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Diffstat (limited to 'Documentation/intel_txt.txt')
| -rw-r--r-- | Documentation/intel_txt.txt | 63 |
1 files changed, 40 insertions, 23 deletions
diff --git a/Documentation/intel_txt.txt b/Documentation/intel_txt.txt index 91d89c540709..d83c1a2122c9 100644 --- a/Documentation/intel_txt.txt +++ b/Documentation/intel_txt.txt @@ -1,4 +1,5 @@ -Intel(R) TXT Overview: +===================== +Intel(R) TXT Overview ===================== Intel's technology for safer computing, Intel(R) Trusted Execution @@ -8,9 +9,10 @@ provide the building blocks for creating trusted platforms. Intel TXT was formerly known by the code name LaGrande Technology (LT). Intel TXT in Brief: -o Provides dynamic root of trust for measurement (DRTM) -o Data protection in case of improper shutdown -o Measurement and verification of launched environment + +- Provides dynamic root of trust for measurement (DRTM) +- Data protection in case of improper shutdown +- Measurement and verification of launched environment Intel TXT is part of the vPro(TM) brand and is also available some non-vPro systems. It is currently available on desktop systems @@ -24,16 +26,21 @@ which has been updated for the new released platforms. Intel TXT has been presented at various events over the past few years, some of which are: - LinuxTAG 2008: + + - LinuxTAG 2008: http://www.linuxtag.org/2008/en/conf/events/vp-donnerstag.html - TRUST2008: + + - TRUST2008: http://www.trust-conference.eu/downloads/Keynote-Speakers/ 3_David-Grawrock_The-Front-Door-of-Trusted-Computing.pdf - IDF, Shanghai: + + - IDF, Shanghai: http://www.prcidf.com.cn/index_en.html - IDFs 2006, 2007 (I'm not sure if/where they are online) -Trusted Boot Project Overview: + - IDFs 2006, 2007 + (I'm not sure if/where they are online) + +Trusted Boot Project Overview ============================= Trusted Boot (tboot) is an open source, pre-kernel/VMM module that @@ -87,11 +94,12 @@ Intel-provided firmware). How Does it Work? ================= -o Tboot is an executable that is launched by the bootloader as +- Tboot is an executable that is launched by the bootloader as the "kernel" (the binary the bootloader executes). -o It performs all of the work necessary to determine if the +- It performs all of the work necessary to determine if the platform supports Intel TXT and, if so, executes the GETSEC[SENTER] processor instruction that initiates the dynamic root of trust. + - If tboot determines that the system does not support Intel TXT or is not configured correctly (e.g. the SINIT AC Module was incorrect), it will directly launch the kernel with no changes @@ -99,12 +107,14 @@ o It performs all of the work necessary to determine if the - Tboot will output various information about its progress to the terminal, serial port, and/or an in-memory log; the output locations can be configured with a command line switch. -o The GETSEC[SENTER] instruction will return control to tboot and + +- The GETSEC[SENTER] instruction will return control to tboot and tboot then verifies certain aspects of the environment (e.g. TPM NV lock, e820 table does not have invalid entries, etc.). -o It will wake the APs from the special sleep state the GETSEC[SENTER] +- It will wake the APs from the special sleep state the GETSEC[SENTER] instruction had put them in and place them into a wait-for-SIPI state. + - Because the processors will not respond to an INIT or SIPI when in the TXT environment, it is necessary to create a small VT-x guest for the APs. When they run in this guest, they will @@ -112,8 +122,10 @@ o It will wake the APs from the special sleep state the GETSEC[SENTER] VMEXITs, and then disable VT and jump to the SIPI vector. This approach seemed like a better choice than having to insert special code into the kernel's MP wakeup sequence. -o Tboot then applies an (optional) user-defined launch policy to + +- Tboot then applies an (optional) user-defined launch policy to verify the kernel and initrd. + - This policy is rooted in TPM NV and is described in the tboot project. The tboot project also contains code for tools to create and provision the policy. @@ -121,30 +133,34 @@ o Tboot then applies an (optional) user-defined launch policy to then any kernel will be launched. - Policy action is flexible and can include halting on failures or simply logging them and continuing. -o Tboot adjusts the e820 table provided by the bootloader to reserve + +- Tboot adjusts the e820 table provided by the bootloader to reserve its own location in memory as well as to reserve certain other TXT-related regions. -o As part of its launch, tboot DMA protects all of RAM (using the +- As part of its launch, tboot DMA protects all of RAM (using the VT-d PMRs). Thus, the kernel must be booted with 'intel_iommu=on' in order to remove this blanket protection and use VT-d's page-level protection. -o Tboot will populate a shared page with some data about itself and +- Tboot will populate a shared page with some data about itself and pass this to the Linux kernel as it transfers control. + - The location of the shared page is passed via the boot_params struct as a physical address. -o The kernel will look for the tboot shared page address and, if it + +- The kernel will look for the tboot shared page address and, if it exists, map it. -o As one of the checks/protections provided by TXT, it makes a copy +- As one of the checks/protections provided by TXT, it makes a copy of the VT-d DMARs in a DMA-protected region of memory and verifies them for correctness. The VT-d code will detect if the kernel was launched with tboot and use this copy instead of the one in the ACPI table. -o At this point, tboot and TXT are out of the picture until a +- At this point, tboot and TXT are out of the picture until a shutdown (S<n>) -o In order to put a system into any of the sleep states after a TXT +- In order to put a system into any of the sleep states after a TXT launch, TXT must first be exited. This is to prevent attacks that attempt to crash the system to gain control on reboot and steal data left in memory. + - The kernel will perform all of its sleep preparation and populate the shared page with the ACPI data needed to put the platform in the desired sleep state. @@ -172,7 +188,7 @@ o In order to put a system into any of the sleep states after a TXT That's pretty much it for TXT support. -Configuring the System: +Configuring the System ====================== This code works with 32bit, 32bit PAE, and 64bit (x86_64) kernels. @@ -181,7 +197,8 @@ In BIOS, the user must enable: TPM, TXT, VT-x, VT-d. Not all BIOSes allow these to be individually enabled/disabled and the screens in which to find them are BIOS-specific. -grub.conf needs to be modified as follows: +grub.conf needs to be modified as follows:: + title Linux 2.6.29-tip w/ tboot root (hd0,0) kernel /tboot.gz logging=serial,vga,memory |