[PATCH 1/3] module: Rename module_alloc() to text_alloc() and move to kernel proper

[Jarkko Sakkinen]

On Tue, Jul 14, 2020 at 10:53:46AM +0100, Russell King - ARM Linux admin wrote:
> On Tue, Jul 14, 2020 at 12:49:28PM +0300, Jarkko Sakkinen wrote:
> > On Mon, Jul 13, 2020 at 07:34:10PM +0100, Russell King - ARM Linux admin wrote:
> > > On Mon, Jul 13, 2020 at 09:19:37PM +0300, Jarkko Sakkinen wrote:
> > > > Rename module_alloc() to text_alloc() and module_memfree() to
> > > > text_memfree(), and move them to kernel/text.c, which is unconditionally
> > > > compiled to the kernel proper. This allows kprobes, ftrace and bpf to
> > > > allocate space for executable code without requiring to compile the modules
> > > > support (CONFIG_MODULES=y) in.
> > > 
> > > I'm not sure this is a good idea for 32-bit ARM.  The code you are
> > > moving for 32-bit ARM is quite specific to module use in that it also
> > > supports allocating from the vmalloc area, where the module code
> > > knows to add PLT entries.
> > > 
> > > If the other proposed users of this text_alloc() do not have the logic
> > > to add PLT entries when branches between kernel code and this
> > > allocation are not reachable by, e.g. a 26-bit signed offset for 32-bit
> > > ARM code, then this code is not suitable for that use.
> > 
> > My intention is to use this in kprobes code in the place of
> > module_alloc().  I'm not sure why moving this code out of the module
> > subsystem could possibly break anything.  Unfortunately I forgot to add
> > covere letter to my series. Sending v2 with that to explain my use case
> > for this.
> 
> Ah, so you're merely renaming module_alloc() to text_alloc() everywhere?
> It sounded from the initial patch like you were also converting other
> users to use module_alloc().

Yes, exactly. I'm making the allocators unconditionally part of the
kernel proper.

My application for this is test kernels. I never compile anything as
modules when I test a release.

Also, I could imagine that especially in small scale embedded devices,
it could be sometimes useful to be able to have tracing support w/o
module support.

/Jarkko