On 05.12.14 11:39, Arnd Bergmann wrote: > On Thursday 04 December 2014 15:48:50 Olof Johansson wrote: >> On Thu, Dec 4, 2014 at 3:41 PM, Alexander Graf <ag...@suse.de> wrote: >>> On 04.12.14 22:15, Olof Johansson wrote: >>>> On Thu, Dec 4, 2014 at 7:46 AM, Alexander Graf <ag...@suse.de> wrote: >>>>> With binutils 2.25 the default alignment for 32bit arm sections changed to >>>>> have everything 64k aligned. Armv7 binaries built with this binutils >>>>> version >>>>> run successfully on an arm64 system. >>>>> >>>>> Since effectively there is now the chance to run armv7 code on arm64 even >>>>> with 64k page size, it doesn't make sense to block people from enabling >>>>> CONFIG_COMPAT on those configurations. >>>>> >>>>> Signed-off-by: Alexander Graf <ag...@suse.de> >>>>> --- >>>>> arch/arm64/Kconfig | 1 - >>>>> 1 file changed, 1 deletion(-) >>>>> >>>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >>>>> index 9532f8d..3cf4f238 100644 >>>>> --- a/arch/arm64/Kconfig >>>>> +++ b/arch/arm64/Kconfig >>>>> @@ -409,7 +409,6 @@ source "fs/Kconfig.binfmt" >>>>> >>>>> config COMPAT >>>>> bool "Kernel support for 32-bit EL0" >>>>> - depends on !ARM64_64K_PAGES >>>>> select COMPAT_BINFMT_ELF >>>>> select HAVE_UID16 >>>>> select OLD_SIGSUSPEND3 >>>> >>>> This is hardly "compat". Sure, it's great to have a new binutils that >>>> has larger alignment, but practically not a single existing binary >>>> will work today if someone tries to do this. >>> >>> Yes, but IMHO that's an implementation detail. The same applies for >>> 32bit PPC binaries if you use 4k aligned segments. If your applications >>> are not aligned for your page size, you can't run them. The only >>> platform that managed nevertheless FWIW was IA64 ;). >> >> Yes, but there the binutils change happened early enough that by the >> time the kernel change went in, all major distros had binaries that >> were compatible. > > What is the exact symptom you see when running an unaligned user > space binary on 64k-pages? Do we at least print a helpful error > message somewhere or does it just crash?
It simply doesn't start: init-4.2# /hello.binutils-2.23 init-4.2# echo $? 139 init-4.2# /hello.binutils-2.25 Hello world! init-4.2# echo $? 0 init-4.2# I'm not sure how to give the user an actually helpful error output here though. The only real handle we have for executing a binary is to return an error code. Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/