dtrace: enforce inlining of dtrace_dif_variable

The dtrace_dif_variable() function is inlined during some compilations
and not during others, causing the number of frames to be skipped in
DTrace kernel stack traces to not be a constant.  That causes incorrect
values for stackdepth to be reported.

This commit requests dtrace_dif_variable() to always be inlined, and
adjusts the aframes values in function of the inlining.

Orabug: 25872472
Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Reviewed-by: Tomas jedlicka <tomas.jedlicka@oracle.com>
Acked-by: Nick Alcock <nick.alcock@oracle.com>

diff --git a/dtrace/dtrace_dif.c b/dtrace/dtrace_dif.c
index bfa3e124747d299f94e999c64c0a8ba993208028..f3cc294d696f4968b538fce66353411873cbe8b7 100644 (file)
--- a/dtrace/dtrace_dif.c
+++ b/dtrace/dtrace_dif.c
@@ -2013,10 +2013,15 @@ static uintptr_t dtrace_dif_varstr(uintptr_t addr, dtrace_state_t *state,
 /*
  * This function implements the DIF emulator's variable lookups.  The emulator
  * passes a reserved variable identifier and optional built-in array index.
+ *
+ * This function is annotated to be always inlined in dtrace_dif_emulate()
+ * because (1) that is the only place where it is called from, and (2) it has
+ * come to our attention that some GCC versions inline i automatically while
+ * others do not and that messes up the number of frames to skip (aframes).
  */
-static uint64_t dtrace_dif_variable(dtrace_mstate_t *mstate,
-                                   dtrace_state_t *state, uint64_t v,
-                                   uint64_t ndx)
+static uint64_t __always_inline dtrace_dif_variable(dtrace_mstate_t *mstate,
+                                                   dtrace_state_t *state,
+                                                   uint64_t v, uint64_t ndx)
 {
        /*
         * If we're accessing one of the uncached arguments, we'll turn this
@@ -2034,7 +2039,7 @@ static uint64_t dtrace_dif_variable(dtrace_mstate_t *mstate,
                if (ndx >=
                    sizeof(mstate->dtms_arg) / sizeof(mstate->dtms_arg[0])) {
                        int                     aframes =
-                                       mstate->dtms_probe->dtpr_aframes + 2;
+                                       mstate->dtms_probe->dtpr_aframes + 1;
                        dtrace_provider_t       *pv;
                        uint64_t                val;
 
@@ -2153,7 +2158,7 @@ static uint64_t dtrace_dif_variable(dtrace_mstate_t *mstate,
                        return 0;
 
                if (!(mstate->dtms_present & DTRACE_MSTATE_CALLER)) {
-                       int     aframes = mstate->dtms_probe->dtpr_aframes + 3;
+                       int     aframes = mstate->dtms_probe->dtpr_aframes + 1;
 
                        if (!DTRACE_ANCHORED(mstate->dtms_probe)) {
                                /*