> On Sep 10, 2024, at 6:58 AM, Breno Leitao <leitao@xxxxxxxxxx> wrote: > > > We've seen a problem in upstream kernel kexec, where a EFI TPM log event table > is being overwritten. This problem happen on real machine, as well as in a > recent EDK2 qemu VM. > > Digging deep, the table is being overwritten during kexec, more precisely when > relocating kernel (relocate_kernel() function). > > I've also found that the table is being properly reserved using > memblock_reserve() early in the boot, and that range gets overwritten later in > by relocate_kernel(). In other words, kexec is overwriting a memory that was > previously reserved (as memblock_reserve()). > > Usama found that kexec only honours memory reservations from /sys/firmware/memmap > which comes from e820_table_firmware table. > The E820 table is not part of the UEFI standard and it is produced by a library in the OvmfPkg for “special cases” so I guess that lib could have a bug? > Looking at the TPM spec, I found the following part: > > If the ACPI TPM2 table contains the address and size of the Platform Firmware TCG log, > firmware “pins” the memory associated with the Platform Firmware TCG log, and reports > this memory as “Reserved” memory via the INT 15h/E820 interface. > INT 15h is Legacy BIOS not UEFI. For UEFI there is just the UEFI memory map and ACPI. Thanks, Andrew Fish > > From: https://trustedcomputinggroup.org/wp-content/uploads/PC-ClientPlatform_Profile_for_TPM_2p0_Systems_v49_161114_public-review.pdf > > I am wondering if that memory region/range should be part of e820 table that is > passed by EFI firmware to kernel, and if it is not passed (as it is not being > passed today), then the kernel doesn't need to respect it, and it is free to > overwrite (as it does today). In other words, this is a firmware bug and not a > kernel bug. > > Am I missing something? > > Thanks > --breno > > > -=-=-=-=-=-=-=-=-=-=-=- > Groups.io Links: You receive all messages sent to this group. > View/Reply Online (#120541): https://edk2.groups.io/g/devel/message/120541 > Mute This Topic: https://groups.io/mt/108376671/1755084 > Group Owner: devel+owner@xxxxxxxxxxxxxx > Unsubscribe: https://edk2.groups.io/g/devel/unsub [afish@xxxxxxxxx] > -=-=-=-=-=-=-=-=-=-=-=- > >
