[PATCH 1/2] kbuild: add '-fno-stack-check' to barebox build options

[Ahmad Fatoum]

Hello Sascha,

On 24.02.21 09:49, Sascha Hauer wrote:
> On Tue, Feb 23, 2021 at 08:24:26AM +0100, Ahmad Fatoum wrote:
>> This ports over Linux commit 3ce120b16cc5 ("kbuild: add
>> '-fno-stack-check' to kernel build options"):
>>
>>   Author:     Linus Torvalds <torvalds at linux-foundation.org>
>>
>>     kbuild: add '-fno-stack-check' to kernel build options
>>
>>     It appears that hardened gentoo enables "-fstack-check" by default for
>>     gcc.
>>
>>     That doesn't work _at_all_ for the kernel, because the kernel stack
>>     doesn't act like a user stack at all: it's much smaller, and it doesn't
>>     auto-expand on use.  So the extra "probe one page below the stack" code
>>     generated by -fstack-check just breaks the kernel in horrible ways,
>>     causing infinite double faults etc.
>>
>>     [ I have to say, that the particular code gcc generates looks very
>>       stupid even for user space where it works, but that's a separate
>>       issue.  ]
>>
>>     Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
>>
>> I am porting it, because it may become more acute with the incoming
>> support for multiple stacks (via initjmp).
>>
>> Signed-off-by: Ahmad Fatoum <ahmad at a3f.at>
>> ---
> 
> Applied, thanks

Can't find both patches in next.

Cheers,
Ahmad

> 
> Sascha
> 
>>  Makefile | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/Makefile b/Makefile
>> index f3c85cff9430..fa7fbbeb35f0 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -622,6 +622,9 @@ KBUILD_CFLAGS += $(call cc-option, -fno-delete-null-pointer-checks,)
>>  # disable invalid "can't wrap" optimizations for signed / pointers
>>  KBUILD_CFLAGS	+= $(call cc-option,-fno-strict-overflow)
>>  
>> +# Make sure -fstack-check isn't enabled (like gentoo apparently did)
>> +KBUILD_CFLAGS  += $(call cc-option,-fno-stack-check)
>> +
>>  KBUILD_CFLAGS   += $(call cc-disable-warning, address-of-packed-member)
>>  
>>  # Align the bit size of userspace programs with the kernel
>> -- 
>> 2.30.0
>>
>>
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>>
> 

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