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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>struct user_regset</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="The utrace User Debugging Infrastructure" /><link rel="up" href="ch03.html#regset" title="struct user_regset" /><link rel="prev" href="re25.html" title="user_regset_writeback_fn" /><link rel="next" href="re27.html" title="struct user_regset_view" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>struct user_regset</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re25.html">Prev</a> </td><th width="60%" align="center"><span class="structname">struct user_regset</span></th><td width="20%" align="right"> <a accesskey="n" href="re27.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="struct user_regset"><a id="API-struct-user-regset"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>struct user_regset —
accessible thread CPU state
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><pre class="programlisting">
struct user_regset {
user_regset_get_fn * get;
user_regset_set_fn * set;
user_regset_active_fn * active;
user_regset_writeback_fn * writeback;
unsigned int n;
unsigned int size;
unsigned int align;
unsigned int bias;
unsigned int core_note_type;
}; </pre></div><div class="refsect1" title="Members"><a id="id3102187"></a><h2>Members</h2><div class="variablelist"><dl><dt><span class="term">get</span></dt><dd><p>
Function to fetch values.
</p></dd><dt><span class="term">set</span></dt><dd><p>
Function to store values.
</p></dd><dt><span class="term">active</span></dt><dd><p>
Function to report if regset is active, or <code class="constant">NULL</code>.
</p></dd><dt><span class="term">writeback</span></dt><dd><p>
Function to write data back to user memory, or <code class="constant">NULL</code>.
</p></dd><dt><span class="term">n</span></dt><dd><p>
Number of slots (registers).
</p></dd><dt><span class="term">size</span></dt><dd><p>
Size in bytes of a slot (register).
</p></dd><dt><span class="term">align</span></dt><dd><p>
Required alignment, in bytes.
</p></dd><dt><span class="term">bias</span></dt><dd><p>
Bias from natural indexing.
</p></dd><dt><span class="term">core_note_type</span></dt><dd><p>
ELF note <em class="parameter"><code>n_type</code></em> value used in core dumps.
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id3102311"></a><h2>Description</h2><p>
This data structure describes a machine resource we call a register set.
This is part of the state of an individual thread, not necessarily
actual CPU registers per se. A register set consists of a number of
similar slots, given by <em class="parameter"><code>n</code></em>. Each slot is <em class="parameter"><code>size</code></em> bytes, and aligned to
<em class="parameter"><code>align</code></em> bytes (which is at least <em class="parameter"><code>size</code></em>).
</p><p>
These functions must be called only on the current thread or on a
thread that is in <code class="constant">TASK_STOPPED</code> or <code class="constant">TASK_TRACED</code> state, that we are
guaranteed will not be woken up and return to user mode, and that we
have called <code class="function">wait_task_inactive</code> on. (The target thread always might
wake up for SIGKILL while these functions are working, in which case
that thread's user_regset state might be scrambled.)
</p><p>
The <em class="parameter"><code>pos</code></em> argument must be aligned according to <em class="parameter"><code>align</code></em>; the <em class="parameter"><code>count</code></em>
argument must be a multiple of <em class="parameter"><code>size</code></em>. These functions are not
responsible for checking for invalid arguments.
</p><p>
When there is a natural value to use as an index, <em class="parameter"><code>bias</code></em> gives the
difference between the natural index and the slot index for the
register set. For example, x86 GDT segment descriptors form a regset;
the segment selector produces a natural index, but only a subset of
that index space is available as a regset (the TLS slots); subtracting
<em class="parameter"><code>bias</code></em> from a segment selector index value computes the regset slot.
</p><p>
If nonzero, <em class="parameter"><code>core_note_type</code></em> gives the n_type field (NT_* value)
of the core file note in which this regset's data appears.
NT_PRSTATUS is a special case in that the regset data starts at
offsetof(struct elf_prstatus, pr_reg) into the note data; that is
part of the per-machine ELF formats userland knows about. In
other cases, the core file note contains exactly the whole regset
(<em class="parameter"><code>n</code></em> * <em class="parameter"><code>size</code></em>) and nothing else. The core file note is normally
omitted when there is an <em class="parameter"><code>active</code></em> function and it returns zero.
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