Date: Wed, 25 Oct 1995 14:43:02 -0400 (EDT) From: "Ron G. Minnich" <rminnich@Sarnoff.COM> To: Theo de Raadt <deraadt@theos.com>, hackers@freebsd.org Subject: anatomy of rfork, part 1: minherit Message-ID: <Pine.SUN.3.91.951025143802.28686A-100000@terra>
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i've had enough q's on this, and time is tight, so i thought i'd just put
out a few messages on how to do rfork. The code is small, so bear with
me.
To do rfork as i needed it, you really need two parts to start with: a
way to share data after fork and a way to share file tables after fork.
AIX/370 implemented DCE threads with these two things. I thought i'd show
minherit first. I don't know the plan9 environment erasing stuff,
although that is pretty easy to add -- could be useful.
minherit is shown below. Calls are much like mprotect:
minherit(caddr, len, new inherit values)
Look in vm/vm_inherit.h
All you need to do is take the mprotect call code and redo it just a bit
so it calls vm_map_inherit. Here we go:
struct mprotect_args {
caddr_t addr;
int len;
int inherit;
};
int
minherit(p, uap, retval)
struct proc *p;
struct mprotect_args *uap;
int *retval;
{
vm_offset_t addr;
vm_size_t size;
register vm_inherit_t inherit;
#ifdef DEBUG
printf("minherit(%d): addr %x len %x prot %d\n",
p->p_pid, uap->addr, uap->len, uap->inherit);
#endif
addr = (vm_offset_t)uap->addr;
if ((addr & PAGE_MASK) || uap->len < 0)
return(EINVAL);
size = (vm_size_t)uap->len;
inherit = uap->inherit;
switch (vm_map_inherit(&p->p_vmspace->vm_map, addr, addr+size,
inherit)) {
case KERN_SUCCESS:
#ifdef DEBUG
printf("works\n");
#endif
return (0);
case KERN_PROTECTION_FAILURE:
#ifdef DEBUG
printf("fails\n");
#endif
return (EACCES);
}
#ifdef DEBUG
printf("return einval\n");
#endif
return (EINVAL);
}
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