linux-kernel - [PATCH 13/13] tools/nolibc: sys_gettimeofday: riscv: use __NR_clock

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Message-Id: <e35cf1de35fdb0a236064ff645ae4734d32bacd4.1684949845.git.falcon@tinylab.org>
Date:   Thu, 25 May 2023 02:03:32 +0800
From:   Zhangjin Wu <falcon@...ylab.org>
To:     w@....eu
Cc:     falcon@...ylab.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-riscv@...ts.infradead.org,
        palmer@...belt.com, paul.walmsley@...ive.com, thomas@...ch.de
Subject: [PATCH 13/13] tools/nolibc: sys_gettimeofday: riscv: use __NR_clock_gettime64 for rv32

rv32 uses the generic include/uapi/asm-generic/unistd.h and it has no
__NR_gettimeofday and __NR_clock_gettime after kernel commit d4c08b9776b3
("riscv: Use latest system call ABI"), use __NR_clock_gettime64 instead.

This code is based on src/time/gettimeofday.c of musl and
sysdeps/unix/sysv/linux/clock_gettime.c of glibc.

Both __NR_clock_gettime and __NR_clock_gettime64 are added for
sys_gettimeofday() for they share most of the code.

Notes:

* Both tv and tz are not directly passed to kernel clock_gettime*
  syscalls, so, it isn't able to check the pointer automatically with the
  get_user/put_user helpers just like kernel gettimeofday syscall does.
  instead, we emulate (but not completely) such checks in our new
  __NR_clock_gettime* branch of nolibc.

* kernel clock_gettime* syscalls can not get tz info, just like musl and
  glibc do, we set tz to zero to avoid a random number.

Signed-off-by: Zhangjin Wu <falcon@...ylab.org>
---
 tools/include/nolibc/sys.h | 46 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index 2642b380c6aa..ad38cc3856be 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -26,6 +26,7 @@
 
 #include "arch.h"
 #include "errno.h"
+#include "string.h"
 #include "types.h"
 
 
@@ -51,6 +52,11 @@
  * should not be placed here.
  */
 
+/*
+ * This is the first address past the end of the text segment (the program code).
+ */
+
+extern char etext;
 
 /*
  * int brk(void *addr);
@@ -554,7 +560,47 @@ long getpagesize(void)
 static __attribute__((unused))
 int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
+#ifdef __NR_gettimeofday
 	return my_syscall2(__NR_gettimeofday, tv, tz);
+#elif defined(__NR_clock_gettime) || defined(__NR_clock_gettime64)
+#ifdef __NR_clock_gettime
+	struct timespec ts;
+#else
+	struct timespec64 ts;
+#define __NR_clock_gettime __NR_clock_gettime64
+#endif
+	int ret;
+
+	/* make sure tv pointer is at least after code segment */
+	if (tv != NULL && (char *)tv <= &etext)
+		return -EFAULT;
+
+	/* set tz to zero to avoid random number */
+	if (tz != NULL) {
+		if ((char *)tz > &etext)
+			memset(tz, 0, sizeof(struct timezone));
+		else
+			return -EFAULT;
+	}
+
+	if (tv == NULL)
+		return 0;
+
+	ret = my_syscall2(__NR_clock_gettime, CLOCK_REALTIME, &ts);
+	if (ret)
+		return ret;
+
+	tv->tv_sec = (time_t) ts.tv_sec;
+#ifdef __NR_clock_gettime64
+	if (tv->tv_sec != ts.tv_sec)
+		return -EOVERFLOW;
+#endif
+
+	tv->tv_usec = ts.tv_nsec / 1000;
+	return 0;
+#else
+#error None of __NR_gettimeofday, __NR_clock_gettime and __NR_clock_gettime64 defined, cannot implement sys_gettimeofday()
+#endif
 }
 
 static __attribute__((unused))
-- 
2.25.1