Re: [PATCH v4 1/2] ptrace: save the type of syscall-stop in ptrace_message

On 11/28, Dmitry V. Levin wrote:

+/*
+ * These values are stored in task->ptrace_message by tracehook_report_syscall_*
+ * to describe current syscall-stop.
+ *
+ * Values for these constants are chosen so that they do not appear
+ * in task->ptrace_message by other means.
+ */
+#define PTRACE_EVENTMSG_SYSCALL_ENTRY	0x80000000U
+#define PTRACE_EVENTMSG_SYSCALL_EXIT	0x90000000U

Again, I do not really understand the comment... Why should we care about
"do not appear in task->ptrace_message by other means" ?

2/2 should detect ptrace_report_syscall() case correctly, so we can use any
numbers, say, 1 and 2?

If debugger does PTRACE_GETEVENTMSG it should know how to interpet the value
anyway after wait(status).

Oleg.