[PATCH v2 12/12] linux-user: fix clock_nanosleep()

["Alex Bennée" <alex.bennee@linaro.org>]

From: Laurent Vivier <laurent@vivier.eu>

If clock_nanosleep() encounters an error, it returns one of the positive
error number.

If the call is interrupted by a signal handler, it fails with error EINTR
and if "remain" is not NULL and "flags" is not TIMER_ABSTIME, it returns
the remaining unslept time in "remain".

Update linux-user to not overwrite the "remain" structure if there is no
error.

Found with "make check-tcg", linux-test fails on nanosleep test:

  TEST    linux-test on x86_64
.../tests/tcg/multiarch/linux-test.c:242: nanosleep
make[2]: *** [../Makefile.target:153: run-linux-test] Error 1
make[1]: *** [.../tests/tcg/Makefile.qemu:76: run-guest-tests] Error 2
make: *** [.../tests/Makefile.include:857: run-tcg-tests-x86_64-linux-user] Error 2

Reported-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200721201754.2731479-1-laurent@vivier.eu>
---
 linux-user/syscall.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 1211e759c26..caa7cd3cab9 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -11829,10 +11829,19 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
     {
         struct timespec ts;
         target_to_host_timespec(&ts, arg3);
-        ret = get_errno(safe_clock_nanosleep(arg1, arg2,
-                                             &ts, arg4 ? &ts : NULL));
-        if (arg4)
+        /*
+         * clock_nanosleep() returns 0 or one of the *positive* error number.
+         */
+        ret = host_to_target_errno(safe_clock_nanosleep(arg1, arg2, &ts,
+                                                        arg4 ? &ts : NULL));
+        /*
+         * if the call is interrupted by a signal handler, it fails
+         * with error TARGET_EINTR and if arg4 is not NULL and arg2 is not
+         * TIMER_ABSTIME, it returns the remaining unslept time in arg4.
+         */
+        if (ret == TARGET_EINTR && arg4 && arg2 != TIMER_ABSTIME) {
             host_to_target_timespec(arg4, &ts);
+        }
 
 #if defined(TARGET_PPC)
         /* clock_nanosleep is odd in that it returns positive errno values.
-- 
2.20.1