Re: [PATCH bpf-next 1/3] mm/vmalloc: introduce vmalloc_exec which allocates RO+X memory

Song Liu
2022-07-13T21:21:47Z

> On Jul 13, 2022, at 1:26 PM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Wed, Jul 13, 2022 at 03:48:35PM +0000, Song Liu wrote:
>
>>> So how about instead we separate them? Then much of the problem goes
>>> away, you don't need to track these 2M chunks at all.
>>
>> If we manage the memory in < 2MiB granularity, either 4kB or smaller,
>> we still need some way to track which parts are being used, no? I mean
>> the bitmap.
>
> I was thinking the vmalloc vmap_area tree could help out there.

Interesting. vmap_area tree indeed keeps a lot of useful information.

Currently, powerpc supports CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC,
which leaves module_alloc just for module text. If this works, we get
separation between RO+X and RW memory. What would it take to enable
CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC for x86_64?

Thanks,
Song