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Message-ID: <172bdd35-e9b3-95ca-c1bc-58bd7894483b@redhat.com>
Date: Tue, 26 Jun 2018 17:55:40 -0700
From: Laura Abbott <labbott@...hat.com>
To: Kees Cook <keescook@...omium.org>
Cc: Alexander Popov <alex.popov@...ux.com>,
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Subject: Re: [PATCH v13 (resend) 2/6] x86/entry: Add STACKLEAK erasing the
kernel stack at the end of syscalls
On 06/26/2018 05:21 PM, Kees Cook wrote:
> On Tue, Jun 26, 2018 at 5:13 PM, Kees Cook <keescook@...omium.org> wrote:
>> The only arch-specific part is current_top_of_stack(), so it seems
>> like just solving current_top_of_stack() and copying on_thread_stack()
>> directly should work, yes? I would think sticking those directly into
>> asm/processor.h on arm64 would be okay?
>
> The difference in the earlier x86 and arm64 erase_kstack was:
>
> x86:
> if (on_thread_stack())
> boundary = current_stack_pointer;
> else
> boundary = current_top_of_stack();
>
> arm64:
> boundary = current_stack_pointer;
>
> If a sane current_top_of_stack() isn't possible on arm64, I'm not
> opposed to a small bit of arch-specific ifdef in there:
>
> boundary = get_stack_boundary();
>
> static inline unsigned long get_stack_boundary(void)
> {
> #ifdef CONFIG_X86
> if (!on_thread_stack())
> return current_top_of_stack();
> #else
> return current_stack_pointer;
> }
>
> -Kees
>
I _think_ I have reasonable implementations for both functions,
I was asking about pulling stuff out into a new header because
I wanted to see about reusing on_task_stack which was defined
in asm/stacktrace.h and I was concerned about include nightmares
with asm/processor.h . I'll see what I come up with.
Thanks,
Laura
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