ECC: optimize the pool of temporary variables

ECC is using a lot (80) temporary variables. These variables
are taken from a static pool, each being of the maximum key size
supported in OP-TEE: 4096bits, times 2 to include
wrapping multiplication in temporary computation.

With the introduction of being able to get temporary variables
of a given size, the current patch optimize the use of the variables
in case of ECC.

Thanks to this patch, the number of temporary variables is back to 50,
and the emulated esram size (QEMU / FVP / HiKey) is back to 200KB.

Note that further optimization can be performed, for ECC and also
for other algorithms (RSA,...).

Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Tested-by: Pascal Brand <pascal.brand@linaro.org> (QEMU platform)
Signed-off-by: Pascal Brand <pascal.brand@st.com>
[jf: pick 6d914f6, keep LTC changes only, use new header paths]
[jf: resolve conflicts, applying 0c6c51d on top of LTC v1.18.2-681-ge6be20bf]
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>

core/lib/libtomcrypt/src/headers/tomcrypt_math.h

@@ -43,6 +43,13 @@ typedef struct {
    */
    int (*init)(void **a);
 
+   /** initialize a bignum
+     @param   size_bits   The size of the number we compute on
+     @param   a           The number to initialize
+     @return  CRYPT_OK on success
+   */
+   int (*init_size)(int size_bits, void **a);
+
    /** init copy
      @param  dst    The number to initialize and write to
      @param  src    The number to copy from
@@ -503,6 +510,7 @@ typedef struct {
 extern ltc_math_descriptor ltc_mp;
 
 int ltc_init_multi(void **a, ...) LTC_NULL_TERMINATED;
+int ltc_init_multi_size(int size_bits, void **a, ...) LTC_NULL_TERMINATED;
 void ltc_deinit_multi(void *a, ...) LTC_NULL_TERMINATED;
 void ltc_cleanup_multi(void **a, ...) LTC_NULL_TERMINATED;
 

core/lib/libtomcrypt/src/headers/tomcrypt_private.h

@@ -169,6 +169,8 @@ void ocb3_int_xor_blocks(unsigned char *out, const unsigned char *block_a, const
 /* some handy macros */
 #define mp_init(a)                   ltc_mp.init(a)
 #define mp_init_multi                ltc_init_multi
+#define mp_init_size(a, b)           ltc_mp.init_size(a, b)
+#define mp_init_multi_size           ltc_init_multi_size
 #define mp_clear(a)                  ltc_mp.deinit(a)
 #define mp_clear_multi               ltc_deinit_multi
 #define mp_cleanup_multi             ltc_cleanup_multi

core/lib/libtomcrypt/src/math/multi.c

@@ -34,6 +34,34 @@ int ltc_init_multi(void **a, ...)
    return CRYPT_OK;
 }
 
+int ltc_init_multi_size(int size_bits, void **a, ...)
+{
+   void    **cur = a;
+   int       np  = 0;
+   va_list   args;
+
+   va_start(args, a);
+   while (cur != NULL) {
+       if (mp_init_size(size_bits, cur) != CRYPT_OK) {
+          /* failed */
+          va_list clean_list;
+
+          va_start(clean_list, a);
+          cur = a;
+          while (np--) {
+              mp_clear(*cur);
+              cur = va_arg(clean_list, void**);
+          }
+          va_end(clean_list);
+          return CRYPT_MEM;
+       }
+       ++np;
+       cur = va_arg(args, void**);
+   }
+   va_end(args);
+   return CRYPT_OK;
+}
+
 void ltc_deinit_multi(void *a, ...)
 {
    void     *cur = a;

core/lib/libtomcrypt/src/pk/ecc/ltc_ecc_points.c

@@ -21,7 +21,8 @@ ecc_point *ltc_ecc_new_point(void)
    if (p == NULL) {
       return NULL;
    }
-   if (mp_init_multi(&p->x, &p->y, &p->z, LTC_NULL) != CRYPT_OK) {
+   if (mp_init_multi_size(LTC_MAX_ECC * 2,
+			  &p->x, &p->y, &p->z, LTC_NULL) != CRYPT_OK) {
       XFREE(p);
       return NULL;
    }