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From: Guenter Roeck <linux@roeck-us.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Marc Zyngier <maz@kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	Shuah Khan <shuah@kernel.org>,
	patches@kernelci.org, lkft-triage@lists.linaro.org,
	Ben Hutchings <ben.hutchings@codethink.co.uk>,
	linux- stable <stable@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Willy Tarreau <w@1wt.eu>,
	Grygorii Strashko <grygorii.strashko@ti.com>
Subject: Re: [PATCH 5.7 0/6] 5.7.14-rc1 review
Date: Wed, 5 Aug 2020 12:24:46 -0700	[thread overview]
Message-ID: <7e1c9df5-d334-461d-56fc-53625c6ca163@roeck-us.net> (raw)
In-Reply-To: <CAHk-=wi0WGMs6+Jz6rXbQO4mfzf8LGVc3TwmCdz0OwRtj7GgMQ@mail.gmail.com>

On 8/5/20 11:37 AM, Linus Torvalds wrote:
> On Wed, Aug 5, 2020 at 11:24 AM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> Same with older versions of gcc. I don't see the problem with the
>> mainline kernel.
> 
>   https://www.youtube.com/watch?v=-b5aW08ivHU
> 
>> I think this is caused by more recursive includes.
>> arch/arm64/include/asm/archrandom.h includes include/linux/random.h
>> which includes arch/arm64/include/asm/archrandom.h to get the definition
>> of arch_get_random_seed_long_early (which it won't get because of
>> the recursion).
>>
>> What I don't really understand is how this works with new versions
>> of gcc.
> 
> Is that the only place it triggers?
> 
> Because the trivial fix would be something like the appended, which is
> the right thing to do anyway.
> 

Correct.

gcc-7.x and older don't support CONFIG_ARM64_PTR_AUTH. Result is that
./arch/arm64/include/asm/pointer_auth.h doesn't include <linux/random.h>
for those compiler versions, which results in the problem.

In the mainline kernel, ./arch/arm64/include/asm/pointer_auth.h
always includes <linux/random.h>, so the problem isn't seen (or, rather,
it is hidden) there.

The problem is caused (exposed) by Marc's commit ("arm64: Workaround
circular dependency in pointer_auth.h"), which makes the include of
linux/random.h conditional.

Guenter

>               Linus
> 
> diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> index 07c4c8cc4a67..9ded4237e1c1 100644
> --- a/arch/arm64/kernel/kaslr.c
> +++ b/arch/arm64/kernel/kaslr.c
> @@ -11,8 +11,8 @@
>  #include <linux/sched.h>
>  #include <linux/types.h>
>  #include <linux/pgtable.h>
> +#include <linux/random.h>
> 
> -#include <asm/archrandom.h>
>  #include <asm/cacheflush.h>
>  #include <asm/fixmap.h>
>  #include <asm/kernel-pgtable.h>
> 


  reply	other threads:[~2020-08-05 19:24 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-05 15:52 [PATCH 5.7 0/6] 5.7.14-rc1 review Greg Kroah-Hartman
2020-08-05 15:52 ` [PATCH 5.7 1/6] random32: update the net random state on interrupt and activity Greg Kroah-Hartman
2020-08-05 15:52 ` [PATCH 5.7 2/6] ARM: percpu.h: fix build error Greg Kroah-Hartman
2020-08-05 15:52 ` [PATCH 5.7 3/6] random: fix circular include dependency on arm64 after addition of percpu.h Greg Kroah-Hartman
2020-08-05 15:52 ` [PATCH 5.7 4/6] random32: remove net_rand_state from the latent entropy gcc plugin Greg Kroah-Hartman
2020-08-05 15:52 ` [PATCH 5.7 5/6] random32: move the pseudo-random 32-bit definitions to prandom.h Greg Kroah-Hartman
2020-08-05 15:52 ` [PATCH 5.7 6/6] [PATCH] arm64: Workaround circular dependency in pointer_auth.h Greg Kroah-Hartman
2020-08-05 17:39 ` [PATCH 5.7 0/6] 5.7.14-rc1 review Naresh Kamboju
2020-08-05 18:01   ` Linus Torvalds
2020-08-05 18:27     ` Guenter Roeck
2020-08-05 18:24   ` Guenter Roeck
2020-08-05 18:37     ` Linus Torvalds
2020-08-05 19:24       ` Guenter Roeck [this message]
2020-08-05 19:45         ` Linus Torvalds
2020-08-05 19:58           ` Greg Kroah-Hartman
2020-08-06  0:09           ` Guenter Roeck
2020-08-05 19:26       ` Daniel Díaz
2020-08-05 19:52 ` Jon Hunter

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