Implement paging

11 files changed, 144 insertions, 1 deletions

diff --git a/OBJ b/OBJ
index 1bc9ae6..2d81e14 100644
--- a/OBJ
+++ b/OBJ
@@ -18,6 +18,7 @@ drivers/tty.o
 kernel/fpu.o
 kernel/gdt-as.o
 kernel/gdt.o
+kernel/heap.o
 kernel/idt-as.o
 kernel/idt.o
 kernel/io.o
diff --git a/bochs.cfg b/bochs.cfg
index e22e703..dd579e2 100644
--- a/bochs.cfg
+++ b/bochs.cfg
@@ -26,7 +26,7 @@ cpuid: aes=0, sha=0, xsave=0, xsaveopt=0, avx_f16c=0, avx_fma=0, bmi=0, xop=0, f
 cpuid: tbm=0, x86_64=1, 1g_pages=0, pcid=0, fsgsbase=0, smep=0, smap=0, mwait=1
 print_timestamps: enabled=0
 debugger_log: -
-magic_break: enabled=0
+magic_break: enabled=1
 port_e9_hack: enabled=1
 private_colormap: enabled=0
 clock: sync=none, time0=local, rtc_sync=0
diff --git a/drivers/gfx.c b/drivers/gfx.c
index 028a5e5..3417fda 100644
--- a/drivers/gfx.c
+++ b/drivers/gfx.c
@@ -541,5 +541,7 @@ bool gfx_init(struct vbe_info_t *vbe_mode_info)
         gfx_reset();
     }
 
+    printf("Real FB addr: 0x%x\n", (uint32_t)real_framebuffer);
+
     return true;
 }
diff --git a/kernel/heap.c b/kernel/heap.c
new file mode 100644
index 0000000..d1f1021
--- /dev/null
+++ b/kernel/heap.c
@@ -0,0 +1,45 @@
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include "paging.h"
+
+/* a simple pointer-arithmetic-based malloc */
+
+/* a symbol put there by the linker */
+extern uint32_t link_mem_end;
+uint32_t kmalloc_addr = &link_mem_end;
+
+static void *kmalloc_int(size_t sz, int align, void **phys)
+{
+    if(align)
+    {
+        kmalloc_addr += (PAGE_SIZE - 1);
+        kmalloc_addr &= PAGE_MASK;
+    }
+    if(phys)
+        *phys = (void*)kmalloc_addr;
+    void *ret = (void*)kmalloc_addr;
+    kmalloc_addr += sz;
+    assert(((uint32_t)ret & 0xFFF) == 0);
+    return ret;
+}
+
+void *kmalloc(size_t sz)
+{
+    return kmalloc_int(sz, 0, NULL);
+}
+
+void *kmalloc_a(size_t sz)
+{
+    return kmalloc_int(sz, 1, NULL);
+}
+
+void *kmalloc_p(size_t sz, void **phys)
+{
+     return kmalloc_int(sz, 0, phys);
+}
+
+void *kmalloc_ap(size_t sz, void **phys)
+{
+    return kmalloc_int(sz, 1, phys);
+}
diff --git a/kernel/include/paging.h b/kernel/include/paging.h
new file mode 100644
index 0000000..0481069
--- /dev/null
+++ b/kernel/include/paging.h
@@ -0,0 +1,8 @@
+#define PAGE_PRESENT (1<<0)
+#define PAGE_RW      (1<<1)
+#define PAGE_USER    (1<<2)
+
+#define PAGE_MASK 0xFFFFF000
+#define PAGE_SIZE     0x1000
+
+void paging_init(void);
diff --git a/kernel/linker.ld b/kernel/linker.ld
index 9b47325..c032991 100644
--- a/kernel/linker.ld
+++ b/kernel/linker.ld
@@ -41,4 +41,5 @@ SECTIONS
 
         /* The compiler may produce other sections, by default it will put them in
            a segment with the same name. Simply add stuff here as needed. */
+        link_mem_end = .;
 }
diff --git a/kernel/main.c b/kernel/main.c
index 04ef369..005ac1d 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -61,6 +61,7 @@ void main(struct multiboot_info_t *hdr, uint32_t magic)
 
     printf("GFX init\n");
     bool gfx_status = gfx_init((struct vbe_info_t*)hdr->vbe_mode_info);
+    //bool gfx_status = false;
     printf("GFX init done.\n");
 
     /* if graphical initialization fails, fall back to text mode */
diff --git a/kernel/paging-as.S b/kernel/paging-as.S
new file mode 100644
index 0000000..cafaab4
--- /dev/null
+++ b/kernel/paging-as.S
@@ -0,0 +1,9 @@
+        .global do_paging_enable
+do_paging_enable:
+        movl 4(%esp), %eax # loads page directory address
+        mov %eax, %cr3
+        mov %cr0, %eax
+        orl $0x80000000, %eax # set PG bit
+        sti
+        mov %eax, %cr0
+        ret
diff --git a/kernel/paging.c b/kernel/paging.c
new file mode 100644
index 0000000..408ced8
--- /dev/null
+++ b/kernel/paging.c
@@ -0,0 +1,65 @@
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include "frame.h"
+#include "heap.h"
+#include "isr.h"
+#include "paging.h"
+#include "panic.h"
+
+uint32_t *current_directory;
+
+static void page_fault(struct regs_t *regs)
+{
+    volatile uint32_t fault_addr;
+    asm("mov %%cr2, %0" : "=r"(fault_addr));
+    printf("=== Page Fault ===\n");
+    printf("Faulting address: 0x%x\n", fault_addr);
+    /* dump the regs */
+    printf("EAX: 0x%x EBX: 0x%x\n", regs->eax, regs->ebx);
+    printf("ECX: 0x%x EDX: 0x%x\n", regs->ecx, regs->edx);
+    printf("ESP: 0x%x EBP: 0x%x\n", regs->esp, regs->ebp);
+    printf("ESI: 0x%x EDI: 0x%x\n", regs->esi, regs->edi);
+    printf("EIP: 0x%x\n", regs->eip);
+    panic("Page fault!\n");
+}
+
+ void paging_switch_directory(uint32_t *dir)
+{
+    current_directory = dir;
+    extern void do_paging_enable(uint32_t);
+    do_paging_enable((uint32_t)current_directory);
+}
+
+static uint32_t *identity_map_table(uint32_t start, int flags)
+{
+    /* make a page table */
+    uint32_t *table = kmalloc_a(0x1000);
+    /* identity map 4MB */
+    for(uint32_t i = start; i < start + 1024; ++i)
+    {
+        table[i - start] = (i * PAGE_SIZE) | flags;
+    }
+    return table;
+}
+
+void paging_init(void)
+{
+    uint32_t *kernel_directory = kmalloc_a(0x1000);
+    memset(kernel_directory, 0, 0x1000);
+    /* blank the kernel directory */
+    for(int i = 0; i < 1024; ++i)
+    {
+        kernel_directory[i] = PAGE_RW;
+    }
+
+    /* identity map all 4GB */
+    for(int i=0; i < 1024; ++i)
+        kernel_directory[i] = (uint32_t)identity_map_table(i * 1024, PAGE_PRESENT | PAGE_RW) |
+            PAGE_PRESENT | PAGE_RW;
+
+    set_interrupt_handler(14, page_fault);
+
+    paging_switch_directory(kernel_directory);
+}
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index 49116df..ffe9073 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -2,6 +2,7 @@
 #define _STDLIB_H_
 
 #include <stddef.h>
+#include <stdio.h>
 
 /* this is by no means standards-compliant... but who cares? :P */
 
@@ -18,5 +19,8 @@ void srand(unsigned int);
 int abs(int);
 void *malloc(size_t);
 int snprintf(char*, int, const char*, ...);
+void assert_fail(const char*, const char*, int);
+
+#define assert(x) if(!(x))assert_fail(__func__, __FILE__, __LINE__);
 
 #endif
diff --git a/libc/stdlib.c b/libc/stdlib.c
index c6a9c3d..bb30039 100644
--- a/libc/stdlib.c
+++ b/libc/stdlib.c
@@ -2,6 +2,7 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <stdlib.h>
+#include "panic.h"
 
 /* adapted from <http://www.strudel.org.uk/itoa/> */
 char* itoa(int val, int base)
@@ -150,3 +151,9 @@ int snprintf(char *buf, int sz, const char *fmt, ...)
     va_end(ap);
     return 0;
 }
+
+void assert_fail(const char *func, const char *file, int line)
+{
+    printf("\nAssertion failed in function %s in file %s, line %d\n", func, file, line);
+    panic("assertion failed!\n");
+}