wrote a shell but have an error will debug tomorrow

common.h

@@ -20,6 +20,8 @@ typedef uint32_t vaddr_t;
 #define va_end    __builtin_va_end
 #define va_arg    __builtin_va_arg
 #define PAGE_SIZE 4096
+#define SYS_PUTCHAR 1
+#define SYS_GETCHAR 2
 
 void *memset(void *buf, char c, size_t n);
 void *memcpy(void *dst, const void *src, size_t n);

kernel.c

@@ -67,6 +67,11 @@ void putchar(char ch) {
     sbi_call(ch, 0, 0, 0, 0, 0, 0, 1 /* Console Putchar */);
 }
 
+long getchar(void) {
+    struct sbiret ret = sbi_call(0, 0, 0, 0, 0, 0, 0, 2);
+    return ret.error;
+}
+
 __attribute__((naked))
 __attribute__((aligned(4)))
 void kernel_entry(void) {
@@ -308,15 +313,41 @@ void proc_b_entry(void) {
     }
 }
 
+void handle_syscall(struct trap_frame *f) {
+    switch (f->a3) {
+        case SYS_GETCHAR:
+            while (1) {
+                long ch = getchar();
+                if (ch >= 0) {
+                    f->a0 = ch;
+                    break;
+                }
+
+                yield();
+            }
+            break;
+        case SYS_PUTCHAR:
+            putchar(f->a0);
+            break;
+        default:
+            PANIC("unexpected syscall a3=%x\n", f->a3);
+    }
+}
+
 void handle_trap(struct trap_frame *f) {
     uint32_t scause = READ_CSR(scause);
     uint32_t stval = READ_CSR(stval);
     uint32_t user_pc = READ_CSR(sepc);
+    if (scause == SCAUSE_ECALL) {
+        handle_syscall(f);
+        user_pc += 4;
+    } else {
+        PANIC("unexpected trap scause=%x, stval=%x, sepc=%x\n", scause, stval, user_pc);
+    }
 
-    PANIC("Unexpected trap: scause=%x, stval=%x, sepc=%x\n", scause, stval, user_pc);
+    WRITE_CSR(sepc, user_pc);
 }
 
-
 void kernel_main(void) {
     // printf("\n\nHello %s\n", "friend :3");
     // printf("60 + 9 = %d, %x\n", 60 + 9, 0x1234abcd);
@@ -324,11 +355,8 @@ void kernel_main(void) {
     // for (;;) {
     //     __asm__ __volatile__("wfi");
     // }
-
     memset(__bss, 0, (size_t) __bss_end - (size_t) __bss);
-    
     printf("\n\n");
-
     WRITE_CSR(stvec, (uint32_t) kernel_entry);
 
     idle_proc = create_process(NULL, 0);
@@ -345,8 +373,8 @@ void kernel_main(void) {
 
     // NEW
     create_process(_binary_shell_bin_start, (size_t) _binary_shell_bin_size);
-
     yield();
+
     PANIC("Switched to idle process");
 
     // __asm__ __volatile__("unimp"); // calls a unimp which triggers kernel panic

kernel.h

@@ -5,13 +5,14 @@
 #define PROC_UNUSED 0           // Unused processes control structure
 #define PROC_RUNNABLE 1         // Runnable proccess
 #define SATP_SV32 (1u << 31)
+#define SSTATUS_SPIE (1 << 5)
+#define SCAUSE_ECALL 8
 #define PAGE_V (1 << 0) // "Valid" bit (entry is allowed)
 #define PAGE_R (1 << 1) // Readable
 #define PAGE_W (1 << 2) // Writable
 #define PAGE_X (1 << 3) // Executable
 #define PAGE_U (1 << 4) // User (accessible in user mode)
 #define USER_BASE 0x1000000
-#define SSTATUS_SPIE (1 << 5)
 
 struct process {
     int pid;                    // ID of a process

run.sh

@@ -9,6 +9,7 @@ OBJCOPY=/usr/bin/llvm-objcopy
 CC=clang
 CFLAGS="-std=c11 -O2 -g3 -Wall -Wextra --target=riscv32-unknown-elf -fno-stack-protector -ffreestanding -nostdlib"
 
+# Build the shell
 $CC $CFLAGS -Wl,-Tuser.ld -Wl,-Map=shell.map -o shell.elf shell.c user.c common.c
 $OBJCOPY --set-section-flags .bss=alloc,contents -O binary shell.elf shell.bin
 $OBJCOPY -Ibinary -Oelf32-littleriscv shell.bin shell.bin.o

shell.c

@@ -1,17 +1,29 @@
 #include "user.h"
 
 void main(void) {
-    // *((volatile int *) 0x80200000) = 0x1234;
-    // printf("      ___           ___           ___           ___           ___       ___           ___     \\n");
-    // printf("     /\\  \\         /\\__\\         /\\  \\         /\\  \\         /\\__\\     /\\  \\         /\\  \\    \\n");
-    // printf("    /::\\  \\       /::|  |       /::\\  \\       /::\\  \\       /:/  /    /::\\  \\       /::\\  \\   \\n");
-    // printf("   /:/\\:\\  \\     /:|:|  |      /:/\\:\\  \\     /:/\\:\\  \\     /:/  /    /:/\\:\\  \\     /:/\\ \\  \\  \\n");
-    // printf("  /::\\~\\:\\  \\   /:/|:|__|__   /:/  \\:\\  \\   /::\\~\\:\\  \\   /:/  /    /:/  \\:\\  \\   _\\:\\~\\ \\  \\ \\n");
-    // printf(" /:/\\:\\ \\:\\__\\ /:/ |::::\\__\\ /:/__/ \\:\\__\\ /:/\\:\\ \\:\\__\\ /:/__/    /:/__/ \\:\\__\\ /\\ \\:\\ \\ \\__\\\\n");
-    // printf(" \\/__\\:\\/:/  / \\/__/~~/:/  / \\:\\  \\ /:/  / \\:\\~\\:\\ \\/__/ \\:\\  \\    \\:\\  \\ /:/  / \\:\\ \\:\\ \\/__/\\n");
-    // printf("      \\::/  /        /:/  /   \\:\\  /:/  /   \\:\\ \\:\\__\\    \\:\\  \\    \\:\\  /:/  /   \\:\\ \\:\\__\\  \\n");
-    // printf("      /:/  /        /:/  /     \\:\\/:/  /     \\:\\ \\/__/     \\:\\  \\    \\:\\/:/  /     \\:\\/:/  /  \\n");
-    // printf("     /:/  /        /:/  /       \\::/  /       \\:\\__\\        \\:\\__\\    \\::/  /       \\::/  /   \\n");
-    // printf("     \\/__/         \\/__/         \\/__/         \\/__/         \\/__/     \\/__/         \\/__/    \\n");
-    for (;;);
+    while (1) {
+prompt:
+        printf("# > ");
+        char cmdline[128];
+        for (int i = 0;; i++) {
+            char ch = getchar();
+            putchar(ch);
+            if (i == sizeof(cmdline) - 1) {
+                printf("too much yapping bro :(\n");
+                goto prompt;
+            } else if (ch == '\r') {
+                printf("\n");
+                cmdline[i] = '\0';
+                break;
+            } else {
+                cmdline[i] = ch;
+            }
+        }
+
+        if (strcmp(cmdline, "hello") == 0) {
+            printf("Hellow :3\n");
+        } else {
+            printf("I don't know what is %s yet :(", cmdline);
+        }
+    }
 }

user.c

@@ -1,13 +1,32 @@
 #include "user.h"
+#include "common.h"
 
 extern char __stack_top[];
 
+int syscall(int sysno, int arg0, int arg1, int arg2) {
+    register int a0 __asm__("a0") = arg0;
+    register int a1 __asm__("a1") = arg1;
+    register int a2 __asm__("a2") = arg2;
+    register int a3 __asm__("a3") = sysno;
+
+    __asm__ __volatile__("ecall"
+                         : "=r"(a0)
+                         : "r"(a0), "r"(a1), "r"(a2), "r"(a3)
+                         : "memory");
+
+    return a0;
+}
+
 __attribute__((noreturn)) void exit(void) {
     for(;;);
 }
 
 void putchar(char ch) {
-    // TODO
+    syscall(SYS_PUTCHAR, ch, 0, 0);
+}
+
+int getchar(void) {
+    return syscall(SYS_GETCHAR, 0, 0, 0);
 }
 
 __attribute__((section(".text.start")))

user.h

@@ -3,3 +3,4 @@
 
 __attribute__((noreturn)) void exit(void);
 void putchar(char ch);
+int getchar(void);