From: Volodymyr Babchuk vlad.babchuk@gmail.com
Some fast SMCCC calls to OP-TEE should be handled in a special way. Capabilities exchange should be filtered out, so only caps known to mediator are used. Also mediator disables static SHM memory capability, because it can't share OP-TEE memory with a domain. Only domain can share memory with OP-TEE, so it ensures that OP-TEE supports dynamic SHM.
Basically, static SHM is a reserved memory region which is always mapped into OP-TEE address space. It belongs to OP-TEE. Normally, NW is allowed to access there, so it can communicate with OP-TEE.
On other hand, dynamic SHM is NW's own memory, which it can share with OP-TEE. OP-TEE maps this memory dynamically, when it wants to access it.
Because mediator can't share one static SHM region with all guests, it just disables it for all.
Signed-off-by: Volodymyr Babchuk vlad.babchuk@gmail.com ---
Changes from v2: - Defined known capabilities explicitely - Fixed code style
xen/arch/arm/tee/optee.c | 58 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 56 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/tee/optee.c b/xen/arch/arm/tee/optee.c index 73ad25ee0b..584241b03a 100644 --- a/xen/arch/arm/tee/optee.c +++ b/xen/arch/arm/tee/optee.c @@ -22,6 +22,11 @@ /* Client ID 0 is reserved for hypervisor itself */ #define OPTEE_CLIENT_ID(domain) (domain->domain_id + 1)
+#define OPTEE_KNOWN_NSEC_CAPS OPTEE_SMC_NSEC_CAP_UNIPROCESSOR +#define OPTEE_KNOWN_SEC_CAPS (OPTEE_SMC_SEC_CAP_HAVE_RESERVED_SHM | \ + OPTEE_SMC_SEC_CAP_UNREGISTERED_SHM | \ + OPTEE_SMC_SEC_CAP_DYNAMIC_SHM) + static bool optee_probe(void) { struct dt_device_node *node; @@ -94,6 +99,18 @@ static void forward_call(struct cpu_user_regs *regs) set_user_reg(regs, 7, 0); }
+static void set_return(struct cpu_user_regs *regs, uint32_t ret) +{ + set_user_reg(regs, 0, ret); + set_user_reg(regs, 1, 0); + set_user_reg(regs, 2, 0); + set_user_reg(regs, 3, 0); + set_user_reg(regs, 4, 0); + set_user_reg(regs, 5, 0); + set_user_reg(regs, 6, 0); + set_user_reg(regs, 7, 0); +} + static void optee_domain_destroy(struct domain *d) { struct arm_smccc_res resp; @@ -109,6 +126,39 @@ static void optee_domain_destroy(struct domain *d) &resp); }
+static bool handle_exchange_capabilities(struct cpu_user_regs *regs) +{ + uint32_t caps; + + /* Filter out unknown guest caps */ + caps = get_user_reg(regs, 1); + caps &= OPTEE_KNOWN_NSEC_CAPS; + set_user_reg(regs, 1, caps); + + forward_call(regs); + if ( get_user_reg(regs, 0) != OPTEE_SMC_RETURN_OK ) + return true; + + caps = get_user_reg(regs, 1); + + /* Filter out unknown OP-TEE caps */ + caps &= OPTEE_KNOWN_SEC_CAPS; + + /* Drop static SHM_RPC cap */ + caps &= ~OPTEE_SMC_SEC_CAP_HAVE_RESERVED_SHM; + + /* Don't allow guests to work without dynamic SHM */ + if ( !(caps & OPTEE_SMC_SEC_CAP_DYNAMIC_SHM) ) + { + set_return(regs, OPTEE_SMC_RETURN_ENOTAVAIL); + return true; + } + + set_user_reg(regs, 1, caps); + + return true; +} + static bool optee_handle_call(struct cpu_user_regs *regs) { switch ( get_user_reg(regs, 0) ) @@ -120,12 +170,16 @@ static bool optee_handle_call(struct cpu_user_regs *regs) case OPTEE_SMC_FUNCID_GET_OS_REVISION: case OPTEE_SMC_ENABLE_SHM_CACHE: case OPTEE_SMC_DISABLE_SHM_CACHE: - case OPTEE_SMC_GET_SHM_CONFIG: - case OPTEE_SMC_EXCHANGE_CAPABILITIES: case OPTEE_SMC_CALL_WITH_ARG: case OPTEE_SMC_CALL_RETURN_FROM_RPC: forward_call(regs); return true; + case OPTEE_SMC_GET_SHM_CONFIG: + /* No static SHM available for guests */ + set_return(regs, OPTEE_SMC_RETURN_ENOTAVAIL); + return true; + case OPTEE_SMC_EXCHANGE_CAPABILITIES: + return handle_exchange_capabilities(regs); default: return false; }