Messages in this thread | | | Date | Mon, 13 Apr 2020 09:25:31 -0700 | From | Kees Cook <> | Subject | Re: [PATCH v4] MIPS: Truncate link address into 32bit for 32bit kernel |
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On Mon, Apr 13, 2020 at 02:26:49PM +0800, Jiaxun Yang wrote: > LLD failed to link vmlinux with 64bit load address for 32bit ELF > while bfd will strip 64bit address into 32bit silently. > To fix LLD build, we should truncate load address provided by platform > into 32bit for 32bit kernel. > > Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
-Kees
> Link: https://github.com/ClangBuiltLinux/linux/issues/786 > Link: https://sourceware.org/bugzilla/show_bug.cgi?id=25784 > Cc: Fangrui Song <maskray@google.com> > Cc: Nathan Chancellor <natechancellor@gmail.com> > -- > V2: Take MaskRay's shell magic. > > V3: After spent an hour on dealing with special character issue in > Makefile, I gave up to do shell hacks and write a util in C instead. > Thanks Maciej for pointing out Makefile variable problem. > > v4: Finally we managed to find a Makefile method to do it properly > thanks to Kees. As it's too far from the initial version, I removed > Review & Test tag from Nick and Fangrui and Cc instead. > --- > arch/mips/Makefile | 12 +++++++++++- > arch/mips/kernel/vmlinux.lds.S | 2 +- > 2 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/mips/Makefile b/arch/mips/Makefile > index e1c44aed8156..18495568f03e 100644 > --- a/arch/mips/Makefile > +++ b/arch/mips/Makefile > @@ -288,9 +288,19 @@ ifdef CONFIG_64BIT > endif > endif > > +# When linking a 32-bit executable the LLVM linker cannot cope with a > +# 32-bit load address that has been sign-extended to 64 bits. Simply > +# remove the upper 32 bits then, as it is safe to do so with other > +# linkers. > +ifdef CONFIG_64BIT > + load-ld = $(load-y) > +else > + load-ld = $(subst 0xffffffff,0x,$(load-y)) > +endif > + > KBUILD_AFLAGS += $(cflags-y) > KBUILD_CFLAGS += $(cflags-y) > -KBUILD_CPPFLAGS += -DVMLINUX_LOAD_ADDRESS=$(load-y) > +KBUILD_CPPFLAGS += -DVMLINUX_LOAD_ADDRESS=$(load-y) -DVMLINUX_LINK_ADDRESS=$(load-ld) > KBUILD_CPPFLAGS += -DDATAOFFSET=$(if $(dataoffset-y),$(dataoffset-y),0) > > bootvars-y = VMLINUX_LOAD_ADDRESS=$(load-y) \ > diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S > index a5f00ec73ea6..5226cd8e4bee 100644 > --- a/arch/mips/kernel/vmlinux.lds.S > +++ b/arch/mips/kernel/vmlinux.lds.S > @@ -55,7 +55,7 @@ SECTIONS > /* . = 0xa800000000300000; */ > . = 0xffffffff80300000; > #endif > - . = VMLINUX_LOAD_ADDRESS; > + . = VMLINUX_LINK_ADDRESS; > /* read-only */ > _text = .; /* Text and read-only data */ > .text : { > -- > 2.26.0.rc2 >
-- Kees Cook
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