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Subject: Re: [RFC PATCH v1] powerpc: Enable KFENCE for PPC32
To:     Marco Elver <elver@google.com>
Cc:     Alexander Potapenko <glider@google.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Dmitry Vyukov <dvyukov@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linuxppc-dev@lists.ozlabs.org,
        kasan-dev <kasan-dev@googlegroups.com>
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 <08a96c5d-4ae7-03b4-208f-956226dee6bb@csgroup.eu>
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From:   Christophe Leroy <christophe.leroy@csgroup.eu>
Message-ID: <4b46ecc9-ae47-eee1-843e-e0638a356b51@csgroup.eu>
Date:   Thu, 4 Mar 2021 15:08:31 +0100
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Precedence: bulk


Le 04/03/2021 à 13:48, Marco Elver a écrit :
>  From d118080eb9552073f5dcf1f86198f3d86d5ea850 Mon Sep 17 00:00:00 2001
> From: Marco Elver <elver@google.com>
> Date: Thu, 4 Mar 2021 13:15:51 +0100
> Subject: [PATCH] kfence: fix reports if constant function prefixes exist
> 
> Some architectures prefix all functions with a constant string ('.' on
> ppc64). Add ARCH_FUNC_PREFIX, which may optionally be defined in
> <asm/kfence.h>, so that get_stack_skipnr() can work properly.


It works, thanks.

> 
> Link: https://lkml.kernel.org/r/f036c53d-7e81-763c-47f4-6024c6c5f058@csgroup.eu
> Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> Signed-off-by: Marco Elver <elver@google.com>

Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>

> ---
>   mm/kfence/report.c | 18 ++++++++++++------
>   1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/kfence/report.c b/mm/kfence/report.c
> index 519f037720f5..e3f71451ad9e 100644
> --- a/mm/kfence/report.c
> +++ b/mm/kfence/report.c
> @@ -20,6 +20,11 @@
>   
>   #include "kfence.h"
>   
> +/* May be overridden by <asm/kfence.h>. */
> +#ifndef ARCH_FUNC_PREFIX
> +#define ARCH_FUNC_PREFIX ""
> +#endif
> +
>   extern bool no_hash_pointers;
>   
>   /* Helper function to either print to a seq_file or to console. */
> @@ -67,8 +72,9 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries
>   	for (skipnr = 0; skipnr < num_entries; skipnr++) {
>   		int len = scnprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skipnr]);
>   
> -		if (str_has_prefix(buf, "kfence_") || str_has_prefix(buf, "__kfence_") ||
> -		    !strncmp(buf, "__slab_free", len)) {
> +		if (str_has_prefix(buf, ARCH_FUNC_PREFIX "kfence_") ||
> +		    str_has_prefix(buf, ARCH_FUNC_PREFIX "__kfence_") ||
> +		    !strncmp(buf, ARCH_FUNC_PREFIX "__slab_free", len)) {
>   			/*
>   			 * In case of tail calls from any of the below
>   			 * to any of the above.
> @@ -77,10 +83,10 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries
>   		}
>   
>   		/* Also the *_bulk() variants by only checking prefixes. */
> -		if (str_has_prefix(buf, "kfree") ||
> -		    str_has_prefix(buf, "kmem_cache_free") ||
> -		    str_has_prefix(buf, "__kmalloc") ||
> -		    str_has_prefix(buf, "kmem_cache_alloc"))
> +		if (str_has_prefix(buf, ARCH_FUNC_PREFIX "kfree") ||
> +		    str_has_prefix(buf, ARCH_FUNC_PREFIX "kmem_cache_free") ||
> +		    str_has_prefix(buf, ARCH_FUNC_PREFIX "__kmalloc") ||
> +		    str_has_prefix(buf, ARCH_FUNC_PREFIX "kmem_cache_alloc"))
>   			goto found;
>   	}
>   	if (fallback < num_entries)
>