linux-kernel - Re: [PATCH v5 7/8] execmem: add support for cache of large ROX pages

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Message-ID: <ZwuIPZkjX0CfzhjS@kernel.org>
Date: Sun, 13 Oct 2024 11:43:41 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Christoph Hellwig <hch@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
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Subject: Re: [PATCH v5 7/8] execmem: add support for cache of large ROX pages

On Fri, Oct 11, 2024 at 12:46:23AM -0700, Christoph Hellwig wrote:
> On Thu, Oct 10, 2024 at 03:57:33PM +0300, Mike Rapoport wrote:
> > On Wed, Oct 09, 2024 at 11:58:33PM -0700, Christoph Hellwig wrote:
> > > On Wed, Oct 09, 2024 at 09:08:15PM +0300, Mike Rapoport wrote:
> > > >  /**
> > > >   * struct execmem_info - architecture parameters for code allocations
> > > > + * @fill_trapping_insns: set memory to contain instructions that will trap
> > > >   * @ranges: array of parameter sets defining architecture specific
> > > >   * parameters for executable memory allocations. The ranges that are not
> > > >   * explicitly initialized by an architecture use parameters defined for
> > > >   * @EXECMEM_DEFAULT.
> > > >   */
> > > >  struct execmem_info {
> > > > +	void (*fill_trapping_insns)(void *ptr, size_t size, bool writable);
> > > >  	struct execmem_range	ranges[EXECMEM_TYPE_MAX];
> > > 
> > > Why is the filler an indirect function call and not an architecture
> > > hook?
> > 
> > The idea is to keep everything together and have execmem_info describe all
> > that architecture needs. 
> 
> But why?  That's pretty different from our normal style of arch hooks,
> and introduces an indirect call in a security sensitive area.

Will change to __weak hook. 

-- 
Sincerely yours,
Mike.