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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>
This commit is contained in:
Bob Moore 2008-11-12 15:15:29 +08:00 committed by Len Brown
parent 96411a6304
commit fc37445733
4 changed files with 29 additions and 4 deletions
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24
drivers/acpi/dispatcher/dsopcode.c
View File

@ -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;
}

4
include/acpi/acconfig.h
View File

@ -119,6 +119,10 @@
#define ACPI_ROOT_TABLE_SIZE_INCREMENT 4
/* Maximum number of While() loop iterations before forced abort */
#define ACPI_MAX_LOOP_ITERATIONS 0xFFFF
/******************************************************************************
*
* ACPI Specification constants (Do not change unless the specification changes)

4
include/acpi/acexcep.h
View File

@ -153,8 +153,9 @@
#define AE_AML_CIRCULAR_REFERENCE (acpi_status) (0x001E | AE_CODE_AML)
#define AE_AML_BAD_RESOURCE_LENGTH (acpi_status) (0x001F | AE_CODE_AML)
#define AE_AML_ILLEGAL_ADDRESS (acpi_status) (0x0020 | AE_CODE_AML)
#define AE_AML_INFINITE_LOOP (acpi_status) (0x0021 | AE_CODE_AML)
#define AE_CODE_AML_MAX 0x0020
#define AE_CODE_AML_MAX 0x0021
/*
* Internal exceptions used for control
@ -267,6 +268,7 @@ char const *acpi_gbl_exception_names_aml[] = {
"AE_AML_CIRCULAR_REFERENCE",
"AE_AML_BAD_RESOURCE_LENGTH",
"AE_AML_ILLEGAL_ADDRESS",
"AE_AML_INFINITE_LOOP"
};
char const *acpi_gbl_exception_names_ctrl[] = {

1
include/acpi/aclocal.h
View File

@ -566,6 +566,7 @@ struct acpi_control_state {
union acpi_parse_object *predicate_op;
u8 *aml_predicate_start; /* Start of if/while predicate */
u8 *package_end; /* End of if/while block */
u32 loop_count; /* While() loop counter */
};
/*