Messages in this thread Patch in this message | | | Date | Tue, 7 Apr 2020 11:00:23 -0700 | From | Fangrui Song <> | Subject | Re: [PATCH v2] MIPS: Truncate load-y into 32bit for 32bit kernel |
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On 2020-04-07, Nick Desaulniers wrote: >On Tue, Apr 7, 2020 at 1:07 AM Jiaxun Yang <jiaxun.yang@flygoat.com> 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: Fangrui Song <maskray@google.com> >> Tested-by: Nathan Chancellor <natechancellor@gmail.com> >> >> -- >> V2: Take MaskRay's shell magic. > >V2 is way too clever, V1 was much more readable.
This is difficult:/ https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04 The POSIX shell is only required to do signed long integer arithmetic. "signed long" can be 32-bit.
awk may not provide precision more than a double ("... decimal-floating-constant token as specified by the ISO C standard")
% gawk 'BEGIN {printf("%x", (0xffffffff80101234 % 0x100000000))}' /dev/null 80101000
>Can this tag be added to the commit to help us track when and where it lands? >Link: https://github.com/ClangBuiltLinux/linux/issues/786
And this tag for GNU ld enhancement:
Link: https://sourceware.org/bugzilla/show_bug.cgi?id=25784
>> --- >> arch/mips/Makefile | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/arch/mips/Makefile b/arch/mips/Makefile >> index e1c44aed8156..f8fd3c39fb55 100644 >> --- a/arch/mips/Makefile >> +++ b/arch/mips/Makefile >> @@ -286,6 +286,9 @@ ifdef CONFIG_64BIT >> $(error CONFIG_CPU_DADDI_WORKAROUNDS unsupported without -msym32) >> endif >> endif >> +else >> + # Truncate address into 32-bit >> + load-y := 0x$(shell echo "$(load-y)" | rev | head -c 8 | rev) >> endif >> >> KBUILD_AFLAGS += $(cflags-y) >> -- > >-- >Thanks, >~Nick Desaulniers
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