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<title>Debugging with GDB: PowerPC Embedded</title>
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<a name="PowerPC-Embedded"></a>
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<div class="header">
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<p>
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Next: <a href="AVR.html#AVR" accesskey="n" rel="next">AVR</a>, Previous: <a href="OpenRISC-1000.html#OpenRISC-1000" accesskey="p" rel="previous">OpenRISC 1000</a>, Up: <a href="Embedded-Processors.html#Embedded-Processors" accesskey="u" rel="up">Embedded Processors</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
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<a name="PowerPC-Embedded-1"></a>
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<h4 class="subsection">21.3.8 PowerPC Embedded</h4>
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<a name="index-DVC-register"></a>
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<p><small>GDB</small> supports using the DVC (Data Value Compare) register to
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implement in hardware simple hardware watchpoint conditions of the form:
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) watch <var>ADDRESS|VARIABLE</var> \
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if <var>ADDRESS|VARIABLE</var> == <var>CONSTANT EXPRESSION</var>
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</pre></div>
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<p>The DVC register will be automatically used when <small>GDB</small> detects
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such pattern in a condition expression, and the created watchpoint uses one
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debug register (either the <code>exact-watchpoints</code> option is on and the
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variable is scalar, or the variable has a length of one byte). This feature
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is available in native <small>GDB</small> running on a Linux kernel version 2.6.34
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or newer.
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</p>
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<p>When running on PowerPC embedded processors, <small>GDB</small> automatically uses
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ranged hardware watchpoints, unless the <code>exact-watchpoints</code> option is on,
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in which case watchpoints using only one debug register are created when
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watching variables of scalar types.
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</p>
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<p>You can create an artificial array to watch an arbitrary memory
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region using one of the following commands (see <a href="Expressions.html#Expressions">Expressions</a>):
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</p>
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<div class="smallexample">
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<pre class="smallexample">(gdb) watch *((char *) <var>address</var>)@<var>length</var>
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(gdb) watch {char[<var>length</var>]} <var>address</var>
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</pre></div>
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<p>PowerPC embedded processors support masked watchpoints. See the discussion
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about the <code>mask</code> argument in <a href="Set-Watchpoints.html#Set-Watchpoints">Set Watchpoints</a>.
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</p>
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<a name="index-ranged-breakpoint"></a>
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<p>PowerPC embedded processors support hardware accelerated
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<em>ranged breakpoints</em>. A ranged breakpoint stops execution of
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the inferior whenever it executes an instruction at any address within
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the range it specifies. To set a ranged breakpoint in <small>GDB</small>,
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use the <code>break-range</code> command.
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</p>
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<p><small>GDB</small> provides the following PowerPC-specific commands:
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</p>
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<dl compact="compact">
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<dd><a name="index-break_002drange"></a>
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</dd>
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<dt><code>break-range <var>start-location</var>, <var>end-location</var></code></dt>
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<dd><p>Set a breakpoint for an address range given by
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<var>start-location</var> and <var>end-location</var>, which can specify a function name,
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a line number, an offset of lines from the current line or from the start
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location, or an address of an instruction (see <a href="Specify-Location.html#Specify-Location">Specify Location</a>,
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for a list of all the possible ways to specify a <var>location</var>.)
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The breakpoint will stop execution of the inferior whenever it
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executes an instruction at any address within the specified range,
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(including <var>start-location</var> and <var>end-location</var>.)
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</p>
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<a name="index-set-powerpc"></a>
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</dd>
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<dt><code>set powerpc soft-float</code></dt>
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<dt><code>show powerpc soft-float</code></dt>
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<dd><p>Force <small>GDB</small> to use (or not use) a software floating point calling
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convention. By default, <small>GDB</small> selects the calling convention based
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on the selected architecture and the provided executable file.
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</p>
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</dd>
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<dt><code>set powerpc vector-abi</code></dt>
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<dt><code>show powerpc vector-abi</code></dt>
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<dd><p>Force <small>GDB</small> to use the specified calling convention for vector
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arguments and return values. The valid options are ‘<samp>auto</samp>’;
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‘<samp>generic</samp>’, to avoid vector registers even if they are present;
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‘<samp>altivec</samp>’, to use AltiVec registers; and ‘<samp>spe</samp>’ to use SPE
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registers. By default, <small>GDB</small> selects the calling convention
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based on the selected architecture and the provided executable file.
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</p>
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</dd>
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<dt><code>set powerpc exact-watchpoints</code></dt>
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<dt><code>show powerpc exact-watchpoints</code></dt>
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<dd><p>Allow <small>GDB</small> to use only one debug register when watching a variable
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of scalar type, thus assuming that the variable is accessed through the
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address of its first byte.
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</p>
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</dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Next: <a href="AVR.html#AVR" accesskey="n" rel="next">AVR</a>, Previous: <a href="OpenRISC-1000.html#OpenRISC-1000" accesskey="p" rel="previous">OpenRISC 1000</a>, Up: <a href="Embedded-Processors.html#Embedded-Processors" accesskey="u" rel="up">Embedded Processors</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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