Add ARM HW feature detection module and add NEON detection

* configure.ac: Add option --disable-neon-support.
(HAVE_GCC_INLINE_ASM_NEON): New.
(ENABLE_NEON_SUPPORT): New.
[arm]: Add 'hwf-arm.lo' as HW feature module.
* src/Makefile.am: Add 'hwf-arm.c'.
* src/g10lib.h (HWF_ARM_NEON): New macro.
* src/global.c (hwflist): Add HWF_ARM_NEON entry.
* src/hwf-arm.c: New file.
* src/hwf-common.h (_gcry_hwf_detect_arm): New prototype.
* src/hwfeatures.c (_gcry_detect_hw_features) [HAVE_CPU_ARCH_ARM]: Add
call to _gcry_hwf_detect_arm.
--

Add HW detection module for detecting ARM NEON instruction set. ARM does not
have cpuid instruction so we have to rely on OS to pass feature set information
to user-space. For linux, NEON support can be detected by parsing
'/proc/self/auxv' for hardware capabilities information. For other OSes, NEON
can be detected by checking if platform/compiler only supports NEON capable
CPUs (by check if __ARM_NEON__ macro is defined).

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>

1 files changed, 113 insertions, 0 deletions

diff --git a/src/hwf-arm.c b/src/hwf-arm.c
new file mode 100644
index 00000000..9ab4cd0f
--- /dev/null
+++ b/src/hwf-arm.c
@@ -0,0 +1,113 @@
+/* hwf-arm.c - Detect hardware features - ARM part
+ * Copyright © 2013  Jussi Kivilinna <jussi.kivilinna@iki.fi>
+ *
+ * This file is part of Libgcrypt.
+ *
+ * Libgcrypt is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * Libgcrypt is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdarg.h>
+#include <unistd.h>
+
+#include "g10lib.h"
+#include "hwf-common.h"
+
+#if !defined (__arm__)
+# error Module build for wrong CPU.
+#endif
+
+#undef HAS_SYS_AT_HWCAP
+#ifdef __linux__
+
+#define HAS_SYS_AT_HWCAP 1
+
+#define AT_HWCAP 16
+#define HWCAP_NEON 4096
+
+static int get_hwcap(unsigned int *hwcap)
+{
+  struct { unsigned int a_type; unsigned int a_val; } auxv;
+  FILE *f;
+  int err = -1;
+  static int hwcap_initialized = 0;
+  static unsigned int stored_hwcap;
+
+  if (hwcap_initialized)
+    {
+      *hwcap = stored_hwcap;
+      return 0;
+    }
+
+  f = fopen("/proc/self/auxv", "r");
+  if (!f)
+    {
+      *hwcap = stored_hwcap;
+      return -1;
+    }
+
+  while (fread(&auxv, sizeof(auxv), 1, f) > 0)
+    {
+      if (auxv.a_type != AT_HWCAP)
+        continue;
+
+      stored_hwcap = auxv.a_val;
+      hwcap_initialized = 1;
+      err = 0;
+      break;
+    }
+
+  fclose(f);
+  *hwcap = stored_hwcap;
+  return err;
+}
+
+static unsigned int detect_arm_at_hwcap(void)
+{
+  unsigned int hwcap;
+  unsigned int features = 0;
+
+  if (get_hwcap(&hwcap) < 0)
+    return features;
+
+#ifdef ENABLE_NEON_SUPPORT
+  if (hwcap & HWCAP_NEON)
+    features |= HWF_ARM_NEON;
+#endif
+
+  return features;
+}
+
+#endif /* __linux__ */
+
+unsigned int
+_gcry_hwf_detect_arm (void)
+{
+  unsigned int ret = 0;
+
+#if defined (HAS_SYS_AT_HWCAP)
+  ret |= detect_arm_at_hwcap ();
+#else
+  ret |= 0;
+#endif
+
+#if defined(__ARM_NEON__) && defined(ENABLE_NEON_SUPPORT)
+  ret |= HWF_ARM_NEON;
+#endif
+
+  return ret;
+}