Andy Chiu <andy.chiu@xxxxxxxxxx> writes: > To support Vector extension, the series exports variable-length vector > registers on the signal frame. However, this potentially breaks abi if > processing vector registers is required in the signal handler for old > binaries. For example, there is such need if user-level context switch > is triggerred via signals[1]. > > For this reason, it is best to leave a decision to distro maintainers, > where the enablement of userspace Vector for new launching programs can > be controlled. Developers may also need the switch to experiment with. > The parameter is configurable through sysctl interface so a distro may > turn off Vector early at init script if the break really happens in the > wild. > > The switch will only take effects on new execve() calls once set. This > will not effect existing processes that do not call execve(), nor > processes which has been set with a non-default vstate_ctrl by making > explicit PR_RISCV_V_SET_CONTROL prctl() calls. > > Link: https://lore.kernel.org/all/87cz4048rp.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ > Signed-off-by: Andy Chiu <andy.chiu@xxxxxxxxxx> > Reviewed-by: Greentime Hu <greentime.hu@xxxxxxxxxx> > Reviewed-by: Vincent Chen <vincent.chen@xxxxxxxxxx> > --- > arch/riscv/kernel/vector.c | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > diff --git a/arch/riscv/kernel/vector.c b/arch/riscv/kernel/vector.c > index 16ccb35625a9..1c4ac821e008 100644 > --- a/arch/riscv/kernel/vector.c > +++ b/arch/riscv/kernel/vector.c > @@ -233,3 +233,34 @@ unsigned int riscv_v_vstate_ctrl_set_current(unsigned long arg) > > return -EINVAL; > } > + > +#ifdef CONFIG_SYSCTL > + > +static struct ctl_table riscv_v_default_vstate_table[] = { > + { > + .procname = "riscv_v_default_allow", > + .data = &riscv_v_implicit_uacc, Now that riscv_v_implicit_uacc can be changed via sysctl, I'd add explicit READ_ONCE() to the accesses to make race checkers happy. Björn
