neingeist
/
arduinisten
Archived
1
0
Fork 0
You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
This repo is archived. You can view files and clone it, but cannot push or open issues/pull-requests.

179 lines
8.0 KiB
HTML

<html lang="en">
<head>
<title>CFI directives - Using as</title>
<meta http-equiv="Content-Type" content="text/html">
<meta name="description" content="Using as">
<meta name="generator" content="makeinfo 4.7">
<link title="Top" rel="start" href="index.html#Top">
<link rel="up" href="Pseudo-Ops.html#Pseudo-Ops" title="Pseudo Ops">
<link rel="prev" href="Comm.html#Comm" title="Comm">
<link rel="next" href="Data.html#Data" title="Data">
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
<!--
This file documents the GNU Assembler "as".
Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
2006, 2007 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1
or any later version published by the Free Software Foundation;
with no Invariant Sections, with no Front-Cover Texts, and with no
Back-Cover Texts. A copy of the license is included in the
section entitled ``GNU Free Documentation License''.
man end-->
<meta http-equiv="Content-Style-Type" content="text/css">
<style type="text/css"><!--
pre.display { font-family:inherit }
pre.format { font-family:inherit }
pre.smalldisplay { font-family:inherit; font-size:smaller }
pre.smallformat { font-family:inherit; font-size:smaller }
pre.smallexample { font-size:smaller }
pre.smalllisp { font-size:smaller }
span.sc { font-variant:small-caps }
span.roman { font-family: serif; font-weight: normal; }
--></style>
</head>
<body>
<div class="node">
<p>
<a name="CFI-directives"></a>Next:&nbsp;<a rel="next" accesskey="n" href="Data.html#Data">Data</a>,
Previous:&nbsp;<a rel="previous" accesskey="p" href="Comm.html#Comm">Comm</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="Pseudo-Ops.html#Pseudo-Ops">Pseudo Ops</a>
<hr><br>
</div>
<h3 class="section">7.9 <code>.cfi_startproc [simple]</code></h3>
<p><a name="index-_0040code_007bcfi_005fstartproc_007d-directive-290"></a><code>.cfi_startproc</code> is used at the beginning of each function that
should have an entry in <code>.eh_frame</code>. It initializes some internal
data structures. Don't forget to close the function by
<code>.cfi_endproc</code>.
<p>Unless <code>.cfi_startproc</code> is used along with parameter <code>simple</code>
it also emits some architecture dependent initial CFI instructions.
<h3 class="section">7.10 <code>.cfi_endproc</code></h3>
<p><a name="index-_0040code_007bcfi_005fendproc_007d-directive-291"></a><code>.cfi_endproc</code> is used at the end of a function where it closes its
unwind entry previously opened by
<code>.cfi_startproc</code>, and emits it to <code>.eh_frame</code>.
<h3 class="section">7.11 <code>.cfi_personality </code><var>encoding</var><code> [, </code><var>exp</var><code>]</code></h3>
<p><code>.cfi_personality</code> defines personality routine and its encoding.
<var>encoding</var> must be a constant determining how the personality
should be encoded. If it is 255 (<code>DW_EH_PE_omit</code>), second
argument is not present, otherwise second argument should be
a constant or a symbol name. When using indirect encodings,
the symbol provided should be the location where personality
can be loaded from, not the personality routine itself.
The default after <code>.cfi_startproc</code> is <code>.cfi_personality 0xff</code>,
no personality routine.
<h3 class="section">7.12 <code>.cfi_lsda </code><var>encoding</var><code> [, </code><var>exp</var><code>]</code></h3>
<p><code>.cfi_lsda</code> defines LSDA and its encoding.
<var>encoding</var> must be a constant determining how the LSDA
should be encoded. If it is 255 (<code>DW_EH_PE_omit</code>), second
argument is not present, otherwise second argument should be a constant
or a symbol name. The default after <code>.cfi_startproc</code> is <code>.cfi_lsda 0xff</code>,
no LSDA.
<h3 class="section">7.13 <code>.cfi_def_cfa </code><var>register</var><code>, </code><var>offset</var></h3>
<p><code>.cfi_def_cfa</code> defines a rule for computing CFA as: <i>take
address from </i><var>register</var><i> and add </i><var>offset</var><i> to it</i>.
<h3 class="section">7.14 <code>.cfi_def_cfa_register </code><var>register</var></h3>
<p><code>.cfi_def_cfa_register</code> modifies a rule for computing CFA. From
now on <var>register</var> will be used instead of the old one. Offset
remains the same.
<h3 class="section">7.15 <code>.cfi_def_cfa_offset </code><var>offset</var></h3>
<p><code>.cfi_def_cfa_offset</code> modifies a rule for computing CFA. Register
remains the same, but <var>offset</var> is new. Note that it is the
absolute offset that will be added to a defined register to compute
CFA address.
<h3 class="section">7.16 <code>.cfi_adjust_cfa_offset </code><var>offset</var></h3>
<p>Same as <code>.cfi_def_cfa_offset</code> but <var>offset</var> is a relative
value that is added/substracted from the previous offset.
<h3 class="section">7.17 <code>.cfi_offset </code><var>register</var><code>, </code><var>offset</var></h3>
<p>Previous value of <var>register</var> is saved at offset <var>offset</var> from
CFA.
<h3 class="section">7.18 <code>.cfi_rel_offset </code><var>register</var><code>, </code><var>offset</var></h3>
<p>Previous value of <var>register</var> is saved at offset <var>offset</var> from
the current CFA register. This is transformed to <code>.cfi_offset</code>
using the known displacement of the CFA register from the CFA.
This is often easier to use, because the number will match the
code it's annotating.
<h3 class="section">7.19 <code>.cfi_register </code><var>register1</var><code>, </code><var>register2</var></h3>
<p>Previous value of <var>register1</var> is saved in register <var>register2</var>.
<h3 class="section">7.20 <code>.cfi_restore </code><var>register</var></h3>
<p><code>.cfi_restore</code> says that the rule for <var>register</var> is now the
same as it was at the beginning of the function, after all initial
instruction added by <code>.cfi_startproc</code> were executed.
<h3 class="section">7.21 <code>.cfi_undefined </code><var>register</var></h3>
<p>From now on the previous value of <var>register</var> can't be restored anymore.
<h3 class="section">7.22 <code>.cfi_same_value </code><var>register</var></h3>
<p>Current value of <var>register</var> is the same like in the previous frame,
i.e. no restoration needed.
<h3 class="section">7.23 <code>.cfi_remember_state</code>,</h3>
<p>First save all current rules for all registers by <code>.cfi_remember_state</code>,
then totally screw them up by subsequent <code>.cfi_*</code> directives and when
everything is hopelessly bad, use <code>.cfi_restore_state</code> to restore
the previous saved state.
<h3 class="section">7.24 <code>.cfi_return_column </code><var>register</var></h3>
<p>Change return column <var>register</var>, i.e. the return address is either
directly in <var>register</var> or can be accessed by rules for <var>register</var>.
<h3 class="section">7.25 <code>.cfi_signal_frame</code></h3>
<p>Mark current function as signal trampoline.
<h3 class="section">7.26 <code>.cfi_window_save</code></h3>
<p>SPARC register window has been saved.
<h3 class="section">7.27 <code>.cfi_escape</code> <var>expression</var>[, <small class="dots">...</small>]</h3>
<p>Allows the user to add arbitrary bytes to the unwind info. One
might use this to add OS-specific CFI opcodes, or generic CFI
opcodes that GAS does not yet support.
<h3 class="section">7.28 <code>.cfi_val_encoded_addr </code><var>register</var><code>, </code><var>encoding</var><code>, </code><var>label</var></h3>
<p>The current value of <var>register</var> is <var>label</var>. The value of <var>label</var>
will be encoded in the output file according to <var>encoding</var>; see the
description of <code>.cfi_personality</code> for details on this encoding.
<p>The usefulness of equating a register to a fixed label is probably
limited to the return address register. Here, it can be useful to
mark a code segment that has only one return address which is reached
by a direct branch and no copy of the return address exists in memory
or another register.
</body></html>