SETGATE（idt[i],0,GD_KTEXT,__vectors[i],DPL_KERNEL）;
}
SETGATE（idt[T_SYSCALL],1,GD_KTEXT,__vectors[T_SYSCALL],DPL_USER）;
lidt（&idt_pd）;
Kern/process/proc.c:
staticstructproc_struct*
alloc_proc（void）{
structproc_struct*proc=kmalloc（sizeof（structproc_struct））;
if（proc!
=NULL）{
//LAB4:
EXERCISE1YOURCODE
/*
*belowfieldsinproc_structneedtobeinitialized
*enumproc_statestate;//Processstate
*intpid;//ProcessID
*intruns;//therunningtimesofProces
*uintptr_tkstack;//Processkernelstack
*volatileboolneed_resched;//boolvalue:
needtoberescheduledtoreleaseCPU?
*structproc_struct*parent;//theparentprocess
*structmm_struct*mm;//Process'smemorymanagementfield
*structcontextcontext;//Switchheretorunprocess
*structtrapframe*tf;//Trapframeforcurrentinterrupt
*uintptr_tcr3;//CR3register:
thebaseaddrofPageDirectroyTable（PDT）
*uint32_tflags;//Processflag
*charname[PROC_NAME_LEN+1];//Processname
*/
proc->state=PROC_UNINIT;
proc->pid=-1;
proc->runs=0;
proc->kstack=0;
proc->need_resched=0;
proc->parent=NULL;
proc->mm=NULL;
memset（&（proc->context）,0,sizeof（structcontext））;
proc->tf=NULL;
proc->cr3=boot_cr3;
proc->flags=0;
memset（proc->name,0,PROC_NAME_LEN）;
//LAB5YOURCODE:
（updateLAB4steps）
/*
*belowfields（addinLAB5）inproc_structneedtobeinitialized
*uint32_twait_state;//waitingstate
*structproc_struct*cptr,*yptr,*optr;//relationsbetweenprocesses
*/
proc->wait_state=0;
proc->cptr=proc->yptr=proc->optr=NULL;
}
returnproc;
}
int
do_fork（uint32_tclone_flags,uintptr_tstack,structtrapframe*tf）{
intret=-E_NO_FREE_PROC;
structproc_struct*proc;
if（nr_process>=MAX_PROCESS）{
gotofork_out;
}
ret=-E_NO_MEM;
//LAB4:
EXERCISE2YOURCODE
/*
*SomeUsefulMACROs,FunctionsandDEFINEs,youcanusetheminbelowimplementation.
*MACROsorFunctions:
*alloc_proc:
createaprocstructandinitfields（lab4:
exercise1）
*setup_kstack:
allocpageswithsizeKSTACKPAGEasprocesskernelstack
*copy_mm:
process"proc"duplicateORshareprocess"current"'smmaccordingclone_flags
*ifclone_flags&CLONE_VM,then"share";else"duplicate"
*copy_thread:
setupthetrapframeontheprocess'skernelstacktopand
*setupthekernelentrypointandstackofprocess
*hash_proc:
addprocintoprochash_list
*get_pid:
allocauniquepidforprocess
*wakup_proc:
setproc->state=PROC_RUNNABLE
*VARIABLES:
*proc_list:
theprocessset'slist
*nr_process:
thenumberofprocessset
*/
//1.callalloc_proctoallocateaproc_struct
//2.callsetup_kstacktoallocateakernelstackforchildprocess
//3.callcopy_mmtodupORsharemmaccordingclone_flag
//4.callcopy_threadtosetuptf&contextinproc_struct
//5.insertproc_structintohash_list&&proc_list
//6.callwakup_proctomakethenewchildprocessRUNNABLE
//7.setretvauleusingchildproc'spid
if（（proc=alloc_proc（））==NULL）{
gotofork_out;
}
proc->parent=current;
assert（current->wait_state==0）;
if（setup_kstack（proc）!
=0）{
gotobad_fork_cleanup_proc;
}
if（copy_mm（clone_flags,proc）!
=0）{
gotobad_fork_cleanup_kstack;
}
copy_thread（proc,stack,tf）;
boolintr_flag;
local_intr_save（intr_flag）;
{
proc->pid=get_pid（）;
hash_proc（proc）;
set_links（proc）;
}
local_intr_restore（intr_flag）;
wakeup_proc（proc）;
ret=proc->pid;
//LAB5YOURCODE:
（updateLAB4steps）
/*SomeFunctions
*set_links:
settherelationlinksofprocess.ALSOSEE:
remove_links:
leantherelationlinksofprocess
*-------------------
*updatestep1:
setchildproc'sparenttocurrentprocess,makesurecurrentprocess'swait_stateis0
*updatestep5:
insertproc_structintohash_list&&proc_list,settherelationlinksofprocess
*/
fork_out:
returnret;
bad_fork_cleanup_kstack:
put_kstack（proc）;
bad_fork_cleanup_proc:
kfree（proc）;
gotofork_out;
}
练习1：
加载应用程序并执行
do_execv函数调用load_icode（位于kern/process/proc.c中）来加载并解析一个处于内存中的ELF执行文件格式的应用程序，建立相应的用户内存空间来放置应用程序的代码段、数据段等，且要设置好proc_struct结构中的成员变量trapframe中的内容，确保在执行此进程后，能够从应用程序设定的起始执行地址开始执行。
需设置正确的trapframe内容。
程序代码：
staticintload_icode（unsignedchar*binary,size_tsize）{
if（current->mm!
=NULL）{
panic（"load_icode:
current->mmmustbeempty.\n"）;
}
intret=-E_NO_MEM;
structmm_struct*mm;
//为当前进程申请内存
if（（mm=mm_create（））==NULL）{
gotobad_mm;
}
//建立一个新的PDT,设置mm->pgdir为PDT的内核虚拟地址
if（setup_pgdir（mm）!
=0）{
gotobad_pgdir_cleanup_mm;
}
//复制上下文和数据部分,建立二进制程序的BSS段
structPage*page;
//getthefileheaderofthebianryprogram（ELFformat）
structelfhdr*elf=（structelfhdr*）binary;
//gettheentryoftheprogramsectionheadersofthebianryprogram（ELFformat）
structproghdr*ph=（structproghdr*）（binary+elf->e_phoff）;
//Thisprogramisvalid?
if（elf->e_magic!
=ELF_MAGIC）{
ret=-E_INVAL_ELF;
gotobad_elf_cleanup_pgdir;
}
uint32_tvm_flags,perm;
structproghdr*ph_end=ph+elf->e_phnum;
for（;ph//findeveryprogramsectionheaders
if（ph->p_type!
=ELF_PT_LOAD）{
continue;
}
if（ph->p_filesz>ph->p_memsz）{
ret=-E_INVAL_ELF;
gotobad_cleanup_mmap;
}
if（ph->p_filesz==0）{
continue;
}
//callmm_mapfuntosetupthenewvma（ph->p_va,ph->p_memsz）
vm_flags=0,perm=PTE_U;
if（ph->p_flags&ELF_PF_X）vm_flags|=VM_EXEC;
if（ph->p_flags&ELF_PF_W）vm_flags|=VM_WRITE;
if（ph->p_flags&ELF_PF_R）vm_flags|=VM_READ;
if（vm_flags&VM_WRITE）perm|=PTE_W;
if（（ret=mm_map（mm,ph->p_va,ph->p_memsz,vm_flags,NULL））!
=0）{
gotobad_cleanup_mmap;
}
unsignedchar*from=binary+ph->p_offset;
size_toff,size;
uintptr_tstart=ph->p_va,end,la=ROUNDDOWN（start,PGSIZE）;
ret=-E_NO_MEM;
//allocmemory,andcopythecontentsofeveryprogramsection（from,from+end）toprocess'smemory（la,la+end）
end=ph->p_va+ph->p_filesz;
//copyTEXT/DATAsectionofbianryprogram
while（startif（（page=pgdir_alloc_page（mm->pgdir,la,perm））==NULL）{
gotobad_cleanup_mmap;
}
off=start-la,size=PGSIZE-off,la+=PGSIZE;
if（endsize-=la-end;
}
memcpy（page2kva（page）+off,from,size）;
start+=size,from+=size;
}
//buildBSSsectionofbinaryprogram
end=ph->p_va+ph->p_memsz;
if（start/*ph->p_memsz==ph->p_filesz*/
if（start==end）{
continue;
}
off=start+PGSIZE-la,size=PGSIZE-off;
if（endsize-=la-end;
}
memset（page2kva（page）+off,0,size）;
start+=size;
assert（（end=la&&start==la））;
}
while（startif（（page=pgdir_alloc_page（mm->pgdir,la,perm））==NULL）{
gotobad_cleanup_mmap;
}
off=start-la,size=PGSIZE-off,la+=PGSIZE;
if（endsize-=la-end;
}
memset（page2kva（page）+off,0,size）;
start+=size;
}
}
//设置用户堆栈内存
vm_flags=VM_READ|VM_WRITE|VM_STACK;
if（（ret=mm_map（mm,USTACKTOP-USTACKSIZE,USTACKSIZE,vm_flags,NULL））!
=0）{
gotobad_cleanup_mmap;
}
assert（pgdir_alloc_page（mm->pgdir,USTACKTOP-PGSIZE,PTE_USER）!
=NULL）;
assert（pgdir_alloc_page（mm->pgdir,USTACKTOP-2*PGSIZE,PTE_USER）!
=NULL）;
assert（pgdir_alloc_page（mm->pgdir,USTACKTOP-3*PGSIZE,PTE_USER）!
=
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