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Add FAQ about sandboxing. Minor fixes.

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This commit is contained in:
Mike Pall 2020-07-12 15:09:55 +02:00
parent 53f82e6e2e
commit 7eb96843ff
2 changed files with 33 additions and 9 deletions
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2
doc/extensions.html
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@ -326,7 +326,7 @@ the toolchain used to compile LuaJIT:
</tr>
<tr class="odd">
<td class="excplatform">Windows/x64</td>
<td class="exccompiler">MSVC or WinSDK</td>
<td class="exccompiler">MSVC</td>
<td class="excinterop"><b style="color: #00a000;">Full</b></td>
</tr>
<tr class="even">

40
doc/faq.html
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@ -55,7 +55,7 @@ dd { margin-left: 1.5em; }
</li></ul>
</div>
<div id="main">
<dl>
<dl id="info">
<dt>Q: Where can I learn more about LuaJIT and Lua?</dt>
<dd>
<ul style="padding: 0;">
@ -75,7 +75,7 @@ has information about diverse topics.</li>
</ul>
</dl>
<dl>
<dl id="tech">
<dt>Q: Where can I learn more about the compiler technology used by LuaJIT?</dt>
<dd>
I'm planning to write more documentation about the internals of LuaJIT.
@ -91,7 +91,7 @@ And, you know, reading the source is of course the only way to enlightenment. :-
</dd>
</dl>
<dl>
<dl id="arg">
<dt>Q: Why do I get this error: "attempt to index global 'arg' (a nil value)"?<br>
Q: My vararg functions fail after switching to LuaJIT!</dt>
<dd>LuaJIT is compatible to the Lua 5.1 language standard. It doesn't
@ -101,7 +101,7 @@ functions from Lua 5.0.<br>Please convert your code to the
vararg syntax</a>.</dd>
</dl>
<dl>
<dl id="x87">
<dt>Q: Why do I get this error: "bad FPU precision"?<br>
<dt>Q: I get weird behavior after initializing Direct3D.<br>
<dt>Q: Some FPU operations crash after I load a Delphi DLL.<br>
@ -123,7 +123,7 @@ Please check the Delphi docs for the Set8087CW method.
</dl>
<dl>
<dl id="ctrlc">
<dt>Q: Sometimes Ctrl-C fails to stop my Lua program. Why?</dt>
<dd>The interrupt signal handler sets a Lua debug hook. But this is
currently ignored by compiled code (this will eventually be fixed). If
@ -134,7 +134,31 @@ twice to get stop your program. That's similar to when it's stuck
running inside a C function under the Lua interpreter.</dd>
</dl>
<dl>
<dl id="sandbox">
<dt>Q: Can Lua code be safely sandboxed?</dt>
<dd>
Maybe for an extremly restricted subset of Lua and if you relentlessly
scrutinize every single interface function you offer to the untrusted code.<br>
Although Lua provides some sandboxing functionality (<tt>setfenv()</tt>, hooks),
it's very hard to get this right even for the Lua core libraries. Of course,
you'll need to inspect any extension library, too. And there are libraries
that are inherently unsafe, e.g. the <a href="ext_ffi.html">FFI library</a>.<br>
Relatedly, <b>loading untrusted bytecode is not safe!</b> It's trivial
to crash the Lua or LuaJIT VM with maliciously crafted bytecode. This is
well known and there's no bytecode verification on purpose, so please
don't report a bug about it. Check the <tt>mode</tt> parameter for the
<tt>load*()</tt> functions to disable loading of bytecode.<br>
In general, the only promising approach is to sandbox Lua code at the
process level and not the VM level.<br>
More reading material at the <a href="http://lua-users.org/wiki/SandBoxes"><span class="ext">&raquo;</span>&nbsp;Lua Wiki</a> and <a href="https://en.wikipedia.org/wiki/Sandbox_(computer_security)">Wikipedia</a>.
</dd>
</dl>
<dl id="patches">
<dt>Q: Why doesn't my favorite power-patch for Lua apply against LuaJIT?</dt>
<dd>Because it's a completely redesigned VM and has very little code
in common with Lua anymore. Also, if the patch introduces changes to
@ -145,7 +169,7 @@ can use source transformations or use wrapper or proxy functions.
The compiler will happily optimize away such indirections.</dd>
</dl>
<dl>
<dl id="arch">
<dt>Q: Lua runs everywhere. Why doesn't LuaJIT support my CPU?</dt>
<dd>Because it's a compiler &mdash; it needs to generate native
machine code. This means the code generator must be ported to each
@ -156,7 +180,7 @@ architectures. Other architectures will follow based on sufficient user
demand and/or sponsoring.</dd>
</dl>
<dl>
<dl id="when">
<dt>Q: When will feature X be added? When will the next version be released?</dt>
<dd>When it's ready.<br>
C'mon, it's open source &mdash; I'm doing it on my own time and you're