Re: [PATCH RFC] kprobes: Remove MODULES dependency

Jarkko Sakkinen
2020-07-13T05:50:11Z

On Fri, Jul 10, 2020 at 01:32:38PM +0200, Peter Zijlstra wrote:
> On Fri, Jul 10, 2020 at 07:32:57PM +0900, Masami Hiramatsu wrote:
> > > - page = module_alloc(PAGE_SIZE);
> > > + page = vmalloc(PAGE_SIZE);
> >
> > No, you can not use vmalloc here. The reason why we use module_alloc()
> > is to allocate the executable memory for trampoline code.
> > So, you need to use vmalloc_exec() instead.
>
> vmalloc_exec() would be broken too, also hch recently got rid of that
> thing.
>
> module_alloc() really is the only sane choice here.
>
> We should make module_alloc() unconditionally available, and maybe even
> rename it to text_alloc().

Thanks for the remarks.

The current module_alloc looks like this:

void * __weak module_alloc(unsigned long size)
{
return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
GFP_KERNEL, PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS,
NUMA_NO_NODE, __builtin_return_address(0));
}

What if I create inline functions for text_alloc() and text_memfree() and
convert this function as:

void * __weak module_alloc(unsigned long size)
{
return text_alloc(size);
}

/Jarkko