Re: [PATCH v4 07/17] x86/traps: Assert that we're in CONTEXT_KERNEL in exception entries

Borislav Petkov
2015-06-30T17:01:33Z

On Mon, Jun 29, 2015 at 12:33:39PM -0700, Andy Lutomirski wrote:
> Other than the super-atomic exception entries, all exception entries
> are supposed to switch our context tracking state to CONTEXT_KERNEL.
> Assert that they do. These assertions appear trivial at this point,
> as exception_enter is the function responsible for switching
> context, but I'm planning on reworking x86's exception context
> tracking, and these assertions will help make sure that all of this
> code keeps working.
>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/kernel/traps.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index f5791927aa64..2a783c4fe0e9 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -292,6 +292,8 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str,
> enum ctx_state prev_state = exception_enter();
> siginfo_t info;
>
> + CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
> +
> if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) !=
> NOTIFY_STOP) {
> conditional_sti(regs);
> @@ -376,6 +378,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
> siginfo_t *info;
>
> prev_state = exception_enter();
> + CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
> if (notify_die(DIE_TRAP, "bounds", regs, error_code,
> X86_TRAP_BR, SIGSEGV) == NOTIFY_STOP)
> goto exit;
> @@ -457,6 +460,7 @@ do_general_protection(struct pt_regs *regs, long error_code)
> enum ctx_state prev_state;
>
> prev_state = exception_enter();
> + CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
> conditional_sti(regs);
>
> if (v8086_mode(regs)) {
> @@ -514,6 +518,7 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
> return;
>
> prev_state = ist_enter(regs);
> + CT_WARN_ON(ct_state() != CONTEXT_KERNEL);

Yeah, so any chance those assertions can be moved at the end of both
ist_enter() and exception_enter()?

Yeah, I read above that you're planning to rework it but it is cleaner
to have them at the end of the _enter() functions instead in all those
trap handlers, no...?

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
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