MFC r267759, r267761

r267759:
Fix a couple of bugs on amd64 when fetching probe arguments beyond the
first five for probes entered through a UD fault (i.e. FBT probes).

Specifically, handle the fact that dtrace_invop_callsite must be
16 byte-aligned and thus may not immediately follow the call to
dtrace_invop() in dtrace_invop_start(). Also fetch register arguments and
the stack pointer through a struct trapframe instead of a struct reg.

r267761:
Fix some bugs when fetching probe arguments in i386. Firstly ensure that
the 4 byte-aligned dtrace_invop_callsite can be found and that it
immediately follows the call to dtrace_invop(). Secondly, fix some pointer
arithmetic to account for differences between struct i386_frame and illumos'
struct frame. Finally, ensure that dtrace_getarg() isn't inlined. It works
by following a fixed number of frame pointers to the probe site, so inlining
breaks it.

PR:		191260

1 files changed, 4 insertions, 3 deletions

diff --git a/sys/cddl/dev/dtrace/i386/dtrace_isa.c b/sys/cddl/dev/dtrace/i386/dtrace_isa.c
index 3f73a50..21a8154 100644
--- a/sys/cddl/dev/dtrace/i386/dtrace_isa.c
+++ b/sys/cddl/dev/dtrace/i386/dtrace_isa.c
@@ -413,7 +413,8 @@ dtrace_getarg(int arg, int aframes)
 	for (i = 1; i <= aframes; i++) {
 		fp = fp->f_frame;
 
-		if (fp->f_retaddr == (long)dtrace_invop_callsite) {
+		if (P2ROUNDUP(fp->f_retaddr, 4) ==
+		    (long)dtrace_invop_callsite) {
 			/*
 			 * If we pass through the invalid op handler, we will
 			 * use the pointer that it passed to the stack as the
@@ -422,7 +423,7 @@ dtrace_getarg(int arg, int aframes)
 			 * beyond the EIP/RIP that was pushed when the trap was
 			 * taken -- hence the "+ 1" below.
 			 */
-			stack = ((uintptr_t **)&fp[1])[1] + 1;
+			stack = ((uintptr_t **)&fp[1])[0] + 1;
 			goto load;
 		}
 
@@ -438,7 +439,7 @@ dtrace_getarg(int arg, int aframes)
 	 */
 	arg++;
 
-	stack = (uintptr_t *)&fp[1];
+	stack = (uintptr_t *)fp + 2;
 
 load:
 	DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);