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exec.c
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exec.c
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#include "types.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "x86.h"
#include "elf.h"
int
exec(char *path, char **argv)
{
// TASK 1-2: Store father process data in case of unsuccessful exec
int num_pg_in_mem = proc->num_pages_in_phys_mem;
int num_pg_file = proc->num_pages_in_file;
int pg_faults = proc->number_of_pgFLTS;
int paging_out_times = proc->number_of_paging_out_times;
uint pgIndex;
struct page_in_mem * tmp;
struct page_in_mem pages_array[MAX_TOTAL_PAGES];
struct page_in_mem * listHead;
char *s, *last;
int i, off;
uint argc, sz, sp, ustack[3+MAXARG+1];
struct elfhdr elf;
struct inode *ip;
struct proghdr ph;
pde_t *pgdir, *oldpgdir;
begin_op();
if((ip = namei(path)) == 0){
end_op();
return -1;
}
ilock(ip);
pgdir = 0;
// Check ELF header
if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))
goto bad;
if(elf.magic != ELF_MAGIC)
goto bad;
if((pgdir = setupkvm()) == 0)
goto bad;
// TASK 1-2: case of exec, (forking from shell), we'll want to initialize pages data in a different manner:
if (SELECTION != NONE)
{
// Store page, next and prev data of father process pages array
for(int i = 0; i < MAX_TOTAL_PAGES; i++)
{
pages_array[i].pg = proc->paging_meta_data[i].pg;
if (proc->paging_meta_data[i].prev != 0)
{
tmp = proc->paging_meta_data[i].prev;
pgIndex = tmp->pg.pages_array_index;
pages_array[i].prev = &pages_array[pgIndex];
}
if (proc->paging_meta_data[i].next != 0)
{
tmp = proc->paging_meta_data[i].next;
pgIndex = tmp->pg.pages_array_index;
pages_array[i].next = &pages_array[pgIndex];
}
}
// Store pointer to header of physical memory list of father process
if (proc->mem_pages_head != 0)
{
tmp = proc->mem_pages_head;
pgIndex = tmp->pg.pages_array_index;
listHead = &pages_array[pgIndex];
}
// Reset the father's pages data in case of success (will store in case of failure)
resetProcessPagesData(proc);
}
// Load program into memory.
sz = 0;
for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph))
goto bad;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.memsz < ph.filesz)
goto bad;
if((sz = allocuvm(pgdir, sz, ph.vaddr + ph.memsz)) == 0)
goto bad;
if(loaduvm(pgdir, (char*)ph.vaddr, ip, ph.off, ph.filesz) < 0)
goto bad;
}
iunlockput(ip);
end_op();
ip = 0;
// Allocate two pages at the next page boundary.
// Make the first inaccessible. Use the second as the user stack.
sz = PGROUNDUP(sz);
if((sz = allocuvm(pgdir, sz, sz + 2*PGSIZE)) == 0)
goto bad;
clearpteu(pgdir, (char*)(sz - 2*PGSIZE));
sp = sz;
// Push argument strings, prepare rest of stack in ustack.
for(argc = 0; argv[argc]; argc++) {
if(argc >= MAXARG)
goto bad;
sp = (sp - (strlen(argv[argc]) + 1)) & ~3;
if(copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
goto bad;
ustack[3+argc] = sp;
}
ustack[3+argc] = 0;
ustack[0] = 0xffffffff; // fake return PC
ustack[1] = argc;
ustack[2] = sp - (argc+1)*4; // argv pointer
sp -= (3+argc+1) * 4;
if(copyout(pgdir, sp, ustack, (3+argc+1)*4) < 0)
goto bad;
// Save program name for debugging.
for(last=s=path; *s; s++)
if(*s == '/')
last = s+1;
safestrcpy(proc->name, last, sizeof(proc->name));
// Commit to the user image.
oldpgdir = proc->pgdir;
proc->pgdir = pgdir;
proc->sz = sz;
proc->tf->eip = elf.entry; // main
proc->tf->esp = sp;
// TASK 1-2: If a swap file has been created in father process, remove it and create a new one, since the former is irrelevant
if (SELECTION != NONE)
{
if (proc->swapFile != 0)
{
removeSwapFile(proc);
createSwapFile(proc);
}
}
switchuvm(proc);
freevm(oldpgdir);
return 0;
bad:
if(pgdir)
freevm(pgdir);
if(ip){
iunlockput(ip);
end_op();
}
// TASK 3: If unsuccesful exec --> restore old data
if (SELECTION != NONE)
{
proc->num_pages_in_phys_mem = num_pg_in_mem;
proc->num_pages_in_file = num_pg_file;
proc->number_of_pgFLTS = pg_faults;
proc->number_of_paging_out_times = paging_out_times;
proc->mem_pages_head = listHead;
for (i = 0; i < MAX_PSYC_PAGES; i++) {
proc->paging_meta_data[i].pg = pages_array[i].pg;
if (pages_array[i].prev != 0)
{
tmp = pages_array[i].prev;
pgIndex = tmp->pg.pages_array_index;
proc->paging_meta_data[i].prev = &proc->paging_meta_data[pgIndex];
}
if (pages_array[i].next != 0)
{
tmp = pages_array[i].next;
pgIndex = tmp->pg.pages_array_index;
proc->paging_meta_data[i].next = &proc->paging_meta_data[pgIndex];
}
}
// Set pointer to header of physical memory list in child process
if (proc->mem_pages_head != 0)
{
tmp = proc->mem_pages_head;
pgIndex = tmp->pg.pages_array_index;
proc->mem_pages_head = &proc->paging_meta_data[pgIndex];
}
}
return -1;
}