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mem.c File Reference

Low level (i386) memory manager. More...

#include <const.h>
#include <arch/i386.h>
#include <arch/paging.h>
#include <kernel/console.h>
#include <kernel/kernel.h>
#include <kernel/task.h>
#include <arch/mem.h>

Go to the source code of this file.

Functions
word	setup_GDT_entry (word limit, dword base, byte attribs0_7, byte attribs8_15)
	Initialize a GDT entry. Parameters: limit  The size of the memory segment. base  The starting linear address of the memory segment. attribs0_7  The first 8-bit of the segment descriptor attributes. attribs8_15  The last 8-bit of the segment descriptor attributes. Returns: The selector of the new GDT entry.
void	remove_GDT_entry (word sel)
	Remove a GDT entry. Parameters: sel  The selector to remove from the GDT.
void	install_GDT ()
	Initialize the Global Descriptor Table with the default selectors and update the segment registers.
Variables
volatile gdt_entry_t	gdt [GDT_DIM]
	Global Descriptor Table (GDT).
gdt_reg	gdt_ptr
	GDT pointer.

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Detailed Description

Low level (i386) memory manager.

Author:

Andrea Righi <drizzt@inwind.it>

Date:

Last update: 2004-01-20

Note:

Copyright (©) 2003 Andrea Righi

For a complete documentation about GDT and descriptors you can see the "IA-32 Intel® Architecture Software Developer's Manual - Volume 3: System Programming Guide" (http://www.intel.com/design/pentium4/manuals).
For an intalian documentation you can download the "Minirighi32 - Documentazione Ufficiale" (http://sourceforge.net/project/showfiles.php?group_id=80923&release_id=180542).

Definition in file mem.c.

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Function Documentation

void install_GDT (    )

Initialize the Global Descriptor Table with the default selectors and update the segment registers. Definition at line 93 of file mem.c. { // First of all reset all entries in the GDT // memset(&gdt, 0, sizeof(gdt)); // ------------- Reserved entries in the GDT ------------------ // // Dummy descriptor// setup_GDT_entry(0, 0, 0, 0); // KERNEL_DATA descriptor 0x08 // setup_GDT_entry(0xFFFF, 0, DATA_SEG, (ATTR_GRANUL | ATTR_32BIT | 0xF)); // KERNEL_CODE descriptor 0x10 // setup_GDT_entry(0xFFFF, 0, CODE_SEG, (ATTR_GRANUL | ATTR_32BIT | 0xF)); // USER_DATA descriptor 0x18 // setup_GDT_entry(0xFFFF, 0, (DATA_SEG | DPL_3), (ATTR_GRANUL | ATTR_32BIT | 0xF)); // USER_CODE descriptor 0x20 // setup_GDT_entry(0xFFFF, 0, (CODE_SEG | DPL_3), (ATTR_GRANUL | ATTR_32BIT | 0xF)); // --------- End of reserved entries in the GDT --------------- // // Set up the GDT pointer // gdt_ptr.limit = (uint16_t)(GDT_DIM * GDT_ENTRY_DIM - 1); gdt_ptr.base = (size_t)gdt; // Load info into GDTR // __asm__ __volatile__ ("lgdtl (%0)" : : "r"(&gdt_ptr)); // Update segment registers // k_update_segment_regs(); }

void remove_GDT_entry (  word    sel )

Remove a GDT entry. Parameters: sel  The selector to remove from the GDT. Definition at line 74 of file mem.c. { dword IF = GET_IF(); disable(); gdt[sel/GDT_ENTRY_DIM].limit = 0; gdt[sel/GDT_ENTRY_DIM].base0_15 = 0; gdt[sel/GDT_ENTRY_DIM].base16_23 = 0; gdt[sel/GDT_ENTRY_DIM].base24_31 = 0; gdt[sel/GDT_ENTRY_DIM].attribs0_7 = 0; gdt[sel/GDT_ENTRY_DIM].attribs8_15 = 0; SET_IF(IF); }

word setup_GDT_entry (  word    limit, dword    base, byte    attribs0_7, byte    attribs8_15 )

Initialize a GDT entry. Parameters: limit  The size of the memory segment. base  The starting linear address of the memory segment. attribs0_7  The first 8-bit of the segment descriptor attributes. attribs8_15  The last 8-bit of the segment descriptor attributes. Returns: The selector of the new GDT entry. Definition at line 44 of file mem.c. { // Skip the dummy entry (#0). register unsigned short i=1; dword IF = GET_IF(); disable(); for (; i<GDT_DIM; i++) { if (!(gdt[i].limit)) { gdt[i].limit = limit; gdt[i].base0_15 = base & 0xFFFF; gdt[i].base16_23 = (base >> 16) & 0xFF; gdt[i].base24_31 = (base >> 24) & 0xFF; gdt[i].attribs0_7 = attribs0_7; gdt[i].attribs8_15 = attribs8_15; SET_IF(IF); // Return the selector. return(i * GDT_ENTRY_DIM); } } error("Out of GDT entries!"); return( NULL ); }

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Variable Documentation

volatile gdt_entry_t gdt[GDT_DIM]

Global Descriptor Table (GDT). Definition at line 31 of file mem.c.

gdt_reg gdt_ptr [static]

GDT pointer. Definition at line 33 of file mem.c.

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