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| <h4 class="subsection">21.3.7 PowerPC Embedded</h4> |
| |
| <p><a name="index-DVC-register-1589"></a><span class="sc">gdb</span> supports using the DVC (Data Value Compare) register to |
| implement in hardware simple hardware watchpoint conditions of the form: |
| |
| <pre class="smallexample"> (gdb) watch <var>ADDRESS|VARIABLE</var> \ |
| if <var>ADDRESS|VARIABLE</var> == <var>CONSTANT EXPRESSION</var> |
| </pre> |
| <p>The DVC register will be automatically used when <span class="sc">gdb</span> detects |
| such pattern in a condition expression, and the created watchpoint uses one |
| debug register (either the <code>exact-watchpoints</code> option is on and the |
| variable is scalar, or the variable has a length of one byte). This feature |
| is available in native <span class="sc">gdb</span> running on a Linux kernel version 2.6.34 |
| or newer. |
| |
| <p>When running on PowerPC embedded processors, <span class="sc">gdb</span> automatically uses |
| ranged hardware watchpoints, unless the <code>exact-watchpoints</code> option is on, |
| in which case watchpoints using only one debug register are created when |
| watching variables of scalar types. |
| |
| <p>You can create an artificial array to watch an arbitrary memory |
| region using one of the following commands (see <a href="Expressions.html#Expressions">Expressions</a>): |
| |
| <pre class="smallexample"> (gdb) watch *((char *) <var>address</var>)@<var>length</var> |
| (gdb) watch {char[<var>length</var>]} <var>address</var> |
| </pre> |
| <p>PowerPC embedded processors support masked watchpoints. See the discussion |
| about the <code>mask</code> argument in <a href="Set-Watchpoints.html#Set-Watchpoints">Set Watchpoints</a>. |
| |
| <p><a name="index-ranged-breakpoint-1590"></a>PowerPC embedded processors support hardware accelerated |
| <dfn>ranged breakpoints</dfn>. A ranged breakpoint stops execution of |
| the inferior whenever it executes an instruction at any address within |
| the range it specifies. To set a ranged breakpoint in <span class="sc">gdb</span>, |
| use the <code>break-range</code> command. |
| |
| <p><span class="sc">gdb</span> provides the following PowerPC-specific commands: |
| |
| |
| <a name="index-break_002drange-1591"></a> |
| <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 |
| <var>start-location</var> and <var>end-location</var>, which can specify a function name, |
| a line number, an offset of lines from the current line or from the start |
| location, or an address of an instruction (see <a href="Specify-Location.html#Specify-Location">Specify Location</a>, |
| for a list of all the possible ways to specify a <var>location</var>.) |
| The breakpoint will stop execution of the inferior whenever it |
| executes an instruction at any address within the specified range, |
| (including <var>start-location</var> and <var>end-location</var>.) |
| |
| <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 |
| convention. By default, <span class="sc">gdb</span> selects the calling convention based |
| on the selected architecture and the provided executable file. |
| |
| <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 |
| arguments and return values. The valid options are ‘<samp><span class="samp">auto</span></samp>’; |
| ‘<samp><span class="samp">generic</span></samp>’, to avoid vector registers even if they are present; |
| ‘<samp><span class="samp">altivec</span></samp>’, to use AltiVec registers; and ‘<samp><span class="samp">spe</span></samp>’ to use SPE |
| registers. By default, <span class="sc">gdb</span> selects the calling convention |
| based on the selected architecture and the provided executable file. |
| |
| <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 |
| of scalar type, thus assuming that the variable is accessed through the |
| address of its first byte. |
| |
| </dl> |
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