Add an kinfo sysctl to retrieve signal trampoline location for the

given process.

Note that the correctness of the trampoline length returned for ABIs
which do not use shared page depends on the correctness of the struct
sysvec sv_szsigcodebase member, which will be fixed on as-need basis.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

sys/compat/freebsd32/freebsd32.h

@@ -362,6 +362,12 @@ struct kinfo_proc32 {
 	int	ki_tdflags;
 };
 
+struct kinfo_sigtramp32 {
+	uint32_t ksigtramp_start;
+	uint32_t ksigtramp_end;
+	uint32_t ksigtramp_spare[4];
+};
+
 struct kld32_file_stat_1 {
 	int	version;	/* set to sizeof(struct kld_file_stat_1) */
 	char	name[MAXPATHLEN];

sys/kern/kern_proc.c

@@ -2631,6 +2631,60 @@ sysctl_kern_proc_osrel(SYSCTL_HANDLER_ARGS)
 	return (error);
 }
 
+static int
+sysctl_kern_proc_sigtramp(SYSCTL_HANDLER_ARGS)
+{
+	int *name = (int *)arg1;
+	u_int namelen = arg2;
+	struct proc *p;
+	struct kinfo_sigtramp kst;
+	const struct sysentvec *sv;
+	int error;
+#ifdef COMPAT_FREEBSD32
+	struct kinfo_sigtramp32 kst32;
+#endif
+
+	if (namelen != 1)
+		return (EINVAL);
+
+	error = pget((pid_t)name[0], PGET_CANDEBUG, &p);
+	if (error != 0)
+		return (error);
+	sv = p->p_sysent;
+#ifdef COMPAT_FREEBSD32
+	if ((req->flags & SCTL_MASK32) != 0) {
+		bzero(&kst32, sizeof(kst32));
+		if (SV_PROC_FLAG(p, SV_ILP32)) {
+			if (sv->sv_sigcode_base != 0) {
+				kst32.ksigtramp_start = sv->sv_sigcode_base;
+				kst32.ksigtramp_end = sv->sv_sigcode_base +
+				    *sv->sv_szsigcode;
+			} else {
+				kst32.ksigtramp_start = sv->sv_psstrings -
+				    *sv->sv_szsigcode;
+				kst32.ksigtramp_end = sv->sv_psstrings;
+			}
+		}
+		PROC_UNLOCK(p);
+		error = SYSCTL_OUT(req, &kst32, sizeof(kst32));
+		return (error);
+	}
+#endif
+	bzero(&kst, sizeof(kst));
+	if (sv->sv_sigcode_base != 0) {
+		kst.ksigtramp_start = (char *)sv->sv_sigcode_base;
+		kst.ksigtramp_end = (char *)sv->sv_sigcode_base +
+		    *sv->sv_szsigcode;
+	} else {
+		kst.ksigtramp_start = (char *)sv->sv_psstrings -
+		    *sv->sv_szsigcode;
+		kst.ksigtramp_end = (char *)sv->sv_psstrings;
+	}
+	PROC_UNLOCK(p);
+	error = SYSCTL_OUT(req, &kst, sizeof(kst));
+	return (error);
+}
+
 SYSCTL_NODE(_kern, KERN_PROC, proc, CTLFLAG_RD,  0, "Process table");
 
 SYSCTL_PROC(_kern_proc, KERN_PROC_ALL, all, CTLFLAG_RD|CTLTYPE_STRUCT|
@@ -2739,3 +2793,7 @@ static SYSCTL_NODE(_kern_proc, KERN_PROC_UMASK, umask, CTLFLAG_RD |
 static SYSCTL_NODE(_kern_proc, KERN_PROC_OSREL, osrel, CTLFLAG_RW |
 	CTLFLAG_ANYBODY | CTLFLAG_MPSAFE, sysctl_kern_proc_osrel,
 	"Process binary osreldate");
+
+static SYSCTL_NODE(_kern_proc, KERN_PROC_SIGTRAMP, sigtramp, CTLFLAG_RD |
+	CTLFLAG_MPSAFE, sysctl_kern_proc_sigtramp,
+	"Process signal trampoline location");

sys/sys/sysctl.h

@@ -530,6 +530,7 @@ SYSCTL_ALLOWED_TYPES(UINT64, uint64_t *a; unsigned long long *b; );
 #define	KERN_PROC_PS_STRINGS	38	/* get ps_strings location */
 #define	KERN_PROC_UMASK		39	/* process umask */
 #define	KERN_PROC_OSREL		40	/* osreldate for process binary */
+#define	KERN_PROC_SIGTRAMP	41	/* signal trampoline location */
 
 /*
  * KERN_IPC identifiers

sys/sys/user.h

@@ -498,6 +498,12 @@ struct kinfo_kstack {
 	int	 _kkst_ispare[16];		/* Space for more stuff. */
 };
 
+struct kinfo_sigtramp {
+	void	*ksigtramp_start;
+	void	*ksigtramp_end;
+	void	*ksigtramp_spare[4];
+};
+
 #ifdef _KERNEL
 /* Flags for kern_proc_out function. */
 #define KERN_PROC_NOTHREADS	0x1