Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 25 Oct 2022 09:53:27 -0700 | Subject | Re: [PATCH] x86/mm: Do not verify W^X at boot up |
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On Tue, Oct 25, 2022 at 3:16 AM Peter Zijlstra <peterz@infradead.org> wrote: > > This seems to boot...
This looks much better, thanks.
But this:
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c > @@ -801,8 +803,9 @@ void __init poking_init(void) > spinlock_t *ptl; > pte_t *ptep; > > - poking_mm = copy_init_mm(); > - BUG_ON(!poking_mm); > + __poking_mm = init_mm; > + mm_init(&__poking_mm, NULL, __poking_mm.user_ns); > + poking_mm = &__poking_mm;
Should probably be just
poking_mm = mm_alloc();
because we shouldn't be messing with 'mm_init()' in places like this, and we shouldn't be exporting it either:
> --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -1104,7 +1104,7 @@ static void mm_init_uprobes_state(struct mm_struct *mm) > #endif > } > > -static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, > +struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
since "mm_alloc()" would seem to be exactly what we need, and it's what execve() already uses. It creates a new VM with nothing attached, ready to be populated.
Or is there some reason why mm_alloc() doesn't work? It does require "current" and "current->user_ns" to be set up, but that should be true even during _very_ early boot.
Linus
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