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4928dfd872
Changed "Use Keep-Alive Hack" to "Disable Keep-Alive Hack" to emphasize that it defaults to enabled. Added a menu item for "Disable Security Sandbox". Added a warning to both that tells the user that they must reopen the current project for the change to take effect. Note neither of these is persisted in app settings.
460 lines
21 KiB
HTML
460 lines
21 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta content="text/html; charset=utf-8" http-equiv="Content-Type" />
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<meta name="viewport" content="width=device-width, initial-scale=1" />
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<link href="main.css" rel="stylesheet" type="text/css" />
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<title>Advanced Topics - 6502bench SourceGen</title>
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</head>
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<body>
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<div id="content">
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<h1>6502bench SourceGen: Advanced Topics</h1>
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<p><a href="index.html">Back to index</a></p>
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<h2><a name="platform-symbols">Platform Symbol Files (.sym65)</a></h2>
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<p>Platform symbol files contain lists of symbols, each of which has a
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label and a value. SourceGen comes with a collection of symbols for
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popular systems, but you can create your own. This can be handy if a
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few different projects are coded against a common library.</p>
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<p>If two symbols have the same value, the older symbol is replaced by
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the newer one. This is why the order in which symbol files are loaded
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matters.</p>
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<p>Platform symbol files consist of comments, commands, and symbols.
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Blank lines, and lines that begin with a semicolon (';'), are ignored. Lines
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that begin with an asterisk ('*') are commands. Three are currently
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defined:</p>
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<ul>
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<li><code>*SYNOPSIS</code> - a short summary of the file contents.</li>
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<li><code>*TAG</code> - a tag string to apply to all symbols that follow
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in this file.</li>
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<li><code>*MULTI_MASK</code> - specify a mask for symbols that appear
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at multiple addresses.</li>
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</ul>
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<p>Tags can be used by extension scripts to identify a subset of symbols.
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The symbols are still part of the global set; the tag just provides a
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way to extract a subset. Tags should be comprised of non-whitespace ASCII
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characters. Tags are global, so use a long, descriptive string. If
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<code>*TAG</code> is not followed by a string, the symbols that follow
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are treated as untagged.</p>
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<p>All other lines are symbols, which have the form:</p>
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<pre>
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LABEL {=|@|<|>} VALUE [WIDTH] [;COMMENT]
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</pre>
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<p>The LABEL must be at least two characters long, begin with a letter or
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underscore, and consist entirely of alphanumeric ASCII characters
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(A-Z, a-z, 0-9) and the underscore ('_'). (This is the same format
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required for line labels in SourceGen.)</p>
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<p>The next token can be one of:</p>
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<ul>
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<li>@: general addresses</li>
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<li><: read-only addresses</li>
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<li>>: write-only addresses</li>
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<li>=: constants</li>
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</ul>
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<p>If an instruction references an address, and that address is outside
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the bounds of the file, the list of address symbols (i.e. everything
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that's not a constant) will be scanned for a match.
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If found, the symbol is applied automatically. You normally want to
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use '@', but can use '<' and '>' for memory-mapped I/O locations
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that have different behavior depending on whether they are read or
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written.</p>
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<p>The VALUE is a number in decimal, hexadecimal (with a leading '$'), or
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binary (with a leading '%'). The numeric base will be recorded and used when
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formatting the symbol in generated output, so use whichever form is most
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appropriate. Values are unsigned 24-bit numbers. The special value
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"erase" may be used for an address to erase a symbol defined in an earlier
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platform file.</p>
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<p>The WIDTH is optional, and ignored for constants. It must be a
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decimal or hexadecimal value between 1 and 65536, inclusive. If omitted,
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the default width is 1.</p>
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<p>The COMMENT is optional. If present, it will be saved and used as the
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end-of-line comment on the .EQ directive if the symbol is used.</p>
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<h4>Using MULTI_MASK</h4>
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<p>The multi-address mask is used for systems like the Atari 2600, where
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RAM, ROM, and I/O registers appear at multiple addresses. The hardware
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looks for certain address lines to be set or clear, and if the pattern
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matches, another set of bits is examined to determine which register or
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RAM address is being accessed.</p>
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<p>This is expressed in symbol files with the MULTI_MASK statement.
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Address symbol declarations that follow have the mask set applied. Symbols
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whose addresses don't fit the pattern cause a warning and will be
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ignored. Constants are not affected.</p>
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<p>The mask set is best explained with an example. Suppose the address
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pattern for a set of registers is <code>???0 ??1? 1??x xxxx</code>
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(where '?' can be any value, 0/1 must be that value, and 'x' means the bit
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is used to determine the register).
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So any address between $0280-029F matches, as does $23C0-23DF, but
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$0480 and $1280 don't. The register number is found in the low five bits.</p>
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<p>The corresponding MULTI_MASK line, with values specifed in binary,
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would be:</p>
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<pre> *MULTI_MASK %0001001010000000 %0000001010000000 %0000000000011111</pre>
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<p>The values are CompareMask, CompareValue, and AddressMask. To
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determine if an address is in the register set, we check to see if
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<code>(address & CompareMask) == CompareValue</code>. If so, we can
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extract the register number with <code>(address & AddressMask)</code>.</p>
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<p>We don't want to have a huge collection of equates at the top of the
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generated source file, so whatever value is used in the symbol declaration
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is considered the "canonical" value. All other matching values are output
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with an offset.</p>
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<p>All mask values must fall between 0 and $00FFFFFF. The set bits in
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CompareMask and AddressMask must not overlap, and CompareValue must not
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have any bits set that aren't also set in CompareMask.</p>
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<p>If an address can be mapped to a masked value and an unmasked value,
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the unmasked value takes precedence for exact matches. In the example
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above, if you declare <code>REG1 @ $0281</code> outside the MULTI_MASK
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declaration, the disassembler will use <code>REG1</code> for all operands
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that reference $0281. If other code accesses the same register as $23C1,
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the symbol established for the masked value will be used instead.</p>
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<p>If there are multiple masked values for a given address, the precedence
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is undefined.</p>
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<p>To disable the MULTI_MASK and resume normal declarations, write the
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tag without arguments:
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<pre> *MULTI_MASK</pre></p>
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<h3>Creating a Project-Specific Symbol File</h3>
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<p>To create a platform symbol file for your project, just create a new
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text file, named with a ".sym65" extension. (If your text editor of choice
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doesn't like that, you can put a ".txt" on the end while you're editing.)
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Make sure you create it in the same directory where your project file
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(the file that ends with ".dis65") lives. Add a <code>*SYNOPSIS</code>,
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then add the desired symbols.</p>
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<p>Finally, add it to your project. Select Edit > Project Properties,
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switch to the Symbol Files tab, click Add Symbol Files from Project, and
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select your symbol file. It should appear in the list with a
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"PROJ:" prefix.</p>
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<p>If an example helps, the A2-Amper-fdraw project in the Examples
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directory has a project-local symbol file, called "fdraw-exports".
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(fdraw-exports is a list of exported symbols from the fdraw library,
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for which Amper-fdraw provides an Applesoft BASIC interface.)
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<p>NOTE: in the current version of SourceGen, changes to .sym65 files are
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not detected automatically. Closing and re-opening the project
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(File > Recent Projects, then select the first entry) will reload
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them.</p>
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<h2><a name="extension-scripts">Extension Scripts</a></h2>
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<p>Extension scripts, also called "plugins", are C# programs with access to
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the full .NET Standard 2.0 APIs. They're compiled at run time by SourceGen
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and executed in a sandbox with security restrictions.</p>
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<p>SourceGen defines an interface that plugins must implement, and an
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interface that plugins can use to interact with SourceGen. See
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Interfaces.cs in the PluginCommon directory.</p>
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<p>The current interfaces can be used to generate visualizations, to
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identify inline data that follows JSR, JSL, or BRK instructions, and to
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format operands. The latter can be used to format code and data, e.g.
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replacing immediate load operands with symbolic constants.</p>
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<p>Scripts may be loaded from the RuntimeData directory, or from the directory
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where the project file lives. Attempts to load them from other locations
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will fail.</p>
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<p>A project may load multiple scripts. The order in which they are
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invoked is not defined.</p>
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<h4>Known Issues and Limitations</h4>
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<p>Scripts are currently limited to C# version 5, because the compiler
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built into .NET only handles that. C# 6 and later require installing an
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additional package ("Roslyn"), so SourceGen does not support this.</p>
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<p>When a project is opened, any errors encountered by the script compiler
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are reported to the user. If the project is already open, and a script
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is added to the project through the Project Properties editor, compiler
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messages are silently discarded. (This also applies if you undo/redo across
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the property edit.)</p>
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<h4>Development</h4>
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<p>The easiest way to develop extension scripts is inside the 6502bench
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solution in Visual Studio. This way you have the interfaces available
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for IntelliSense completion, and get all the usual syntax and compile
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checking in the editor. (This is why there's a RuntimeData project for
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Visual Studio.)</p>
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<p>If you have the solution configured for debug builds, SourceGen will pass
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<code>IncludeDebugInformation=true</code> to the script compiler. This
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causes a .PDB file to be created. While this can help with debugging,
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it can sometimes get in the way: if you edit the script source code and
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reload the project without restarting the app, SourceGen will recompile
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the script, but the old .PDB file will still be open by VisualStudio
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and you'll get error messages.</p>
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<p>Some commonly useful functions are defined in the
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<code>PluginCommon.Util</code> class, which is available to plugins. These
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call into the CommonUtil library, which is shared with SourceGen.
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While plugins could use CommonUtil directly, they should avoid doing so. The
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APIs there are not guaranteed to be stable, so plugins that rely on them
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may break in a subsequent release of SourceGen.</p>
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<h4>PluginDllCache Directory</h4>
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<p>Extension scripts are compiled into .DLLs, and saved in the PluginDllCache
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directory, which lives next to the application executable and RuntimeData.
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If the extension script is the same age or older than the DLL, SourceGen
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will continue to use the existing DLL.</p>
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<p>The DLL names are a combination of the script filename and script location.
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The compiled name for "MyPlatform/MyScript.cs" in the RuntimeData directory
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will be "RT_MyPlatform_MyScript.dll". For a project-specific script, it
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would look like "PROJ_MyProject_MyScript.dll".</p>
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<p>The PluginCommon and CommonUtil DLLs will be copied into the directory, so
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that code in the sandbox has access to them.</p>
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<p>The contents of the directory are generated as needed, and can be deleted
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entirely whenever SourceGen isn't running.</p>
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<h4>Sandboxing</h4>
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<p>Extension scripts are executed in an App Domain sandbox. App domains are
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a .NET feature that creates a partition inside the virtual machine, isolating
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code. It still runs in the same address space, on the same threads, so the
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isolation is only effective for "partially trusted" code that has been
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declared safe by the bytecode verifier.</p>
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<p>SourceGen disallows most actions, notably file access. An exception is
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made for reading files from the directory where the plugin DLLs live, but
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scripts are otherwise unable to read or write from the filesystem. (A
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future version of SourceGen may provide an API that allows limited access
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to data files.)</p>
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<p>App domain security is not absolute. I don't really expect SourceGen to
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be used as a malware vector, so there's no value in forcing scripts to
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execute in an isolated server process, or to jump through the other hoops
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required to really lock things down. I do believe there's value in
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defining the API in such a way that we <b>could</b> implement full security if
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circumstances change, so I'm using app domains as a way to keep the API
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honest.</p>
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<h2><a name="multi-bin">Working With Multiple Binaries</a></h2>
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<p>Sometimes a program is split into multiple files on disk. They
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may be all loaded at once, or some may be loaded into the same place
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at different times. In such situations it's not uncommon for one
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file to provide a set of interfaces that other files use. It's
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useful to have symbols for these interfaces be available to all
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projects.</p>
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<p>There are two ways to do this: (1) define a common platform symbol
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file with the relevant addresses, and keep it up to date as you work;
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or (2) declare the labels as global and exported, and import them
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as project symbols into the other projects.</p>
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<p>Support for this is currently somewhat weak, requiring a manual
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symbol-import step in every interested project. This step must be
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repeated whenever the labels are updated.</p>
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<p>A different but related problem is typified by arcade ROM sets,
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where files are split apart because each file must be burned into a
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separate PROM. All files are expected to be present in memory at
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once, so there's no reason to treat them as separate projects. Currently,
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the best way to deal with this is to concatenate the files into a single
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file, and operate on that.</p>
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<h2><a name="overlap">Overlapping Address Spaces</a></h2>
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<p>Some programs use memory overlays, where multiple parts of the
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code run in the same address in RAM. Others use bank switching to access
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parts of the program that reside in separate physical RAM, but appear at
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the same address.</p>
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<p>SourceGen allows you to set the same address on multiple parts of
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a file. Branches to a given address are resolved against the current
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segment first. For example, consider this:</p>
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<pre>
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.ORG $1000
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JMP L1100
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.ORG $1100
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L1100 BIT L1100
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L1103 LDA #$11
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BRA L1103
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.ORG $1100
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L1100_0 BIT L1100_0
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L1103_0 LDA #$22
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JMP L1103_0
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</pre>
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<p>Both sections start at $1100, and have branches to $1103. The branch
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in the first section resolves to the label in the first version of
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that address chunk, while the branch in the second section resolves to
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the label in the second chunk. When branches originate outside the current
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address chunk, the first chunk that includes that address is used, as
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it is with the <code>JMP $1000</code> at the start of the file.</p>
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<h2><a name="reloc-data">OMF Relocation Dictionaries</a></h2>
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<p><i>This feature is considered experimental. Some features,
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like cross-reference tracking, may not work correctly with it.</i></p>
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<p>65816 code can be tricky to disassemble for a number of reasons.
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24-bit addresses are formed from 16-bit data-access operands by combining
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with the Data Bank Register, which often requires a bit of manual
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intervention. But the problems go beyond that. Consider the following
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bit of source code for the Apple IIgs:</p>
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<pre>
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rsrcmsg pea rsrcmsg2|-16
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pea rsrcmsg2
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_WriteCString
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lda #buffer
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sta pArcRead+$04
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lda #buffer|-16
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sta pArcRead+$06
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</pre>
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<p>In both cases we're referencing a 24-bit address as two 16-bit values.
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Without context, the disassembler will treat the PEA instruction as two
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independent 16-bit addresses, and the immediate values as constants:</p>
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<pre>
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.dbank $02
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02/317c: f4 02 00 L2317C pea L20002 & $ffff
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02/317f: f4 54 32 pea L23254 & $ffff
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02/3182: a2 0c 20 ldx #WriteCString
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02/3185: 22 00 00 e1 jsl Toolbox
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02/3189: a9 00 00 L23189 lda #$0000
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02/318c: 8d 78 3f sta L23F78 & $ffff
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02/318f: a9 03 00 lda #$0003
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02/3192: 8d 7a 3f sta L23F78 & $ffff +2
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</pre>
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<p>Worse yet, those <code>STA</code> instruction operands would have been
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shown as hex values or incorrect labels if the DBR had been set incorrectly.
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However, if we have the relocation data, we know the full
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address from which the addresses were formed, and we can tell when
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immediate values are addresses rather than constants. And we can do this
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even without setting the DBR.</p>
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<pre>
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02/317c: f4 02 00 L2317C pea L23254 >> 16
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02/317f: f4 54 32 pea L23254 & $ffff
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02/3182: a2 0c 20 ldx #WriteCString
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02/3185: 22 00 00 e1 jsl Toolbox
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02/3189: a9 00 00 L23189 lda #L30000 & $ffff
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02/318c: 8d 78 3f sta L23F78 & $ffff
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02/318f: a9 03 00 lda #L30000 >> 16
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02/3192: 8d 7a 3f sta L23F78 & $ffff +2
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</pre>
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<p>The absence of relocation data can be a useful signal as well. For
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example, when pushing arguments for a toolbox call, the disassembler
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can tell the difference between addresses and constants without needing
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emulation or pattern-matching, because only the addresses get
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relocated. Consider this bit of source code:</p>
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<pre>
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lda <total_records
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pha
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pea linebuf|-16
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pea linebuf+65
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pea $0005
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pea $0000
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_Int2Dec
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</pre>
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<p>Without relocation data, it becomes:</p>
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<pre>
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02/0aa8: a5 42 lda $42
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02/0aaa: 48 pha
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02/0aab: f4 02 00 pea L20002 & $ffff
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02/0aae: f4 03 31 pea L23103 & $ffff
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02/0ab1: f4 05 00 pea L20005 & $ffff
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02/0ab4: f4 00 00 pea L20000 & $ffff
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02/0ab7: a2 0b 26 ldx #Int2Dec
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02/0aba: 22 00 00 e1 jsl Toolbox
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</pre>
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<p>If we treat the non-relocated operands as constants:</p>
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<pre>
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02/0aa8: a5 42 lda $42
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02/0aaa: 48 pha
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02/0aab: f4 02 00 pea L230C2 >> 16
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02/0aae: f4 03 31 pea L23103 & $ffff
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02/0ab1: f4 05 00 pea $0005
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02/0ab4: f4 00 00 pea $0000
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02/0ab7: a2 0b 26 ldx #Int2Dec
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02/0aba: 22 00 00 e1 jsl Toolbox
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</pre>
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<h2><a name="debug">Debug Menu Options</a></h2>
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<p>The DEBUG menu is hidden by default in release builds, but can be
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exposed by checking the "enable DEBUG menu" box in the application
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settings. These features are used for debugging SourceGen. They will
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not help you debug 6502 projects.</p>
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<p>Features:</p>
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<ul>
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<li>Re-analyze (F5). Causes a full re-analysis. Useful if you think
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the display is out of sync.</li>
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<li>Source Generation Tests. Opens the regression test harness. See
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<code>README.md</code> in the SGTestData directory for more information.
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If the regression tests weren't included in the SourceGen distribution,
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this will have nothing to do.</li>
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<li>Show Analyzer Output. Opens a floating window with a text log from
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the most recent analysis pass. The exact contents will vary depending
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on how the verbosity level is configured internally. Debug messages
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from extension scripts appear here.</li>
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<li>Show Analysis Timers. Opens a floating window with a dump of
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timer results from the most recent analysis pass. Times for individual
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stages are noted, as are times for groups of functions. This
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provides a crude sense of where time is being spent.</li>
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<li>Show Undo/Redo History. Opens a floating window that lets you
|
|
watch the contents of the undo buffer while you work.</li>
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|
<li>Extension Script Info. Shows a bit about the currently-loaded
|
|
extension scripts.</li>
|
|
<li>Show Comment Rulers. Adds a string of digits above every
|
|
multi-line comment (long comment, note). Useful for confirming that
|
|
the width limitation is being obeyed. These are added exactly
|
|
as shown, without comment delimiters, into generated assembly output,
|
|
which doesn't work out well if you run the assembler.</li>
|
|
<li>Disable Security Sandbox. Extension scripts are loaded and run in
|
|
a "sandbox" to prevent security issues. Setting this flag allows
|
|
them to execute with full permissions.
|
|
This setting is not persistent.</li>
|
|
<li>Disable Keep-Alive Hack. The hack sends a "ping" to the extension
|
|
script sandbox every 60 seconds. This seems to be required to avoid
|
|
an infrequently-encountered Windows bug. (See code for notes and
|
|
stackoverflow.com links.)
|
|
This setting is not persistent.</li>
|
|
<li>Applesoft to HTML. An experimental feature that formats an
|
|
Applesoft program as HTML.</li>
|
|
<li>Export Edit Commands. Outputs comments and notes in
|
|
SourceGen Edit Command format. This is an experimental feature.</li>
|
|
<li>Apply Edit Commands. Reads a file in SourceGen Edit Command
|
|
format and applies the commands.</li>
|
|
<li>Apply Platform Symbols. An experimental feature for turning platform
|
|
symbols into address labels. This will run through the list of all
|
|
symbols loaded from .sym65 files and find addresses that fall within
|
|
the bounds of the file. If it finds an address that is the start
|
|
of a code/data line and doesn't already have a user-supplied label,
|
|
and the platform symbol's label isn't already defined elsewhere, the
|
|
platform label will be applied. Useful when disassembling ROM images
|
|
or other code with an established set of public entry points.
|
|
(Tip: disable "analyze uncategorized data" from the project
|
|
properties editor first.)</li>
|
|
</ul>
|
|
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