On Thu, May 30, 2019 at 11:25:13AM +0530, Anshuman Khandual wrote:
> Similar notify_page_fault() definitions are being used by architectures
> duplicating much of the same code. This attempts to unify them into a
> single implementation, generalize it and then move it to a common place.
> kprobes_built_in() can detect CONFIG_KPROBES, hence notify_page_fault()
> must not be wrapped again within CONFIG_KPROBES. Trap number argument can
This is a funny quirk of the English language. "must not" means "is not
allowed to be", not "does not have to be".
> @@ -141,6 +142,19 @@ static int __init init_zero_pfn(void)
> core_initcall(init_zero_pfn);
>
>
> +int __kprobes notify_page_fault(struct pt_regs *regs, unsigned int trap)
> +{
> + int ret = 0;
> +
> + if (kprobes_built_in() && !user_mode(regs)) {
> + preempt_disable();
> + if (kprobe_running() && kprobe_fault_handler(regs, trap))
> + ret = 1;
> + preempt_enable();
> + }
> + return ret;
> +}
> +
> #if defined(SPLIT_RSS_COUNTING)
Comparing this to the canonical implementation (ie x86), it looks similar.
static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
{
if (!kprobes_built_in())
return 0;
if (user_mode(regs))
return 0;
/*
* To be potentially processing a kprobe fault and to be allowed to call
* kprobe_running(), we have to be non-preemptible.
*/
if (preemptible())
return 0;
if (!kprobe_running())
return 0;
return kprobe_fault_handler(regs, X86_TRAP_PF);
}
The two handle preemption differently. Why is x86 wrong and this one
correct?
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