tpm: rename established_flag to established_bit and match TCG semantics

The helper used to communicate the TPM Establishment bit between the
swtpm backend and the CRB device had inverted semantics:

    self.established_flag = est.resp.bit == 0;

so `established_flag == true` actually meant "*not* established". The
device-side call site then double-negated:

    if !self.emulator.get_established_flag() {
        val |= 0x1;  // tpmEstablished in TPM_LOC_STATE
    }

The end-to-end behaviour was correct but the boundary between the
swtpm-specific backend and the (TCG-spec defined) CRB device was hard
to follow and easy to misuse -- the now-removed pre-init check in
Emulator::new() was an example of that confusion (it errored out with
"TPM not in established state" precisely when the TPM *was*
established).

Per the TCG PC Client Platform TPM Profile (PTP) specification, bit 0
of TPM_LOC_STATE_x is `tpmEstablished`:

  * 0 = default state after a cold reset
  * 1 = a TPM2_Startup from Locality 3 or 4 has occurred

Rename the backend accessor to `get_established_bit()` and return the
bit value directly (true == 1, false == 0). The CRB device then simply
forwards the bit, with no inversion, which makes the spec mapping
obvious and removes swtpm-flavoured naming from the device layer.

No functional change.

Asissted-by: Copilot:GPT-5.5
Signed-off-by: Wei Liu <liuwe@microsoft.com>

devices/src/tpm.rs

@@ -363,7 +363,10 @@ impl BusDevice for Tpm {
             offset &= 0xff;
             let mut val = self.regs[offset as usize];
 
-            if offset == CRB_LOC_STATE && !self.emulator.get_established_flag() {
+            // Per the TCG PC Client Platform TPM Profile (PTP) spec, bit 0
+            // of TPM_LOC_STATE_x is `tpmEstablished`. Reflect the live value
+            // from the backend rather than the (zero-initialised) shadow.
+            if offset == CRB_LOC_STATE && self.emulator.get_established_bit() {
                 val |= 0x1;
             }
 

tpm/src/emulator.rs

@@ -75,8 +75,8 @@ pub struct Emulator {
     caps: PtmCap, /* capabilities of the TPM */
     control_socket: SocketDev,
     data_fd: RawFd,
-    established_flag_cached: bool,
-    established_flag: bool,
+    established_bit_cached: bool,
+    established_bit: bool,
 }
 
 impl Emulator {
@@ -103,8 +103,8 @@ impl Emulator {
             caps: 0,
             control_socket: socket,
             data_fd: -1,
-            established_flag_cached: false,
-            established_flag: false,
+            established_bit_cached: false,
+            established_bit: false,
         };
 
         emulator.prepare_data_fd()?;
@@ -322,11 +322,17 @@ impl Emulator {
         Ok(())
     }
 
-    pub fn get_established_flag(&mut self) -> bool {
+    /// Returns the value of the TPM Establishment bit as defined by the
+    /// TCG PC Client Platform TPM Profile (PTP) specification:
+    ///   * `true`  - a TPM2_Startup from Locality 3 or 4 has occurred
+    ///   * `false` - default state after a cold reset
+    ///
+    /// The value is cached on first successful query.
+    pub fn get_established_bit(&mut self) -> bool {
         let mut est: PtmEst = PtmEst::new();
 
-        if self.established_flag_cached {
-            return self.established_flag;
+        if self.established_bit_cached {
+            return self.established_bit;
         }
 
         if let Err(e) = self.run_control_cmd(
@@ -339,10 +345,10 @@ impl Emulator {
             return false;
         }
 
-        self.established_flag_cached = true;
-        self.established_flag = est.resp.bit == 0;
+        self.established_bit_cached = true;
+        self.established_bit = est.resp.bit != 0;
 
-        self.established_flag
+        self.established_bit
     }
 
     /// Function to write to data socket and read the response from it