// SPDX-License-Identifier: GPL-2.0
/*
 * TPM handling.
 *
 * Copyright (C) 2016 CoreOS, Inc
 * Copyright (C) 2017 Google, Inc.
 *     Matthew Garrett <mjg59@google.com>
 *     Thiebaud Weksteen <tweek@google.com>
 */
#include <linux/efi.h>
#include <linux/tpm_eventlog.h>
#include <asm/efi.h>

#include "efistub.h"

#ifdef CONFIG_RESET_ATTACK_MITIGATION
static const efi_char16_t efi_MemoryOverWriteRequest_name[] =
        L"MemoryOverwriteRequestControl";

#define MEMORY_ONLY_RESET_CONTROL_GUID \
        EFI_GUID(0xe20939be, 0x32d4, 0x41be, 0xa1, 0x50, 0x89, 0x7f, 0x85, 0xd4, 0x98, 0x29)

/*
 * Enable reboot attack mitigation. This requests that the firmware clear the
 * RAM on next reboot before proceeding with boot, ensuring that any secrets
 * are cleared. If userland has ensured that all secrets have been removed
 * from RAM before reboot it can simply reset this variable.
 */
void efi_enable_reset_attack_mitigation(void)
{
        u8 val = 1;
        efi_guid_t var_guid = MEMORY_ONLY_RESET_CONTROL_GUID;
        efi_status_t status;
        unsigned long datasize = 0;

        status = get_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
                             NULL, &datasize, NULL);

        if (status == EFI_NOT_FOUND)
                return;

        set_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
                    EFI_VARIABLE_NON_VOLATILE |
                    EFI_VARIABLE_BOOTSERVICE_ACCESS |
                    EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val);
}

#endif

static void efi_retrieve_tcg2_eventlog(int version, efi_physical_addr_t log_location,
                                       efi_physical_addr_t log_last_entry,
                                       efi_bool_t truncated,
                                       struct efi_tcg2_final_events_table *final_events_table)
{
        efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
        efi_status_t status;
        struct linux_efi_tpm_eventlog *log_tbl = NULL;
        unsigned long first_entry_addr, last_entry_addr;
        size_t log_size, last_entry_size;
        u32 final_events_size = 0;

        first_entry_addr = (unsigned long) log_location;

        /*
         * We populate the EFI table even if the logs are empty.
         */
        if (!log_last_entry) {
                log_size = 0;
        } else {
                last_entry_addr = (unsigned long) log_last_entry;
                /*
                 * get_event_log only returns the address of the last entry.
                 * We need to calculate its size to deduce the full size of
                 * the logs.
                 *
                 * CC Event log also uses TCG2 format, handle it same as TPM2.
                 */
                if (version > EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2) {
                        /*
                         * The TCG2 log format has variable length entries,
                         * and the information to decode the hash algorithms
                         * back into a size is contained in the first entry -
                         * pass a pointer to the final entry (to calculate its
                         * size) and the first entry (so we know how long each
                         * digest is)
                         */
                        last_entry_size =
                                __calc_tpm2_event_size((void *)last_entry_addr,
                                                    (void *)(long)log_location,
                                                    false);
                } else {
                        last_entry_size = sizeof(struct tcpa_event) +
                           ((struct tcpa_event *) last_entry_addr)->event_size;
                }
                log_size = log_last_entry - log_location + last_entry_size;
        }

        /* Allocate space for the logs and copy them. */
        status = efi_bs_call(allocate_pool, EFI_ACPI_RECLAIM_MEMORY,
                             sizeof(*log_tbl) + log_size, (void **)&log_tbl);

        if (status != EFI_SUCCESS) {
                efi_err("Unable to allocate memory for event log\n");
                return;
        }

        /*
         * Figure out whether any events have already been logged to the
         * final events structure, and if so how much space they take up
         */
        if (final_events_table && final_events_table->nr_events) {
                struct tcg_pcr_event2_head *header;
                u32 offset;
                void *data;
                u32 event_size;
                int i = final_events_table->nr_events;

                data = (void *)final_events_table;
                offset = sizeof(final_events_table->version) +
                        sizeof(final_events_table->nr_events);

                while (i > 0) {
                        header = data + offset + final_events_size;
                        event_size = __calc_tpm2_event_size(header,
                                                   (void *)(long)log_location,
                                                   false);
                        /* If calc fails this is a malformed log */
                        if (!event_size)
                                break;
                        final_events_size += event_size;
                        i--;
                }
        }

        memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
        log_tbl->size = log_size;
        log_tbl->final_events_preboot_size = final_events_size;
        log_tbl->version = version;
        memcpy(log_tbl->log, (void *) first_entry_addr, log_size);

        status = efi_bs_call(install_configuration_table,
                             &linux_eventlog_guid, log_tbl);
        if (status != EFI_SUCCESS)
                goto err_free;
        return;

err_free:
        efi_bs_call(free_pool, log_tbl);
}

void efi_retrieve_eventlog(void)
{
        struct efi_tcg2_final_events_table *final_events_table = NULL;
        efi_physical_addr_t log_location = 0, log_last_entry = 0;
        efi_guid_t tpm2_guid = EFI_TCG2_PROTOCOL_GUID;
        int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2;
        efi_tcg2_protocol_t *tpm2 = NULL;
        efi_bool_t truncated;
        efi_status_t status;

        status = efi_bs_call(locate_protocol, &tpm2_guid, NULL, (void **)&tpm2);
        if (status == EFI_SUCCESS) {
                status = efi_call_proto(tpm2, get_event_log, version, &log_location,
                                        &log_last_entry, &truncated);

                if (status != EFI_SUCCESS || !log_location) {
                        version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
                        status = efi_call_proto(tpm2, get_event_log, version,
                                                &log_location, &log_last_entry,
                                                &truncated);
                } else {
                        final_events_table =
                                get_efi_config_table(EFI_TCG2_FINAL_EVENTS_TABLE_GUID);
                }
        } else {
                efi_guid_t cc_guid = EFI_CC_MEASUREMENT_PROTOCOL_GUID;
                efi_cc_protocol_t *cc = NULL;

                status = efi_bs_call(locate_protocol, &cc_guid, NULL, (void **)&cc);
                if (status != EFI_SUCCESS)
                        return;

                version = EFI_CC_EVENT_LOG_FORMAT_TCG_2;
                status = efi_call_proto(cc, get_event_log, version, &log_location,
                                        &log_last_entry, &truncated);

                final_events_table =
                        get_efi_config_table(EFI_CC_FINAL_EVENTS_TABLE_GUID);
        }

        if (status != EFI_SUCCESS || !log_location)
                return;

        efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry,
                                   truncated, final_events_table);
}