On Fri, Jan 21, 2022 at 11:47 AM H.J. Lu <hjl.to...@gmail.com> wrote: > > On Fri, Jan 21, 2022 at 11:23 AM Richard Sandiford via Gcc-patches > <gcc-patches@gcc.gnu.org> wrote: > > > > soe...@soeren-tempel.net writes: > > > From: Sören Tempel <soe...@soeren-tempel.net> > > > > > > The -fsplit-stack option requires the pthread_t TCB definition in the > > > libc to provide certain struct fields at specific hardcoded offsets. As > > > far as I know, only glibc provides these fields at the required offsets. > > > Most notably, musl libc does not have these fields. However, since gcc > > > accesses the fields using a fixed offset, this does not cause a > > > compile-time error, but instead results in a silent memory corruption at > > > run-time with musl libc. For example, on s390x libgcc's > > > __stack_split_initialize CTOR will overwrite the cancel field in the > > > pthread_t TCB on musl. > > > > > > The -fsplit-stack option is used within the gcc code base itself by > > > gcc-go (if available). On musl-based systems with split-stack support > > > (i.e. s390x or x86) this causes Go programs compiled with gcc-go to > > > misbehave at run-time. > > > > > > This patch fixes gcc-go on musl by disabling -fsplit-stack in gcc itself > > > since it is not supported on non-glibc targets anyhow. This is achieved > > > by checking if gcc targets a glibc-based system. This check has been > > > added for x86 and s390x, the rs6000 config already checks for > > > TARGET_GLIBC_MAJOR. Other architectures do not have split-stack > > > support. With this patch applied, the gcc-go configure script will > > > detect that -fsplit-stack support is not available and will not use it. > > > > > > See https://www.openwall.com/lists/musl/2012/10/16/12 > > > > > > This patch was written under the assumption that glibc is the only libc > > > implementation which supports the required fields at the required > > > offsets in the pthread_t TCB. The patch has been tested on Alpine Linux > > > Edge on the s390x and x86 architectures by bootstrapping Google's Go > > > implementation with gcc-go. > > > > > > Signed-off-by: Sören Tempel <soe...@soeren-tempel.net> > > > > > > gcc/ChangeLog: > > > > > > * common/config/s390/s390-common.c (s390_supports_split_stack): > > > Only support split-stack on glibc targets. > > > * config/i386/gnu-user-common.h (STACK_CHECK_STATIC_BUILTIN): Ditto. > > > * config/i386/gnu.h (defined): Ditto. > > > > Thanks, pushed to trunk. > > This broke GCC bootstrap on Linux/i686: > > https://gcc.gnu.org/pipermail/gcc-regression/2022-January/076271.html >
I opened: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104170 H.J.
