Merge pull request #1 from n-canter/master

add kernel files

.gitignore

@@ -0,0 +1,4 @@
+boot.o
+kernel
+kernel.o
+md5.o

Makefile

@@ -0,0 +1,17 @@
+CC=gcc
+CFLAGS=-c -m32
+OBJECT_FILES=boot.o kernel.o md5.o
+LDFLAGS=-m elf_i386
+
+all: kernel
+
+%.o: %.S
+	$(CC) $(CFLAGS) $< -o $@
+
+kernel: boot.o kernel.o md5.o
+	$(LD) $(LDFLAGS) $^ -o $@
+
+.PHONY: all clean
+
+clean:
+	rm $(OBJECT_FILES) kernel

README.md

@@ -1,2 +1,6 @@
 # multiboot-test-kernel
 A multiboot test kernel.
+
+This is a slightly modified kernel provided by the Multiboot v1 [spec](https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Example-OS-code).
+
+The kernel writes received Multiboot information to a serial output in JSON format and computes md5 sum for each loaded module.

boot.S

@@ -0,0 +1,99 @@
+/* boot.S - bootstrap the kernel */
+/* Copyright (C) 1999, 2001, 2010  Free Software Foundation, Inc.
+*
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#define ASM_FILE	1
+#include "multiboot.h"
+/* C symbol format. HAVE_ASM_USCORE is defined by configure. */
+#ifdef HAVE_ASM_USCORE
+#define EXT_C(sym)	_ ## sym
+#else
+#define EXT_C(sym)	sym
+#endif
+
+/* The size of our stack (16KB). */
+#define STACK_SIZE	0x4000
+
+/* The flags for the Multiboot header. */
+#ifdef __ELF__
+# define AOUT_KLUDGE 0
+#else
+# define AOUT_KLUDGE MULTIBOOT_AOUT_KLUDGE
+#endif
+#define MULTIBOOT_HEADER_FLAGS	MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_VIDEO_MODE | AOUT_KLUDGE
+
+
+	.text
+
+	.globl	start, _start
+start:
+_start:
+	 jmp	 multiboot_entry
+
+	 /* Align 32 bits boundary. */
+	 .align	 4
+
+	 /* Multiboot header. */
+multiboot_header:
+	/* magic */
+	.long	MULTIBOOT_HEADER_MAGIC
+	/* flags */
+	.long	MULTIBOOT_HEADER_FLAGS
+	/* checksum */
+	.long	-(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
+	#ifndef __ELF__
+	/* header_addr */
+	.long	multiboot_header
+	/* load_addr */
+	.long	_start
+	/* load_end_addr */
+	.long	_edata
+	/* bss_end_addr */
+	.long	_end
+	/* entry_addr */
+	.long   multiboot_entry
+	#else /* ! __ELF__ */
+	.long	0
+	.long	0
+	.long	0
+	.long	0
+	.long	0
+	#endif /* __ELF__ */
+	.long	0
+	.long	1024
+	.long	768
+	.long	32
+
+multiboot_entry:
+	/* Initialize the stack pointer. */
+	movl	$(stack + STACK_SIZE), %esp
+
+	/* Reset EFLAGS. */
+	pushl	$0
+	popf
+
+	/* Push the pointer to the Multiboot information structure. */
+	pushl	%ebx
+	/* Push the magic value. */
+	pushl	%eax
+
+	/* Now enter the C main function... */
+	call	EXT_C(cmain)
+	hlt
+
+
+/* Our stack area. */
+.comm	stack, STACK_SIZE

kernel.c

@@ -0,0 +1,250 @@
+/* kernel.c - the C part of the kernel */
+/* Copyright (C) 1999, 2010  Free Software Foundation, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <sys/io.h>
+#include "md5.h"
+#include "multiboot.h"
+/* Macros. */
+
+/* Check if the bit BIT in FLAGS is set. */
+#define CHECK_FLAG(flags, bit) ((flags) & (1 << (bit)))
+
+/* Forward declarations. */
+void cmain(unsigned long magic, unsigned long addr);
+static void itoa(char *buf, int base, int d);
+static void putchar(int c);
+void printf(const char *format, ...);
+
+void print_module(multiboot_uint32_t start, multiboot_uint32_t end,
+                  multiboot_uint32_t cmdline) {
+  MD5_CTX ctx;
+  MD5_Init(&ctx);
+  MD5_Update(&ctx, (void *)start, end - start);
+  unsigned char res[16];
+  MD5_Final(res, &ctx);
+
+  printf("{\"start\": %u, \"end\": %u, \"cmdline\": \"%s\", \"md5\": \"",
+         (unsigned)start, (unsigned)end, (char *)cmdline);
+  for (int i = 0; i < 16; i++) {
+    printf("%02x", res[i]);
+  }
+  printf("\"}");
+}
+
+/* Check if MAGIC is valid and print the Multiboot information structure
+   pointed by ADDR. */
+void cmain(unsigned long magic, unsigned long addr) {
+  multiboot_info_t *mbi;
+  /* Clear the screen. */
+  printf("Starting multiboot kernel\n");
+
+  printf("{\n");
+  /* Am I booted by a Multiboot-compliant boot loader? */
+  if (magic != MULTIBOOT_BOOTLOADER_MAGIC) {
+    printf("\"status\": \"Invalid magic number\"\n}\n");
+    return;
+  }
+
+  /* Set MBI to the address of the Multiboot information structure. */
+  mbi = (multiboot_info_t *)addr;
+
+  /* Print out the flags. */
+  printf("\"flags\": %u,\n", (unsigned)mbi->flags);
+
+  /* Are mem_* valid? */
+  if (CHECK_FLAG(mbi->flags, 0))
+    printf("\"mem_lower\": %u, \"mem_upper\": %u,\n", (unsigned)mbi->mem_lower,
+           (unsigned)mbi->mem_upper);
+
+  /* Is boot_device valid? */
+  if (CHECK_FLAG(mbi->flags, 1))
+    printf("\"boot_device\": %u,\n", (unsigned)mbi->boot_device);
+
+  /* Is the command line passed? */
+  if (CHECK_FLAG(mbi->flags, 2))
+    printf("\"cmdline\": \"%s\",\n", (char *)mbi->cmdline);
+
+  /* Are mods_* valid? */
+  if (CHECK_FLAG(mbi->flags, 3)) {
+    multiboot_module_t *mod;
+    int i;
+
+    printf("\"mods_count\": %d, \"mods_addr\": %u,\n", (int)mbi->mods_count,
+           (int)mbi->mods_addr);
+    printf("\"modules\": [\n");
+    for (i = 0, mod = (multiboot_module_t *)mbi->mods_addr; i < mbi->mods_count;
+         i++, mod++) {
+      print_module(mod->mod_start, mod->mod_end, mod->cmdline);
+      if (i != mbi->mods_count - 1) printf(",\n");
+    }
+    printf("\n],\n");
+  }
+
+  /* Bits 4 and 5 are mutually exclusive! */
+  if (CHECK_FLAG(mbi->flags, 4) && CHECK_FLAG(mbi->flags, 5)) {
+    printf("\"status\":\"Both bits 4 and 5 are set\"\n}\n");
+    return;
+  }
+
+  /* Is the symbol table of a.out valid? */
+  if (CHECK_FLAG(mbi->flags, 4)) {
+    multiboot_aout_symbol_table_t *multiboot_aout_sym = &(mbi->u.aout_sym);
+
+    printf(
+        "\"multiboot_aout_symbol_table\": {\"tabsize\" = 0x%0x, "
+        "\"strsize\" = 0x%x, \"addr\" = 0x%x},\n",
+        (unsigned)multiboot_aout_sym->tabsize,
+        (unsigned)multiboot_aout_sym->strsize,
+        (unsigned)multiboot_aout_sym->addr);
+  }
+
+  /* Is the section header table of ELF valid? */
+  if (CHECK_FLAG(mbi->flags, 5)) {
+    multiboot_elf_section_header_table_t *multiboot_elf_sec = &(mbi->u.elf_sec);
+
+    printf(
+        "\"multiboot_elf_sec\": {\"num\": %u, \"size\": %u,"
+        " \"addr\": %u, \"shndx\": %u},\n",
+        (unsigned)multiboot_elf_sec->num, (unsigned)multiboot_elf_sec->size,
+        (unsigned)multiboot_elf_sec->addr, (unsigned)multiboot_elf_sec->shndx);
+  }
+
+  /* Are mmap_* valid? */
+  if (CHECK_FLAG(mbi->flags, 6)) {
+    multiboot_memory_map_t *mmap;
+
+    printf("\"mmap_addr\": %u, \"mmap_length\": %u,\n",
+           (unsigned)mbi->mmap_addr, (unsigned)mbi->mmap_length);
+    printf("\"mmap\": [\n");
+    int first = 1;
+    for (mmap = (multiboot_memory_map_t *)mbi->mmap_addr;
+         (unsigned long)mmap < mbi->mmap_addr + mbi->mmap_length;
+         mmap = (multiboot_memory_map_t *)((unsigned long)mmap + mmap->size +
+                                           sizeof(mmap->size))) {
+      if (!first) printf(",\n");
+      first = 0;
+      printf(
+          "{\"size\": %u, \"base_addr\": \"0x%x%08x\", "
+          "\"length\": \"0x%x%08x\", \"type\": %u}",
+          (unsigned)mmap->size, (unsigned)(mmap->addr >> 32),
+          (unsigned)(mmap->addr & 0xffffffff), (unsigned)(mmap->len >> 32),
+          (unsigned)(mmap->len & 0xffffffff), (unsigned)mmap->type);
+    }
+    printf("\n],\n");
+  }
+  if (CHECK_FLAG(mbi->flags, 9))
+    printf("\"bootloader\": \"%s\",\n", (char *)mbi->boot_loader_name);
+
+  printf("\"status\": \"ok\"\n}\n");
+}
+
+/* Convert the integer D to a string and save the string in BUF. If
+   BASE is equal to 'd', interpret that D is decimal, and if BASE is
+   equal to 'x', interpret that D is hexadecimal. */
+static void itoa(char *buf, int base, int d) {
+  char *p = buf;
+  char *p1, *p2;
+  unsigned long ud = d;
+  int divisor = 10;
+
+  /* If %d is specified and D is minus, put `-' in the head. */
+  if (base == 'd' && d < 0) {
+    *p++ = '-';
+    buf++;
+    ud = -d;
+  } else if (base == 'x')
+    divisor = 16;
+
+  /* Divide UD by DIVISOR until UD == 0. */
+  do {
+    int remainder = ud % divisor;
+
+    *p++ = (remainder < 10) ? remainder + '0' : remainder + 'a' - 10;
+  } while (ud /= divisor);
+
+  /* Terminate BUF. */
+  *p = 0;
+
+  /* Reverse BUF. */
+  p1 = buf;
+  p2 = p - 1;
+  while (p1 < p2) {
+    char tmp = *p1;
+    *p1 = *p2;
+    *p2 = tmp;
+    p1++;
+    p2--;
+  }
+}
+
+/* Put the character C on the screen. */
+static void putchar(int c) { outb(c, 0x3f8); }
+
+/* Format a string and print it on the screen, just like the libc
+   function printf. */
+void printf(const char *format, ...) {
+  char **arg = (char **)&format;
+  int c;
+  char buf[20];
+
+  arg++;
+
+  while ((c = *format++) != 0) {
+    if (c != '%')
+      putchar(c);
+    else {
+      char *p, *p2;
+      int pad0 = 0, pad = 0;
+
+      c = *format++;
+      if (c == '0') {
+        pad0 = 1;
+        c = *format++;
+      }
+
+      if (c >= '0' && c <= '9') {
+        pad = c - '0';
+        c = *format++;
+      }
+
+      switch (c) {
+        case 'd':
+        case 'u':
+        case 'x':
+          itoa(buf, c, *((int *)arg++));
+          p = buf;
+          goto string;
+          break;
+
+        case 's':
+          p = *arg++;
+          if (!p) p = "(null)";
+
+        string:
+          for (p2 = p; *p2; p2++)
+            ;
+          for (; p2 < p + pad; p2++) putchar(pad0 ? '0' : ' ');
+          while (*p) putchar(*p++);
+          break;
+
+        default:
+          putchar(*((int *)arg++));
+          break;
+      }
+    }
+  }
+}