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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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