[PATCH v8 01/17] eal: introduce new secure memory zero

[Stephen Hemminger <stephen@networkplumber.org>]

When memset() is used before a release function such as free,
the compiler if allowed to optimize the memset away under
the as-if rules. This is normally ok, but in certain cases such
as passwords or security keys it is problematic.

Introduce a DPDK wrapper which uses the bzero_explicit function
or SecureZeroMemory on Windows.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Morten Brørup <mb@smartsharesystems.com>
---
 lib/eal/common/eal_common_string_fns.c | 14 ++++++++++++++
 lib/eal/include/rte_string_fns.h       | 18 ++++++++++++++++++
 lib/eal/version.map                    |  3 +++
 3 files changed, 35 insertions(+)

diff --git a/lib/eal/common/eal_common_string_fns.c b/lib/eal/common/eal_common_string_fns.c
index 9ca2045b18..31804101cc 100644
--- a/lib/eal/common/eal_common_string_fns.c
+++ b/lib/eal/common/eal_common_string_fns.c
@@ -10,6 +10,10 @@
 #include <rte_string_fns.h>
 #include <rte_errno.h>
 
+#ifdef RTE_EXEC_ENV_WINDOWS
+#include <rte_windows.h>
+#endif
+
 /* split string into tokens */
 int
 rte_strsplit(char *string, int stringlen,
@@ -98,3 +102,13 @@ rte_str_to_size(const char *str)
 	}
 	return size;
 }
+
+void
+rte_memzero_explicit(void *dst, size_t sz)
+{
+#ifdef RTE_EXEC_ENV_WINDOWS
+	SecureZeroMemory(dst, sz);
+#else
+	explicit_bzero(dst, sz);
+#endif
+}
diff --git a/lib/eal/include/rte_string_fns.h b/lib/eal/include/rte_string_fns.h
index 702bd81251..79ca9abd67 100644
--- a/lib/eal/include/rte_string_fns.h
+++ b/lib/eal/include/rte_string_fns.h
@@ -149,6 +149,24 @@ rte_str_skip_leading_spaces(const char *src)
 	return p;
 }
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Fill memory with zero's (e.g. sensitive keys).
+ * Normally using memset() is fine, but in cases where clearing out local data
+ * before going out of scope is required, use rte_memzero_explicit() instead
+ * to prevent the compiler from optimizing away the zeroing operation.
+ *
+ * @param dst
+ *   target buffer
+ * @param sz
+ *   number of bytes to fill
+ */
+__rte_experimental
+void
+rte_memzero_explicit(void *dst, size_t sz);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/eal/version.map b/lib/eal/version.map
index a20c713eb1..82a3e91c97 100644
--- a/lib/eal/version.map
+++ b/lib/eal/version.map
@@ -398,6 +398,9 @@ EXPERIMENTAL {
 	# added in 24.11
 	rte_bitset_to_str;
 	rte_lcore_var_alloc;
+
+	# added in 25.03
+	rte_memzero_explicit;
 };
 
 INTERNAL {
-- 
2.47.2