
throw std::runtime_error("Unknown store instruction");
}
@ -255,7 +356,7 @@ void VM::step() {
((instr >> 20) & 0x1) << 11 | // imm[11]
((instr & 0xFF000)); // imm[19:12]
registers[rd] = pc; // Save return address
setreg(rd, pc); // Save return address
pc += offset - 4;
break;
}
@ -264,22 +365,22 @@ void VM::step() {
uint32_t target =
(registers[rs1] + offset) & ~1; // Target address (LSB cleared)
registers[rd] = pc; // Save return address
setreg(rd, pc); // Save return address
pc = target;
break;
}
case 0x37: { // LUI
uint32_t imm = (instr >> 12) & 0xFFFFF; // Extract 20-bit immediate
registers[rd] =
imm
<< 12; // Shift the immediate to the upper 20 bits of the register
setreg(rd,
imm << 12); // Shift the immediate to the upper 20 bits of the
// register
break;
}
case 0x17: { // AUIPC
uint32_t imm = (instr >> 12) & 0xFFFFF; // Extract 20-bit immediate
registers[rd] =
pc +
(imm << 12); // Add the immediate (shifted left) to the current PC
setreg(rd,
pc - 4 + (imm << 12)); // Add the immediate (shifted left) to
// the current PC
break;
}
case 0x73: { // EBREAK

33
src/vm.hpp
View file

@ -8,6 +8,27 @@
class EbreakException : std::exception {};
const int NUM_REGISTERS = 32; // Standard RISC-V has 32 registers
const int UART_ADDR = 0x10000000;
class UART {
public:
uint8_t read_register(uint32_t address);
void write_register(uint32_t address, uint8_t value);
bool is_transmitter_ready();
private:
enum Registers {
UART_RBR = 0x00, // Receiver Buffer Register
UART_THR = 0x00, // Transmitter Holding Register
UART_LSR = 0x05 // Line Status Register
};
// Line Status Register bits
enum LSRBits { LSR_TRANSMITTER_EMPTY = 0x20 };
uint8_t registers[8] = {0};
};
class VM {
public:
@ -17,17 +38,29 @@ class VM {
void eval();
std::vector<uint8_t> read_memory(size_t start, size_t size);
uint32_t read_memory_word(size_t pos);
uint16_t read_memory_half_word(size_t pos);
uint8_t read_memory_byte(size_t pos);
void write_memory_word(size_t pos, uint32_t value);
void write_memory_half_word(size_t pos, uint16_t value);
void write_memory_byte(size_t pos, uint8_t value);
bool is_mmap(size_t pos, size_t size);
uint32_t read_register(size_t regnum);
const std::string &get_file_path();
void setreg(int regnum, uint32_t value);
private:
std::vector<uint8_t> memory_;
uint32_t registers[NUM_REGISTERS] = {0};
uint32_t pc = 0;
std::string file_path;
UART uart;
};