arm64: ssbd: Add support for PSTATE.SSBS rather than trapping to EL3
On CPUs with support for PSTATE.SSBS, the kernel can toggle the SSBD
state without needing to call into firmware.
This patch hooks into the existing SSBD infrastructure so that SSBS is
used on CPUs that support it, but it's all made horribly complicated by
the very real possibility of big/little systems that don't uniformly
provide the new capability.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 79657ad..f683537 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -174,6 +174,10 @@ static inline void start_thread(struct pt_regs *regs, unsigned long pc,
{
start_thread_common(regs, pc);
regs->pstate = PSR_MODE_EL0t;
+
+ if (arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE)
+ regs->pstate |= PSR_SSBS_BIT;
+
regs->sp = sp;
}
@@ -190,6 +194,9 @@ static inline void compat_start_thread(struct pt_regs *regs, unsigned long pc,
regs->pstate |= PSR_AA32_E_BIT;
#endif
+ if (arm64_get_ssbd_state() != ARM64_SSBD_FORCE_ENABLE)
+ regs->pstate |= PSR_AA32_SSBS_BIT;
+
regs->compat_sp = sp;
}
#endif