On 06/05/2019 12.10, David Hildenbrand wrote:
> On 06.05.19 12:01, David Hildenbrand wrote:
>> On 29.04.19 15:09, Jason J. Herne wrote:
>>> Newer versions of zipl have the ability to write signature entries to the
>>> boot
>>> script for secure boot. We don't yet support secure boot, but we need to
>>> skip
>>> over signature entries while reading the boot script in order to maintain
>>> our
>>> ability to boot guest operating systems that have a secure bootloader.
>>>
>>> Signed-off-by: Jason J. Herne <jjhe...@linux.ibm.com>
>>> Reviewed-by: Farhan Ali <al...@linux.ibm.com>
>>> ---
>>> pc-bios/s390-ccw/bootmap.c | 19 +++++++++++++++++--
>>> pc-bios/s390-ccw/bootmap.h | 10 ++++++----
>>> 2 files changed, 23 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/pc-bios/s390-ccw/bootmap.c b/pc-bios/s390-ccw/bootmap.c
>>> index 7aef65a..d13b7cb 100644
>>> --- a/pc-bios/s390-ccw/bootmap.c
>>> +++ b/pc-bios/s390-ccw/bootmap.c
>>> @@ -254,7 +254,14 @@ static void run_eckd_boot_script(block_number_t
>>> bmt_block_nr,
>>> memset(sec, FREE_SPACE_FILLER, sizeof(sec));
>>> read_block(block_nr, sec, "Cannot read Boot Map Script");
>>>
>>> - for (i = 0; bms->entry[i].type == BOOT_SCRIPT_LOAD; i++) {
>>> + for (i = 0; bms->entry[i].type == BOOT_SCRIPT_LOAD ||
>>> + bms->entry[i].type == BOOT_SCRIPT_SIGNATURE; i++) {
>>> +
>>> + /* We don't support secure boot yet, so we skip signature entries
>>> */
>>> + if (bms->entry[i].type == BOOT_SCRIPT_SIGNATURE) {
>>> + continue;
>>> + }
>>> +
>>> address = bms->entry[i].address.load_address;
>>> block_nr = eckd_block_num(&bms->entry[i].blkptr.xeckd.bptr.chs);
>>>
>>> @@ -489,7 +496,15 @@ static void zipl_run(ScsiBlockPtr *pte)
>>>
>>> /* Load image(s) into RAM */
>>> entry = (ComponentEntry *)(&header[1]);
>>> - while (entry->component_type == ZIPL_COMP_ENTRY_LOAD) {
>>> + while (entry->component_type == ZIPL_COMP_ENTRY_LOAD ||
>>> + entry->component_type == ZIPL_COMP_ENTRY_SIGNATURE) {
>>> +
>>> + /* We don't support secure boot yet, so we skip signature entries
>>> */
>>> + if (entry->component_type == ZIPL_COMP_ENTRY_SIGNATURE) {
>>> + entry++;
>>> + continue;
>>> + }
>>> +
>>> zipl_load_segment(entry);
>>>
>>> entry++;
>>> diff --git a/pc-bios/s390-ccw/bootmap.h b/pc-bios/s390-ccw/bootmap.h
>>> index a085212..94f53a5 100644
>>> --- a/pc-bios/s390-ccw/bootmap.h
>>> +++ b/pc-bios/s390-ccw/bootmap.h
>>> @@ -98,8 +98,9 @@ typedef struct ScsiMbr {
>>> #define ZIPL_COMP_HEADER_IPL 0x00
>>> #define ZIPL_COMP_HEADER_DUMP 0x01
>>>
>>> -#define ZIPL_COMP_ENTRY_LOAD 0x02
>>> -#define ZIPL_COMP_ENTRY_EXEC 0x01
>>> +#define ZIPL_COMP_ENTRY_EXEC 0x01
>>> +#define ZIPL_COMP_ENTRY_LOAD 0x02
>>> +#define ZIPL_COMP_ENTRY_SIGNATURE 0x03
>>>
>>> typedef struct XEckdMbr {
>>> uint8_t magic[4]; /* == "xIPL" */
>>> @@ -117,8 +118,9 @@ typedef struct BootMapScriptEntry {
>>> BootMapPointer blkptr;
>>> uint8_t pad[7];
>>> uint8_t type; /* == BOOT_SCRIPT_* */
>>> -#define BOOT_SCRIPT_EXEC 0x01
>>> -#define BOOT_SCRIPT_LOAD 0x02
>>> +#define BOOT_SCRIPT_EXEC 0x01
>>> +#define BOOT_SCRIPT_LOAD 0x02
>>> +#define BOOT_SCRIPT_SIGNATURE 0x03
>>> union {
>>> uint64_t load_address;
>>> uint64_t load_psw;
>>>
>>
>> Naive question from me:
>>
>> Can't we place the signatures somewhere else, and instead associate them
>> with entries? This avoids breaking backwards compatibility for the sake
>> of signatures we want unmodified zipl loaders to ignore.
>>
>
>
> ... but I guess this is already documented somewhere internally and
> other components have been adjusted. IOW, cannot be changed anymore.
>
> Guess our implementation should have tolerated other entries than
> "BOOT_SCRIPT_LOAD" right from the beginning.
Hmm, now we only tolerate the _LOAD and _SIGNATURE entries, but still
nothing else... would it make sense to rewrite the code a little bit to
tolerate all other kind of entries, but just act on the well-known _LOAD
entries, so that we do not step into this trap in the future anymore?
Thomas
