C exercise

.gitignore

@@ -0,0 +1,3 @@
+.vscode
+*.o
+runbin

Makefile

@@ -0,0 +1,46 @@
+ENDIAN         := EL
+
+QEMU           := qemu-system-mipsel
+CROSS_COMPILE  := mips-linux-gnu-
+CC             := $(CROSS_COMPILE)gcc
+CFLAGS         += --std=gnu99 -$(ENDIAN) -G 0 -mno-abicalls -fno-pic \
+                  -ffreestanding -fno-stack-protector -fno-builtin \
+                  -Wa,-xgot -Wall -mxgot -mno-fix-r4000 -march=4kc -g -ggdb
+LD             := $(CROSS_COMPILE)ld
+LDFLAGS        += -$(ENDIAN) -G 0 -static -n -nostdlib --fatal-warnings
+INCLUDES       := -I./include
+
+qemu_flags     += -cpu 4Kc -m 64 -nographic -M malta -no-reboot
+
+qemu_files     += $(target)
+
+link_script    := linker.lds
+target         := runbin
+
+objs           := blib.o machine.o start.o test.o
+
+all: $(objs)
+	$(LD) $(LDFLAGS) -o $(target) -N -T $(link_script) $(objs)
+
+%.o: %.c
+	$(CC) $(CFLAGS) $(INCLUDES) -c $<
+
+%.o: %.S
+	$(CC) $(CFLAGS) $(INCLUDES) -c $<
+
+dbg_run: qemu_flags += -s -S
+dbg_run: run
+
+dbg:
+	make dbg_run >/dev/null 2>&1 &
+	gdb-multiarch $(target) -ex "target remote localhost:1234"
+	killall $(QEMU)
+
+run:
+	$(QEMU) $(qemu_flags) -kernel $(qemu_files)
+
+clean:
+	rm -f *.o $(target)
+
+.PHONY: all clean run
+

blib.c

@@ -0,0 +1,142 @@
+#include <blib.h>
+
+size_t strlen(const char *s) {
+    size_t i  = 0;
+    while(s[i] != '\0') {
+        i++;
+    }
+    return i;
+}
+
+char *strcpy(char *dst, const char *src) {
+    char *res = dst;
+    while ((*dst++ = *src++))
+        ;
+    return res;
+}
+
+char *strncpy(char *dst, const char *src, size_t n) {
+    char *res = dst;
+    while (*src && n--) {
+        *dst++ = *src++;
+    }
+    *dst = '\0';
+    return res;
+}
+
+int strcmp(const char *str1, const char *str2) {
+    while (*str1 && (*str1 == *str2)) {
+        str1++;
+        str2++;
+    }
+    return *(unsigned char *)str1 - *(unsigned char *)str2;
+}
+
+int strncmp(const char *s1, const char *s2, size_t n) {
+    while (n--) {
+        if (*s1 != *s2) {
+            return *s1 - *s2;
+        }
+        if (*s1 == 0) {
+            break;
+        }
+        s1++;
+        s2++;
+    }
+    return 0;
+}
+
+char *strcat(char *dst, const char *src) {
+    char *temp = dst;
+    while(*temp != '\0'){
+        temp++;
+    }
+    while(*src != '\0'){
+        *temp = *src;
+        temp++;
+        src++;
+    }
+    *temp = '\0';
+    return dst;
+}
+
+char *strncat(char *dst, const char *src, size_t n){
+    size_t oplength = n;
+    if(strlen(src) < n) {
+        oplength = strlen(src);
+    }
+    char * temp = dst;
+    while(*temp != '\0') {
+        temp++;
+    }
+    for(size_t i = 0;i < oplength;i++) {
+        *temp++ = *src++;
+    }
+    *temp = '\0';
+    return dst;
+}
+
+char *strchr(const char *str, int character){
+    while (*str != '\0') {
+        if (*str == (char)character) {
+            return (char *)str;
+        }
+        str++;
+    }
+
+    return NULL;
+}
+
+char* strsep(char** stringp, const char* delim){
+    char *temp = *stringp;
+    char *preStringp = *stringp;
+    if(temp == NULL) {
+        return NULL;
+    } else {
+        while(*temp != '\0') {
+            const char* delete = delim;
+            while(*delete != '\0') {
+                if(*delete == *temp) {
+                    *temp = '\0';
+                    *stringp = temp + 1;
+                    return preStringp;
+                }
+                delete++;
+            }
+            temp++;
+        }
+        if(*temp == '\0'){
+            *stringp = NULL;
+        }
+        return preStringp;
+    }
+}
+
+
+void *memset(void *s, int c, size_t n) {
+    unsigned char *p = s;
+    while (n--) {
+        *p++ = (unsigned char)c;
+    }
+    return s;
+}
+
+void *memcpy(void *out, const void *in, size_t n) {
+    char *csrc = (char *)in;
+    char *cdst = (char *)out;
+    for (size_t i = 0; i < n; i++) {
+        cdst[i] = csrc[i];
+    }
+    return out;
+}
+
+int memcmp(const void *s1, const void *s2, size_t n) {
+    const unsigned char *p1 = s1, *p2 = s2;
+    while (n--) {
+        if (*p1 != *p2) {
+            return *p1 - *p2;
+        }
+        p1++, p2++;
+    }
+    return 0;
+}

include/asm/asm.h

@@ -0,0 +1,41 @@
+#include <asm/cp0regdef.h>
+#include <asm/regdef.h>
+
+/*
+ * LEAF - declare leaf routine
+ */
+#define LEAF(symbol)                                                                               \
+	.globl symbol;                                                                             \
+	.align 2;                                                                                  \
+	.type symbol, @function;                                                                   \
+	.ent symbol;                                                                               \
+	symbol:                                                                                    \
+	.frame sp, 0, ra
+
+/*
+ * NESTED - declare nested routine entry point
+ */
+#define NESTED(symbol, framesize, rpc)                                                             \
+	.globl symbol;                                                                             \
+	.align 2;                                                                                  \
+	.type symbol, @function;                                                                   \
+	.ent symbol;                                                                               \
+	symbol:                                                                                    \
+	.frame sp, framesize, rpc
+
+/*
+ * END - mark end of function
+ */
+#define END(function)                                                                              \
+	.end function;                                                                             \
+	.size function, .- function
+
+#define EXPORT(symbol)                                                                             \
+	.globl symbol;                                                                             \
+	symbol:
+
+#define FEXPORT(symbol)                                                                            \
+	.globl symbol;                                                                             \
+	.type symbol, @function;                                                                   \
+	symbol:
+

include/asm/cp0regdef.h

@@ -0,0 +1,52 @@
+#ifndef _cp0regdef_h_
+#define _cp0regdef_h_
+
+#define CP0_INDEX $0
+#define CP0_RANDOM $1
+#define CP0_ENTRYLO0 $2
+#define CP0_ENTRYLO1 $3
+#define CP0_CONTEXT $4
+#define CP0_PAGEMASK $5
+#define CP0_WIRED $6
+#define CP0_BADVADDR $8
+#define CP0_COUNT $9
+#define CP0_ENTRYHI $10
+#define CP0_COMPARE $11
+#define CP0_STATUS $12
+#define CP0_CAUSE $13
+#define CP0_EPC $14
+#define CP0_PRID $15
+#define CP0_EBASE $15, 1
+#define CP0_CONFIG $16
+#define CP0_LLADDR $17
+#define CP0_WATCHLO $18
+#define CP0_WATCHHI $19
+#define CP0_XCONTEXT $20
+#define CP0_FRAMEMASK $21
+#define CP0_DIAGNOSTIC $22
+#define CP0_PERFORMANCE $25
+#define CP0_ECC $26
+#define CP0_CACHEERR $27
+#define CP0_TAGLO $28
+#define CP0_TAGHI $29
+#define CP0_ERROREPC $30
+
+#define STATUS_CU3 0x80000000
+#define STATUS_CU2 0x40000000
+#define STATUS_CU1 0x20000000
+#define STATUS_CU0 0x10000000
+#define STATUS_BEV 0x00400000
+#define STATUS_IM0 0x0100
+#define STATUS_IM1 0x0200
+#define STATUS_IM2 0x0400
+#define STATUS_IM3 0x0800
+#define STATUS_IM4 0x1000
+#define STATUS_IM5 0x2000
+#define STATUS_IM6 0x4000
+#define STATUS_IM7 0x8000
+#define STATUS_UM 0x0010
+#define STATUS_R0 0x0008
+#define STATUS_ERL 0x0004
+#define STATUS_EXL 0x0002
+#define STATUS_IE 0x0001
+#endif

include/asm/regdef.h

@@ -0,0 +1,43 @@
+#ifndef __ASM_MIPS_REGDEF_H
+#define __ASM_MIPS_REGDEF_H
+
+/*
+ * Symbolic register names for 32 bit ABI
+ */
+#define zero $0 /* wired zero */
+#define AT $1	/* assembler temp  - uppercase because of ".set at" */
+#define v0 $2	/* return value */
+#define v1 $3
+#define a0 $4 /* argument registers */
+#define a1 $5
+#define a2 $6
+#define a3 $7
+#define t0 $8 /* caller saved */
+#define t1 $9
+#define t2 $10
+#define t3 $11
+#define t4 $12
+#define t5 $13
+#define t6 $14
+#define t7 $15
+#define s0 $16 /* callee saved */
+#define s1 $17
+#define s2 $18
+#define s3 $19
+#define s4 $20
+#define s5 $21
+#define s6 $22
+#define s7 $23
+#define t8 $24 /* caller saved */
+#define t9 $25
+#define jp $25 /* PIC jump register */
+#define k0 $26 /* kernel scratch */
+#define k1 $27
+#define gp $28 /* global pointer */
+#define sp $29 /* stack pointer */
+#define fp $30 /* frame pointer */
+#define s8 $30 /* same like fp! */
+#define ra $31 /* return address */
+
+#endif /* __ASM_MIPS_REGDEF_H */
+

include/blib.h

@@ -0,0 +1,24 @@
+#ifndef _BLIB_H
+#define _BLIB_H
+
+#include <blib_macros.h>
+#include <machine.h>
+
+typedef unsigned int size_t;
+#define NULL 0
+
+
+size_t strlen(const char *s);
+char *strcpy(char *dst, const char *src);
+char *strncpy(char *dst, const char *src, size_t n);
+char *strcat(char *dst, const char *src);
+char *strncat(char *dest, const char *src, size_t n); 
+int strcmp(const char *s1, const char *s2);
+int strncmp(const char *s1, const char *s2, size_t n);
+char *strchr(const char *str, int character);
+char* strsep(char** stringp, const char* delim);
+void *memset(void *s, int c, size_t n);
+void *memcpy(void *dst, const void *src, size_t n);
+int memcmp(const void *s1, const void *s2, size_t n);
+
+#endif

include/blib_macros.h

@@ -0,0 +1,28 @@
+#ifndef _BLIB_MACROS_H__
+#define _BLIB_MACROS_H__
+
+#define STRINGIFY(s) #s
+#define TOSTRING(s) STRINGIFY(s)
+
+#define putstr(s)                                                                                  \
+	({                                                                                         \
+		for (const char *p = s; *p; p++)                                                   \
+			m_putch(*p);                                                               \
+	})
+
+
+
+#define panic_on(cond, s)                                                                          \
+	({                                                                                         \
+		if (cond) {                                                                        \
+			putstr("panic: ");                                                         \
+			putstr(s);                                                                 \
+			putstr(" @ " __FILE__ ":" TOSTRING(__LINE__) "  \n");                      \
+			m_halt();                                                                  \
+		}                                                                                  \
+	})
+
+#define panic(s) panic_on(1, s)
+
+
+#endif /* _printk_h_ */