commit c9efa00871a253203be3a3fa1d618d4fd5567236
author Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Thu Aug 24 10:25:06 2017 +0200
committer Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Thu Aug 24 10:25:06 2017 +0200
tree 8b751c82405e9deeabee8d2c4021238d4e2bbbee
parent db4a8eb992f0d563a86ddf3998d8c45c619dad31

ECP: Use explicit state assignments

Incrementing the state is error-prone as we can end up doing it too many times
(loops) or not enough (skipped branches), or just make programming mistakes
(eg. the state was incremented twice at the end, so it ended up with a value
not in the enum...)

This is the first step of the rework, the next one will rationalize where the
state assignments are done.

library/ecp.c

diff --git a/library/ecp.c b/library/ecp.c
index f2c7448..fc4838a 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1563,7 +1563,7 @@
     if( rs_ctx != NULL && rs_ctx->rsm != NULL )
     {
         rs_ctx->rsm->i = 0;
-        rs_ctx->rsm->state++;
+        rs_ctx->rsm->state = ecp_rsm_pre_norm_dbl;
     }
 #endif
 
@@ -1585,7 +1585,7 @@
 
 #if defined(MBEDTLS_ECP_RESTARTABLE)
     if( rs_ctx != NULL && rs_ctx->rsm != NULL )
-        rs_ctx->rsm->state++;
+        rs_ctx->rsm->state = ecp_rsm_pre_add;
 #endif
 
     /*
@@ -1607,7 +1607,7 @@
 
 #if defined(MBEDTLS_ECP_RESTARTABLE)
     if( rs_ctx != NULL && rs_ctx->rsm != NULL )
-        rs_ctx->rsm->state++;
+        rs_ctx->rsm->state = ecp_rsm_pre_norm_add;
 #endif
 
     /*
@@ -1628,7 +1628,7 @@
 
 #if defined(MBEDTLS_ECP_RESTARTABLE)
     if( rs_ctx != NULL && rs_ctx->rsm != NULL )
-        rs_ctx->rsm->state++;
+        rs_ctx->rsm->state = ecp_rsm_T_done;
 #endif
 
 cleanup:
@@ -1730,7 +1730,7 @@
     {
         if( ret == 0 )
         {
-            rs_ctx->rsm->state++;
+            rs_ctx->rsm->state = ecp_rsm_final_norm;
             rs_ctx->rsm->i = 0;
         }
         else if( ret == MBEDTLS_ERR_ECP_IN_PROGRESS )
@@ -1834,7 +1834,7 @@
 
 #if defined(MBEDTLS_ECP_RESTARTABLE)
         if( rs_ctx != NULL && rs_ctx->rsm != NULL )
-            rs_ctx->rsm->state++;
+            rs_ctx->rsm->state = ecp_rsm_final_norm;
 #endif
     }
 
@@ -2420,14 +2420,14 @@
     MBEDTLS_MPI_CHK( mbedtls_ecp_mul_shortcuts( grp, pmP, m, P, rs_ctx ) );
 #if defined(MBEDTLS_ECP_RESTARTABLE)
     if( rs_ctx != NULL && rs_ctx->ma != NULL )
-        rs_ctx->ma->state++;
+        rs_ctx->ma->state = ecp_rsma_mul2;
 
 mul2:
 #endif
     MBEDTLS_MPI_CHK( mbedtls_ecp_mul_shortcuts( grp, pR,  n, Q, rs_ctx ) );
 #if defined(MBEDTLS_ECP_RESTARTABLE)
     if( rs_ctx != NULL && rs_ctx->ma != NULL )
-        rs_ctx->ma->state++;
+        rs_ctx->ma->state = ecp_rsma_add;
 
 add:
 #endif
@@ -2435,7 +2435,7 @@
     MBEDTLS_MPI_CHK( ecp_add_mixed( grp, pR, pmP, pR ) );
 #if defined(MBEDTLS_ECP_RESTARTABLE)
     if( rs_ctx != NULL && rs_ctx->ma != NULL )
-        rs_ctx->ma->state++;
+        rs_ctx->ma->state = ecp_rsma_norm;
 
 norm:
 #endif