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/plugins/core.c b/plugins/core.c
index 4b55aacd2d..1113bfe567 100644
--- a/plugins/core.c
+++ b/plugins/core.c
@@ -573,7 +573,7 @@ bool
 qemu_plugin_vcpu_syscall_filter(CPUState *cpu, int64_t num, uint64_t a1,
                                 uint64_t a2, uint64_t a3, uint64_t a4,
                                 uint64_t a5, uint64_t a6, uint64_t a7,
-                                uint64_t a8, uint64_t *sysret)
+                                uint64_t a8, int64_t *sysret)
 {
     struct qemu_plugin_cb *cb, *next;
     enum qemu_plugin_event ev = QEMU_PLUGIN_EV_VCPU_SYSCALL_FILTER;