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even more fabulous exec

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This commit is contained in:
Robert Morris 2010-09-29 14:12:26 -04:00
parent 06feabecee
commit 2ea6c764c3
1 changed files with 8 additions and 19 deletions
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27
exec.c
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@ -81,30 +81,19 @@ exec(char *path, char **argv)
copyout(pgdir, sp, argv[i], strlen(argv[i]) + 1);
}
// push 0 for argv[argc]
sp -= 4;
int zero = 0;
copyout(pgdir, sp, &zero, 4);
#define PUSH(x) { int xx = (int)(x); sp -= 4; copyout(pgdir, sp, &xx, 4); }
PUSH(0); // argv[argc] is zero
// push argv[] elements
for(i = argc - 1; i >= 0; --i){
sp -= 4;
copyout(pgdir, sp, &strings[i], 4);
}
for(i = argc - 1; i >= 0; --i)
PUSH(strings[i]);
// push argv
uint argvaddr = sp;
sp -= 4;
copyout(pgdir, sp, &argvaddr, 4);
PUSH(sp); // argv
// push argc
sp -= 4;
copyout(pgdir, sp, &argc, 4);
PUSH(argc);
// push 0 in case main returns
sp -= 4;
uint ffffffff = 0xffffffff;
copyout(pgdir, sp, &ffffffff, 4);
PUSH(0xffffffff); // in case main tries to return
if(sp < sz - PGSIZE)
goto bad;