posix: implement the XSI_SINGLE_PROCESS Option Group

gettimeofday() was already implemented, but incorrectly lumped into
POSIX_TIMERS.

putenv() is really just a wrapper around setenv().

The only one left to implement was gethostid() which was relatively
trivial.

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

include/zephyr/posix/unistd.h

@@ -77,6 +77,10 @@ size_t confstr(int name, char *buf, size_t len);
 long sysconf(int opt);
 #endif /* CONFIG_POSIX_SYSCONF_IMPL_FULL */
 
+#if _XOPEN_SOURCE >= 500
+long gethostid(void);
+#endif
+
 #ifdef __cplusplus
 }
 #endif

lib/posix/options/CMakeLists.txt

@@ -3,6 +3,7 @@
 set(GEN_DIR ${ZEPHYR_BINARY_DIR}/include/generated)
 
 zephyr_syscall_header_ifdef(CONFIG_POSIX_TIMERS posix_clock.h)
+zephyr_syscall_header_ifdef(CONFIG_XSI_SINGLE_PROCESS posix_clock.h)
 
 if(CONFIG_POSIX_API)
   zephyr_include_directories(${ZEPHYR_BASE}/include/zephyr/posix)
@@ -155,6 +156,14 @@ endif()
 
 zephyr_library_sources_ifdef(CONFIG_XOPEN_STREAMS stropts.c)
 
+if (NOT CONFIG_TC_PROVIDES_XSI_SINGLE_PROCESS)
+  zephyr_library_sources_ifdef(CONFIG_XSI_SINGLE_PROCESS
+    clock_common.c
+    env_common.c
+    xsi_single_process.c
+  )
+endif()
+
 if (NOT CONFIG_TC_PROVIDES_XSI_SYSTEM_LOGGING)
   zephyr_library_sources_ifdef(CONFIG_XSI_SYSTEM_LOGGING syslog.c)
 endif()

lib/posix/options/Kconfig.proc1

@@ -49,8 +49,12 @@ config POSIX_UNAME_NODENAME_LEN
 	help
 	  Defines the maximum string length of nodename version.
 
+endif # POSIX_SINGLE_PROCESS
+
+if POSIX_SINGLE_PROCESS || XSI_SINGLE_PROCESS
+
 module = POSIX_ENV
 module-str = POSIX env logging
 source "subsys/logging/Kconfig.template.log_config"
 
-endif # POSIX_SINGLE_PROCESS
+endif # POSIX_SINGLE_PROCESS || XSI_SINGLE_PROCESS

lib/posix/options/Kconfig.profile

@@ -12,6 +12,7 @@ config POSIX_API
 	imply EVENTFD # eventfd(), eventfd_read(), eventfd_write()
 	imply POSIX_FD_MGMT # open(), close(), read(), write()
 	imply POSIX_MULTI_PROCESS # sleep(), getpid(), etc
+	imply XSI_SINGLE_PROCESS # gettimeofday()
 	help
 	  This option enables the required POSIX System Interfaces (base definitions), all of PSE51,
 	  and some features found in PSE52.

lib/posix/options/Kconfig.xsi_single_process

@@ -4,11 +4,14 @@
 
 config XSI_SINGLE_PROCESS
 	bool "X/Open single process"
-	depends on POSIX_SINGLE_PROCESS
+	select HWINFO
-	depends on POSIX_TIMERS
 	help
 	  Select 'y' here and Zephyr will provide implementations of
 	  gethostid(), gettimeofday(), and putenv().
 
 	  For more information, please see
 	  https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_subprofiles.html
+
+module = XSI_SINGLE_PROCESS
+module-str = XSI Single Process
+source "subsys/logging/Kconfig.template.log_config"

lib/posix/options/clock.c

@@ -91,27 +91,6 @@ int nanosleep(const struct timespec *rqtp, struct timespec *rmtp)
 	return z_clock_nanosleep(CLOCK_MONOTONIC, 0, rqtp, rmtp);
 }
 
-/**
- * @brief Get current real time.
- *
- * See IEEE 1003.1
- */
-int gettimeofday(struct timeval *tv, void *tz)
-{
-	struct timespec ts;
-	int res;
-
-	/* As per POSIX, "if tzp is not a null pointer, the behavior
-	 * is unspecified."  "tzp" is the "tz" parameter above. */
-	ARG_UNUSED(tz);
-
-	res = clock_gettime(CLOCK_REALTIME, &ts);
-	tv->tv_sec = ts.tv_sec;
-	tv->tv_usec = ts.tv_nsec / NSEC_PER_USEC;
-
-	return res;
-}
-
 int clock_getcpuclockid(pid_t pid, clockid_t *clock_id)
 {
 	/* We don't allow any process ID but our own.  */

lib/posix/options/xsi_single_process.c

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2018 Intel Corporation
+ * Copyright (c) 2023 Meta
+ * Copyright (c) 2025 Tenstorrent AI ULC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <errno.h>
+#include <string.h>
+#include <sys/time.h>
+#include <time.h>
+
+#include <zephyr/drivers/hwinfo.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/sys_clock.h>
+#include <zephyr/toolchain.h>
+
+LOG_MODULE_REGISTER(xsi_single_process, CONFIG_XSI_SINGLE_PROCESS_LOG_LEVEL);
+
+extern int z_setenv(const char *name, const char *val, int overwrite);
+extern int z_clock_gettime(clockid_t clockid, struct timespec *tp);
+
+long gethostid(void)
+{
+	int rc;
+	uint32_t buf = 0;
+
+	rc = hwinfo_get_device_id((uint8_t *)&buf, sizeof(buf));
+	if ((rc < 0) || (rc != sizeof(buf)) || (buf == 0)) {
+		LOG_DBG("%s() failed: %d", "hwinfo_get_device_id", rc);
+		return (long)rc;
+	}
+
+	return (long)buf;
+}
+
+int gettimeofday(struct timeval *tv, void *tz)
+{
+	struct timespec ts;
+	int res;
+
+	/*
+	 * As per POSIX, "if tzp is not a null pointer, the behavior is unspecified."  "tzp" is the
+	 * "tz" parameter above.
+	 */
+	ARG_UNUSED(tz);
+
+	res = z_clock_gettime(CLOCK_REALTIME, &ts);
+	if (res < 0) {
+		LOG_DBG("%s() failed: %d", "clock_gettime", res);
+		return res;
+	}
+
+	tv->tv_sec = ts.tv_sec;
+	tv->tv_usec = ts.tv_nsec / NSEC_PER_USEC;
+
+	return 0;
+}
+
+int putenv(char *string)
+{
+	if (string == NULL) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	char *const name = string;
+
+	for (char *val = name; *val != '\0'; ++val) {
+		if (*val == '=') {
+			int rc;
+
+			*val = '\0';
+			++val;
+			rc = z_setenv(name, val, 1);
+			--val;
+			*val = '=';
+
+			if (rc < 0) {
+				LOG_DBG("%s() failed: %d", "setenv", rc);
+				return rc;
+			}
+
+			return 0;
+		}
+	}
+
+	/* was unable to find '=' in string */
+	errno = EINVAL;
+	return -1;
+}

tests/lib/time/prj.conf

@@ -1,3 +1,4 @@
 CONFIG_ZTEST=y
 CONFIG_POSIX_TIMERS=y
+CONFIG_XSI_SINGLE_PROCESS=y
 CONFIG_PICOLIBC=y

tests/posix/headers/src/sys_time_h.c

@@ -29,7 +29,7 @@ ZTEST(posix_headers, test_sys_time_h)
 	/* zassert_not_equal(-1, ITIMER_VIRTUAL); */ /* not implemented */
 	/* zassert_not_equal(-1, ITIMER_PROF); */ /* not implemented */
 
-	if (IS_ENABLED(CONFIG_POSIX_API)) {
+	if (IS_ENABLED(CONFIG_XSI_SINGLE_PROCESS)) {
 		/* zassert_not_null(getitimer); */ /* not implemented */
 		zassert_not_null(gettimeofday);
 		/* zassert_not_null(setitimer); */ /* not implemented */