linux-kernel - Re: [PATCH v3 3/3] module: Make __tracepoints

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Date:   Wed, 10 Apr 2019 20:44:01 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
        keescook@...omium.org, mathieu.desnoyers@...icios.com,
        Jessica Yu <jeyu@...nel.org>,
        kernel-hardening@...ts.openwall.com, kernel-team@...roid.com,
        rcu@...r.kernel.org
Subject: Re: [PATCH v3 3/3] module: Make __tracepoints_ptrs as read-only

On Wed, 10 Apr 2019 16:29:02 -0400
Joel Fernandes <joel@...lfernandes.org> wrote:

> The srcu structure pointer array is modified at module load time because the
> array is fixed up by the module loader at load-time with the final locations
> of the tracepoints right?  Basically relocation fixups. At compile time, I
> believe it is not know what the values in the ptr array are. I believe same
> is true for the tracepoint ptrs array.
> 
> Also it needs to be in a separate __tracepoint_ptrs so that this code works:
> 
> 
> #ifdef CONFIG_TRACEPOINTS
> 	mod->tracepoints_ptrs = section_objs(info, "__tracepoints_ptrs",
> 					     sizeof(*mod->tracepoints_ptrs),
> 					     &mod->num_tracepoints);
> #endif
> 
> Did I  miss some point? Thanks,

But there's a lot of others too. Hmm, does this mean that the RO data
sections that are in modules are not set to RO?

There's a bunch of separate sections that are RO. Just look in
include/asm-generic/vmlinux.lds.h under the RO_DATA_SECTION() macro.

A lot of the sections saved in module.c:find_module_sections() are in
that RO_DATA when compiled as a builtin. Are they not RO when loaded via
a module?

If this is the case, there probably is going to be a lot more sections
added to your list.

-- Steve