Redefine SMC_UNK as -1 instead of 0xFFFFFFFF

According to the SMC Calling Convention (ARM DEN0028B):

    The Unknown SMC Function Identifier is a sign-extended value of
    (-1) that is returned in R0, W0 or X0 register.

The value wasn't sign-extended because it was defined as a 32-bit
unsigned value (0xFFFFFFFF).

SMC_PREEMPT has been redefined as -2 for the same reason.

NOTE: This might be a compatibility break for some AArch64 platforms
that don't follow the previous version of the SMCCC (ARM DEN0028A)
correctly. That document specifies that only the bottom 32 bits of the
returned value must be checked. If a platform relies on the top 32 bits
of the result being 0 (so that SMC_UNK is 0x00000000FFFFFFFF), it will
have to fix its code to comply with the SMCCC.

Change-Id: I7f7b109f6b30c114fe570aa0ead3c335383cb54d
Signed-off-by: Antonio Nino Diaz <[email protected]>

diff --git a/bl31/aarch64/runtime_exceptions.S b/bl31/aarch64/runtime_exceptions.S
index 57c065c6a8b2dc60d9213499e907567b708ee870..60be932745161cfb0c5dd4786884c6d4acf93250 100644 (file)
--- a/bl31/aarch64/runtime_exceptions.S
+++ b/bl31/aarch64/runtime_exceptions.S
@@ -390,12 +390,12 @@ smc_unknown:
         * content). Either way, we aren't leaking any secure information
         * through them.
         */
-       mov     w0, #SMC_UNK
+       mov     x0, #SMC_UNK
        b       restore_gp_registers_callee_eret
 
 smc_prohibited:
        ldr     x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
-       mov     w0, #SMC_UNK
+       mov     x0, #SMC_UNK
        eret
 
 rt_svc_fw_critical_error:

diff --git a/include/lib/smcc.h b/include/lib/smcc.h
index a273b3af4a90ea9e9328389c93aaf228f313f471..0a2d9277ef695e2633ff146b45907fe14e5a9ca3 100644 (file)
--- a/include/lib/smcc.h
+++ b/include/lib/smcc.h
@@ -35,13 +35,13 @@
 #define SMC_64                         U(1)
 #define SMC_32                         U(0)
 #define SMC_OK                         U(0)
-#define SMC_UNK                                U(0xffffffff)
+#define SMC_UNK                                -1
 #define SMC_TYPE_FAST                  ULL(1)
 #if !ERROR_DEPRECATED
 #define SMC_TYPE_STD                   ULL(0)
 #endif
 #define SMC_TYPE_YIELD                 U(0)
-#define SMC_PREEMPTED          U(0xfffffffe)
+#define SMC_PREEMPTED                  -2
 /*******************************************************************************
  * Owning entity number definitions inside the function id as per the SMC
  * calling convention
@@ -99,7 +99,7 @@
  */
 #define DEFINE_SVC_UUID(_name, _tl, _tm, _th, _cl, _ch, \
                _n0, _n1, _n2, _n3, _n4, _n5) \
-       CASSERT(_tl != SMC_UNK, invalid_svc_uuid);\
+       CASSERT((uint32_t)(_tl) != (uint32_t) SMC_UNK, invalid_svc_uuid);\
        static const uuid_t _name = { \
                _tl, _tm, _th, _cl, _ch, \
                { _n0, _n1, _n2, _n3, _n4, _n5 } \