Implement sysconf for Arm

- add support for using sysconf to get page size in _mallocr.c via
  HAVE_SYSCONF_PAGESIZE flag set in configure.host
- set flag in configure.host for arm and add a default sysconf implementation
  in libc/sys/arm that returns the page size
- the default implementation can be overridden outside newlib to allow a
  different page size to improve malloc on devices with a small footprint
  without needing to rebuild newlib
- this patch is based on a contribution from Torbjorn Svensson and
  Niklas Dahlquist (https://ecos.sourceware.org/ml/newlib/current/017616.html)

1 files changed, 34 insertions, 0 deletions

diff --git a/newlib/libc/sys/arm/sysconf.c b/newlib/libc/sys/arm/sysconf.c
new file mode 100644
index 0000000..0fbbe31
--- /dev/null
+++ b/newlib/libc/sys/arm/sysconf.c
@@ -0,0 +1,34 @@
+/* libc/sys/arm/sysconf.c - The sysconf function */
+
+/* Copyright 2020, STMicroelectronics
+ *
+ * All rights reserved.
+ *
+ * Redistribution, modification, and use in source and binary forms is permitted
+ * provided that the above copyright notice and following paragraph are
+ * duplicated in all such forms.
+ *
+ * This file is distributed WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#include <unistd.h>
+#include <errno.h>
+
+long sysconf(int name)
+{
+  switch (name)
+  {
+  case _SC_PAGESIZE:
+#ifdef SMALL_MEMORY
+    return 128;
+#else
+    return 4096;
+#endif
+
+  default:
+    errno = EINVAL;
+    return -1;
+  }
+  return -1; /* Can't get here */
+}