| Message ID | 1532684275-13041-10-git-send-email-Richard.Earnshaw@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | (v2) Mitigation against unsafe data speculation (CVE-2017-5753) | expand |
> On Jul 27, 2018, at 5:37 AM, Richard Earnshaw <Richard.Earnshaw@arm.com> wrote: > > > This patch is intended as an example of all that is needed if the > target system doesn't support CPUs that have speculative execution. > I've chosen the pdp11 port on the basis that it's old enough that this > is likely to be true for all existing implementations and that there > is also little chance of that changing in future! > > * config/pdp11/pdp11.c (TARGET_HAVE_SPECULATION_SAFE_VALUE): Redefine > to speculation_safe_value_not_needed. > --- > gcc/config/pdp11/pdp11.c | 3 +++ > 1 file changed, 3 insertions(+) > > <0009-pdp11-example-of-a-port-not-needing-a-speculation-ba.patch> Correct, no speculative instruction now, and I don't think any of the people constructing PDP11s (yes there are some) are going to be adding it. Thanks Richard. paul
On July 27, 2018 3:27:49 PM GMT+02:00, Paul Koning <paulkoning@comcast.net> wrote: > > >> On Jul 27, 2018, at 5:37 AM, Richard Earnshaw ><Richard.Earnshaw@arm.com> wrote: >> >> >> This patch is intended as an example of all that is needed if the >> target system doesn't support CPUs that have speculative execution. >> I've chosen the pdp11 port on the basis that it's old enough that >this >> is likely to be true for all existing implementations and that there >> is also little chance of that changing in future! >> >> * config/pdp11/pdp11.c (TARGET_HAVE_SPECULATION_SAFE_VALUE): >Redefine >> to speculation_safe_value_not_needed. >> --- >> gcc/config/pdp11/pdp11.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> <0009-pdp11-example-of-a-port-not-needing-a-speculation-ba.patch> > >Correct, no speculative instruction now, and I don't think any of the >people constructing PDP11s (yes there are some) are going to be adding >it. It's not really about speculative instructions but about things like having a branch predictor and ways to recover from badly predicted ones and thus from wrongly speculatively executed regular instructions. Probably every pipelined CPU implementation nowadays has speculative execution. Richard. >Thanks Richard. > > paul
diff --git a/gcc/config/pdp11/pdp11.c b/gcc/config/pdp11/pdp11.c index 1bcdaed..62c653f 100644 --- a/gcc/config/pdp11/pdp11.c +++ b/gcc/config/pdp11/pdp11.c @@ -291,6 +291,9 @@ static bool pdp11_scalar_mode_supported_p (scalar_mode); #undef TARGET_INVALID_WITHIN_DOLOOP #define TARGET_INVALID_WITHIN_DOLOOP hook_constcharptr_const_rtx_insn_null + +#undef TARGET_HAVE_SPECULATION_SAFE_VALUE +#define TARGET_HAVE_SPECULATION_SAFE_VALUE speculation_safe_value_not_needed /* A helper function to determine if REGNO should be saved in the current function's stack frame. */