[committed] libstdc++: Support getentropy and arc4random in std::random_device
Jonathan Wakely
jwakely@redhat.com
Tue Nov 9 14:41:59 GMT 2021
Tested x86_64-linux, and Iain Sandoe tested the arc4random code on
darwin too. Pushed to trunk.
This adds additional "getentropy" and "arc4random" tokens to
std::random_device. The former is supported on Glibc and OpenBSD (and
apparently wasm), and the latter is supported on various BSDs.
libstdc++-v3/ChangeLog:
* acinclude.m4 (GLIBCXX_CHECK_GETENTROPY, GLIBCXX_CHECK_ARC4RANDOM):
Define.
* configure.ac (GLIBCXX_CHECK_GETENTROPY, GLIBCXX_CHECK_ARC4RANDOM):
Use them.
* config.h.in: Regenerate.
* configure: Regenerate.
* src/c++11/random.cc (random_device): Add getentropy and
arc4random as sources.
* testsuite/26_numerics/random/random_device/cons/token.cc:
Check new tokens.
* testsuite/26_numerics/random/random_device/entropy.cc:
Likewise.
---
libstdc++-v3/acinclude.m4 | 46 ++++++++
libstdc++-v3/config.h.in | 6 +
libstdc++-v3/configure | 103 ++++++++++++++++++
libstdc++-v3/configure.ac | 4 +
libstdc++-v3/src/c++11/random.cc | 69 +++++++++++-
.../random/random_device/cons/token.cc | 1 +
.../random/random_device/entropy.cc | 7 ++
7 files changed, 234 insertions(+), 2 deletions(-)
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 90ecc4a87a2..497af5723e1 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4830,6 +4830,52 @@ AC_DEFUN([GLIBCXX_CHECK_EXCEPTION_PTR_SYMVER], [
fi
])
+dnl
+dnl Check whether getentropy is present in <unistd.h>.
+dnl
+AC_DEFUN([GLIBCXX_CHECK_GETENTROPY], [
+
+ AC_LANG_SAVE
+ AC_LANG_CPLUSPLUS
+ AC_MSG_CHECKING([for getentropy])
+ AC_CACHE_VAL(glibcxx_cv_getentropy, [
+ AC_TRY_COMPILE(
+ [#include <unistd.h>],
+ [unsigned i;
+ ::getentropy(&i, sizeof(i));],
+ [glibcxx_cv_getentropy=yes], [glibcxx_cv_getentropy=no])
+ ])
+
+ if test $glibcxx_cv_getentropy = yes; then
+ AC_DEFINE(HAVE_GETENTROPY, 1, [Define if getentropy is available in <unistd.h>.])
+ fi
+ AC_MSG_RESULT($glibcxx_cv_getentropy)
+ AC_LANG_RESTORE
+])
+
+dnl
+dnl Check whether arc4random is present in <stdlib.h>.
+dnl
+AC_DEFUN([GLIBCXX_CHECK_ARC4RANDOM], [
+
+ AC_LANG_SAVE
+ AC_LANG_CPLUSPLUS
+ AC_MSG_CHECKING([for arc4random])
+ AC_CACHE_VAL(glibcxx_cv_arc4random, [
+ AC_TRY_COMPILE(
+ [#include <stdlib.h>],
+ [unsigned i = ::arc4random();],
+ [glibcxx_cv_arc4random=yes], [glibcxx_cv_arc4random=no])
+ ])
+
+ if test $glibcxx_cv_arc4random = yes; then
+ AC_DEFINE(HAVE_ARC4RANDOM, 1, [Define if arc4random is available in <stdlib.h>.])
+ fi
+ AC_MSG_RESULT($glibcxx_cv_arc4random)
+ AC_LANG_RESTORE
+])
+
+
# Macros from the top-level gcc directory.
m4_include([../config/gc++filt.m4])
m4_include([../config/tls.m4])
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index 2d68b3672b9..5b3c92f4bd7 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -468,6 +468,10 @@ GLIBCXX_CHECK_X86_RDRAND
# Check if assembler supports rdseed opcode.
GLIBCXX_CHECK_X86_RDSEED
+# Check for other random number APIs
+GLIBCXX_CHECK_GETENTROPY
+GLIBCXX_CHECK_ARC4RANDOM
+
# This depends on GLIBCXX_ENABLE_SYMVERS and GLIBCXX_IS_NATIVE.
GLIBCXX_CONFIGURE_TESTSUITE
diff --git a/libstdc++-v3/src/c++11/random.cc b/libstdc++-v3/src/c++11/random.cc
index 4b88818646f..4a553e0d84f 100644
--- a/libstdc++-v3/src/c++11/random.cc
+++ b/libstdc++-v3/src/c++11/random.cc
@@ -68,7 +68,12 @@
# include <stdlib.h>
#endif
-#if defined _GLIBCXX_USE_CRT_RAND_S || defined _GLIBCXX_USE_DEV_RANDOM
+#ifdef _GLIBCXX_HAVE_GETENTROPY
+# include <unistd.h>
+#endif
+
+#if defined _GLIBCXX_USE_CRT_RAND_S || defined _GLIBCXX_USE_DEV_RANDOM \
+ || _GLIBCXX_HAVE_GETENTROPY
// The OS provides a source of randomness we can use.
# pragma GCC poison _M_mt
#elif defined USE_RDRAND || defined USE_RDSEED || defined USE_DARN
@@ -166,6 +171,25 @@ namespace std _GLIBCXX_VISIBILITY(default)
}
#endif
+#ifdef _GLIBCXX_HAVE_GETENTROPY
+ unsigned int
+ __libc_getentropy(void*)
+ {
+ unsigned int val;
+ if (::getentropy(&val, sizeof(val)) != 0)
+ std::__throw_runtime_error(__N("random_device: getentropy failed"));
+ return val;
+ }
+#endif
+
+#ifdef _GLIBCXX_HAVE_ARC4RANDOM
+ unsigned int
+ __libc_arc4random(void*)
+ {
+ return ::arc4random();
+ }
+#endif
+
#ifdef USE_LCG
// TODO: use this to seed std::mt19937 engine too.
unsigned
@@ -214,7 +238,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
#endif
enum Which : unsigned {
- device_file = 1, prng = 2, rand_s = 4,
+ device_file = 1, prng = 2, rand_s = 4, getentropy = 8, arc4random = 16,
rdseed = 64, rdrand = 128, darn = 256,
any = 0xffff
};
@@ -256,6 +280,16 @@ namespace std _GLIBCXX_VISIBILITY(default)
return device_file;
#endif
+#ifdef _GLIBCXX_HAVE_ARC4RANDOM
+ if (func == __libc_arc4random)
+ return arc4random;
+#endif
+
+#ifdef _GLIBCXX_HAVE_GETENTROPY
+ if (func == __libc_getentropy)
+ return getentropy;
+#endif
+
#ifdef USE_LCG
if (func == &__lcg)
return prng;
@@ -311,6 +345,14 @@ namespace std _GLIBCXX_VISIBILITY(default)
else if (token == "rand_s")
which = rand_s;
#endif // _GLIBCXX_USE_CRT_RAND_S
+#ifdef _GLIBCXX_HAVE_GETENTROPY
+ else if (token == "getentropy")
+ which = getentropy;
+#endif // _GLIBCXX_HAVE_GETENTROPY
+#ifdef _GLIBCXX_HAVE_ARC4RANDOM
+ else if (token == "arc4random")
+ which = arc4random;
+#endif // _GLIBCXX_HAVE_ARC4RANDOM
#ifdef _GLIBCXX_USE_DEV_RANDOM
else if (token == "/dev/urandom" || token == "/dev/random")
{
@@ -395,6 +437,26 @@ namespace std _GLIBCXX_VISIBILITY(default)
}
#endif // USE_DARN
+#ifdef _GLIBCXX_HAVE_ARC4RANDOM
+ if (which & arc4random)
+ {
+ _M_func = &__libc_arc4random;
+ return;
+ }
+#endif // _GLIBCXX_HAVE_ARC4RANDOM
+
+#ifdef _GLIBCXX_HAVE_GETENTROPY
+ if (which & getentropy)
+ {
+ unsigned int i;
+ if (::getentropy(&i, sizeof(i)) == 0) // On linux the syscall can fail.
+ {
+ _M_func = &__libc_getentropy;
+ return;
+ }
+ }
+#endif // _GLIBCXX_HAVE_GETENTROPY
+
#ifdef _GLIBCXX_USE_DEV_RANDOM
if (which & device_file)
{
@@ -548,6 +610,9 @@ namespace std _GLIBCXX_VISIBILITY(default)
case rdseed:
case darn:
return (double) max;
+ case arc4random:
+ case getentropy:
+ return (double) max;
case rand_s:
case prng:
return 0.0;
diff --git a/libstdc++-v3/testsuite/26_numerics/random/random_device/cons/token.cc b/libstdc++-v3/testsuite/26_numerics/random/random_device/cons/token.cc
index 07713e5c67f..e56afbc9c97 100644
--- a/libstdc++-v3/testsuite/26_numerics/random/random_device/cons/token.cc
+++ b/libstdc++-v3/testsuite/26_numerics/random/random_device/cons/token.cc
@@ -53,6 +53,7 @@ test03()
const std::string tokens[] = {
"rdseed", "rdrand", "darn",
"rand_s", "/dev/urandom", "/dev/random",
+ "getentropy", "arc4random",
"mt19937", "prng"
};
int count = 0;
diff --git a/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc b/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc
index 6f3ebb1b38e..63b7043bf9b 100644
--- a/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc
+++ b/libstdc++-v3/testsuite/26_numerics/random/random_device/entropy.cc
@@ -28,6 +28,13 @@ test01()
const double entropy = std::random_device(token).entropy();
VERIFY( entropy == max );
}
+
+ for (auto token : { "getentropy", "arc4random" })
+ if (__gnu_test::random_device_available(token))
+ {
+ const double entropy = std::random_device(token).entropy();
+ VERIFY( entropy == max );
+ }
}
int
--
2.31.1
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