libipt, block: turn trailing event processing into iteration
To process trailing events, we recursively call pt_blk_process_trailing_events()
from the individual pt_blk_process_trailing_<event>() functions until we either
run out of events or decide to postpone processing of the next event.
The idea was to allow the compiler to turn those recursive calls into tail calls
and thus the entire event processing into a series of jumps.
If that tail call optimization does not happen, for exmple in debug mode, we
might overflow the call stack on some trace inputs. In the case of trailing TSX
events, for example, the block decoder would crash after a sequence of ~80.000
MODE.TSX packets given an 8KB stack. I'm omitting the test as it is quite big.
Turn the recursion into iteration to avoid a stack overflow.
Change-Id: I92683ce0255770ba924074e573fa796de240d181
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
diff --git a/libipt/src/pt_block_decoder.c b/libipt/src/pt_block_decoder.c
index df8e0cf..c1a4456 100644
--- a/libipt/src/pt_block_decoder.c
+++ b/libipt/src/pt_block_decoder.c
@@ -39,8 +39,6 @@
static int pt_blk_proceed(struct pt_block_decoder *, struct pt_block *);
-static int pt_blk_process_trailing_events(struct pt_block_decoder *,
- struct pt_block *);
static int pt_blk_proceed_no_event_cached(struct pt_block_decoder *,
struct pt_block *,
struct pt_block_cache *,
@@ -644,26 +642,6 @@
return pt_blk_proceed(decoder, block);
}
-/* Process a trailing disabled event.
- *
- * We reached the location of a disabled event after completing a block.
- *
- * Returns a non-negative pt_status_flag bit-vector on success, a negative error
- * code otherwise.
- */
-static int pt_blk_process_trailing_disabled(struct pt_block_decoder *decoder,
- struct pt_block *block,
- const struct pt_event *ev)
-{
- int errcode;
-
- errcode = pt_blk_apply_disabled(decoder, block, ev);
- if (errcode < 0)
- return errcode;
-
- return pt_blk_process_trailing_events(decoder, block);
-}
-
/* Apply an asynchronous branch event.
*
* This is used for proceed events and for trailing events.
@@ -734,28 +712,6 @@
return pt_blk_proceed(decoder, block);
}
-/* Process a trailing asynchronous branch event.
- *
- * We reached the source location of an asynchronous branch after completing a
- * block.
- *
- * Returns a non-negative pt_status_flag bit-vector on success, a negative error
- * code otherwise.
- */
-static int
-pt_blk_process_trailing_async_branch(struct pt_block_decoder *decoder,
- struct pt_block *block,
- const struct pt_event *ev)
-{
- int errcode;
-
- errcode = pt_blk_apply_async_branch(decoder, block, ev);
- if (errcode < 0)
- return errcode;
-
- return pt_blk_process_trailing_events(decoder, block);
-}
-
/* Apply a paging event.
*
* This is used for proceed events and for trailing events.
@@ -796,26 +752,6 @@
return pt_blk_proceed(decoder, block);
}
-/* Process a trailing paging event.
- *
- * We reached the location of a paging event after completing a block.
- *
- * Returns a non-negative pt_status_flag bit-vector on success, a negative error
- * code otherwise.
- */
-static int pt_blk_process_trailing_paging(struct pt_block_decoder *decoder,
- struct pt_block *block,
- const struct pt_event *ev)
-{
- int errcode;
-
- errcode = pt_blk_apply_paging(decoder, block, ev);
- if (errcode < 0)
- return errcode;
-
- return pt_blk_process_trailing_events(decoder, block);
-}
-
/* Apply a vmcs event.
*
* This is used for proceed events and for trailing events.
@@ -856,26 +792,6 @@
return pt_blk_proceed(decoder, block);
}
-/* Process a trailing vmcs event.
- *
- * We reached the location of a vmcs event after completing a block.
- *
- * Returns a non-negative pt_status_flag bit-vector on success, a negative error
- * code otherwise.
- */
-static int pt_blk_process_trailing_vmcs(struct pt_block_decoder *decoder,
- struct pt_block *block,
- const struct pt_event *ev)
-{
- int errcode;
-
- errcode = pt_blk_apply_vmcs(decoder, block, ev);
- if (errcode < 0)
- return errcode;
-
- return pt_blk_process_trailing_events(decoder, block);
-}
-
/* Process an overflow event.
*
* An overflow ends a non-empty block. The overflow itself is indicated in the
@@ -1006,26 +922,6 @@
return pt_blk_proceed(decoder, block);
}
-/* Process a trailing exec mode event.
- *
- * We reached the location of an exec mode event after completing a block.
- *
- * Returns a non-negative pt_status_flag bit-vector on success, a negative error
- * code otherwise.
- */
-static int pt_blk_process_trailing_exec_mode(struct pt_block_decoder *decoder,
- struct pt_block *block,
- const struct pt_event *ev)
-{
- int errcode;
-
- errcode = pt_blk_apply_exec_mode(decoder, block, ev);
- if (errcode < 0)
- return errcode;
-
- return pt_blk_process_trailing_events(decoder, block);
-}
-
/* Apply a tsx event.
*
* This is used for proceed events and for trailing events.
@@ -1086,26 +982,6 @@
return pt_blk_proceed(decoder, block);
}
-/* Process a trailing tsx event.
- *
- * We reached the location of a tsx event after completing a block.
- *
- * Returns a non-negative pt_status_flag bit-vector on success, a negative error
- * code otherwise.
- */
-static int pt_blk_process_trailing_tsx(struct pt_block_decoder *decoder,
- struct pt_block *block,
- const struct pt_event *ev)
-{
- int errcode;
-
- errcode = pt_blk_apply_tsx(decoder, block, ev);
- if (errcode < 0)
- return errcode;
-
- return pt_blk_process_trailing_events(decoder, block);
-}
-
/* Apply a stop event.
*
* This is used for proceed events and for trailing events.
@@ -1154,26 +1030,6 @@
return pt_blk_proceed(decoder, block);
}
-/* Process a trailing stop event.
- *
- * We got a stop event. This always succeeds a disabled event.
- *
- * Returns a non-negative pt_status_flag bit-vector on success, a negative error
- * code otherwise.
- */
-static int pt_blk_process_trailing_stop(struct pt_block_decoder *decoder,
- struct pt_block *block,
- const struct pt_event *ev)
-{
- int errcode;
-
- errcode = pt_blk_apply_stop(decoder, block, ev);
- if (errcode < 0)
- return errcode;
-
- return pt_blk_process_trailing_events(decoder, block);
-}
-
/* Proceed to the next IP using trace.
*
* We failed to proceed without trace. This ends the current block. Now use
@@ -2603,6 +2459,38 @@
return 1;
}
+/* Handle a trailing TSX event.
+ *
+ * This involves handling erratum BDM64.
+ *
+ * Returns a positive integer if the event is to be postponed.
+ * Returns zero if the event was handled successfully.
+ * Returns a negative error code otherwise.
+ */
+static inline int pt_blk_handle_trailing_tsx(struct pt_block_decoder *decoder,
+ struct pt_block *block,
+ const struct pt_event *ev)
+{
+ if (!decoder || !ev)
+ return -pte_internal;
+
+ if (!ev->ip_suppressed) {
+ if (decoder->query.config.errata.bdm64) {
+ int status;
+
+ status = pt_blk_handle_erratum_bdm64(decoder, block,
+ ev);
+ if (status < 0)
+ return 1;
+ }
+
+ if (decoder->ip != ev->variant.tsx.ip)
+ return 1;
+ }
+
+ return pt_blk_apply_tsx(decoder, block, ev);
+}
+
/* Process events that bind to the current decoder IP.
*
* We filled a block and proceeded to the next IP, which will become the start
@@ -2615,90 +2503,115 @@
static int pt_blk_process_trailing_events(struct pt_block_decoder *decoder,
struct pt_block *block)
{
- struct pt_event *ev;
- int event_pending, status;
-
if (!decoder)
return -pte_internal;
- event_pending = pt_blk_fetch_event(decoder);
- if (event_pending <= 0) {
- if (event_pending < 0)
- return event_pending;
+ for (;;) {
+ struct pt_event *ev;
+ int status;
- return pt_blk_status(decoder);
- }
+ status = pt_blk_fetch_event(decoder);
+ if (status <= 0) {
+ if (status < 0)
+ return status;
- ev = &decoder->event;
- switch (ev->type) {
- case ptev_enabled:
- case ptev_disabled:
- case ptev_paging:
- case ptev_vmcs:
- case ptev_overflow:
- break;
-
- case ptev_async_disabled:
- if (decoder->ip != ev->variant.async_disabled.at)
break;
-
- if (decoder->query.config.errata.skd022) {
- status = pt_blk_handle_erratum_skd022(decoder, ev);
- if (status != 0) {
- if (status < 0)
- break;
-
- return pt_blk_process_trailing_events(decoder,
- block);
- }
}
- return pt_blk_process_trailing_disabled(decoder, block, ev);
-
- case ptev_async_branch:
- if (decoder->ip != ev->variant.async_branch.from)
+ ev = &decoder->event;
+ switch (ev->type) {
+ case ptev_enabled:
+ case ptev_disabled:
+ case ptev_paging:
+ case ptev_vmcs:
+ case ptev_overflow:
break;
- return pt_blk_process_trailing_async_branch(decoder, block, ev);
-
- case ptev_async_paging:
- if (!ev->ip_suppressed &&
- decoder->ip != ev->variant.async_paging.ip)
- break;
-
- return pt_blk_process_trailing_paging(decoder, block, ev);
-
- case ptev_async_vmcs:
- if (!ev->ip_suppressed &&
- decoder->ip != ev->variant.async_vmcs.ip)
- break;
-
- return pt_blk_process_trailing_vmcs(decoder, block, ev);
-
- case ptev_exec_mode:
- if (!ev->ip_suppressed &&
- decoder->ip != ev->variant.exec_mode.ip)
- break;
-
- return pt_blk_process_trailing_exec_mode(decoder, block, ev);
-
- case ptev_tsx:
- if (!ev->ip_suppressed) {
- if (decoder->query.config.errata.bdm64) {
- status = pt_blk_handle_erratum_bdm64(decoder,
- block, ev);
- if (status < 0)
- break;
- }
-
- if (decoder->ip != ev->variant.tsx.ip)
+ case ptev_async_disabled:
+ if (decoder->ip != ev->variant.async_disabled.at)
break;
+
+ if (decoder->query.config.errata.skd022) {
+ status = pt_blk_handle_erratum_skd022(decoder,
+ ev);
+ if (status != 0) {
+ if (status < 0)
+ break;
+
+ continue;
+ }
+ }
+
+
+ status = pt_blk_apply_disabled(decoder, block, ev);
+ if (status < 0)
+ return status;
+
+ continue;
+
+ case ptev_async_branch:
+ if (decoder->ip != ev->variant.async_branch.from)
+ break;
+
+ status = pt_blk_apply_async_branch(decoder, block, ev);
+ if (status < 0)
+ return status;
+
+ continue;
+
+ case ptev_async_paging:
+ if (!ev->ip_suppressed &&
+ decoder->ip != ev->variant.async_paging.ip)
+ break;
+
+ status = pt_blk_apply_paging(decoder, block, ev);
+ if (status < 0)
+ return status;
+
+ continue;
+
+ case ptev_async_vmcs:
+ if (!ev->ip_suppressed &&
+ decoder->ip != ev->variant.async_vmcs.ip)
+ break;
+
+ status = pt_blk_apply_vmcs(decoder, block, ev);
+ if (status < 0)
+ return status;
+
+ continue;
+
+ case ptev_exec_mode:
+ if (!ev->ip_suppressed &&
+ decoder->ip != ev->variant.exec_mode.ip)
+ break;
+
+ status = pt_blk_apply_exec_mode(decoder, block, ev);
+ if (status < 0)
+ return status;
+
+ continue;
+
+ case ptev_tsx:
+ status = pt_blk_handle_trailing_tsx(decoder, block, ev);
+ if (status < 0)
+ return status;
+
+ if (status > 0)
+ break;
+
+ continue;
+
+ case ptev_stop:
+ status = pt_blk_apply_stop(decoder, block, ev);
+ if (status < 0)
+ return status;
+
+ continue;
}
- return pt_blk_process_trailing_tsx(decoder, block, ev);
-
- case ptev_stop:
- return pt_blk_process_trailing_stop(decoder, block, ev);
+ /* If we fall out of the switch, we're done. */
+ break;
}
return pt_blk_status(decoder);
