Messages in this thread | | | Date | Thu, 23 Apr 2020 13:42:52 +0800 | From | Jiaxun Yang <> | Subject | Re: [PATCH v5] MIPS: Truncate link address into 32bit for 32bit kernel |
| |
于 2020年4月23日 GMT+08:00 上午8:10:12, "Maciej W. Rozycki" <macro@linux-mips.org> 写到: >On Wed, 22 Apr 2020, Jiaxun Yang wrote: > >> Reviewed-by: Maciej W. Rozycki <macro@linux-mips.org> > > Hmm, that was for an earlier version of the patch, and reviews obviously >do not automatically carry over to subsequent versions, as it cannot be >claimed that they are as good in the reviewer's eyes as the actual version >reviewed was. > >> diff --git a/arch/mips/Makefile b/arch/mips/Makefile >> index e1c44aed8156..68c0f22fefc0 100644 >> --- a/arch/mips/Makefile >> +++ b/arch/mips/Makefile >> @@ -288,12 +288,23 @@ 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=$(load-y) \ >> + VMLINUX_LINK_ADDRESS=$(load-ld) \ >> VMLINUX_ENTRY_ADDRESS=$(entry-y) \ >> PLATFORM="$(platform-y)" \ >> ITS_INPUTS="$(its-y)" > > Hmm, to be honest I find the nomenclature confusing: VMLINUX_LOAD_ADDRESS >and VMLINUX_LINK_ADDRESS sound like synonyms to me and also look very >similar, so I expect people will be confused and scratch their heads in >the future. Due to the obscurity of the problem I think there is little >room for manoeuvre here really, but how about using LINKER_LOAD_ADDRESS >for the new variable? > > Alternatively, have you made any attempt to verify if actually replacing >the setting for VMLINUX_LOAD_ADDRESS would be safe? Glancing over its use >there do not appear to be many places.
Limited experiments showed it should be fine...
But MIPS kernel has some design I'm not really familiar with like SYM32 for 64-bit kernel and special address space design for Trap-and-emul KVM.
I'm not 100 sure it's safe so I didn't do so.
> > Maciej
-- Jiaxun Yang
| |