Add Multiboot information struct and pass it in to kmain()

Print memory availability

src/Main.cc

@@ -1,8 +1,17 @@
+/* Main.cc
+ * vim: set tw=80:
+ * Eryn Wells <eryn@erynwells.me>
+ */
+/**
+ * Entry point for the kernel in C/C++.
+ */
+
 #include <stddef.h>
 #include <stdint.h>
 #include "Console.hh"
 #include "Descriptors.hh"
 #include "Interrupts.hh"
+#include "Multiboot.hh"
 
 #if defined(__linux__)
 #error "This file should be compiled with a cross-compiler, not the Linux system compiler!"
@@ -19,10 +28,7 @@ kearly()
 {
     using kernel::Console;
 
-    /*
-     * Create a console object for early use because global initialization
-     * hasn't happened yet.
-     */
+    // Create a console object for early use because global initialization hasn't happened yet.
     Console console;
     console.clear(kernel::Console::Color::Blue);
     console.printString("Loading system ...\n");
@@ -32,12 +38,19 @@ kearly()
 /** The beginning of the world... */
 extern "C"
 void
-kmain()
+kmain(multiboot::Information *information)
 {
+    multiboot::Information::setInformation(information);
+    auto info = multiboot::Information::information();
+
     // Reinitialize the system console now that we have global static objects.
     auto& console = kernel::Console::systemConsole();
     console.clear(kernel::Console::Color::Blue);
 
+    console.printString("Loading Polka ...\n");
+
+    console.printFormat("Detected memory: lower = %ld KB, upper = %ld KB\n", info->lowerMemoryKB(), info->upperMemoryKB());
+
     auto& gdt = x86::GDT::systemGDT();
     gdt.setNullDescriptor(0);
     gdt.setDescriptor(1, x86::GDT::DescriptorSpec::kernelSegment(0, 0xFFFFFFFF, x86::GDT::Type::CodeEXR));

src/Multiboot.cc

@@ -0,0 +1,87 @@
+/* Multiboot.cc
+ * vim: set tw=80:
+ * Eryn Wells <eryn@erynwells.me>
+ */
+/**
+ * Definition of multiboot stuff.
+ */
+
+#include "Multiboot.hh"
+
+namespace {
+
+enum Present {
+    Memory = 1 << 0,
+    BootDevice = 1 << 1,
+    CommandLine = 1 << 2,
+    Modules = 1 << 3,
+    AOutSymbols = 1 << 4,
+    ElfSymbols = 1 << 5,
+    MemoryMap = 1 << 6,
+    Drives = 1 << 7,
+    ConfigurationTable = 1 << 8,
+    BootLoaderName = 1 << 9,
+    APMTable = 1 << 10,
+    VBE = 1 << 11,
+};
+
+multiboot::Information *sInformation = 0;
+
+}
+
+namespace multiboot {
+
+/*
+ * Static
+ */
+
+const Information *
+Information::information()
+{
+    return sInformation;
+}
+
+
+void
+Information::setInformation(Information *info)
+{
+    sInformation = info;
+}
+
+/*
+ * Public
+ */
+
+uint32_t
+Information::lowerMemoryKB()
+    const
+{
+    if ((mFlags & Present::Memory) == 0) {
+        return 0;
+    }
+    return mMemLower;
+}
+
+
+uint32_t
+Information::upperMemoryKB()
+    const
+{
+    if ((mFlags & Present::Memory) == 0) {
+        return 0;
+    }
+    return mMemUpper;
+}
+
+
+const char *
+Information::commandLine()
+    const
+{
+    if ((mFlags & Present::CommandLine) == 0) {
+        return 0;
+    }
+    return reinterpret_cast<const char *>(mCommandLine);
+}
+    
+} /* namespace multiboot */

src/Multiboot.hh

@@ -0,0 +1,167 @@
+/* Multiboot.hh
+ * vim: set tw=80:
+ * Eryn Wells <eryn@erynwells.me>
+ */
+/**
+ * Definition of the Multiboot structure. When grub boots, it fills in this
+ * structure and leaves a pointer to it in the EBX register.
+ */
+
+#ifndef __MULTIBOOT_HH__
+#define __MULTIBOOT_HH__
+
+#include "stdint.h"
+#include "Attributes.hh"
+
+namespace multiboot {
+
+/**
+ * The multiboot information struct. Defined by the multiboot spec.
+ * See http://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Machine-state
+ */
+struct PACKED Information
+{
+    static const Information *information();
+    static void setInformation(Information* info);
+
+    uint32_t lowerMemoryKB() const;
+    uint32_t upperMemoryKB() const;
+    const char* commandLine() const;
+
+private:
+    /**
+     * Bit field of flags. Fields below are only defined if the appropriate
+     * flag is set.
+     */
+    uint32_t mFlags;
+
+    /** Amount of lower (0 to 1 MB) memory, in KB. */
+    uint32_t mMemLower;
+    /** Amount of upper (1 MB to ...) memory, in KB. Maximally, this value is the address of the first upper memory hole, minus 1 MB. */
+    uint32_t mMemUpper;
+
+    /**
+     * Indicates which BIOS disk the boot loader loaded the OS image from.
+     * Defined only if `bootDevice == true`.
+     */
+    struct PACKED
+    {
+        /** Third level partition number. If unused this is set to 0xFF. */
+        uint8_t partitionLevel3;
+        /** Sub-partition number. If unused this is set to 0xFF. */
+        uint8_t partitionLevel2;
+        /** Top-level partition number. */
+        uint8_t partitionLevel1;
+        /**
+         * BIOS drive number, as returned by the `INT 0x13` low-level disk
+         * interface.
+         */
+        uint8_t driveNumber;
+    } bootDevice;
+
+    /**
+     * Pointer to a C-style string containing the command line arguments.
+     * Defined only if `commandLinePresent == true`.
+     */
+    uint32_t mCommandLine;
+
+    /**
+     * Indicates what boot modules were loaded along with the kernel image.
+     * Defined only if `modulesPresent == true`.
+     */
+    struct PACKED
+    {
+        /** Number of boot modules present. */
+        uint32_t count;
+        /** Pointer to start of boot modules array. */
+        uint32_t address;
+    } modules;
+
+    // TODO: Document these.
+    union PACKED
+    {
+        struct PACKED
+        {
+            uint32_t tableSize;
+            uint32_t stringSize;
+            uint32_t address;
+            uint32_t reserved;
+        } aout;
+
+        struct PACKED
+        {
+            uint32_t number;
+            uint32_t size;
+            uint32_t address;
+            uint32_t shndx;
+        } elf;
+    } symbols;
+
+    /**
+     * Points to a buffer containing a memory map of the machine provided by the
+     * BIOS. Defined only if `memoryMapPresent == true`.
+     */
+    struct PACKED
+    {
+        /** Number of memory map entries present. */
+        uint32_t count;
+        /** Pointer to start of memory map entry array. */
+        uint32_t address;
+    } memoryMap;
+
+    /**
+     * Points to a buffer containing a list of drive definitions provided by the
+     * BIOS. Defined only if `drivesPresent == true`.
+     */
+    struct PACKED
+    {
+        /** Number of memory map entries present. */
+        uint32_t count;
+        /** Pointer to start of memory map entry array. */
+        uint32_t address;
+    } drives;
+
+    /**
+     * Pointer to the table containing APM information. Defined only if
+     * `apmTablePresent == true`.
+     */
+    uint32_t apmTable;
+
+    /**
+     * I dunno some VBE stuff. TODO.
+     */
+    struct PACKED {
+        uint32_t controlInformation;
+        uint32_t modeInformation;
+        uint32_t mode;
+        uint32_t interfaceSegment;
+        uint32_t interfaceOff;
+        uint32_t interfaceLength;
+    } vbe;
+};
+
+struct PACKED Module
+{
+    /** Start address of boot module. */
+    uint32_t start;
+    /** End address of boot module. */
+    uint32_t end;
+    /** Pointer to a C-style boot module string. */
+    uint32_t string;
+    /** Reserved and ignored. */
+    uint32_t reserved;
+};
+
+// TODO: Define the MemoryMap struct
+struct PACKED MemoryChunk
+{
+};
+
+// TODO: Define the Drive struct
+struct PACKED Drive
+{
+};
+
+} /* namespace multiboot */
+
+#endif /* __MULTIBOOT_HH__ */

src/boot.s

@@ -41,7 +41,8 @@ _start:
     # Global initialization done here.
     call _init
 
-    # Here we go...
+    # Here we go... Give kmain the address of the multiboot info structure.
+    pushl %ebx
     call kmain
 
     # In case the function returns, we'll want to put the computer into an