Add ptrace op PT_GET_SC_RET.

This ptrace operation returns a structure containing the error and
return values from the current system call.  It is only valid when a
thread is stopped during a system call exit (PL_FLAG_SCX is set).

The sr_error member holds the error value from the system call.  Note
that this error value is the native FreeBSD error value that has _not_
been translated to an ABI-specific error value similar to the values
logged to ktrace.

If sr_error is zero, then the return values of the system call will be
set in sr_retval[0] and sr_retval[1].

Reviewed by:	kib
MFC after:	1 month
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D20901

1 files changed, 7 insertions, 0 deletions

diff --git a/sys/sys/ptrace.h b/sys/sys/ptrace.h
index e41f7a3ef024..1ee42318e57e 100644
--- a/sys/sys/ptrace.h
+++ b/sys/sys/ptrace.h
@@ -72,6 +72,7 @@
 #define	PT_SET_EVENT_MASK 26	/* set mask of optional events */
 
 #define	PT_GET_SC_ARGS	27	/* fetch syscall args */
+#define	PT_GET_SC_RET	28	/* fetch syscall results */
 
 #define PT_GETREGS      33	/* get general-purpose registers */
 #define PT_SETREGS      34	/* set general-purpose registers */
@@ -155,6 +156,12 @@ struct ptrace_lwpinfo32 {
 };
 #endif
 
+/* Argument structure for PT_GET_SC_RET. */
+struct ptrace_sc_ret {
+	register_t	sr_retval[2];	/* Only valid if sr_error == 0. */
+	int		sr_error;
+};
+
 /* Argument structure for PT_VM_ENTRY. */
 struct ptrace_vm_entry {
 	int		pve_entry;	/* Entry number used for iteration. */