[qemu-xen master] linux-user: fix clock_nanosleep()

[patchbot@xxxxxxx]

commit 8ec68a0a873d24d3f81e0f34892ec4b8b1215ccf
Author:     Laurent Vivier <laurent@xxxxxxxxx>
AuthorDate: Fri Jul 24 07:45:05 2020 +0100
Commit:     Alex Bennée <alex.bennee@xxxxxxxxxx>
CommitDate: Mon Jul 27 09:41:41 2020 +0100

    linux-user: fix clock_nanosleep()
    
    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
    
    Reported-by: Philippe Mathieu-Daudé <f4bug@xxxxxxxxx>
    Signed-off-by: Laurent Vivier <laurent@xxxxxxxxx>
    Signed-off-by: Alex Bennée <alex.bennee@xxxxxxxxxx>
    Reviewed-by: Richard Henderson <richard.henderson@xxxxxxxxxx>
    Message-Id: <20200722174612.2917566-2-laurent@xxxxxxxxx>
    Message-Id: <20200724064509.331-13-alex.bennee@xxxxxxxxxx>
---
 linux-user/syscall.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 1211e759c2..43a6e28396 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -11831,8 +11831,14 @@ static abi_long do_syscall1(void *cpu_env, int num, 
abi_long arg1,
         target_to_host_timespec(&ts, arg3);
         ret = get_errno(safe_clock_nanosleep(arg1, arg2,
                                              &ts, arg4 ? &ts : NULL));
-        if (arg4)
+        /*
+         * 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.
--
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