Messages in this thread | | | Subject | Re: [PATCH v3] x86/vmlinux: Fix vmlinux.lds.S with pre-2.23 binutils | From | "H. Peter Anvin" <> | Date | Mon, 13 Jan 2020 17:57:23 -0800 |
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On 2020-01-13 17:53, Kees Cook wrote:>> >> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S >> index 3a1a819da137..bad4e22384dc 100644 >> --- a/arch/x86/kernel/vmlinux.lds.S >> +++ b/arch/x86/kernel/vmlinux.lds.S >> @@ -144,10 +144,12 @@ SECTIONS >> *(.text.__x86.indirect_thunk) >> __indirect_thunk_end = .; >> #endif >> + >> + /* End of text section */ >> + _etext = .; >> } :text =0xcccc >> >> - /* End of text section, which should occupy whole number of pages */ >> - _etext = .; >> + /* .text should occupy whole number of pages */ >> . = ALIGN(PAGE_SIZE); > > NAK: linkers can add things at the end of .text that will go missing from > the kernel if _etext isn't _outside_ the .text section, truly beyond the > end of the .text section. This patch will break Control Flow Integrity > checking since the jump tables are at the end of .text. > > Boris, we're always working around weird linker problems; I don't see a > problem with the v2 patch to fix up old binutils... >
Why not add the marker into a separate section instead of leaving it as an absolute "floater"? Very old binutils would botch that case, but I think that has been long since addressed well below our current minimum version.
-hpa
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