From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "kent.overstreet@linux.dev" <kent.overstreet@linux.dev>
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Subject: Re: [PATCH 12/13] x86/jitalloc: prepare to allocate exectuatble memory as ROX
Date: Thu, 1 Jun 2023 18:13:44 +0000 [thread overview]
Message-ID: <a51c041b61e2916d2b91c990349aabc6cb9836aa.camel@intel.com> (raw)
In-Reply-To: <ZHjcr26YskTm+0EF@moria.home.lan>
On Thu, 2023-06-01 at 14:00 -0400, Kent Overstreet wrote:
> On Thu, Jun 01, 2023 at 04:54:27PM +0000, Edgecombe, Rick P wrote:
> > It is just a local flush, but I wonder how much text_poke()ing is
> > too
> > much. A lot of the are even inside loops. Can't it do the batch
> > version
> > at least?
> >
> > The other thing, and maybe this is in paranoia category, but it's
> > probably at least worth noting. Before the modules were not made
> > executable until all of the code was finalized. Now they are made
> > executable in an intermediate state and then patched later. It
> > might
> > weaken the CFI stuff, but also it just kind of seems a bit
> > unbounded
> > for dealing with executable code.
>
> I believe bpf starts out by initializing new executable memory with
> illegal opcodes, maybe we should steal that and make it standard.
I was thinking of modules which have a ton of alternatives, errata
fixes, etc applied to them after the initial sections are written to
the to-be-executable mapping. I thought this had zeroed pages to start,
which seems ok.
>
> > Preparing the modules in a separate RW mapping, and then
> > text_poke()ing
> > the whole thing in when you are done would resolve both of these.
>
> text_poke() _does_ create a separate RW mapping.
Sorry, I meant a separate RW allocation.
>
> The thing that sucks about text_poke() is that it always does a full
> TLB
> flush, and AFAICT that's not remotely needed. What it really wants to
> be
> doing is conceptually just
>
> kmap_local()
> mempcy()
> kunmap_loca()
> flush_icache();
>
> ...except that kmap_local() won't actually create a new mapping on
> non-highmem architectures, so text_poke() open codes it.
Text poke creates only a local CPU RW mapping. It's more secure because
other threads can't write to it. It also only needs to flush the local
core when it's done since it's not using a shared MM. It used to use
the fixmap, which is similar to what you are describing I think.
next prev parent reply other threads:[~2023-06-01 18:13 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-01 10:12 [PATCH 00/13] mm: jit/text allocator Mike Rapoport
2023-06-01 10:12 ` [PATCH 01/13] nios2: define virtual address space for modules Mike Rapoport
2023-06-13 22:16 ` Dinh Nguyen
2023-06-01 10:12 ` [PATCH 02/13] mm: introduce jit_text_alloc() and use it instead of module_alloc() Mike Rapoport
2023-06-01 10:12 ` [PATCH 03/13] mm/jitalloc, arch: convert simple overrides of module_alloc to jitalloc Mike Rapoport
2023-06-01 10:12 ` [PATCH 04/13] mm/jitalloc, arch: convert remaining " Mike Rapoport
2023-06-01 22:35 ` Song Liu
2023-06-01 10:12 ` [PATCH 05/13] module, jitalloc: drop module_alloc Mike Rapoport
2023-06-01 10:12 ` [PATCH 06/13] mm/jitalloc: introduce jit_data_alloc() Mike Rapoport
2023-06-01 10:12 ` [PATCH 07/13] x86/ftrace: enable dynamic ftrace without CONFIG_MODULES Mike Rapoport
2023-06-01 10:12 ` [PATCH 08/13] arch: make jitalloc setup available regardless of CONFIG_MODULES Mike Rapoport
2023-06-01 10:12 ` [PATCH 09/13] kprobes: remove dependcy on CONFIG_MODULES Mike Rapoport
2023-06-01 10:12 ` [PATCH 10/13] modules, jitalloc: prepare to allocate executable memory as ROX Mike Rapoport
2023-06-01 10:12 ` [PATCH 11/13] ftrace: Add swap_func to ftrace_process_locs() Mike Rapoport
2023-06-01 10:12 ` [PATCH 12/13] x86/jitalloc: prepare to allocate exectuatble memory as ROX Mike Rapoport
2023-06-01 10:30 ` Peter Zijlstra
2023-06-01 11:07 ` Mike Rapoport
2023-06-02 0:02 ` Song Liu
2023-06-01 17:52 ` Kent Overstreet
2023-06-01 16:54 ` Edgecombe, Rick P
2023-06-01 18:00 ` Kent Overstreet
2023-06-01 18:13 ` Edgecombe, Rick P [this message]
2023-06-01 18:38 ` Kent Overstreet
2023-06-01 20:50 ` Edgecombe, Rick P
2023-06-01 23:54 ` Nadav Amit
2023-06-05 2:52 ` Steven Rostedt
2023-06-05 8:11 ` Mike Rapoport
2023-06-05 16:10 ` Edgecombe, Rick P
2023-06-05 20:42 ` Mike Rapoport
2023-06-05 21:01 ` Edgecombe, Rick P
2023-06-05 21:11 ` Nadav Amit
2023-06-04 21:47 ` Kent Overstreet
2023-06-01 22:49 ` Song Liu
2023-06-01 10:12 ` [PATCH 13/13] x86/jitalloc: make memory allocated for code ROX Mike Rapoport
2023-06-01 16:12 ` [PATCH 00/13] mm: jit/text allocator Mark Rutland
2023-06-01 18:14 ` Kent Overstreet
2023-06-02 9:35 ` Mark Rutland
2023-06-02 18:20 ` Song Liu
2023-06-03 21:11 ` Puranjay Mohan
2023-06-04 18:02 ` Kent Overstreet
2023-06-04 21:22 ` Song Liu
2023-06-04 21:40 ` Kent Overstreet
2023-06-05 4:05 ` Song Liu
2023-06-05 9:20 ` Mike Rapoport
2023-06-05 10:09 ` Mark Rutland
2023-06-06 10:16 ` Mike Rapoport
2023-06-06 18:21 ` Song Liu
2023-06-08 18:41 ` Mike Rapoport
2023-06-09 17:02 ` Song Liu
2023-06-12 21:34 ` Mike Rapoport
2023-06-13 18:56 ` Kent Overstreet
2023-06-13 21:09 ` Mike Rapoport
2023-07-20 8:53 ` Mike Rapoport
2023-06-05 21:13 ` Kent Overstreet
2023-06-02 0:36 ` Song Liu
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