linux-kernel - Re: [PATCH v5 2/6] vmalloc: Add text_alloc() and text

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Message-ID: <20200724102243.GA2831654@kernel.org>
Date:   Fri, 24 Jul 2020 13:22:43 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andi Kleen <ak@...ux.intel.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v5 2/6] vmalloc: Add text_alloc() and text_free()

On Fri, Jul 24, 2020 at 08:05:49AM +0300, Jarkko Sakkinen wrote:
> Introduce functions for allocating memory for dynamic trampolines, such
> as kprobes. An arch can promote the availability of these functions with
> CONFIG_ARCH_HAS_TEXT_ALLOC.

As it was pointed out at the discussion on the previous version [1],
text_alloc() alone won't necessarily suit other architectures.
 
I don't see a point in defining a "generic" interface that apriory could
not be imeplemented by several architectures.

[1] https://lore.kernel.org/lkml/20200714094625.1443261-1-jarkko.sakkinen@linux.intel.com/

> Cc: linux-mm@...ck.org
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
>  include/linux/vmalloc.h | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 0221f852a7e1..6c151a0ac02a 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -249,4 +249,21 @@ pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
>  int register_vmap_purge_notifier(struct notifier_block *nb);
>  int unregister_vmap_purge_notifier(struct notifier_block *nb);
>  
> +/*
> + * These functions can be optionally implemented by an arch in order to
> + * provide specialized functions for allocating trampoline code.
> + */
> +
> +#ifdef CONFIG_ARCH_HAS_TEXT_ALLOC
> +/*
> + * Allocate memory to be used for trampoline code.
> + */
> +void *text_alloc(unsigned long size);
> +
> +/*
> + * Free memory returned from text_alloc().
> + */
> +void text_free(void *region);
> +#endif /* CONFIG_ARCH_HAS_TEXT_ALLOC */
> +
>  #endif /* _LINUX_VMALLOC_H */
> -- 
> 2.25.1
> 

-- 
Sincerely yours,
Mike.