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| <h3 class="section">10.15 Operating System Auxiliary Information</h3> |
| |
| <p><a name="index-OS-information-613"></a> |
| <span class="sc">gdb</span> provides interfaces to useful OS facilities that can help |
| you debug your program. |
| |
| <p><a name="index-g_t_0040code_007bptrace_007d-system-call-614"></a><a name="index-g_t_0040code_007bstruct-user_007d-contents-615"></a>When <span class="sc">gdb</span> runs on a <dfn>Posix system</dfn> (such as GNU or Unix |
| machines), it interfaces with the inferior via the <code>ptrace</code> |
| system call. The operating system creates a special sata structure, |
| called <code>struct user</code>, for this interface. You can use the |
| command <code>info udot</code> to display the contents of this data |
| structure. |
| |
| <dl> |
| <dt><code>info udot</code><dd><a name="index-info-udot-616"></a>Display the contents of the <code>struct user</code> maintained by the OS |
| kernel for the program being debugged. <span class="sc">gdb</span> displays the |
| contents of <code>struct user</code> as a list of hex numbers, similar to |
| the <code>examine</code> command. |
| </dl> |
| |
| <p><a name="index-auxiliary-vector-617"></a><a name="index-vector_002c-auxiliary-618"></a>Some operating systems supply an <dfn>auxiliary vector</dfn> to programs at |
| startup. This is akin to the arguments and environment that you |
| specify for a program, but contains a system-dependent variety of |
| binary values that tell system libraries important details about the |
| hardware, operating system, and process. Each value's purpose is |
| identified by an integer tag; the meanings are well-known but system-specific. |
| Depending on the configuration and operating system facilities, |
| <span class="sc">gdb</span> may be able to show you this information. For remote |
| targets, this functionality may further depend on the remote stub's |
| support of the ‘<samp><span class="samp">qXfer:auxv:read</span></samp>’ packet, see |
| <a href="qXfer-auxiliary-vector-read.html#qXfer-auxiliary-vector-read">qXfer auxiliary vector read</a>. |
| |
| |
| <a name="index-info-auxv-619"></a> |
| <dl><dt><code>info auxv</code><dd>Display the auxiliary vector of the inferior, which can be either a |
| live process or a core dump file. <span class="sc">gdb</span> prints each tag value |
| numerically, and also shows names and text descriptions for recognized |
| tags. Some values in the vector are numbers, some bit masks, and some |
| pointers to strings or other data. <span class="sc">gdb</span> displays each value in the |
| most appropriate form for a recognized tag, and in hexadecimal for |
| an unrecognized tag. |
| </dl> |
| |
| <p>On some targets, <span class="sc">gdb</span> can access operating-system-specific information |
| and display it to user, without interpretation. For remote targets, |
| this functionality depends on the remote stub's support of the |
| ‘<samp><span class="samp">qXfer:osdata:read</span></samp>’ packet, see <a href="qXfer-osdata-read.html#qXfer-osdata-read">qXfer osdata read</a>. |
| |
| |
| <a name="index-info-os-620"></a> |
| <dl><dt><code>info os</code><dd>List the types of OS information available for the target. If the |
| target does not return a list of possible types, this command will |
| report an error. |
| |
| <p><a name="index-info-os-processes-621"></a><br><dt><code>info os processes</code><dd>Display the list of processes on the target. For each process, |
| <span class="sc">gdb</span> prints the process identifier, the name of the user, and |
| the command corresponding to the process. |
| </dl> |
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