On Thu, May 21, 2020 at 02:17:18PM -0700, Yu-cheng Yu wrote: > When shadow stack is enabled, selftests/x86/sigreturn_64 triggers a fault > when doing sigreturn to 32-bit context but the task's shadow stack pointer > is above 32-bit address range. Fix it by: > > - Allocate a small shadow stack below 32-bit address, > - Switch to the new shadow stack, > - Run tests, > - Switch back to the original 64-bit shadow stack. > > Signed-off-by: Yu-cheng Yu <[email protected]> > --- > tools/testing/selftests/x86/sigreturn.c | 28 +++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > > diff --git a/tools/testing/selftests/x86/sigreturn.c > b/tools/testing/selftests/x86/sigreturn.c > index 57c4f67f16ef..5bcd74d416ff 100644 > --- a/tools/testing/selftests/x86/sigreturn.c > +++ b/tools/testing/selftests/x86/sigreturn.c > @@ -45,6 +45,14 @@ > #include <stdbool.h> > #include <sys/ptrace.h> > #include <sys/user.h> > +#include <x86intrin.h> > +#include <asm/prctl.h> > +#include <sys/prctl.h> > + > +#ifdef __x86_64__ > +int arch_prctl(int code, unsigned long *addr); > +#define ARCH_CET_ALLOC_SHSTK 0x3004 > +#endif > > /* Pull in AR_xyz defines. */ > typedef unsigned int u32; > @@ -766,6 +774,20 @@ int main() > int total_nerrs = 0; > unsigned short my_cs, my_ss; > > +#ifdef __x86_64__ > + /* Alloc a shadow stack within 32-bit address range */ > + unsigned long arg, ssp_64, ssp_32; > + ssp_64 = _get_ssp(); > + > + if (ssp_64 != 0) { > + arg = 0x1001; > + arch_prctl(ARCH_CET_ALLOC_SHSTK, &arg); > + ssp_32 = arg + 0x1000 - 8; > + asm volatile("RSTORSSP (%0)\n":: "r" (ssp_32)); > + asm volatile("SAVEPREVSSP"); > + } > +#endif
If the headers and code are going to be repeated, I would put that in a shared header so they're not copy/pasted between these two tests. -Kees -- Kees Cook
