plugins: use int64_t for the syscall filter return value

The syscall return value passed back through the syscall filter
callback is semantically signed: negative values encode errno codes.
Declaring the sysret pointer as uint64_t * is therefore misleading and
forces callers to launder the value through an unsigned temporary.

Change the sysret pointer to int64_t * across the public plugin API
typedef (qemu_plugin_vcpu_syscall_filter_cb_t), the internal
qemu_plugin_vcpu_syscall_filter() prototypes and stub, its
implementation in plugins/core.c, the linux-user caller, and the
in-tree example plugins.

Signed-off-by: Ziyang Zhang <functioner@sjtu.edu.cn>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>
Link: https://lore.kernel.org/qemu-devel/20260618082426.790315-2-functioner@sjtu.edu.cn
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index fbe357b7e0..d257fb9ca9 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -14619,7 +14619,7 @@ static bool send_through_syscall_filters(CPUState *cpu, int num,
                                          abi_long arg7, abi_long arg8,
                                          abi_long *sysret)
 {
-    uint64_t sysret64 = 0;
+    int64_t sysret64 = 0;
     bool filtered = qemu_plugin_vcpu_syscall_filter(cpu, num, arg1, arg2,
                                                     arg3, arg4, arg5, arg6,
                                                     arg7, arg8, &sysret64);