On 05/30/2019 04:36 PM, Matthew Wilcox wrote:
On Thu, May 30, 2019 at 11:25:13AM +0530, Anshuman Khandual wrote:
quoted
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".
You are right. Noted for future. Thanks !
quoted
@@ -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?
Here it expects context to be already non-preemptible where as the proposed
generic function makes it non-preemptible with a preempt_[disable|enable]()
pair for the required code section, irrespective of it's present state. Is
not this better ?