con_init() is now called during the kernel's boot sequence in kboot()

rather than in kmain() as some subsystems may now require early console
I/O.

Added 16-bit read/write I/O functions to asm/io.h. These functions are
inw() and outw() respectively.

Added the file kernel/fs.h which will contain definitions relating to
filesystem functions.

Defined the type off_t as a signed 32-bit value in sys/types.h. This
type will be required for filesystem functionality.

Added the directory 'kernel/fs' to the project's source tree. The
kernel's makefile has been updated accordingly. This directory will
contain any source files relating to filesystem functionality (both
assembly and C files).

Added the file 'fs/hd.c' to the kernel's source tree. This file
currently contains three main functions (which are defined in
kernel/hd.h). These functions are as follows; hd_init() to enumerate and
initialize the hard disks, hd_read() to read sectors from the disk and
hd_write() to write sectors to the disk. Currently, all transfers are
done in ATA PIO mode using polling, however this will change in future.
The function hd_init() is called during the kernel's boot sequence in
kboot().

Added the file hd.img to the project's root directory. This is a 20MB
raw image file that will be used by Qemu as a 20MB hard disk. The main
makefile has been updated to tell Qemu to use this file on launch.

4 files changed, 179 insertions, 6 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index 29b5566..f9e14e8 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -1,7 +1,7 @@
 TARGET = kernel.o
 
-SRCS = $(wildcard *.c)
-ASMS = $(wildcard *.s)
+SRCS = $(wildcard *.c) $(wildcard fs/*.c)
+ASMS = $(wildcard *.s) $(wildcard fs/*.s)
 OBJS = $(SRCS:.c=.o) $(ASMS:.s=.o)
 
 CFLAGS = -m32 -I../include -ffreestanding -nostdinc -nostdlib -fno-stack-protector -fno-pie -gstabs+ -g
diff --git a/kernel/boot.s b/kernel/boot.s
index 98732f6..96f0e43 100644
--- a/kernel/boot.s
+++ b/kernel/boot.s
@@ -2,8 +2,11 @@ global gdt
 global idt
 global kboot
 global register_isr
+extern con_init
+extern hd_init
 extern kmain
 extern paging_init
+extern printk
 extern syscall_init
 extern timer_init
 extern traps_init
@@ -24,10 +27,18 @@ kboot:
   ; WARNING: don't change this without changing the corresponding
   ; entries in the TSS constructor in sched.c
   mov esp, 0x80000
-  ; setup descriptor tables
+  ; setup descriptor tables and enable paging
   call flush_gdt
   call paging_init
   call flush_idt
+  ; initialize the console
+  call con_init
+  ; add this point, we can display *some* output
+  push .msg
+  call printk
+  add esp, 4
+  ; initialize the disk interface
+  call hd_init
   ; last minute setup, then transfer to kmain
   call timer_init
   call kmain
@@ -35,6 +46,7 @@ kboot:
   ; disable interrupts and halt the system.
   cli
   hlt
+.msg: db "Kernel booting...", 10, 0
 
 gdt:
   ; null descriptor
diff --git a/kernel/fs/hd.c b/kernel/fs/hd.c
new file mode 100644
index 0000000..706d503
--- /dev/null
+++ b/kernel/fs/hd.c
@@ -0,0 +1,132 @@
+#include <asm/io.h>
+#include <kernel/con.h>
+#include <kernel/kernel.h>
+#include <stdint.h>
+
+#define ST_ERR 1
+#define ST_DRQ 8
+#define ST_SRV 16
+#define ST_DF  32
+#define ST_RDY 64
+#define ST_BSY 128
+
+/* sector buffer */
+static char sbuf[512];
+
+void hd_init(void) {
+  int i;
+  uint8_t s;
+  uint16_t *buf = (uint16_t*) sbuf;
+
+  /* select the master drive */
+  outb(0x1F6, 0xA0);
+  /* send the IDENTIFY command */
+  outb(0x1F7, 0xEC);
+
+  while(1) {
+    s = inb(0x1F7);
+    if(!s) {
+      printk("[hd] Master drive not detected on primary bus!\n");
+      panic();
+    }
+    if(s & ST_ERR) {
+      if(!inb(0x1F4) && !inb(0x1F5))
+        continue;
+      printk("[hd] IDENTIFY command error!\n");
+      panic();
+    }
+    if(s & ST_DRQ && !(s & ST_ERR))
+      break;
+  }
+
+  printk("[hd] Master drive detected on primary bus! (status: 0x%02x)\n", s);
+
+  for(i = 0; i < 256; i++)
+    buf[i] = inw(0x1F0);
+}
+
+int hd_read(void *buf, uint32_t lba, uint8_t c) {
+  int n;
+  uint8_t s;
+  uint16_t *p = buf;
+
+  if(!c)
+    return 0;
+
+  /* select the master disk on the primary bus */
+  outb(0x1F6, 0xE0 | ((lba >> 24) & 0xF));
+  /* set the number of sectors to be read */
+  outb(0x1F2, c);
+  /* set the LBA address for the read operation */
+  outb(0x1F3, lba);
+  outb(0x1F4, lba >> 8);
+  outb(0x1F5, lba >> 16);
+  /* send the READ command */
+  outb(0x1F7, 0x20);
+
+  while(c--) {
+    /* wait for the drive */
+    while(1) {
+      /* poll the drive's status */
+      s = inb(0x1F7);
+      if(s & ST_DF) {
+        printk("[hd] Drive failure!\n");
+        panic();
+      }
+      if(s & ST_ERR)
+        return -1;
+      if(!(s & ST_BSY) && s & ST_DRQ)
+        break;
+    }
+
+    /* buffer is full, copy it's data */
+    n = 256;
+    while(n--)
+      *(p++) = inw(0x1F0);
+  }
+
+  return 0;
+}
+
+int hd_write(void *buf, uint32_t lba, uint8_t c) {
+  int n;
+  uint8_t s;
+  uint16_t *p = buf;
+
+  if(!c)
+    return 0;
+
+  /* select the master disk on the primary bus */
+  outb(0x1F6, 0xE0 | ((lba >> 24) & 0xF));
+  /* set the number of sectors to be written */
+  outb(0x1F2, c);
+  /* set the LBA address for the write operation */
+  outb(0x1F3, lba);
+  outb(0x1F4, lba >> 8);
+  outb(0x1F5, lba >> 16);
+  /* send the WRITE command */
+  outb(0x1F7, 0x30);
+
+  while(c--) {
+    /* wait for the drive */
+    while(1) {
+      /* poll the drive's status */
+      s = inb(0x1F7);
+      if(s & ST_DF) {
+        printk("[hd] Drive failure!\n");
+        panic();
+      }
+      if(s & ST_ERR)
+        return -1;
+      if(!(s & ST_BSY) && s & ST_DRQ)
+        break;
+    }
+
+    /* refill the drive's buffer */
+    n = 256;
+    while(n--)
+      outw(0x1F0, *(p++));
+  }
+
+  return 0;
+}
diff --git a/kernel/kmain.c b/kernel/kmain.c
index 6b550b7..00455b7 100644
--- a/kernel/kmain.c
+++ b/kernel/kmain.c
@@ -3,11 +3,40 @@
 #include <kernel/sys.h>
 #include <stdint.h>
 
+extern int hd_read(void*, uint32_t, uint8_t);
+extern int hd_write(void*, uint32_t, uint8_t);
+
+static char buf[0x1000];
+
 void kmain(void) {
-  con_init();
+  int i;
+  int ret;
 
-  printk("Kernel booting...\n");
   printk("Kernel booted!\n\n");
 
-  sched_init();
+  /* sched_init(); */
+
+  /* try to read some data */
+
+  ret = hd_read(buf, 0, 2);
+  if(ret < 0) {
+    printk("Failed to read data!\n");
+    return;
+  }
+  printk("Successfully read first and second sectors!\n");
+  printk("First dword (sector 0): 0x%08x\n", *((uint32_t*) buf));
+  printk("First dword (sector 1): 0x%08x\n", *((uint32_t*) (buf + 512)));
+
+  /* try to write some data */
+
+  for(i = 0; i < 256; i++)
+    ((uint16_t*) buf)[i] = i;
+
+  ret = hd_write(buf, 2, 1);
+  if(ret < 0) {
+    printk("Failed to write data!\n");
+    return;
+  }
+
+  printk("Successfully wrote to sector 2\n");
 }