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Date:   Tue, 14 Jun 2022 15:26:59 +0300
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Luis Chamberlain <mcgrof@kernel.org>
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Subject: Re: [PATCH] kprobes: Enable tracing for mololithic kernel images
Message-ID: <Yqh+k7Udth0IOBrd@iki.fi>
References: <20220608000014.3054333-1-jarkko@profian.com>
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 <YqH5TfN9w35kHFLU@bombadil.infradead.org>
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On Thu, Jun 09, 2022 at 06:44:45AM -0700, Luis Chamberlain wrote:
> On Thu, Jun 09, 2022 at 08:47:38AM +0100, Russell King (Oracle) wrote:
> > On Wed, Jun 08, 2022 at 02:59:27AM +0300, Jarkko Sakkinen wrote:
> > > diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
> > > index 553866751e1a..d2bb954cd54f 100644
> > > --- a/arch/arm/kernel/Makefile
> > > +++ b/arch/arm/kernel/Makefile
> > > @@ -44,6 +44,11 @@ obj-$(CONFIG_CPU_IDLE)		+= cpuidle.o
> > >  obj-$(CONFIG_ISA_DMA_API)	+= dma.o
> > >  obj-$(CONFIG_FIQ)		+= fiq.o fiqasm.o
> > >  obj-$(CONFIG_MODULES)		+= armksyms.o module.o
> > > +ifeq ($(CONFIG_MODULES),y)
> > > +obj-y				+= module_alloc.o
> > > +else
> > > +obj-$(CONFIG_KPROBES)		+= module_alloc.o
> > > +endif
> > 
> > Doesn't:
> > 
> > obj-$(CONFIG_MODULES)		+= module_alloc.o
> > obj-$(CONFIG_KPROBES)		+= module_alloc.o
> 
> That just begs for a new kconfig symbol for the object, and for
> the object then to be built with it.
> 
> The archs which override the default can use ARCH_HAS_VM_ALLOC_EXEC.
> Please note that the respective free is important as well and its
> not clear if we need an another define for the free. Someone has
> to do that work. We want to ensure to noexec the code on free and
> this can vary on each arch.

Let me check if I understand this (not 100% sure).

So if arch define ARCH_HAS_VMALLOC_EXEC, then this would set
config flag CONFIG_VMALLOC_EXEC, which would be used to include
the compilation unit?

BR, Jarkko