Re: [Bug 216905] New: Kernel won't compile with KASAN

Re: [Bug 216905] New: Kernel won't compile with KASAN

[Andrew Morton]

(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Mon, 09 Jan 2023 23:42:40 +0000 bugzilla-daemon@kernel.org wrote:

> https://bugzilla.kernel.org/show_bug.cgi?id=216905
> 
>             Bug ID: 216905
>            Summary: Kernel won't compile with KASAN
>            Product: Memory Management
>            Version: 2.5
>     Kernel Version: 6.1.4
>           Hardware: All
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Other
>           Assignee: akpm@linux-foundation.org
>           Reporter: nanook@eskimo.com
>         Regression: No
> 
> Created attachment 303563
>   --> https://bugzilla.kernel.org/attachment.cgi?id=303563&action=edit
> These are errors when trying to compile KASAN inline
> 
> Using GCC 12.2, can not compile a kernel with KASAN enabled, either inline or
> outline.
> The hardware is an i7-6700k based home brew machine, Asus motherboard.
> running Ubuntu 22.10 32GB of RAM but using gcc 12.2 rather than the Ubuntu
> compiler.

crypto/ecc.c: In function ‘ecc_point_mult_shamir’:
crypto/ecc.c:1414:1: warning: the frame size of 1168 bytes is larger than 1024 bytes [-Wframe-larger-than=]
 1414 | }
      | ^
lib/crypto/curve25519-hacl64.c: In function ‘ladder_cmult.constprop’:
lib/crypto/curve25519-hacl64.c:601:1: warning: the frame size of 1376 bytes is larger than 1024 bytes [-Wframe-larger-than=]
  601 | }
      | ^
lib/zstd/common/entropy_common.c: In function ‘HUF_readStats’:
lib/zstd/common/entropy_common.c:258:1: warning: the frame size of 1088 bytes is larger than 1024 bytes [-Wframe-larger-than=]
  258 | }
      | ^

(etcetera)

Increasing CONFIG_FRAME_WARN should fix this.  Try 2048.

Perhaps KASAN could increase it somehow to prevent others from tripping
over this.

Re: [Bug 216905] New: Kernel won't compile with KASAN

[Robert Dinse]

      Increasing to 2048 did allow kernels to compile with KASAN 
enabled.  I am curious why e-mail only?  It would seem bugzilla, a 
public forum would make this fix available to others who may be 
experiencing the same or related problems.  Interestingly, I could not 
locate the symbol with xconfig, had to hand edit the .config file in 
deference to the fact that it tells you not to.

On 1/9/23 16:09, Andrew Morton wrote:
> (switched to email.  Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
>
> On Mon, 09 Jan 2023 23:42:40 +0000 bugzilla-daemon@kernel.org wrote:
>
>> https://bugzilla.kernel.org/show_bug.cgi?id=216905
>>
>>              Bug ID: 216905
>>             Summary: Kernel won't compile with KASAN
>>             Product: Memory Management
>>             Version: 2.5
>>      Kernel Version: 6.1.4
>>            Hardware: All
>>                  OS: Linux
>>                Tree: Mainline
>>              Status: NEW
>>            Severity: normal
>>            Priority: P1
>>           Component: Other
>>            Assignee: akpm@linux-foundation.org
>>            Reporter: nanook@eskimo.com
>>          Regression: No
>>
>> Created attachment 303563
>>    --> https://bugzilla.kernel.org/attachment.cgi?id=303563&action=edit
>> These are errors when trying to compile KASAN inline
>>
>> Using GCC 12.2, can not compile a kernel with KASAN enabled, either inline or
>> outline.
>> The hardware is an i7-6700k based home brew machine, Asus motherboard.
>> running Ubuntu 22.10 32GB of RAM but using gcc 12.2 rather than the Ubuntu
>> compiler.
> crypto/ecc.c: In function ‘ecc_point_mult_shamir’:
> crypto/ecc.c:1414:1: warning: the frame size of 1168 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>   1414 | }
>        | ^
> lib/crypto/curve25519-hacl64.c: In function ‘ladder_cmult.constprop’:
> lib/crypto/curve25519-hacl64.c:601:1: warning: the frame size of 1376 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>    601 | }
>        | ^
> lib/zstd/common/entropy_common.c: In function ‘HUF_readStats’:
> lib/zstd/common/entropy_common.c:258:1: warning: the frame size of 1088 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>    258 | }
>        | ^
>
> (etcetera)
>
> Increasing CONFIG_FRAME_WARN should fix this.  Try 2048.
>
> Perhaps KASAN could increase it somehow to prevent others from tripping
> over this.

Re: [Bug 216905] New: Kernel won't compile with KASAN

[Theodore Ts'o]

On Mon, Jan 09, 2023 at 08:58:41PM -0800, Robert Dinse wrote:
> 
>  Increasing to 2048 did allow kernels to compile with KASAN enabled. I
> am curious why e-mail only? It would seem bugzilla, a public forum would
> make this fix available to others who may be experiencing the same or
> related problems.

Not all kernel developers pay attention to bugzilla.  (In fact, most
kernel developers do not.)

>  Interestingly, I could not locate the symbol with
> xconfig, had to hand edit the .config file in deference to the fact that it
> tells you not to.

If you search for FRAME_WARN in menuconfig ('/', followed by
"FRAME_WARN", followed by return), it will report:

Symbol: FRAME_WARN [=2048]
 Type  : integer
 Range : [0 8192]
 Defined at lib/Kconfig.debug:395
   Prompt: Warn for stack frames larger than
   Locationf
     -> Kernel hacking
       -> Compile-time checks and compiler options
 (1)     -> Warn for stack frames larger than (FRAME_WARN [=2048])


That being said, you can edit the .config file if you know what you
are doing.  But if it breaks, you get to keep both pieces, since there
aren't the safety checks and guardrails of the supported paths.  For
novices, I recommend saving a copy of .config before editing the
.config, and then afterwards, run "make oldconfig", and then diff the
resulting .config with the saved copy to make sure there aren't any
unexpected changes.

Cheers,

							- Ted