The "set" prctl passes through integral values.
The "get" prctl returns the value into a pointer.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1929
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/syscall.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index bc8c06522f..263b651cc5 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6450,11 +6450,21 @@ static abi_long do_prctl(CPUArchState *env, abi_long option, abi_long arg2,
     case PR_SET_NO_NEW_PRIVS:
     case PR_GET_IO_FLUSHER:
     case PR_SET_IO_FLUSHER:
+    case PR_SET_CHILD_SUBREAPER:
         /* Some prctl options have no pointer arguments and we can pass on. */
         return get_errno(prctl(option, arg2, arg3, arg4, arg5));
 
     case PR_GET_CHILD_SUBREAPER:
-    case PR_SET_CHILD_SUBREAPER:
+        {
+            int val;
+            ret = get_errno(prctl(PR_GET_CHILD_SUBREAPER, &val,
+                                  arg3, arg4, arg5));
+            if (!is_error(ret) && put_user_s32(val, arg2)) {
+                return -TARGET_EFAULT;
+            }
+            return ret;
+        }
+
     case PR_GET_SPECULATION_CTRL:
     case PR_SET_SPECULATION_CTRL:
     case PR_GET_TID_ADDRESS:
-- 
2.34.1

On Sat, 2 Mar 2024 at 04:13, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> The "set" prctl passes through integral values.
> The "get" prctl returns the value into a pointer.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1929
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM