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Like most Tegra based devices, the Switch's GPU also includes a Falcon microprocessor.
Like most Tegra based devices, the Switch's GPU also includes a Falcon microprocessor.
TSEC is a NVIDIA Falcon microprocessor with crypto extensions.
= Driver =
= Driver =
A host driver for communicating with the Falcon is mapped to physical address 0x54500000 with a total size of 0x40000 bytes and exposes several registers.
A host driver for communicating with the TSEC/Falcon is mapped to physical address 0x54500000 with a total size of 0x40000 bytes and exposes several registers.
== Registers ==
== Registers ==
return;
return;
= Firmware =
= TSEC Firmware =
The actual code loaded into Falcon is assembled in NVIDIA's proprietary fuc5 ISA using crypto extensions.
The actual code loaded into TSEC is assembled in NVIDIA's proprietary fuc5 ISA using crypto extensions.
Stored inside the first bootloader, this firmware binary is split into 4 blobs: Stage0, Stage1, Stage2 and key data.
Stored inside the first bootloader, this firmware binary is split into 4 blobs: Stage0, Stage1, Stage2 and key data.
Firmware can be disassembled with http:x//envytools.readthedocs.io/en/latest/" envytools' https:x//github.com/envytools/envytools/tree/master/envydis envydis:
<code>envydis -i tsec_fw.bin -m falcon -V fuc5 -F crypt</code>
Note that the instruction set has variable length instructions, and the disassembler is not very good at detecting locations it should start disassembling from. One needs to disassemble multiple sub-regions and join them together.
== Stage 0 ==
== Stage 0 ==
== Key data ==
== Key data ==
Small buffer stored after Stage 0's code and used across all stages.
Small buffer stored after Stage 0's code and used across all stages.
== Notes ==
https:x//wiki.0x04.net/wiki/Marcin_Ko%C5%9Bcielnicki mwk shared additional info learned from RE of falcon processors over the years, which hasn't made it into envytools documentation yet:
=== cxset ===
cxset instruction provides a way to change behavior of a variable amount of successively executed DMA-related instructions.
for example: <code>000000de: f4 3c 02 cxset 0x2</code>
can be read as: <code>dma_override(type=crypto_reg, count=2)</code>
The argument to cxset specifies the type of behavior change in the top 3 bits, and the number of DMA-related instructions the effect lasts for in the lower 5 bits.
==== Override Types ====
Unlisted values are unknown, but probably do something.
{| class=wikitable
! Value || Effect
|-
| 0b000 || falcon data mem <-> falcon $cX register
|-
| 0b001 || external mem <-> crypto input/output stream
|}
==== DMA-Related Instructions ====
At least the following instructions may have changed behavior, and count against the cxset "count" argument: <code>xdwait</code>, <code>xdst</code>, <code>xdld</code>.
For example, if override type=0b000, then the "length" argument to <code>xdst</code> is instead treated as the index of the target $cX register.
=== Register ACLs ===
Falcon tracks permission metadata about each crypto reg. Permissions include read/write ability per execution mode, as well as ability to use the reg for encrypt/decrypt, among other permissions. Permissions are propagated when registers are referenced by instructions (e.g. moving a value from read-protected $cX to $cY will result in $cY also being read-protected).
=== Authenticated Mode Entry/Exit ===
Entry to Authenticated Mode always sets $pc to the address supplied in $cauth (ie the base of the signature-checked region). This takes effect when trying to branch to any address within the range covered by $cauth.
Exit from Authenticated Mode must poke a special register (this seems to be I[0x10300] = 0) before leaving authenticated code pages. Failure to do this would result in the Falcon core halting.