Re: execve(NULL, argv, envp) for nommu?

From: Rob Landley
Date: Fri Sep 08 2017 - 17:18:19 EST

On 09/05/2017 08:12 PM, Rob Landley wrote:
> On 09/05/2017 08:24 AM, Alan Cox wrote:
>>>> honoring the suid bit if people feel that way. I just wanna unblock
>>>> vfork() while still running this code.
>> Would it make more sense to have a way to promote your vfork into a
>> fork when you hit these cases (I appreciate that fork on NOMMU has a much
>> higher performance cost as you start having to softmmu copy or swap
>> pages).
> It's not the performance cost, it's rewriting all the pointers.
> Without address translation, copying the existing mappings to a new
> range requires finding and adjusting every pointer to the old data,
> which you can do for the executable mappings in PIE* binaries, but
> tracking down all the pointers on the stack, heap, and in your global
> variables? Flaming pain.
> Making fork() work on nommu is basically the same problem as making
> garbage collection work in C on mmu. Thus those of us who defend vfork()
> from the people who don't understand why it exists periodically
> suggesting we remove it.

So is exec(NULL, argv, envp) a reasonable thing to want?