[PATCH 13/13] tools/nolibc: sys_gettimeofday: riscv: use __NR_clock_gettime64 for rv32

Zhangjin Wu
2023-05-24T18:03:53Z

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@tinylab.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