On Wed, Nov 18, 2020 at 03:24:04PM -0800, Nick Desaulniers wrote: > On Wed, Nov 18, 2020 at 3:07 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > On Thu, 19 Nov 2020 at 00:05, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > > > > > > > > > > To avoid playing whack-a-mole with different architectures over time, > > > > > > > > hoist '-z norelro' into the main Makefile. This does not affect ld.bfd > > > > > > > > because '-z norelro' is the default for it. > > > > > > Fangrui pointed out off list that this might need an ld-option wrapper > > > for older versions of GNU binutils. Dan was showing me some build > > > logs today, and I thought I spotted such warnings about `-z norelro > > > will be ignored`. > > > > Does ld-option catch options that cause warnings but no errors? > > $ ld.bfd -z foo /dev/null > ld.bfd: warning: -z foo ignored > ld.bfd: warning: cannot find entry symbol _start; not setting start address > ➜ echo $? > 0 > > Probably not. Can be a version check then (yuck); next is to find when > ld.bfd supported `-z norelro`. > > commit 8c37241be3b1 in binutils looks like it. > Date: Tue May 11 17:08:38 2004 +0000 > > which looks like either > 2004-05-17 19:46:23 +0000 (tag: binutils-2_15) > or > 2005-05-02 22:04:18 +0000 (tag: binutils-2_16) > > So I think that would be fine then, since the kernel only supports 2.23+. > > Though maybe it's > commit 5fd104addfddb68844fb8df67be832ee98ad9888 > Emit a warning when -z relro is unsupported > > ld silently accepts -z relro and -z norelro for targets that lack the > necessary GNU_RELRO support. This patch makes those targets emit a > warning instead, and adds testsuite infrastructure to detect when > relro is unsupported. > > So maybe then alpha and xtensa are getting new warnings (IIUC). If > that's the case, then we might not be able to set `-z norelro` > globally, and instead have to play whack a mole per architecture. Sure, I can just submit the arch/arm patch that I had before this for now and we can always revisit something like this later, if you feel it is best. Cheers, Nathan
