linux-kernel - Re: [PATCH v8 1/5] kasan: support backing vmalloc space with real shadow memory

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Date:   Wed, 02 Oct 2019 09:13:04 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Daniel Axtens <dja@...ens.net>
Cc:     gor@...ux.ibm.com, linuxppc-dev@...ts.ozlabs.org,
        dvyukov@...gle.com, mark.rutland@....com,
        linux-kernel@...r.kernel.org, luto@...nel.org, glider@...gle.com,
        aryabinin@...tuozzo.com, x86@...nel.org, linux-mm@...ck.org,
        kasan-dev@...glegroups.com, Uladzislau Rezki <urezki@...il.com>
Subject: Re: [PATCH v8 1/5] kasan: support backing vmalloc space with real
 shadow memory

Daniel Axtens <dja@...ens.net> a écrit :

> Hi,
>
>>>  	/*
>>>  	 * Find a place in the tree where VA potentially will be
>>>  	 * inserted, unless it is merged with its sibling/siblings.
>>> @@ -741,6 +752,10 @@ merge_or_add_vmap_area(struct vmap_area *va,
>>>  		if (sibling->va_end == va->va_start) {
>>>  			sibling->va_end = va->va_end;
>>>
>>> +			kasan_release_vmalloc(orig_start, orig_end,
>>> +					      sibling->va_start,
>>> +					      sibling->va_end);
>>> +
>> The same.
>
> The call to kasan_release_vmalloc() is a static inline no-op if
> CONFIG_KASAN_VMALLOC is not defined, which I thought was the preferred
> way to do things rather than sprinkling the code with ifdefs?
>
> The complier should be smart enough to eliminate all the
> orig_state/orig_end stuff at compile time because it can see that it's
> not used, so there's no cost in the binary.
>


Daniel,

You are entirely right in your way to do i, that's fully in line with  
Linux kernel codying style  
https://www.kernel.org/doc/html/latest/process/coding-style.html#conditional-compilation

Christophe