/* * User mode context * Copyright (c) 2001,2003,2004 David H. Hovemeyer <daveho@cs.umd.edu> * Copyright (c) 2003, Jeffrey K. Hollingsworth <hollings@cs.umd.edu> * $Revision: 1.42 $ *  * This is free software.  You are permitted to use, * redistribute, and modify it as specified in the file "COPYING". */#ifndef GEEKOS_USER_H#define GEEKOS_USER_H#include <geekos/ktypes.h>#include <geekos/segment.h>#include <geekos/elf.h>#include <geekos/paging.h>struct File;/* Number of files user process can have open. */#define USER_MAX_FILES		10/* * A user mode context which can be attached to a Kernel_Thread, * to allow it to execute in user mode (ring 3).  This struct * has all information needed to create and manage a user * memory space, as well as other kernel resources used by * the process (such as semaphores and files). */struct User_Context {    /* We need one LDT entry each for user code and data segments. */#define NUM_USER_LDT_ENTRIES 2    /*     * Each user context contains a local descriptor table with     * just enough room for one code and one data segment     * describing the process's memory.     */    struct Segment_Descriptor ldt[NUM_USER_LDT_ENTRIES];    struct Segment_Descriptor* ldtDescriptor;    /* The memory space used by the process. */    char* memory;    ulong_t size;    /* Selector for the LDT's descriptor in the GDT */    ushort_t ldtSelector;    /*     * Selectors for the user context's code and data segments     * (which reside in its LDT)     */    ushort_t csSelector;    ushort_t dsSelector;    /* Page directory for user address space. */    pde_t *pageDir;    /* Code entry point */    ulong_t entryAddr;    /* Address of argument block in user memory */    ulong_t argBlockAddr;    /* Initial stack pointer */    ulong_t stackPointerAddr;    /*     * May use this in future to allow multiple threads     * in the same user context     */    int refCount;#if 0    int *semaphores;#endif};struct Kernel_Thread;struct Interrupt_State;/* * Common routines: these are in user.c */void Attach_User_Context(struct Kernel_Thread* kthread, struct User_Context* context);void Detach_User_Context(struct Kernel_Thread* kthread);int Spawn(const char *program, const char *command, struct Kernel_Thread **pThread);void Switch_To_User_Context(struct Kernel_Thread* kthread, struct Interrupt_State* state);/* * Implementation routines: these are in userseg.c or uservm.c */void Destroy_User_Context(struct User_Context* context);int Load_User_Program(char *exeFileData, ulong_t exeFileLength,    struct Exe_Format *exeFormat, const char *command,    struct User_Context **pUserContext);bool Copy_From_User(void* destInKernel, ulong_t srcInUser, ulong_t bufSize);bool Copy_To_User(ulong_t destInUser, void* srcInKernel, ulong_t bufSize);void Switch_To_Address_Space(struct User_Context *userContext);#endif  /* GEEKOS_USER_H */