Looking at the TPM spec [1] If the ACPI TPM2 table contains the address and size of the Platform Firmware TCG log, firmware “pins” the memory associated with the Platform FirmwareTCG log, and reports this memory as “Reserved” memory via the INT 15h/E820 interface. It looks like the firmware should pass this as reserved in e820 memory map. However, it doesn't seem to. The firmware being tested on is: dmidecode -s bios-version edk2-20240214-2.el9 When this area is not reserved, it comes up as usable in /sys/firmware/memmap. This means that kexec, which uses that memmap to find usable memory regions, can select the region where efi.tpm_log is and overwrite it and relocate_kernel. Having a fix in firmware can be difficult to get through. As a secondary fix, this patch marks that region as reserved in e820_table_firmware so that kexec doesn't use it for kernel segments. [1] https://trustedcomputinggroup.org/wp-content/uploads/PC-ClientPlatform_Profile_for_TPM_2p0_Systems_v49_161114_public-review.pdf Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx> --- arch/x86/include/asm/e820/api.h | 2 ++ arch/x86/kernel/e820.c | 6 ++++++ arch/x86/platform/efi/efi.c | 6 ++++++ drivers/firmware/efi/tpm.c | 5 +++-- include/linux/efi.h | 7 +++++++ 5 files changed, 24 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/e820/api.h b/arch/x86/include/asm/e820/api.h index 2e74a7f0e935..4e9aa24f03bd 100644 --- a/arch/x86/include/asm/e820/api.h +++ b/arch/x86/include/asm/e820/api.h @@ -16,6 +16,8 @@ extern bool e820__mapped_all(u64 start, u64 end, enum e820_type type); extern void e820__range_add (u64 start, u64 size, enum e820_type type); extern u64 e820__range_update(u64 start, u64 size, enum e820_type old_type, enum e820_type new_type); +extern u64 e820__range_update_firmware(u64 start, u64 size, enum e820_type old_type, + enum e820_type new_type); extern u64 e820__range_remove(u64 start, u64 size, enum e820_type old_type, bool check_type); extern u64 e820__range_update_table(struct e820_table *t, u64 start, u64 size, enum e820_type old_type, enum e820_type new_type); diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c index 4893d30ce438..912400161623 100644 --- a/arch/x86/kernel/e820.c +++ b/arch/x86/kernel/e820.c @@ -538,6 +538,12 @@ u64 __init e820__range_update_table(struct e820_table *t, u64 start, u64 size, return __e820__range_update(t, start, size, old_type, new_type); } +u64 __init e820__range_update_firmware(u64 start, u64 size, enum e820_type old_type, + enum e820_type new_type) +{ + return __e820__range_update(e820_table_firmware, start, size, old_type, new_type); +} + /* Remove a range of memory from the E820 table: */ u64 __init e820__range_remove(u64 start, u64 size, enum e820_type old_type, bool check_type) { diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index 88a96816de9a..644c5da8fb39 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -171,6 +171,12 @@ static void __init do_add_efi_memmap(void) e820__update_table(e820_table); } +void arch_update_firmware_area(u64 addr, u64 size) +{ + e820__range_update_firmware(efi.tpm_log, size, E820_TYPE_RAM, E820_TYPE_RESERVED); + e820__update_table(e820_table_firmware); +} + /* * Given add_efi_memmap defaults to 0 and there is no alternative * e820 mechanism for soft-reserved memory, import the full EFI memory diff --git a/drivers/firmware/efi/tpm.c b/drivers/firmware/efi/tpm.c index e8d69bd548f3..787c5a206010 100644 --- a/drivers/firmware/efi/tpm.c +++ b/drivers/firmware/efi/tpm.c @@ -60,7 +60,9 @@ int __init efi_tpm_eventlog_init(void) } tbl_size = sizeof(*log_tbl) + log_tbl->size; - memblock_reserve(efi.tpm_log, tbl_size); + if (!memblock_reserve(efi.tpm_log, tbl_size)) { + arch_update_firmware_area(efi.tpm_log, tbl_size); + } if (efi.tpm_final_log == EFI_INVALID_TABLE_ADDR) { pr_info("TPM Final Events table not present\n"); @@ -107,4 +109,3 @@ int __init efi_tpm_eventlog_init(void) early_memunmap(log_tbl, sizeof(*log_tbl)); return ret; } - diff --git a/include/linux/efi.h b/include/linux/efi.h index 6bf3c4fe8511..9c239cdff771 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -1371,4 +1371,11 @@ extern struct blocking_notifier_head efivar_ops_nh; void efivars_generic_ops_register(void); void efivars_generic_ops_unregister(void); +#ifdef CONFIG_X86_64 +void __init arch_update_firmware_area(u64 addr, u64 size); +#else +static inline void __init arch_update_firmware_area(u64 addr, u64 size) +{ +} +#endif #endif /* _LINUX_EFI_H */ -- 2.43.5
