handle page faults

Makefile

@@ -19,7 +19,7 @@ ISO := Hazel.iso
 
 CFLAGS    := -ffreestanding -Wall -Wextra -Werror -I $(INCLUDEDIR) -I lib
 LDFLAGS   := -ffreestanding -nostdlib -lgcc -T kernel/kernel.ld
-QEMUFLAGS := -cdrom $(BUILDDIR)/$(ISO) -s -m 512M -serial stdio
+QEMUFLAGS := -d int -cdrom $(BUILDDIR)/$(ISO) -s -m 512M -serial stdio
 
 $(BUILDDIR)/$(KIMG): $(KOBJ) $(LOBJ)
 	$(CC) $^ -o $@ $(LDFLAGS)

include/kernel/acpi.h

@@ -0,0 +1,118 @@
+#ifndef HAZEL_ACPI_H_
+#define HAZEL_ACPI_H_
+
+#include <stdint.h>
+
+#define BIOS_START   0x000E0000
+#define BIOS_END     0x000FFFFF
+#define RSDP_SIG     "RSD PTR "
+#define RSDP_SIG_LEN 8
+#define RSDP_SIZE    20
+
+struct RSDP {
+    char Signature[RSDP_SIG_LEN];
+    uint8_t Checksum;
+    char OEMID[6];
+    uint8_t Revision;
+    uint32_t RsdtAddress;
+} __attribute__ ((packed));
+typedef struct RSDP rsdp_t;
+
+typedef struct {
+    char Signature[4];
+    uint32_t Length;
+    uint8_t Revision;
+    uint8_t Checksum;
+    char OEMID[6];
+    char OEMTableID[8];
+    uint32_t OEMRevision;
+    uint32_t CreatorID;
+    uint32_t CreatorRevision;
+} sdt_hdr_t;
+
+typedef struct {
+    sdt_hdr_t hdr;
+    uint32_t other_tables[];
+} rsdt_t;
+
+struct GenericAddressStructure
+{
+    uint8_t AddressSpace;
+    uint8_t BitWidth;
+    uint8_t BitOffset;
+    uint8_t AccessSize;
+    uint64_t Address;
+};
+
+struct fadt {
+    sdt_hdr_t hdr;
+    uint32_t FirmwareCtrl;
+    uint32_t Dsdt;
+ 
+    // field used in ACPI 1.0; no longer in use, for compatibility only
+    uint8_t  Reserved;
+ 
+    uint8_t  PreferredPowerManagementProfile;
+    uint16_t SCI_Interrupt;
+    uint32_t SMI_CommandPort;
+    uint8_t  AcpiEnable;
+    uint8_t  AcpiDisable;
+    uint8_t  S4BIOS_REQ;
+    uint8_t  PSTATE_Control;
+    uint32_t PM1aEventBlock;
+    uint32_t PM1bEventBlock;
+    uint32_t PM1aControlBlock;
+    uint32_t PM1bControlBlock;
+    uint32_t PM2ControlBlock;
+    uint32_t PMTimerBlock;
+    uint32_t GPE0Block;
+    uint32_t GPE1Block;
+    uint8_t  PM1EventLength;
+    uint8_t  PM1ControlLength;
+    uint8_t  PM2ControlLength;
+    uint8_t  PMTimerLength;
+    uint8_t  GPE0Length;
+    uint8_t  GPE1Length;
+    uint8_t  GPE1Base;
+    uint8_t  CStateControl;
+    uint16_t WorstC2Latency;
+    uint16_t WorstC3Latency;
+    uint16_t FlushSize;
+    uint16_t FlushStride;
+    uint8_t  DutyOffset;
+    uint8_t  DutyWidth;
+    uint8_t  DayAlarm;
+    uint8_t  MonthAlarm;
+    uint8_t  Century;
+ 
+    // reserved in ACPI 1.0; used since ACPI 2.0+
+    uint16_t BootArchitectureFlags;
+ 
+    uint8_t  Reserved2;
+    uint32_t Flags;
+ 
+    // 12 byte structure; see below for details
+    struct GenericAddressStructure ResetReg;
+ 
+    uint8_t  ResetValue;
+    uint8_t  Reserved3[3];
+ 
+    // 64bit pointers - Available on ACPI 2.0+
+    uint64_t                X_FirmwareControl;
+    uint64_t                X_Dsdt;
+ 
+    struct GenericAddressStructure X_PM1aEventBlock;
+    struct GenericAddressStructure X_PM1bEventBlock;
+    struct GenericAddressStructure X_PM1aControlBlock;
+    struct GenericAddressStructure X_PM1bControlBlock;
+    struct GenericAddressStructure X_PM2ControlBlock;
+    struct GenericAddressStructure X_PMTimerBlock;
+    struct GenericAddressStructure X_GPE0Block;
+    struct GenericAddressStructure X_GPE1Block;
+};
+
+rsdp_t *acpi_find_rsdp();
+uint32_t acpi_checksum(void *s, int size);
+void *acpi_find_sdt(rsdt_t *rsdt, const char sig[6]);
+
+#endif

kernel/acpi.c

@@ -0,0 +1,40 @@
+#include <kernel/acpi.h>
+#include <kernel/kernel.h>
+
+rsdp_t *acpi_find_rsdp() {
+    char *ptr = (char *)(KERNEL_VMA + BIOS_START);
+    const char sig[RSDP_SIG_LEN] = RSDP_SIG;
+
+    for (; (uint32_t)ptr - KERNEL_VMA <= BIOS_END; ptr += 16)  {
+        int i = 0;
+        for (; i < RSDP_SIG_LEN; i++)
+            if (ptr[i] != sig[i]) break;
+
+        if (i == RSDP_SIG_LEN) return (rsdp_t *)ptr;
+    }
+
+    return 0;
+}
+
+uint32_t acpi_checksum(void *s, int size) {
+    uint32_t sum = 0;
+    for (int i = 0; i < size; i++) {
+        sum += ((uint8_t *)s)[i];
+    }
+
+    return sum;
+}
+
+void *acpi_find_sdt(rsdt_t *rsdt, const char sig[6]) {
+    int entries = (rsdt->hdr.Length - sizeof(sdt_hdr_t)) / 4;
+    for (int i = 0; i < entries; i++) {
+        const char *ptr = (const char *)rsdt->other_tables[i];
+        int j = 0;
+        for (; j < RSDP_SIG_LEN; j++)
+            if (ptr[j] != sig[j]) break;
+
+        if (j == RSDP_SIG_LEN) return (void *)ptr;
+    }
+    
+    return 0;
+}

kernel/kernel.c

@@ -8,6 +8,7 @@
 #include <kernel/elf.h>
 #include <kernel/task.h>
 #include <kernel/ps2.h>
+#include <kernel/acpi.h>
 #include <stdint.h>
 
 kernel_ctx_t ctx = {0};
@@ -69,7 +70,23 @@ void exception_handler(int_stack_frame_t r) {
             r.int_no, r.err_code, r.eax, r.ecx, r.edx, r.ebx, r.esi, r.edi, r.ebp, r.esp+24); 
     LOG("\nEIP:     0x%08X\nCS:      0x%08X\nEFLAGS:  0x%08X\n",
             r.eip, r.cs, r.eflags);
-    for (;;) {}
+
+    // Page fault
+    if (r.int_no == 0xe) {
+        uint32_t cr2 = 0;
+        asm volatile ("mov %%cr2, %0" : "=r" (cr2));
+
+        if ((boot_page_dir[PAGE_DIR_INDEX(cr2)] & 0xFFFFF000) == 0) {
+            LOG("Creating new page table\n");
+            uint32_t *page_tab = mmap_find_first_free_block();
+            if (!page_tab) for (;;) {}
+            page_tab[PAGE_TAB_INDEX(cr2)] = (cr2 & 0xFFFFF000) | 7;
+            boot_page_dir[PAGE_DIR_INDEX(cr2)] = ((uint32_t)page_tab - KERNEL_VMA) | 7;
+        } else {
+            uint32_t *page_tab = (uint32_t *)(KERNEL_VMA + (boot_page_dir[PAGE_DIR_INDEX(cr2)] & 0xFFFFF000)); 
+            page_tab[PAGE_TAB_INDEX(cr2)] = (cr2 & 0xFFFFF000) | 7;
+        }
+    }
 }
 
 void sleep(int delay) {
@@ -100,12 +117,25 @@ void kernel(multiboot_info_t *info) {
     if (serial_port_init(COM1)) ctx.log_method = LOG_COM1;
     LOG("Kernel log being sent to COM1\n");
 
+    idt_init();
+
     ctx.multi_mmap = (multi_mmap_t *)(info->memmapaddress + KERNEL_VMA);
     ctx.multi_mmap_size = info->memmaplength;
     if (!mmap_init()) goto halt;
     LOG("%d bytes of RAM detected\nCreated a %d byte large physical memory map at 0x%08X\n", ctx.mmap_size*BLOCK_SIZE*8, ctx.mmap_size, (uint32_t)ctx.mmap);
 
-    idt_init();
+    rsdp_t *rsdp = acpi_find_rsdp();
+    if (!rsdp) goto halt;
+    if ((acpi_checksum(rsdp, sizeof(rsdp_t)) & 0xFF) != 0) goto halt;
+    LOG("RSDP found\n");
+
+    rsdt_t *rsdt = (rsdt_t *)(rsdp->RsdtAddress);
+    if (!rsdt) goto halt;
+    LOG("%08X\n", acpi_checksum(rsdt, rsdt->hdr.Length));
+    if (acpi_checksum(rsdt, sizeof(rsdt_t)) != 0) goto halt;
+    LOG("RSDT is valid\n");
+
+//    for (;;) {}
 
     pic_remap(PIC_1_START, PIC_2_START);
     ps2_init();