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   <section id="secvar-binding">
 <span id="device-tree-ibm-opal-secvar"></span><h1>Secvar Binding<a class="headerlink" href="#secvar-binding" title="Link to this heading">¶</a></h1>
 <p>This device tree binding describes the status of secure variable support,
 including any size values, or values relating to the secure state of the
 system.</p>
 <section id="ibm-opal-secvar-node-bindings">
 <h2>/ibm,opal/secvar node bindings<a class="headerlink" href="#ibm-opal-secvar-node-bindings" title="Link to this heading">¶</a></h2>
 <p>Node: secvar</p>
 <p>Description: Container of secvar related properties.</p>
 <p>The node name must be “secvar”.</p>
 <p>It is implemented as a child of the node “/ibm,opal”.</p>
 <p>The node is optional, will be defined if the platform supports secure
 variables. It will not be created if the system does not.</p>
 <p>Properties:</p>
 <ul>
 <li><p>compatible</p>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>required</p>
 </dd>
 <dt>Value type:</dt><dd><p>string</p>
 </dd>
 </dl>
 <p>Definition:</p>
 <p>This property defines the compatibility of the current running
 backend. This defines the binary format of the data buffers passed
 via the related secvar OPAL API functions. This also defines the
 expected behavior of how updates should be processed, such as how
 key updates should be signed, what the key hierarchy is, what
 algorithms are in use, etc.</p>
 <p>This value also determines how a user can signal a desire to require
 all further images to require signature validations. See the
 “On Enforcing Secure Mode” section below.</p>
 <p>This property also contains a generic “ibm,secvar-backend” compatible,
 which defines the basic-level compatibility of the secvar implementation.
 This includes the basic behavior of the API (excluding the data format),
 and the expected device tree properties contained in this node.</p>
 </li>
 <li><p>format</p>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>required</p>
 </dd>
 <dt>Value type:</dt><dd><p>string</p>
 </dd>
 </dl>
 <p>This property defines the format of data passed in and out of the secvar
 API. In most cases, this should be the same string as the backend-specific
 string in compatible.</p>
 <p>The format defined by this string should be documented by the corresponding
 backend.</p>
 </li>
 <li><p>status</p>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>required</p>
 </dd>
 <dt>Value type:</dt><dd><p>string</p>
 </dd>
 </dl>
 <p>Definition:</p>
 <p>This property states the general status of secure variable support. This
 will be set to “okay” if the secvar OPAL API should be working as expected,
 and there were no unrecoverable faults in the basic secure variable
 initialization logic.</p>
 <p>This property may be set to “fail” if the platform does not properly
 select the drivers to use. Failures may also occur if the storage devices
 are inaccessible for some reason.</p>
 <p>Failures are NOT caused by malformed data loaded or processed in either
 storage or backend drivers, as these are faults correctable by a user.</p>
 </li>
 <li><p>update-status</p>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>required</p>
 </dd>
 <dt>Value type:</dt><dd><p>&lt;u64&gt;</p>
 </dd>
 </dl>
 <p>Definition:</p>
 <p>This property should contain the status code of the update processing
 logic, as returned by the backend. This value is intended to be
 consumed by userspace tools to confirm updates were processed as
 intended.</p>
 <p>The value contained in this property should adhere to the table below.
 Any additional error states that may be specific to a backend should
 be stored in the backend node.</p>
 </li>
 <li><p>max-var-size</p>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>required</p>
 </dd>
 <dt>Value type:</dt><dd><p>&lt;u64&gt;</p>
 </dd>
 </dl>
 <p>Definition:</p>
 <p>This is the maximum buffer size accepted for secure variables. The API
 will reject updates larger than this value, and storage drivers must
 reject loading variables larger than this value.</p>
 <p>As this may depend on the persistant storage devices in use, this
 value is determined by the storage driver, and may differ across
 platforms.</p>
 </li>
 <li><p>max-var-key-len</p>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>required</p>
 </dd>
 <dt>Value type:</dt><dd><p>&lt;u64&gt;</p>
 </dd>
 </dl>
 <p>Definition:</p>
 <p>This is the maximum size permitted for the key of a variable. As the
 value is a constant, it should be the same across platforms unless
 changed in code.</p>
 </li>
 </ul>
 </section>
 <section id="example">
 <h2>Example<a class="headerlink" href="#example" title="Link to this heading">¶</a></h2>
 <div class="highlight-dts notranslate"><div class="highlight"><pre><span></span><span class="err">/ibm,opal/</span><span class="nc">secvar</span> <span class="p">{</span>
         <span class="nf">compatible</span> <span class="o">=</span> <span class="s">&quot;ibm,secvar-backend&quot; &quot;ibm,edk2-compat-v1&quot;</span><span class="p">;</span>

         <span class="nf">status</span> <span class="o">=</span> <span class="s">&quot;okay&quot;</span><span class="p">;</span>
         <span class="nf">max-var-size</span> <span class="o">=</span> <span class="p">&lt;</span><span class="mh">0x1000</span><span class="p">&gt;;</span>
         <span class="nf">max-var-key-len</span> <span class="o">=</span> <span class="p">&lt;</span><span class="mh">0x400</span><span class="p">&gt;</span>
 <span class="err">}</span><span class="p">;</span>
 </pre></div>
 </div>
 </section>
 <section id="update-status-code-table">
 <h2>Update Status Code Table<a class="headerlink" href="#update-status-code-table" title="Link to this heading">¶</a></h2>
 <p>The update status property should be set by the backend driver to a value
 that best fits its error condition. The following table defines the
 general intent of each error code, check backend specific documentation
 for more detail.</p>
 <table class="docutils align-default">
 <tbody>
 <tr class="row-odd"><td><p>update-status</p></td>
 <td><p>Generic Reason</p></td>
 </tr>
 <tr class="row-even"><td><p>OPAL_SUCCESS</p></td>
 <td><p>Updates were found and processed successfully</p></td>
 </tr>
 <tr class="row-odd"><td><p>OPAL_EMPTY</p></td>
 <td><p>No updates were found, none processed</p></td>
 </tr>
 <tr class="row-even"><td><p>OPAL_PARAMETER</p></td>
 <td><p>Malformed, or unexpected update data blob</p></td>
 </tr>
 <tr class="row-odd"><td><p>OPAL_PERMISSION</p></td>
 <td><p>Update failed to apply, possible auth failure</p></td>
 </tr>
 <tr class="row-even"><td><p>OPAL_HARDWARE</p></td>
 <td><p>Misc. storage-related error</p></td>
 </tr>
 <tr class="row-odd"><td><p>OPAL_RESOURCE</p></td>
 <td><p>Out of space (reported by storage</p></td>
 </tr>
 <tr class="row-even"><td><p>OPAL_NO_MEM</p></td>
 <td><p>Out of memory</p></td>
 </tr>
 </tbody>
 </table>
 </section>
 <section id="on-enforcing-secure-mode">
 <h2>On Enforcing Secure Mode<a class="headerlink" href="#on-enforcing-secure-mode" title="Link to this heading">¶</a></h2>
 <p>The os-secureboot-enforcing property in /ibm,secureboot/ is created by the
 backend if the owner has expressed a desire for boot loaders, kernels, etc
 to require any images to be signed by an appropriate key stored in secure
 variables. As this property is created by the backend, it is up to the
 backend to define what the required state of the secure variables should
 be to enter this mode.</p>
 <p>For example, we may want to only enable secure boot if we have a top-
 level “Platform Key”, so this property is created by the backend if
 by the end of update processing, a “PK” variable exists. By enrolling a
 PK, the system will be in “secure mode” until the PK is deleted.</p>
 </section>
 </section>


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     <ul>
 <li><a class="reference internal" href="#">Secvar Binding</a><ul>
 <li><a class="reference internal" href="#ibm-opal-secvar-node-bindings">/ibm,opal/secvar node bindings</a></li>
 <li><a class="reference internal" href="#example">Example</a></li>
 <li><a class="reference internal" href="#update-status-code-table">Update Status Code Table</a></li>
 <li><a class="reference internal" href="#on-enforcing-secure-mode">On Enforcing Secure Mode</a></li>
 </ul>
 </li>
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	<section id="secvar-binding">
	<span id="device-tree-ibm-opal-secvar"></span><h1>Secvar Binding<a class="headerlink" href="#secvar-binding" title="Link to this heading">¶</a></h1>
	<p>This device tree binding describes the status of secure variable support,
	including any size values, or values relating to the secure state of the
	system.</p>
	<section id="ibm-opal-secvar-node-bindings">
	<h2>/ibm,opal/secvar node bindings<a class="headerlink" href="#ibm-opal-secvar-node-bindings" title="Link to this heading">¶</a></h2>
	<p>Node: secvar</p>
	<p>Description: Container of secvar related properties.</p>
	<p>The node name must be “secvar”.</p>
	<p>It is implemented as a child of the node “/ibm,opal”.</p>
	<p>The node is optional, will be defined if the platform supports secure
	variables. It will not be created if the system does not.</p>
	<p>Properties:</p>
	<ul>
	<li><p>compatible</p>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>required</p>
	</dd>
	<dt>Value type:</dt><dd><p>string</p>
	</dd>
	</dl>
	<p>Definition:</p>
	<p>This property defines the compatibility of the current running
	backend. This defines the binary format of the data buffers passed
	via the related secvar OPAL API functions. This also defines the
	expected behavior of how updates should be processed, such as how
	key updates should be signed, what the key hierarchy is, what
	algorithms are in use, etc.</p>
	<p>This value also determines how a user can signal a desire to require
	all further images to require signature validations. See the
	“On Enforcing Secure Mode” section below.</p>
	<p>This property also contains a generic “ibm,secvar-backend” compatible,
	which defines the basic-level compatibility of the secvar implementation.
	This includes the basic behavior of the API (excluding the data format),
	and the expected device tree properties contained in this node.</p>
	</li>
	<li><p>format</p>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>required</p>
	</dd>
	<dt>Value type:</dt><dd><p>string</p>
	</dd>
	</dl>
	<p>This property defines the format of data passed in and out of the secvar
	API. In most cases, this should be the same string as the backend-specific
	string in compatible.</p>
	<p>The format defined by this string should be documented by the corresponding
	backend.</p>
	</li>
	<li><p>status</p>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>required</p>
	</dd>
	<dt>Value type:</dt><dd><p>string</p>
	</dd>
	</dl>
	<p>Definition:</p>
	<p>This property states the general status of secure variable support. This
	will be set to “okay” if the secvar OPAL API should be working as expected,
	and there were no unrecoverable faults in the basic secure variable
	initialization logic.</p>
	<p>This property may be set to “fail” if the platform does not properly
	select the drivers to use. Failures may also occur if the storage devices
	are inaccessible for some reason.</p>
	<p>Failures are NOT caused by malformed data loaded or processed in either
	storage or backend drivers, as these are faults correctable by a user.</p>
	</li>
	<li><p>update-status</p>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>required</p>
	</dd>
	<dt>Value type:</dt><dd><p><u64></p>
	</dd>
	</dl>
	<p>Definition:</p>
	<p>This property should contain the status code of the update processing
	logic, as returned by the backend. This value is intended to be
	consumed by userspace tools to confirm updates were processed as
	intended.</p>
	<p>The value contained in this property should adhere to the table below.
	Any additional error states that may be specific to a backend should
	be stored in the backend node.</p>
	</li>
	<li><p>max-var-size</p>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>required</p>
	</dd>
	<dt>Value type:</dt><dd><p><u64></p>
	</dd>
	</dl>
	<p>Definition:</p>
	<p>This is the maximum buffer size accepted for secure variables. The API
	will reject updates larger than this value, and storage drivers must
	reject loading variables larger than this value.</p>
	<p>As this may depend on the persistant storage devices in use, this
	value is determined by the storage driver, and may differ across
	platforms.</p>
	</li>
	<li><p>max-var-key-len</p>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>required</p>
	</dd>
	<dt>Value type:</dt><dd><p><u64></p>
	</dd>
	</dl>
	<p>Definition:</p>
	<p>This is the maximum size permitted for the key of a variable. As the
	value is a constant, it should be the same across platforms unless
	changed in code.</p>
	</li>
	</ul>
	</section>
	<section id="example">
	<h2>Example<a class="headerlink" href="#example" title="Link to this heading">¶</a></h2>
	<div class="highlight-dts notranslate"><div class="highlight"><pre><span></span><span class="err">/ibm,opal/</span><span class="nc">secvar</span> <span class="p">{</span>
	<span class="nf">compatible</span> <span class="o">=</span> <span class="s">"ibm,secvar-backend" "ibm,edk2-compat-v1"</span><span class="p">;</span>

	<span class="nf">status</span> <span class="o">=</span> <span class="s">"okay"</span><span class="p">;</span>
	<span class="nf">max-var-size</span> <span class="o">=</span> <span class="p"><</span><span class="mh">0x1000</span><span class="p">>;</span>
	<span class="nf">max-var-key-len</span> <span class="o">=</span> <span class="p"><</span><span class="mh">0x400</span><span class="p">></span>
	<span class="err">}</span><span class="p">;</span>
	</pre></div>
	</div>
	</section>
	<section id="update-status-code-table">
	<h2>Update Status Code Table<a class="headerlink" href="#update-status-code-table" title="Link to this heading">¶</a></h2>
	<p>The update status property should be set by the backend driver to a value
	that best fits its error condition. The following table defines the
	general intent of each error code, check backend specific documentation
	for more detail.</p>
	<table class="docutils align-default">
	<tbody>
	<tr class="row-odd"><td><p>update-status</p></td>
	<td><p>Generic Reason</p></td>
	</tr>
	<tr class="row-even"><td><p>OPAL_SUCCESS</p></td>
	<td><p>Updates were found and processed successfully</p></td>
	</tr>
	<tr class="row-odd"><td><p>OPAL_EMPTY</p></td>
	<td><p>No updates were found, none processed</p></td>
	</tr>
	<tr class="row-even"><td><p>OPAL_PARAMETER</p></td>
	<td><p>Malformed, or unexpected update data blob</p></td>
	</tr>
	<tr class="row-odd"><td><p>OPAL_PERMISSION</p></td>
	<td><p>Update failed to apply, possible auth failure</p></td>
	</tr>
	<tr class="row-even"><td><p>OPAL_HARDWARE</p></td>
	<td><p>Misc. storage-related error</p></td>
	</tr>
	<tr class="row-odd"><td><p>OPAL_RESOURCE</p></td>
	<td><p>Out of space (reported by storage</p></td>
	</tr>
	<tr class="row-even"><td><p>OPAL_NO_MEM</p></td>
	<td><p>Out of memory</p></td>
	</tr>
	</tbody>
	</table>
	</section>
	<section id="on-enforcing-secure-mode">
	<h2>On Enforcing Secure Mode<a class="headerlink" href="#on-enforcing-secure-mode" title="Link to this heading">¶</a></h2>
	<p>The os-secureboot-enforcing property in /ibm,secureboot/ is created by the
	backend if the owner has expressed a desire for boot loaders, kernels, etc
	to require any images to be signed by an appropriate key stored in secure
	variables. As this property is created by the backend, it is up to the
	backend to define what the required state of the secure variables should
	be to enter this mode.</p>
	<p>For example, we may want to only enable secure boot if we have a top-
	level “Platform Key”, so this property is created by the backend if
	by the end of update processing, a “PK” variable exists. By enrolling a
	PK, the system will be in “secure mode” until the PK is deleted.</p>
	</section>
	</section>


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	<h3><a href="../../index.html">Table of Contents</a></h3>
	<ul>
	<li><a class="reference internal" href="#">Secvar Binding</a><ul>
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