linux-kernel - Re: [PATCH v5 5/6] kprobes: Use text_alloc() and text

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Message-ID: <20200724092746.GD517988@gmail.com>
Date:   Fri, 24 Jul 2020 11:27:46 +0200
From:   Ingo Molnar <mingo@...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>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jessica Yu <jeyu@...nel.org>, Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH v5 5/6] kprobes: Use text_alloc() and text_free()


* Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> wrote:

> Use text_alloc() and text_free() instead of module_alloc() and
> module_memfree() when an arch provides them.
> 
> Cc: linux-mm@...ck.org
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
>  kernel/kprobes.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 4e46d96d4e16..611fcda9f6bf 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -40,6 +40,7 @@
>  #include <asm/cacheflush.h>
>  #include <asm/errno.h>
>  #include <linux/uaccess.h>
> +#include <linux/vmalloc.h>
>  
>  #define KPROBE_HASH_BITS 6
>  #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
> @@ -111,12 +112,20 @@ enum kprobe_slot_state {
>  
>  void __weak *alloc_insn_page(void)
>  {
> +#ifdef CONFIG_ARCH_HAS_TEXT_ALLOC
> +	return text_alloc(PAGE_SIZE);
> +#else
>  	return module_alloc(PAGE_SIZE);
> +#endif
>  }
>  
>  void __weak free_insn_page(void *page)
>  {
> +#ifdef CONFIG_ARCH_HAS_TEXT_ALLOC
> +	text_free(page);
> +#else
>  	module_memfree(page);
> +#endif
>  }

I've read the observations in the other threads, but this #ifdef 
jungle is silly, it's a de-facto open coded text_alloc() with a 
module_alloc() fallback...

Thanks,

	Ingo