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tpm: Reserve the TPM final events table

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UEFI systems provide a boot services protocol for obtaining the TPM
event log, but this is unusable after ExitBootServices() is called.
Unfortunately ExitBootServices() itself triggers additional TPM events
that then can't be obtained using this protocol. The platform provides a
mechanism for the OS to obtain these events by recording them to a
separate UEFI configuration table which the OS can then map.

Unfortunately this table isn't self describing in terms of providing its
length, so we need to parse the events inside it to figure out how long
it is. Since the table isn't mapped at this point, we need to extend the
length calculation function to be able to map the event as it goes
along.

(Fixes by Bartosz Szczepanek <[email protected]>)

Signed-off-by: Matthew Garrett <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Bartosz Szczepanek <[email protected]>
Tested-by: Bartosz Szczepanek <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
Tested-by: Jarkko Sakkinen <[email protected]>
Signed-off-by: Jarkko Sakkinen <[email protected]>
This commit is contained in:
Matthew Garrett 2019-05-20 13:54:59 -07:00 • committed by Jarkko Sakkinen
commit c46f340569
5 changed files with 164 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

2
drivers/firmware/efi/efi.c
View file

@ -52,6 +52,7 @@ struct efi __read_mostly efi = {
.mem_attr_table = EFI_INVALID_TABLE_ADDR,
.rng_seed = EFI_INVALID_TABLE_ADDR,
.tpm_log = EFI_INVALID_TABLE_ADDR,
.tpm_final_log = EFI_INVALID_TABLE_ADDR,
.mem_reserve = EFI_INVALID_TABLE_ADDR,
};
EXPORT_SYMBOL(efi);
@ -484,6 +485,7 @@ static __initdata efi_config_table_type_t common_tables[] = {
{EFI_MEMORY_ATTRIBUTES_TABLE_GUID, "MEMATTR", &efi.mem_attr_table},
{LINUX_EFI_RANDOM_SEED_TABLE_GUID, "RNG", &efi.rng_seed},
{LINUX_EFI_TPM_EVENT_LOG_GUID, "TPMEventLog", &efi.tpm_log},
{LINUX_EFI_TPM_FINAL_LOG_GUID, "TPMFinalLog", &efi.tpm_final_log},
{LINUX_EFI_MEMRESERVE_TABLE_GUID, "MEMRESERVE", &efi.mem_reserve},
{NULL_GUID, NULL, NULL},
};

63
drivers/firmware/efi/tpm.c
View file

@ -4,11 +4,34 @@
* Thiebaud Weksteen <tweek@google.com>
*/
#define TPM_MEMREMAP(start, size) early_memremap(start, size)
#define TPM_MEMUNMAP(start, size) early_memunmap(start, size)
#include <asm/early_ioremap.h>
#include <linux/efi.h>
#include <linux/init.h>
#include <linux/memblock.h>
#include <linux/tpm_eventlog.h>
#include <asm/early_ioremap.h>
int efi_tpm_final_log_size;
EXPORT_SYMBOL(efi_tpm_final_log_size);
static int tpm2_calc_event_log_size(void *data, int count, void *size_info)
{
struct tcg_pcr_event2_head *header;
int event_size, size = 0;
while (count > 0) {
header = data + size;
event_size = __calc_tpm2_event_size(header, size_info, true);
if (event_size == 0)
return -1;
size += event_size;
count--;
}
return size;
}
/*
* Reserve the memory associated with the TPM Event Log configuration table.
@ -16,22 +39,54 @@
int __init efi_tpm_eventlog_init(void)
{
struct linux_efi_tpm_eventlog *log_tbl;
struct efi_tcg2_final_events_table *final_tbl;
unsigned int tbl_size;
int ret = 0;
if (efi.tpm_log == EFI_INVALID_TABLE_ADDR)
if (efi.tpm_log == EFI_INVALID_TABLE_ADDR) {
/*
* We can't calculate the size of the final events without the
* first entry in the TPM log, so bail here.
*/
return 0;
}
log_tbl = early_memremap(efi.tpm_log, sizeof(*log_tbl));
if (!log_tbl) {
pr_err("Failed to map TPM Event Log table @ 0x%lx\n",
efi.tpm_log);
efi.tpm_log);
efi.tpm_log = EFI_INVALID_TABLE_ADDR;
return -ENOMEM;
}
tbl_size = sizeof(*log_tbl) + log_tbl->size;
memblock_reserve(efi.tpm_log, tbl_size);
if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR)
goto out;
final_tbl = early_memremap(efi.tpm_final_log, sizeof(*final_tbl));
if (!final_tbl) {
pr_err("Failed to map TPM Final Event Log table @ 0x%lx\n",
efi.tpm_final_log);
efi.tpm_final_log = EFI_INVALID_TABLE_ADDR;
ret = -ENOMEM;
goto out;
}
tbl_size = tpm2_calc_event_log_size((void *)efi.tpm_final_log
+ sizeof(final_tbl->version)
+ sizeof(final_tbl->nr_events),
final_tbl->nr_events,
log_tbl->log);
memblock_reserve((unsigned long)final_tbl,
tbl_size + sizeof(*final_tbl));
early_memunmap(final_tbl, sizeof(*final_tbl));
efi_tpm_final_log_size = tbl_size;
out:
early_memunmap(log_tbl, sizeof(*log_tbl));
return 0;
return ret;
}