On Fri, Feb 1, 2019 at 2:36 PM Andy Lutomirski <[email protected]> wrote: > > > > On Feb 1, 2019, at 12:21 PM, Thomas Garnier <[email protected]> wrote: > > > >> On Fri, Feb 1, 2019 at 11:27 AM Andy Lutomirski <[email protected]> wrote: > >> > >>> On Thu, Jan 31, 2019 at 11:29 AM Thomas Garnier <[email protected]> > >>> wrote: > >>> > >>> Add an off-by-default configuration option to use a global stack cookie > >>> instead of the default TLS. This configuration option will only be used > >>> with PIE binaries. > >>> > >>> For kernel stack cookie, the compiler uses the mcmodel=kernel to switch > >>> between the fs segment to gs segment. A PIE binary does not use > >>> mcmodel=kernel because it can be relocated anywhere, therefore the > >>> compiler will default to the fs segment register. This is fixed on the > >>> latest version of gcc. > >> > >> I hate all these gcc-sucks-so-we-hack-it-and-change-nasty-semantics > >> options. How about just preventing use of both stack protector and > >> PIE unless the version of gcc in use is new enough. > > > > So fail the build in this scenario? > > Fail the build or use some Kconfig magic to prevent this from being > configured in the first place.
Ok, I can do that in next iteration. > > > > >> > >> Also, does -mstack-protector-guard-reg not solve this? See > >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81708. Or is there > >> another bug? Or are you worried about gcc versions that don't have > >> that feature yet? > > > > I am worried about gcc versions that don't have this feature, yes.
