116 lines
6.3 KiB
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116 lines
6.3 KiB
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<title>PowerPC Embedded - Debugging with GDB</title>
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<meta name="description" content="Debugging with GDB">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Embedded-Processors.html#Embedded-Processors" title="Embedded Processors">
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<link rel="prev" href="OpenRISC-1000.html#OpenRISC-1000" title="OpenRISC 1000">
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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<body>
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<div class="node">
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<a name="PowerPC-Embedded"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="AVR.html#AVR">AVR</a>,
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Previous: <a rel="previous" accesskey="p" href="OpenRISC-1000.html#OpenRISC-1000">OpenRISC 1000</a>,
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Up: <a rel="up" accesskey="u" href="Embedded-Processors.html#Embedded-Processors">Embedded Processors</a>
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<hr>
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</div>
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<h4 class="subsection">21.3.7 PowerPC Embedded</h4>
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<p><a name="index-DVC-register-1589"></a><span class="sc">gdb</span> 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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<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>
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<p>The DVC register will be automatically used when <span class="sc">gdb</span> 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 <span class="sc">gdb</span> running on a Linux kernel version 2.6.34
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or newer.
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<p>When running on PowerPC embedded processors, <span class="sc">gdb</span> 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>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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<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>
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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><a name="index-ranged-breakpoint-1590"></a>PowerPC embedded processors support hardware accelerated
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<dfn>ranged breakpoints</dfn>. 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 <span class="sc">gdb</span>,
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use the <code>break-range</code> command.
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<p><span class="sc">gdb</span> provides the following PowerPC-specific commands:
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<a name="index-break_002drange-1591"></a>
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<dl><dt><code>break-range </code><var>start-location</var><code>, </code><var>end-location</var><dd>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><a name="index-set-powerpc-1592"></a><br><dt><code>set powerpc soft-float</code><dt><code>show powerpc soft-float</code><dd>Force <span class="sc">gdb</span> to use (or not use) a software floating point calling
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convention. By default, <span class="sc">gdb</span> selects the calling convention based
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on the selected architecture and the provided executable file.
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<br><dt><code>set powerpc vector-abi</code><dt><code>show powerpc vector-abi</code><dd>Force <span class="sc">gdb</span> to use the specified calling convention for vector
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arguments and return values. The valid options are ‘<samp><span class="samp">auto</span></samp>’;
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‘<samp><span class="samp">generic</span></samp>’, to avoid vector registers even if they are present;
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‘<samp><span class="samp">altivec</span></samp>’, to use AltiVec registers; and ‘<samp><span class="samp">spe</span></samp>’ to use SPE
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registers. By default, <span class="sc">gdb</span> selects the calling convention
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based on the selected architecture and the provided executable file.
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<br><dt><code>set powerpc exact-watchpoints</code><dt><code>show powerpc exact-watchpoints</code><dd>Allow <span class="sc">gdb</span> 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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</dl>
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</body></html>
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