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authorBob Moore <robert.moore@intel.com>2008-11-12 15:15:29 +0800
committerLen Brown <len.brown@intel.com>2008-12-29 22:38:36 -0500
commitfc37445733aeae4fd1a20385850620354263b1d5 (patch)
treea989d6bf8dcc2011f25e365532c3855a48f11c62 /drivers/acpi
parent96411a630412f057d365aa1e9de7d23c069d627a (diff)
ACPICA: Add a mechanism to escape infinite AML While() loops
Add a loop counter to force exit from AML While loops if the count becomes too large. This can occur in poorly written AML when the hardware does not respond within a while loop and the loop does not implement a timeout. The maximum loop count is configurable. A new exception code is returned when a loop is broken, AE_AML_INFINITE_LOOP. Bob Moore, Alexey Starikovskiy. Signed-off-by: Bob Moore <robert.moore@intel.com> Signed-off-by: Lin Ming <ming.m.lin@intel.com> Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'drivers/acpi')
-rw-r--r--drivers/acpi/dispatcher/dsopcode.c24
1 files changed, 21 insertions, 3 deletions
diff --git a/drivers/acpi/dispatcher/dsopcode.c b/drivers/acpi/dispatcher/dsopcode.c
index 5cd406676c2..50c892a49fa 100644
--- a/drivers/acpi/dispatcher/dsopcode.c
+++ b/drivers/acpi/dispatcher/dsopcode.c
@@ -1262,13 +1262,31 @@ acpi_ds_exec_end_control_op(struct acpi_walk_state * walk_state,
ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH, "[WHILE_OP] Op=%p\n", op));
- if (walk_state->control_state->common.value) {
+ control_state = walk_state->control_state;
+ if (control_state->common.value) {
- /* Predicate was true, go back and evaluate it again! */
+ /* Predicate was true, the body of the loop was just executed */
+ /*
+ * This loop counter mechanism allows the interpreter to escape
+ * possibly infinite loops. This can occur in poorly written AML
+ * when the hardware does not respond within a while loop and the
+ * loop does not implement a timeout.
+ */
+ control_state->control.loop_count++;
+ if (control_state->control.loop_count >
+ ACPI_MAX_LOOP_ITERATIONS) {
+ status = AE_AML_INFINITE_LOOP;
+ break;
+ }
+
+ /*
+ * Go back and evaluate the predicate and maybe execute the loop
+ * another time
+ */
status = AE_CTRL_PENDING;
walk_state->aml_last_while =
- walk_state->control_state->control.aml_predicate_start;
+ control_state->control.aml_predicate_start;
break;
}