Re: [PATCH] riscv: export flush_icache_all

[Kees Cook <keescook@chromium.org>]

On Tue, Jun 11, 2019 at 03:49:45PM +0200, Christoph Hellwig wrote:
> NAK.  There is no point to export a symbol that should not generally
> exported just for a tester.

flush_icache_range() is what LKDTM uses (and has done so for years).

> 
> I think the right answer is to just don't allow a modular build of
> lkdtm.

No -- several system builders use a modular build of lkdtm to allow
for testing of "production" kernels, and then do not include lkdtm.ko
in the final image (and that image is either protected by LoadPin or
module signing to keep stray modules from appearing).

-Kees

> On Tue, Jun 11, 2019 at 12:24:32PM +0200, Andreas Schwab wrote:
> > Before 58de77545e53 ("riscv: move flush_icache_{all,mm} to cacheflush.c"),
> > flush_icache_all was a macro, but it is used by a module:
> > 
> >   ERROR: "flush_icache_all" [drivers/misc/lkdtm/lkdtm.ko] undefined!
> > 
> > Signed-off-by: Andreas Schwab <schwab@suse.de>
> > ---
> >  arch/riscv/mm/cacheflush.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
> > index 9ebcff8ba263..4a2e5bf8b21a 100644
> > --- a/arch/riscv/mm/cacheflush.c
> > +++ b/arch/riscv/mm/cacheflush.c
> > @@ -14,6 +14,7 @@ void flush_icache_all(void)
> >  {
> >  	sbi_remote_fence_i(NULL);
> >  }
> > +EXPORT_SYMBOL(flush_icache_all);
> >  
> >  /*
> >   * Performs an icache flush for the given MM context.  RISC-V has no direct
> > -- 
> > 2.22.0
> ---end quoted text---

-- 
Kees Cook

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