On 2013-12-10 21:03, Grant Likely wrote:
[...]
>> +/* Parked Address in ACPI GIC structure can be used as cpu release addr */
>> +int acpi_get_parked_address_with_gic_id(u32 gic_id, u64 *parked_address)
>> +{
>> + struct acpi_table_header *table_header = NULL;
>> + struct acpi_subtable_header *entry;
>> + int err = 0;
>> + unsigned long table_end;
>> + acpi_size tbl_size;
>> + struct acpi_madt_generic_interrupt *processor = NULL;
>> +
>> + if (!parked_address)
>> + return -EINVAL;
>> +
>> + acpi_get_table_with_size(ACPI_SIG_MADT, 0, &table_header, &tbl_size);
>> + if (!table_header) {
>> + pr_warn(PREFIX "MADT table not present\n");
>> + return -ENODEV;
>> + }
>> +
>> + table_end = (unsigned long)table_header + table_header->length;
>> +
>> + /* Parse all entries looking for a match. */
>> + entry = (struct acpi_subtable_header *)
>> + ((unsigned long)table_header + sizeof(struct acpi_table_madt));
>> +
>> + while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) <
>> + table_end) {
>> + if (entry->type != ACPI_MADT_TYPE_GENERIC_INTERRUPT
>> + || BAD_MADT_ENTRY(entry, table_end))
>> + continue;
>> +
>> + processor = (struct acpi_madt_generic_interrupt *)entry;
>> +
>> + if (processor->gic_id == gic_id) {
>> + *parked_address = processor->parked_address;
>> + goto out;
>> + }
>> +
>> + entry = (struct acpi_subtable_header *)
>> + ((unsigned long)entry + entry->length);
>
> All of the casting in this table looks suspicious. If you have to resort
> to casting, then the variable types are very likely wrong.
>
> In the case immediately above, it seems that the entry size doesn't
> necessarily equal the acpi_subtable_header size, in which case you
> should cast the values to a void* instead of an unsigned long. That
> would mean you can do this:
>
> entry = ((void*)entry) + entry->length;
>
> In fact, if I were writing the code, I would have two variables; the
> iterator pointer as a void* and a header pointer as a struct
> acpi_subtable_header*. Like so:
>
> void *entry, *table_end;
> struct acpi_subtable_header *header;
>
> entry = ((void*)table_header) + sizeof(struct acpi_table_madt);
> table_end = ((void*)table_header) + table_header->length;
> while (entry + sizeof(*header)) < table_end) {
> header = entry;
>
> if (header->type != ACPI_MADT_TYPE_GENERIC_INTERRUPT ||
> BAD_MADT_ENTRY(entry, table_end))
> continue;
> processor = entry;
>
> if (processor->gic_id == gic_id) {
> *parked_address = processor->parked_address;
> goto out;
> }
>
> entry += header->length;
> }
>
> See? Much cleaner code.
Aha, much much cleaner, thanks for the guidance, will rework my patch
and test it.
Hanjun
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