X-Git-Url: https://www.bearssl.org/gitweb//home/git/?p=BearSSL;a=blobdiff_plain;f=src%2Fconfig.h;h=9eadaf4a78288d3f895aa1665fcb785ca80b3062;hp=259f5bbb162a33503ea2305095fc9b0da4b29c49;hb=5f045c759957fdff8c85716e6af99e10901fdac0;hpb=3210f38e0491b39aec1ef419cb4114e9483089fb

diff --git a/src/config.h b/src/config.h
index 259f5bb..9eadaf4 100644
--- a/src/config.h
+++ b/src/config.h
@@ -41,6 +41,16 @@
 #define BR_64   1
  */
 
+/*
+ * When BR_LOMUL is enabled, then multiplications of 32-bit values whose
+ * result are truncated to the low 32 bits are assumed to be
+ * substantially more efficient than 32-bit multiplications that yield
+ * 64-bit results. This is typically the case on low-end ARM Cortex M
+ * systems (M0, M0+, M1, and arguably M3 and M4 as well).
+ *
+#define BR_LOMUL   1
+ */
+
 /*
  * When BR_SLOW_MUL is enabled, multiplications are assumed to be
  * substantially slow with regards to other integer operations, thus
@@ -50,6 +60,15 @@
 #define BR_SLOW_MUL   1
  */
 
+/*
+ * When BR_SLOW_MUL15 is enabled, short multplications (on 15-bit words)
+ * are assumed to be substantially slow with regards to other integer
+ * operations, thus making it worth to make more integer operations if
+ * it allows using less multiplications.
+ *
+#define BR_SLOW_MUL15   1
+ */
+
 /*
  * When BR_CT_MUL31 is enabled, multiplications of 31-bit values (used
  * in the "i31" big integer implementation) use an alternate implementation
@@ -60,6 +79,25 @@
 #define BR_CT_MUL31   1
  */
 
+/*
+ * When BR_CT_MUL15 is enabled, multiplications of 15-bit values (held
+ * in 32-bit words) use an alternate implementation which is slower and
+ * larger than the normal multiplication, but should ensure
+ * constant-time multiplications on most/all architectures where the
+ * basic multiplication is not constant-time.
+#define BR_CT_MUL15   1
+ */
+
+/*
+ * When BR_NO_ARITH_SHIFT is enabled, arithmetic right shifts (with sign
+ * extension) are performed with a sequence of operations which is bigger
+ * and slower than a simple right shift on a signed value. This avoids
+ * relying on an implementation-defined behaviour. However, most if not
+ * all C compilers use sign extension for right shifts on signed values,
+ * so this alternate macro is disabled by default.
+#define BR_NO_ARITH_SHIFT   1
+ */
+
 /*
  * When BR_USE_URANDOM is enabled, the SSL engine will use /dev/urandom
  * to automatically obtain quality randomness for seedings its internal
@@ -99,4 +137,29 @@
 #define BR_USE_WIN32_TIME   1
  */
 
+/*
+ * When BR_ARMEL_CORTEXM_GCC is enabled, some operations are replaced with
+ * inline assembly which is shorter and/or faster. This should be used
+ * only when all of the following are true:
+ *   - target architecture is ARM in Thumb mode
+ *   - target endianness is little-endian
+ *   - compiler is GCC (or GCC-compatible for inline assembly syntax)
+ *
+ * This is meant for the low-end cores (Cortex M0, M0+, M1, M3).
+ * Note: if BR_LOMUL is not explicitly enabled or disabled, then
+ * enabling BR_ARMEL_CORTEXM_GCC also enables BR_LOMUL.
+ *
+#define BR_ARMEL_CORTEXM_GCC   1
+ */
+
+/*
+ * When BR_AES_X86NI is enabled, the AES implementation using the x86 "NI"
+ * instructions (dedicated AES opcodes) will be compiled. If this is not
+ * enabled explicitly, then that AES implementation will be compiled only
+ * if a compatible compiler is detected. If set explicitly to 0, the
+ * implementation will not be compiled at all.
+ *
+#define BR_AES_X86NI   1
+ */
+
 #endif