Re: [3/4] Jumper Probes patch to provide function arguments

[Andi Kleen <ak@muc.de>]

Prasanna S Panchamukhi <prasanna@in.ibm.com> writes:

+void jprobe_return(void)
+{
+	preempt_enable_no_resched();
+	asm volatile ("       xchgl   %%ebx,%%esp     \n"
+		      "       int3			\n"::"b"
+		      (jprobe_saved_esp):"memory");
+}

whatever the preempt disable is protecting against, why isn't it a 
problem during the xchgl ? 

> +#define MAX_STACK_SIZE 64
> +#define MIN_STACK_SIZE(ADDR) ((((ADDR) + MAX_STACK_SIZE) <  \
> +	(((ADDR) & PAGE_MASK) + PAGE_SIZE) ? ((ADDR) + MAX_STACK_SIZE) \
> +	: (((ADDR) & PAGE_MASK) + PAGE_SIZE )) - (ADDR))

What is this macro doing exactly? 

If it is an attempt to not read beyond the kernel stack top  i think
it is wrong. It will also randomly fail on 8k stacks at top-4K 

Use something like

max_t(unsigned long,MAX_STACK_SIZE, current_thread_info() + THREAD_SIZE - addr)


The rest looks ok.

-Andi