1a81e38b17
Variable declarations at top of function,
separate from initialization.
Use == 0 instead of ! for checking pointers.
Consistent spacing around {, *, casts.
Declare 0-parameter functions as (void) not ().
Integer valued functions return -1 on failure, 0 on success.
127 lines
2.7 KiB
C
127 lines
2.7 KiB
C
#include "types.h"
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#include "param.h"
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#include "mmu.h"
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#include "proc.h"
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#include "defs.h"
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#include "x86.h"
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#include "elf.h"
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int
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exec(char *path, char **argv)
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{
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char *s, *last;
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int i, off, argc;
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uint sz, sp, strings[MAXARG];
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struct elfhdr elf;
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struct inode *ip;
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struct proghdr ph;
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pde_t *pgdir, *oldpgdir;
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if((ip = namei(path)) == 0)
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return -1;
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ilock(ip);
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pgdir = 0;
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// Check ELF header
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if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))
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goto bad;
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if(elf.magic != ELF_MAGIC)
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goto bad;
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if((pgdir = setupkvm()) == 0)
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goto bad;
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// Load program into memory.
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sz = 0;
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for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
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if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph))
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goto bad;
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if(ph.type != ELF_PROG_LOAD)
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continue;
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if(ph.memsz < ph.filesz)
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goto bad;
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if((sz = allocuvm(pgdir, sz, ph.va + ph.memsz)) == 0)
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goto bad;
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if(loaduvm(pgdir, (char*)ph.va, ip, ph.offset, ph.filesz) < 0)
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goto bad;
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}
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iunlockput(ip);
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ip = 0;
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// Allocate a one-page stack at the next page boundary
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sz = PGROUNDUP(sz);
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if((sz = allocuvm(pgdir, sz, sz + PGSIZE)) == 0)
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goto bad;
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// initialize stack content:
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// "argumentN" -- nul-terminated string
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// ...
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// "argument0"
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// 0 -- argv[argc]
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// address of argumentN
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// ...
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// address of argument0 -- argv[0]
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// address of address of argument0 -- argv argument to main()
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// argc -- argc argument to main()
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// ffffffff -- return PC for main() call
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sp = sz;
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// count arguments
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for(argc = 0; argv[argc]; argc++)
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;
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if(argc >= MAXARG)
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goto bad;
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// push strings and remember where they are
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for(i = argc - 1; i >= 0; --i){
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sp -= strlen(argv[i]) + 1;
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strings[i] = sp;
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copyout(pgdir, sp, argv[i], strlen(argv[i]) + 1);
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}
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#define PUSH(x){ int xx = (int)(x); sp -= 4; copyout(pgdir, sp, &xx, 4); }
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PUSH(0); // argv[argc] is zero
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// push argv[] elements
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for(i = argc - 1; i >= 0; --i)
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PUSH(strings[i]);
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PUSH(sp); // argv
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PUSH(argc);
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PUSH(0xffffffff); // in case main tries to return
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if(sp < sz - PGSIZE)
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goto bad;
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// Save program name for debugging.
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for(last=s=path; *s; s++)
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if(*s == '/')
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last = s+1;
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safestrcpy(proc->name, last, sizeof(proc->name));
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// Commit to the user image.
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oldpgdir = proc->pgdir;
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proc->pgdir = pgdir;
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proc->sz = sz;
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proc->tf->eip = elf.entry; // main
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proc->tf->esp = sp;
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switchuvm(proc);
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freevm(oldpgdir);
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return 0;
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bad:
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if(pgdir)
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freevm(pgdir);
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if(ip)
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iunlockput(ip);
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return -1;
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}
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