arm64: Add support for SB barrier and patch in over DSB; ISB sequences

We currently use a DSB; ISB sequence to inhibit speculation in set_fs().
Whilst this works for current CPUs, future CPUs may implement a new SB
barrier instruction which acts as an architected speculation barrier.

On CPUs that support it, patch in an SB; NOP sequence over the DSB; ISB
sequence and advertise the presence of the new instruction to userspace.

Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index bcc2831399cb..7cb0b08ab0a7 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -82,6 +82,7 @@ static const char *const hwcap_str[] = {
 	"ilrcpc",
 	"flagm",
 	"ssbs",
+	"sb",
 	NULL
 };