Messages in this thread | | | Date | Mon, 13 Jan 2020 18:20:12 -0800 | From | Kees Cook <> | Subject | Re: [PATCH v3] x86/vmlinux: Fix vmlinux.lds.S with pre-2.23 binutils |
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On Mon, Jan 13, 2020 at 05:57:23PM -0800, H. Peter Anvin wrote: > 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.
Can you send a patch with what you're thinking?
-- Kees Cook
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