[PATCH] linux-user: fix pidfd_send_signal()

[Laurent Vivier]

According to pidfd_send_signal(2), info argument can be a NULL pointer.
Fix strace to correctly manage ending comma in parameters.

Fixes: cc054c6f13 ("linux-user: Add pidfd_open(), pidfd_send_signal() and 
pidfd_getfd() syscalls")
cc: Helge Deller <deller@gmx.de>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 linux-user/strace.c  |  4 ++--
 linux-user/syscall.c | 19 ++++++++++++-------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/linux-user/strace.c b/linux-user/strace.c
index 37bc96df9bb6..86c081c83f74 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -3383,10 +3383,10 @@ print_pidfd_send_signal(CPUArchState *cpu_env, const 
struct syscallname *name,
 
         unlock_user(p, arg2, 0);
     } else {
-        print_pointer(arg2, 1);
+        print_pointer(arg2, 0);
     }
 
-    print_raw_param("%u", arg3, 0);
+    print_raw_param("%u", arg3, 1);
     print_syscall_epilogue(name);
 }
 #endif
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 2e954d8dbd9e..b1493917ee07 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8679,16 +8679,21 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int 
num, abi_long arg1,
 #if defined(__NR_pidfd_send_signal) && defined(TARGET_NR_pidfd_send_signal)
     case TARGET_NR_pidfd_send_signal:
         {
-            siginfo_t uinfo;
+            siginfo_t uinfo, *puinfo;
 
-            p = lock_user(VERIFY_READ, arg3, sizeof(target_siginfo_t), 1);
-            if (!p) {
-                return -TARGET_EFAULT;
+            if (arg3) {
+                p = lock_user(VERIFY_READ, arg3, sizeof(target_siginfo_t), 1);
+                if (!p) {
+                    return -TARGET_EFAULT;
+                 }
+                 target_to_host_siginfo(&uinfo, p);
+                 unlock_user(p, arg3, 0);
+                 puinfo = &uinfo;
+            } else {
+                 puinfo = NULL;
             }
-            target_to_host_siginfo(&uinfo, p);
-            unlock_user(p, arg3, 0);
             ret = get_errno(pidfd_send_signal(arg1, 
target_to_host_signal(arg2),
-                &uinfo, arg4));
+                                              puinfo, arg4));
         }
         return ret;
 #endif
-- 
2.37.3