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SubjectRe: linux-next: WARNING: at kernel/panic.c:375 __stack_chk_test+0x50/0x54()
Arjan van de Ven wrote:
> On Wed, 30 Apr 2008 21:24:27 -0300
> Kevin Winchester <kjwinchester@gmail.com> wrote:
>
>> Arjan van de Ven wrote:
>>> Kevin Winchester wrote:
>>>> Hi Arjan,
>>>>
>>>> There doesn't seem to be an entry in MAINTAINERS for stack
>>>> protector, but your signoff was on the last stack protector
>>>> related commit I could find, so it's probably a good bet.
>>>>
>>>> I get the following in my dmesg after testing linux-next with the
>>>> stack protector turned on. This is an x86-64 UP box if that
>>>> helps. It appears to be related to the test for the feature (or
>>>> perhaps that is supposed to happen when the feature is tested, I'm
>>>> not sure...). Config below.
>>>>
>>> the important question is: exactly what gcc are you using? (and if
>>> you use a distro gcc, which distro)
>>>
>>> second question would be, what does the following command give?
>>>
>>> echo "int foo(void) { char X[200]; return 3; }" | $1 -S -xc -c -O0
>>> -mcmodel=kernel -fstack-protector - -o -
>>>
>>> (this is the command from scripts/gcc-x86_64-has-stack-protector.sh
>>> that the kernel uses to test at compiletime if you have stack
>>> protector support)
>> Ubuntu Hardy Heron
>>
>> kevin@alekhine:~$ gcc --version
>> gcc (GCC) 4.2.3 (Ubuntu 4.2.3-2ubuntu7)
>> Copyright (C) 2007 Free Software Foundation, Inc.
>> This is free software; see the source for copying conditions. There
>> is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
>> PARTICULAR PURPOSE.
>>
>>
>> kevin@alekhine:~$ echo "int foo(void) { char X[200]; return 3; }" |
>> $1 -S -xc -c -O0 -mcmodel=kernel -fstack-protector - -o - bash: -S:
>> command not found
>>
>> I assume that $1 was supposed to be gcc, so how about:
>
> eh woops yes
>
>> kevin@alekhine:~/linux/linux-2.6/scripts$ sh
>> gcc-x86_64-has-stack-protector.sh gcc something something
>>
>> So I would assume that means I pass...
>
>
> I would rather really like to see the assembly output this thing spits; to see if your compiler behaves sanely.
> (Some distros tend to badly patch their gcc unfortunately and this may break the stack protector feature)

Sure, here we go:

kevin@alekhine:~$ echo "int foo(void) { char X[200]; return 3; }" | gcc -S -xc -c -O0 -mcmodel=kernel -fstack-protector - -o -
.file ""
.text
.globl foo
.type foo, @function
foo:
.LFB2:
pushq %rbp
.LCFI0:
movq %rsp, %rbp
.LCFI1:
subq $208, %rsp
.LCFI2:
movq %gs:40, %rax
movq %rax, -8(%rbp)
xorl %eax, %eax
movl $3, %eax
movq -8(%rbp), %rdx
xorq %gs:40, %rdx
je .L3
call __stack_chk_fail
.L3:
leave
ret
.LFE2:
.size foo, .-foo
.section .eh_frame,"a",@progbits
.Lframe1:
.long .LECIE1-.LSCIE1
.LSCIE1:
.long 0x0
.byte 0x1
.string ""
.uleb128 0x1
.sleb128 -8
.byte 0x10
.byte 0xc
.uleb128 0x7
.uleb128 0x8
.byte 0x90
.uleb128 0x1
.align 8
.LECIE1:
.LSFDE1:
.long .LEFDE1-.LASFDE1
.LASFDE1:
.long .LASFDE1-.Lframe1
.quad .LFB2
.quad .LFE2-.LFB2
.byte 0x4
.long .LCFI0-.LFB2
.byte 0xe
.uleb128 0x10
.byte 0x86
.uleb128 0x2
.byte 0x4
.long .LCFI1-.LCFI0
.byte 0xd
.uleb128 0x6
.align 8
.LEFDE1:
.ident "GCC: (GNU) 4.2.3 (Ubuntu 4.2.3-2ubuntu7)"
.section .note.GNU-stack,"",@progbits
Does that help?

--
Kevin Winchester


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