posix: implement mprotect()

Provide a stub for mprotect() to satisfy the requirement for the
base definitions / system interfaces and subsequently PSE51,
PSE52, PSE52, etc.

Currently, Zephyr's virtual memory-management API does not seem
to support modifying memory protection bits after pages have
already been mapped.

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

include/zephyr/posix/posix_features.h

@@ -77,7 +77,9 @@
 #define _POSIX_MEMLOCK_RANGE _POSIX_VERSION
 #endif
 
-/* #define _POSIX_MEMORY_PROTECTION (-1L) */
+#ifdef CONFIG_POSIX_MEMORY_PROTECTION
+#define _POSIX_MEMORY_PROTECTION _POSIX_VERSION
+#endif
 
 #ifdef CONFIG_POSIX_MESSAGE_PASSING
 #define _POSIX_MESSAGE_PASSING _POSIX_VERSION

include/zephyr/posix/sys/sysconf.h

@@ -159,7 +159,8 @@ enum {
 	COND_CODE_1(CONFIG_POSIX_MEMLOCK, (_POSIX_MEMLOCK), (-1L))
 #define __z_posix_sysconf_SC_MEMLOCK_RANGE                                                         \
 	COND_CODE_1(CONFIG_POSIX_MEMLOCK_RANGE, (_POSIX_MEMLOCK_RANGE), (-1L))
-#define __z_posix_sysconf_SC_MEMORY_PROTECTION (-1L)
+#define __z_posix_sysconf_SC_MEMORY_PROTECTION                                                     \
+	COND_CODE_1(CONFIG_POSIX_MEMORY_PROTECTION, (_POSIX_MEMORY_PROTECTION), (-1L))
 #define __z_posix_sysconf_SC_MESSAGE_PASSING                                                       \
 	COND_CODE_1(CONFIG_POSIX_MESSAGE_PASSING, (_POSIX_MESSAGE_PASSING), (-1L))
 #define __z_posix_sysconf_SC_MONOTONIC_CLOCK                                                       \

lib/posix/options/CMakeLists.txt

@@ -53,6 +53,7 @@ zephyr_library_sources_ifdef(CONFIG_POSIX_FILE_SYSTEM fs.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_FSYNC fsync.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MEMLOCK mlockall.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MEMLOCK_RANGE mlock.c)
+zephyr_library_sources_ifdef(CONFIG_POSIX_MEMORY_PROTECTION mprotect.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MAPPED_FILES mmap.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MESSAGE_PASSING mqueue.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MULTI_PROCESS

lib/posix/options/Kconfig.mem

@@ -63,4 +63,14 @@ config POSIX_MEMLOCK_RANGE
 
 endif
 
+config POSIX_MEMORY_PROTECTION
+	bool "POSIX memory protection [EXPERIMENTAL]"
+	select EXPERIMENTAL
+	help
+	  Select 'y' here and Zephyr will provide support for mprotect().
+
+	  For more information, please see
+	  https://pubs.opengroup.org/onlinepubs/9699919799.orig/functions/V2_chap02.html
+	  https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_port.html#tag_24_03_04
+
 endmenu

lib/posix/options/mprotect.c

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2024, Tenstorrent AI ULC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <errno.h>
+#include <stddef.h>
+#include <sys/types.h>
+
+#include <zephyr/posix/sys/mman.h>
+
+int mprotect(void *addr, size_t len, int prot)
+{
+	ARG_UNUSED(addr);
+	ARG_UNUSED(len);
+	ARG_UNUSED(prot);
+
+	errno = ENOSYS;
+	return -1;
+}