Re: [RFC V2] mm: Generalize notify_page_fault()

On 06/05/2019 03:23 AM, Matthew Wilcox wrote:

On Tue, Jun 04, 2019 at 12:04:06PM +0530, Anshuman Khandual wrote:

quoted

+++ b/arch/x86/mm/fault.c

@@ -46,23 +46,6 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr)
 	return 0;
 }
 
-static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
-{

...

quoted

-}

quoted

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0e8834a..c5a8dcf 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -1778,6 +1778,7 @@ static inline int pte_devmap(pte_t pte)
 }
 #endif
 
+int notify_page_fault(struct pt_regs *regs, unsigned int trap);

Why is it now out-of-line?  

Did not get it. AFAICS it is the same from last version and does not cross
80 characters limit on that line.

quoted

+++ b/mm/memory.c
+int __kprobes notify_page_fault(struct pt_regs *regs, unsigned int trap)
+{
+	int ret = 0;
+
+	/*
+	 * To be potentially processing a kprobe fault and to be allowed
+	 * to call kprobe_running(), we have to be non-preemptible.
+	 */
+	if (kprobes_built_in() && !preemptible() && !user_mode(regs)) {
+		if (kprobe_running() && kprobe_fault_handler(regs, trap))
+			ret = 1;
+	}
+	return ret;
+}
+

I would argue this should be in kprobes.h as a static nokprobe_inline.

We can do that. Though it will be a stand alone (not inside #ifdef) as it
already takes care of CONFIG_KPROBES via kprobes_built_in(). Will change
it and in which case the above declaration in mm.h would not be required.