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SubjectRe: more build problems with "Makefile: move stackprotector availability out of Kconfig"
On Tue, Oct 17, 2017 at 1:00 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> Hi Kees,
>
> On my test box, current linux-next kernels fail to build due to the
> patch that introduces CONFIG_CC_STACKPROTECTOR_AUTO, with my mainline
> gcc
> builds up to gcc-5.5.0. gcc-6 and higher work fine, as
> scripts/gcc-x86_64-has-stack-protector.sh returns 'y' for those.
>
> Using the compilers provided by Ubuntu (4.6/4.7/4.8/4.9), everything
> also works as expected, so my interpretation is that mainline gcc did
> not enable the stack protector until gcc-6, while distributions did.
>
> Do you agree with that interpretation?

It's probably a little different. I tried bisecting the gcc commit that fixed
the issue for me, and ended up with this commit

https://gitlab.indel.ch/thirdparty/gcc/commit/c14bac81551d6769741c2b1cc55e04d94fe8d3a7

that caused the target to change from x86_64-unknown-linux to
x86_64-pc-linux, and apparently caused the compiler bootstrap
to incorrectly identify the capabilities of the assembler. As a result,
the assembler output inside of scripts/gcc-x86_64-has-stack-protector.sh
that should be

.file ""
.text
.globl foo
.type foo, @function
foo:
pushq %rbp
movq %rsp, %rbp
subq $208, %rsp
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
.size foo, .-foo
.ident "GCC: (GNU) 6.1.1 20160729"
.section .note.GNU-stack,"",@progbits

ends up looking like

.file ""
.text
.globl foo
.type foo, @function
foo:
.LFB0:
pushq %rbp
.LCFI0:
movq %rsp, %rbp
.LCFI1:
subq $208, %rsp
movq __stack_chk_guard(%rip), %rax
movq %rax, -8(%rbp)
xorl %eax, %eax
movl $3, %eax
movq -8(%rbp), %rdx
xorq __stack_chk_guard(%rip), %rdx
je .L3
call __stack_chk_fail
.L3:
leave
.LCFI2:
ret
.LFE0:
.size foo, .-foo
.section .eh_frame,"aw",@progbits
.Lframe1:
.long .LECIE1-.LSCIE1
.LSCIE1:
.long 0
.byte 0x3
.string ""
.byte 0x1
.byte 0x78
.byte 0x10
.byte 0xc
.byte 0x7
.byte 0x8
.byte 0x90
.byte 0x1
.align 8
.LECIE1:
.LSFDE1:
.long .LEFDE1-.LASFDE1
.LASFDE1:
.long .LASFDE1-.Lframe1
.quad .LFB0
.quad .LFE0-.LFB0
.byte 0x4
.long .LCFI0-.LFB0
.byte 0xe
.byte 0x10
.byte 0x86
.byte 0x2
.byte 0x4
.long .LCFI1-.LCFI0
.byte 0xd
.byte 0x6
.byte 0x4
.long .LCFI2-.LCFI1
.byte 0xc
.byte 0x7
.byte 0x8
.align 8
.LEFDE1:
.ident "GCC: (GNU) 6.0.0 20150728 (experimental)"
.section .note.GNU-stack,"",@progbits

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