> On Feb 28, 2017, at 10:35 AM, Khalid Aziz <khalid.a...@oracle.com> wrote: > > diff --git a/arch/sparc/kernel/etrap_64.S b/arch/sparc/kernel/etrap_64.S > index 1276ca2..7be33bf 100644 > --- a/arch/sparc/kernel/etrap_64.S > +++ b/arch/sparc/kernel/etrap_64.S > @@ -132,7 +132,33 @@ etrap_save: save %g2, -STACK_BIAS, %sp > stx %g6, [%sp + PTREGS_OFF + PT_V9_G6] > stx %g7, [%sp + PTREGS_OFF + PT_V9_G7] > or %l7, %l0, %l7 > - sethi %hi(TSTATE_TSO | TSTATE_PEF), %l0 > +661: sethi %hi(TSTATE_TSO | TSTATE_PEF), %l0 > + /* > + * If userspace is using ADI, it could potentially pass > + * a pointer with version tag embedded in it. To maintain > + * the ADI security, we must enable PSTATE.mcde. Userspace > + * would have already set TTE.mcd in an earlier call to > + * kernel and set the version tag for the address being > + * dereferenced. Setting PSTATE.mcde would ensure any > + * access to userspace data through a system call honors > + * ADI and does not allow a rogue app to bypass ADI by > + * using system calls. Setting PSTATE.mcde only affects > + * accesses to virtual addresses that have TTE.mcd set. > + * Set PMCDPER to ensure any exceptions caused by ADI > + * version tag mismatch are exposed before system call > + * returns to userspace. Setting PMCDPER affects only > + * writes to virtual addresses that have TTE.mcd set and > + * have a version tag set as well. > + */ > + .section .sun_m7_1insn_patch, "ax" > + .word 661b > + sethi %hi(TSTATE_TSO | TSTATE_PEF | TSTATE_MCDE), %l0 > + .previous > +661: nop > + .section .sun_m7_1insn_patch, "ax" > + .word 661b > + .word 0xaf902001 /* wrpr %g0, 1, %pmcdper */
Since PMCDPER is never cleared, setting it here is quickly going to set it on all CPUs and then become an expensive "nop" that burns ~50 cycles each time through etrap. Consider setting it at boot time and when a CPU is DR'd into the system. Anthony
