On Tue, Oct 17, 2017 at 1:00 PM, Arnd Bergmann <arnd@xxxxxxxx> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
