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devices: refactor TPM CRB helpers

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Extract CRB completion, register-read, and data-buffer range handling
so the fixed access rules can be tested without a live TPM backend.

Assisted-by: Copilot:GPT-5.5
Signed-off-by: Wei Liu <liuwe@microsoft.com>
This commit is contained in:
Wei Liu
2026-05-30 15:37:59 -07:00
committed by Rob Bradford
parent f91b748253
commit df41b03221
1 changed files with 33 additions and 24 deletions
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57
devices/src/tpm.rs
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@@ -232,6 +232,31 @@ fn update_reg(regs: &mut [u32; TPM_CRB_R_MAX], offset: u32, data: &[u8]) -> u32
regs[reg_offset]
}
fn read_reg_value(value: u32, offset: u32) -> u32 {
let byte_offset = (offset & 0x3) as usize;
value >> (byte_offset * 8)
}
fn complete_request(regs: &mut [u32; TPM_CRB_R_MAX], success: bool) {
regs[CRB_CTRL_START as usize] &= !CRB_START_INVOKE;
if !success {
set_reg_field(regs, CrbRegister::CtrlSts(CtrlStsFields::TpmSts), 1);
}
}
fn data_buffer_range(offset: u32, len: usize, buffer_len: usize) -> Option<std::ops::Range<usize>> {
let end_offset = offset.checked_add(len as u32)?;
let buffer_end = CRB_DATA_BUFFER.checked_add(buffer_len as u32)?;
if offset >= CRB_DATA_BUFFER && end_offset <= buffer_end {
let start = (offset - CRB_DATA_BUFFER) as usize;
Some(start..start + len)
} else {
None
}
}
pub struct Tpm {
emulator: Emulator,
regs: [u32; TPM_CRB_R_MAX],
@@ -270,14 +295,7 @@ impl Tpm {
}
fn request_completed(&mut self, success: bool) {
self.regs[CRB_CTRL_START as usize] &= !CRB_START_INVOKE;
if !success {
set_reg_field(
&mut self.regs,
CrbRegister::CtrlSts(CtrlStsFields::TpmSts),
1,
);
}
complete_request(&mut self.regs, success);
}
fn reset(&mut self) -> Result<()> {
@@ -365,13 +383,9 @@ impl BusDevice for Tpm {
let mut offset: u32 = offset as u32;
let read_len: usize = data.len();
if offset >= CRB_DATA_BUFFER
&& (offset + read_len as u32) <= (CRB_DATA_BUFFER + self.data_buff.len() as u32)
{
if let Some(range) = data_buffer_range(offset, read_len, self.data_buff.len()) {
// Read from Data Buffer
let start: usize = (offset as usize) - (CRB_DATA_BUFFER as usize);
let end: usize = start + read_len;
data[..].clone_from_slice(&self.data_buff[start..end]);
data[..].clone_from_slice(&self.data_buff[range]);
} else {
offset &= 0xff;
let reg_offset = offset & !0x3;
@@ -383,12 +397,10 @@ impl BusDevice for Tpm {
if reg_offset == CRB_LOC_STATE && self.emulator.get_established_bit() {
val |= 0x1;
}
val = read_reg_value(val, offset);
if data.len() <= 4 {
let byte_offset = (offset & 0x3) as usize;
data.clone_from_slice(
(val >> (byte_offset * 8)).to_ne_bytes()[0..read_len].as_ref(),
);
data.clone_from_slice(val.to_ne_bytes()[0..read_len].as_ref());
} else {
error!(
"Invalid tpm read: offset {:#X}, data length {:?}",
@@ -419,17 +431,14 @@ impl BusDevice for Tpm {
let locality = locality_from_addr(offset) as u32;
let write_len = data.len();
if offset >= CRB_DATA_BUFFER
&& (offset + write_len as u32) <= (CRB_DATA_BUFFER + self.data_buff.len() as u32)
{
let start: usize = (offset as usize) - (CRB_DATA_BUFFER as usize);
if let Some(range) = data_buffer_range(offset, write_len, self.data_buff.len()) {
let start = range.start;
if start == 0 {
// If filling data_buff at index 0, reset length to 0
self.data_buff_len = 0;
self.data_buff.fill(0);
}
let end: usize = start + data.len();
self.data_buff[start..end].clone_from_slice(data);
self.data_buff[range].clone_from_slice(data);
self.data_buff_len += data.len();
} else {
// Ctrl Commands that take more than 4 bytes as input are not yet supported