From 7e75d5861000a9177c0d5d12d6a1951233d4d50b Mon Sep 17 00:00:00 2001
From: Mark Johnston <markj@FreeBSD.org>
Date: Mon, 21 Oct 2013 04:15:55 +0000
Subject: [PATCH] When fetching function arguments out of a frame on amd64,
 explicitly select the register based on the argument index rather than
 relying on the fields in struct reg to be in the right order. This assumption
 is incorrect on FreeBSD and generally led to bogus argument values for the
 sixth argument of PID and USDT probes; the first five are passed directly to
 dtrace_probe() via the fasttrap trap handler and so were correctly handled.

MFC after:	2 weeks
---
 .../uts/intel/dtrace/fasttrap_isa.c           | 15 ++++++++++++-
 sys/cddl/dev/dtrace/amd64/dtrace_isa.c        | 22 ++++++++++++++++++-
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c b/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c
index 65991aff0254..8b5ce9f46726 100644
--- a/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c
+++ b/sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c
@@ -272,7 +272,20 @@ fasttrap_anarg(struct reg *rp, int function_entry, int argno)
 		 * registers.
 		 */
 		if (argno < 6)
-			return ((&rp->r_rdi)[argno]);
+			switch (argno) {
+			case 0:
+				return (rp->r_rdi);
+			case 1:
+				return (rp->r_rsi);
+			case 2:
+				return (rp->r_rdx);
+			case 3:
+				return (rp->r_rcx);
+			case 4:
+				return (rp->r_r8);
+			case 5:
+				return (rp->r_r9);
+			}
 
 		stack = (uintptr_t *)rp->r_rsp;
 		DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
diff --git a/sys/cddl/dev/dtrace/amd64/dtrace_isa.c b/sys/cddl/dev/dtrace/amd64/dtrace_isa.c
index 34d6f331ebee..3d3c43cd2e8a 100644
--- a/sys/cddl/dev/dtrace/amd64/dtrace_isa.c
+++ b/sys/cddl/dev/dtrace/amd64/dtrace_isa.c
@@ -367,7 +367,27 @@ dtrace_getarg(int arg, int aframes)
 			    sizeof (uintptr_t));
 
 			if (arg <= inreg) {
-				stack = (uintptr_t *)&rp->r_rdi;
+				switch (arg) {
+				case 0:
+					stack = (uintptr_t *)&rp->r_rdi;
+					break;
+				case 1:
+					stack = (uintptr_t *)&rp->r_rsi;
+					break;
+				case 2:
+					stack = (uintptr_t *)&rp->r_rdx;
+					break;
+				case 3:
+					stack = (uintptr_t *)&rp->r_rcx;
+					break;
+				case 4:
+					stack = (uintptr_t *)&rp->r_r8;
+					break;
+				case 5:
+					stack = (uintptr_t *)&rp->r_r9;
+					break;
+				}
+				arg = 0;
 			} else {
 				stack = (uintptr_t *)(rp->r_rsp);
 				arg -= inreg;