Merge pull request #7 from Germ-99/Shutdown-Command-and-buffer-overflow-fix

Added shutdown command and fixed buffer overflow in cat

Author: gingrspacecadet

Makefile

@@ -57,6 +57,8 @@ clean:
 	@rm -f $(OBJS) boot.bin kernel.bin kernel.elf $(IMAGE)
 	@$(MAKE) --no-print-directory -C tests clean
 
+# If the shutdown command doesn't work, change this to "qemu-system-i386 -fda $< -hda rootfs/kfs.img -device isa-debug-exit,iobase=0x501,iosize=0x1"
+# This same message is also in core/shell.c
 run: $(IMAGE)
 	qemu-system-i386 -fda $< -hda rootfs/kfs.img > /dev/null 2>&1
 

kernel/core/shell.c

@@ -14,9 +14,14 @@
 #include "../lib/math.h"
 
 #define CMD_COMP(name) (strcmp(strtok(chars, " "), name) == 0)
+#define MAX_CAT_SIZE 8192  // Max file size for cat (8KB for now)
 
 extern struct kfs_superblock superblock;
 
+static inline void outb(uint16_t port, uint8_t val) {
+    __asm__ volatile("outb %0, %1" : : "a"(val), "Nd"(port));
+}
+
 void reboot(void) {
     klog("reboot triggered");
     asm volatile (
@@ -26,12 +31,57 @@ void reboot(void) {
     );
 }
 
+// NOTE: This probably won't work for the current qemu run command for testing.
+// If not, try: qemu-system-i386 -fda floppy.img -hda rootfs/kfs.img -device isa-debug-exit,iobase=0x501,iosize=0x1
+void shutdown(void) {
+    klog("shutdown triggered\n");
+    
+    // QEMU ISA debug exit 
+    outb(0x501, 0x00);  // Exit with code 0
+    
+    // Try ACPI shutdown 
+    outb(0xB004, 0x2000);  // Bochs/QEMU 
+    outb(0x604, 0x2000);   // QEMU (but newer)
+    outb(0x4004, 0x3400);  // VirtualBox
+    
+    // Try writing to ACPI PM1a control register
+    outb(0x600, 0x34);
+    outb(0xb004, 0x2000);
+    
+    // If ACPI didn't work, try APM
+    asm volatile(
+        "mov $0x5301, %%ax\n"
+        "xor %%bx, %%bx\n"
+        "int $0x15\n"
+        "jc apm_fail\n"
+        
+        "mov $0x5308, %%ax\n"
+        "mov $1, %%bx\n"
+        "mov $1, %%cx\n"
+        "int $0x15\n"
+        
+        "mov $0x5307, %%ax\n"
+        "mov $1, %%bx\n"
+        "mov $3, %%cx\n"
+        "int $0x15\n"
+        
+        "apm_fail:\n"
+        ::: "ax", "bx", "cx"
+    );
+    
+    klog("shutdown failed - halting\n");
+    asm volatile("cli");
+    for (;;) {
+        asm volatile("hlt");
+    }
+}
 
 void sh(void) {
     klog("sh: scheduler and elfs are not properly implemented yet. dropping into temporary shell.\n");
 
     char chars[128];
     int i;
+    static uint8_t cat_buffer[MAX_CAT_SIZE];  // Static buffer to avoid stack overflow
 
     for (;;) {
         puts("// ");
@@ -49,9 +99,13 @@ void sh(void) {
                     putc('\b');
                 }
             } else {
+                if ((unsigned int)i >= sizeof(chars) - 1) {
+                    chars[i] = 0;
+                    break;
+                }
                 putc(c);
                 chars[i++] = c;
-                if (c == '\n' || (unsigned int)i >= sizeof(chars) - 1) {
+                if (c == '\n') {
                     chars[i - 1] = 0;
                     break;
                 }
@@ -79,23 +133,39 @@ void sh(void) {
             struct kfs_file* f = kfs_find(chars + 4);
             if (!f) {
                 printf("cat: %s: not found\n", chars + 4);
+            } else if (f->size > MAX_CAT_SIZE) {
+                printf("cat: file too large (max %d bytes)\n", MAX_CAT_SIZE);
             } else {
-                uint8_t data[(f->size + 511) & ~511];
-                if (kfs_read(f->name, data) < 0) {
+                uint32_t rounded_size = (f->size + 511) & ~511;
+                if (kfs_read(f->name, cat_buffer) < 0) {
                     puts("kfs: ioerr\n");
                 } else {
                     for (uint32_t j = 0; j < f->size; j++)
-                        putc(data[j]);
+                        putc(cat_buffer[j]);
                     putc('\n');
                 }
             }
         }
         else if (CMD_COMP("reboot")) {
             reboot();
         }
+        else if (CMD_COMP("shutdown")) {
+            shutdown();
+        }
         else if (CMD_COMP("exec")) {
             exec(chars + 5) == ERR_FORMAT ? puts("exec: format error\n") : 0;
         }
+
+        // Placeholder for now
+        // Don't remove these comments until there is a proper implementation for elf.
+        // AHEM *gingrspacecadet*
+        // - Bryson
+
+        /*else if (CMD_COMP("elf")) {
+            extern int elfExec(const char* name, void** entry, struct uexAlloc* out_alloc);
+            elfExec(chars + 4, NULL, NULL);
+        } 
+        */
         else if (CMD_COMP("help")) {
             puts("Available commands:\n"
                  " version      - show kernel version\n"
@@ -104,7 +174,9 @@ void sh(void) {
                  " exec <file>  - execute UEX file\n"
                  " clear        - clear the screen\n"
                  " help         - show this help message\n"
-                 " touch <file> - create an empty file\n");
+                 " touch <file> - create an empty file\n"
+                 " reboot       - reboot the system\n"
+                 " shutdown     - power off the system\n");
         } else if (chars[0] != 0) {
             printf("%s: command not found\n", chars);
         }