path: root/src/juicebox_asm/rt.rs.html


                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
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<a href="#264" id="264">264</a></pre></div><pre class="rust"><code><span class="doccomment">//! Simple `mmap`ed runtime.
//!
//! This runtime supports adding code to executable pages and turn the added code into user
//! specified function pointer.

</span><span class="attr">#[cfg(not(target_os = <span class="string">"linux"</span>))]
</span><span class="macro">compile_error!</span>(<span class="string">"This runtime is only supported on linux"</span>);

<span class="kw">mod </span>perf {
    <span class="kw">use </span>std::fs;
    <span class="kw">use </span>std::io::Write;

    <span class="doccomment">/// Provide support for the simple [perf jit interface][perf-jit].
    ///
    /// This allows a simple (static) jit runtime to generate meta data describing the generated
    /// functions, which is used during post-processing by `perf report` to symbolize addresses
    /// captured while executing jitted code.
    ///
    /// By the nature of this format, this can not be used for dynamic jit runtimes, which reuses
    /// memory which previously contained jitted code.
    ///
    /// [perf-jit]: https://elixir.bootlin.com/linux/v6.6.6/source/tools/perf/Documentation/jit-interface.txt
    </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>PerfMap {
        file: std::fs::File,
    }

    <span class="kw">impl </span>PerfMap {
        <span class="doccomment">/// Create an empty perf map file.
        </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new() -&gt; <span class="self">Self </span>{
            <span class="kw">let </span>name = <span class="macro">format!</span>(<span class="string">"/tmp/perf-{}.map"</span>, <span class="kw">unsafe </span>{ libc::getpid() });
            <span class="kw">let </span>file = fs::OpenOptions::new()
                .truncate(<span class="bool-val">true</span>)
                .create(<span class="bool-val">true</span>)
                .write(<span class="bool-val">true</span>)
                .open(<span class="kw-2">&amp;</span>name)
                .unwrap_or_else(|<span class="kw">_</span>| <span class="macro">panic!</span>(<span class="string">"Failed to open perf map file {}"</span>, <span class="kw-2">&amp;</span>name));

            PerfMap { file }
        }

        <span class="doccomment">/// Add an entry to the perf map file.
        </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>add_entry(<span class="kw-2">&amp;mut </span><span class="self">self</span>, start: usize, len: usize) {
            <span class="comment">// Each line has the following format, fields separated with spaces:
            //   START SIZE NAME
            //
            // START and SIZE are hex numbers without 0x.
            // NAME is the rest of the line, so it could contain special characters.
            </span><span class="macro">writeln!</span>(<span class="self">self</span>.file, <span class="string">"{:x} {:x} jitfn_{:x}"</span>, start, len, start)
                .expect(<span class="string">"Failed to write PerfMap entry"</span>);
        }
    }
}

<span class="doccomment">/// A simple `mmap`ed runtime with executable pages.
</span><span class="kw">pub struct </span>Runtime {
    buf: <span class="kw-2">*mut </span>u8,
    len: usize,
    idx: usize,
    perf: <span class="prelude-ty">Option</span>&lt;perf::PerfMap&gt;,
}

<span class="kw">impl </span>Runtime {
    <span class="doccomment">/// Create a new [Runtime].
    ///
    /// # Panics
    ///
    /// Panics if the `mmap` call fails.
    </span><span class="kw">pub fn </span>new() -&gt; Runtime {
        <span class="comment">// Allocate a single page.
        </span><span class="kw">let </span>len = <span class="number">4096</span>;
        <span class="kw">let </span>buf = <span class="kw">unsafe </span>{
            libc::mmap(
                std::ptr::null_mut(),
                len,
                libc::PROT_NONE,
                libc::MAP_PRIVATE | libc::MAP_ANONYMOUS,
                <span class="number">0</span>, <span class="comment">/* fd */
                </span><span class="number">0</span>, <span class="comment">/* off */
            </span>) <span class="kw">as </span><span class="kw-2">*mut </span>u8
        };
        <span class="macro">assert_ne!</span>(
            buf.cast(),
            libc::MAP_FAILED,
            <span class="string">"Failed to mmap runtime code page"
        </span>);

        Runtime {
            buf,
            len,
            idx: <span class="number">0</span>,
            perf: <span class="prelude-val">None</span>,
        }
    }

    <span class="doccomment">/// Create a new [Runtime] which also generates static perf metat data.
    ///
    /// For each function added to the [Runtime], an entry will be generated in the
    /// `/tmp/perf-&lt;PID&gt;.map` file, which `perf report` uses to symbolicate unknown addresses.
    /// This is applicable for static runtimes only.
    ///
    /// # Panics
    ///
    /// Panics if the `mmap` call fails.
    </span><span class="kw">pub fn </span>with_profile() -&gt; Runtime {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        rt.perf = <span class="prelude-val">Some</span>(perf::PerfMap::new());
        rt
    }

    <span class="doccomment">/// Add the block of `code` to the runtime and a get function pointer of type `F`.
    ///
    /// # Panics
    ///
    /// Panics if the `code` does not fit on the `mmap`ed pages or is empty.
    ///
    /// # Safety
    ///
    /// The code added must fulfill the ABI of the specified function `F` and the returned function
    /// pointer is only valid until the [`Runtime`] is dropped.
    ///
    /// # Examples
    ///
    /// ```
    /// let mut rt = juicebox_asm::Runtime::new();
    ///
    /// let code = [ 0x90 /* nop */, 0xc3 /* ret */ ];
    /// let nop = unsafe { rt.add_code::&lt;extern "C" fn()&gt;(&amp;code) };
    ///
    /// nop();
    /// ```
    </span><span class="kw">pub unsafe fn </span>add_code&lt;F&gt;(<span class="kw-2">&amp;mut </span><span class="self">self</span>, code: <span class="kw">impl </span>AsRef&lt;[u8]&gt;) -&gt; F {
        <span class="comment">// Get pointer to start of next free byte.
        </span><span class="macro">assert!</span>(<span class="self">self</span>.idx &lt; <span class="self">self</span>.len, <span class="string">"Runtime code page full"</span>);
        <span class="kw">let </span>fn_start = <span class="self">self</span>.buf.add(<span class="self">self</span>.idx);

        <span class="comment">// Copy over code.
        </span><span class="kw">let </span>code = code.as_ref();
        <span class="macro">assert!</span>(!code.is_empty(), <span class="string">"Adding empty code not supported"</span>);
        <span class="macro">assert!</span>(
            code.len() &lt;= (<span class="self">self</span>.len - <span class="self">self</span>.idx),
            <span class="string">"Code does not fit on the runtime code page"
        </span>);
        <span class="self">self</span>.unprotect();
        <span class="kw">unsafe </span>{ std::ptr::copy_nonoverlapping(code.as_ptr(), fn_start, code.len()) };
        <span class="self">self</span>.protect();

        <span class="comment">// Increment index to next free byte.
        </span><span class="self">self</span>.idx += code.len();

        <span class="comment">// Add perf map entry.
        </span><span class="kw">if let </span><span class="prelude-val">Some</span>(map) = <span class="kw-2">&amp;mut </span><span class="self">self</span>.perf {
            map.add_entry(fn_start <span class="kw">as </span>usize, code.len());
        }

        <span class="comment">// Return function to newly added code.
        </span><span class="kw">unsafe </span>{ <span class="self">Self</span>::as_fn::&lt;F&gt;(fn_start) }
    }

    <span class="doccomment">/// Disassemble the code currently added to the runtime, using
    /// [`ndisasm`](https://nasm.us/index.php) and print it to _stdout_. If
    /// `ndisasm` is not available on the system this prints a warning and
    /// becomes a nop.
    ///
    /// # Panics
    ///
    /// Panics if anything goes wrong with spawning, writing to or reading from
    /// the `ndisasm` child process.
    </span><span class="kw">pub fn </span>disasm(<span class="kw-2">&amp;</span><span class="self">self</span>) {
        <span class="macro">assert!</span>(<span class="self">self</span>.idx &lt;= <span class="self">self</span>.len);
        <span class="kw">crate</span>::disasm::disasm(<span class="kw">unsafe </span>{ core::slice::from_raw_parts(<span class="self">self</span>.buf, <span class="self">self</span>.idx) });
    }

    <span class="doccomment">/// Reinterpret the block of code pointed to by `fn_start` as `F`.
    </span><span class="attr">#[inline]
    </span><span class="kw">unsafe fn </span>as_fn&lt;F&gt;(fn_start: <span class="kw-2">*mut </span>u8) -&gt; F {
        <span class="kw">unsafe </span>{ std::mem::transmute_copy(<span class="kw-2">&amp;</span>fn_start) }
    }

    <span class="doccomment">/// Add write protection the underlying code page(s).
    ///
    /// # Panics
    ///
    /// Panics if the `mprotect` call fails.
    </span><span class="kw">fn </span>protect(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
        <span class="kw">unsafe </span>{
            <span class="comment">// Remove write permissions from code page and allow to read-execute from it.
            </span><span class="kw">let </span>ret = libc::mprotect(<span class="self">self</span>.buf.cast(), <span class="self">self</span>.len, libc::PROT_READ | libc::PROT_EXEC);
            <span class="macro">assert_eq!</span>(ret, <span class="number">0</span>, <span class="string">"Failed to RX mprotect runtime code page"</span>);
        }
    }

    <span class="doccomment">/// Remove write protection the underlying code page(s).
    ///
    /// # Panics
    ///
    /// Panics if the `mprotect` call fails.
    </span><span class="kw">fn </span>unprotect(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
        <span class="kw">unsafe </span>{
            <span class="comment">// Add write permissions to code page.
            </span><span class="kw">let </span>ret = libc::mprotect(<span class="self">self</span>.buf.cast(), <span class="self">self</span>.len, libc::PROT_WRITE);
            <span class="macro">assert_eq!</span>(ret, <span class="number">0</span>, <span class="string">"Failed to W mprotect runtime code page"</span>);
        }
    }
}

<span class="kw">impl </span>Drop <span class="kw">for </span>Runtime {
    <span class="doccomment">/// Unmaps the code page. This invalidates all the function pointer returned by
    /// [`Runtime::add_code`].
    </span><span class="kw">fn </span>drop(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
        <span class="kw">unsafe </span>{
            <span class="kw">let </span>ret = libc::munmap(<span class="self">self</span>.buf.cast(), <span class="self">self</span>.len);
            <span class="macro">assert_eq!</span>(ret, <span class="number">0</span>, <span class="string">"Failed to munmap runtime"</span>);
        }
    }
}

<span class="attr">#[cfg(test)]
</span><span class="kw">mod </span>test {
    <span class="kw">use super</span>::<span class="kw-2">*</span>;

    <span class="attr">#[test]
    </span><span class="kw">fn </span>test_code_max_size() {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">4096</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }
    }

    <span class="attr">#[test]
    #[should_panic]
    </span><span class="kw">fn </span>test_code_max_size_plus_1() {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">4097</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }
    }

    <span class="attr">#[test]
    #[should_panic]
    </span><span class="kw">fn </span>test_code_max_size_plus_1_2() {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">4096</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }

        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">1</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }
    }

    <span class="attr">#[test]
    #[should_panic]
    </span><span class="kw">fn </span>test_empty_code() {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">0</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }
    }
}
</code></pre></div></section></main></body></html>
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<a href="#264" id="264">264</a></pre></div><pre class="rust"><code><span class="doccomment">//! Simple `mmap`ed runtime.
//!
//! This runtime supports adding code to executable pages and turn the added code into user
//! specified function pointer.

</span><span class="attr">#[cfg(not(target_os = <span class="string">"linux"</span>))]
</span><span class="macro">compile_error!</span>(<span class="string">"This runtime is only supported on linux"</span>);

<span class="kw">mod </span>perf {
    <span class="kw">use </span>std::fs;
    <span class="kw">use </span>std::io::Write;

    <span class="doccomment">/// Provide support for the simple [perf jit interface][perf-jit].
    ///
    /// This allows a simple (static) jit runtime to generate meta data describing the generated
    /// functions, which is used during post-processing by `perf report` to symbolize addresses
    /// captured while executing jitted code.
    ///
    /// By the nature of this format, this can not be used for dynamic jit runtimes, which reuses
    /// memory which previously contained jitted code.
    ///
    /// [perf-jit]: https://elixir.bootlin.com/linux/v6.6.6/source/tools/perf/Documentation/jit-interface.txt
    </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>PerfMap {
        file: std::fs::File,
    }

    <span class="kw">impl </span>PerfMap {
        <span class="doccomment">/// Create an empty perf map file.
        </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new() -&gt; <span class="self">Self </span>{
            <span class="kw">let </span>name = <span class="macro">format!</span>(<span class="string">"/tmp/perf-{}.map"</span>, <span class="kw">unsafe </span>{ libc::getpid() });
            <span class="kw">let </span>file = fs::OpenOptions::new()
                .truncate(<span class="bool-val">true</span>)
                .create(<span class="bool-val">true</span>)
                .write(<span class="bool-val">true</span>)
                .open(<span class="kw-2">&amp;</span>name)
                .unwrap_or_else(|<span class="kw">_</span>| <span class="macro">panic!</span>(<span class="string">"Failed to open perf map file {}"</span>, <span class="kw-2">&amp;</span>name));

            PerfMap { file }
        }

        <span class="doccomment">/// Add an entry to the perf map file.
        </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>add_entry(<span class="kw-2">&amp;mut </span><span class="self">self</span>, start: usize, len: usize) {
            <span class="comment">// Each line has the following format, fields separated with spaces:
            //   START SIZE NAME
            //
            // START and SIZE are hex numbers without 0x.
            // NAME is the rest of the line, so it could contain special characters.
            </span><span class="macro">writeln!</span>(<span class="self">self</span>.file, <span class="string">"{:x} {:x} jitfn_{:x}"</span>, start, len, start)
                .expect(<span class="string">"Failed to write PerfMap entry"</span>);
        }
    }
}

<span class="doccomment">/// A simple `mmap`ed runtime with executable pages.
</span><span class="kw">pub struct </span>Runtime {
    buf: <span class="kw-2">*mut </span>u8,
    len: usize,
    idx: usize,
    perf: <span class="prelude-ty">Option</span>&lt;perf::PerfMap&gt;,
}

<span class="kw">impl </span>Runtime {
    <span class="doccomment">/// Create a new [Runtime].
    ///
    /// # Panics
    ///
    /// Panics if the `mmap` call fails.
    </span><span class="kw">pub fn </span>new() -&gt; Runtime {
        <span class="comment">// Allocate a single page.
        </span><span class="kw">let </span>len = <span class="number">4096</span>;
        <span class="kw">let </span>buf = <span class="kw">unsafe </span>{
            libc::mmap(
                std::ptr::null_mut(),
                len,
                libc::PROT_NONE,
                libc::MAP_PRIVATE | libc::MAP_ANONYMOUS,
                <span class="number">0</span>, <span class="comment">/* fd */
                </span><span class="number">0</span>, <span class="comment">/* off */
            </span>) <span class="kw">as </span><span class="kw-2">*mut </span>u8
        };
        <span class="macro">assert_ne!</span>(
            buf.cast(),
            libc::MAP_FAILED,
            <span class="string">"Failed to mmap runtime code page"
        </span>);

        Runtime {
            buf,
            len,
            idx: <span class="number">0</span>,
            perf: <span class="prelude-val">None</span>,
        }
    }

    <span class="doccomment">/// Create a new [Runtime] which also generates static perf metat data.
    ///
    /// For each function added to the [Runtime], an entry will be generated in the
    /// `/tmp/perf-&lt;PID&gt;.map` file, which `perf report` uses to symbolicate unknown addresses.
    /// This is applicable for static runtimes only.
    ///
    /// # Panics
    ///
    /// Panics if the `mmap` call fails.
    </span><span class="kw">pub fn </span>with_profile() -&gt; Runtime {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        rt.perf = <span class="prelude-val">Some</span>(perf::PerfMap::new());
        rt
    }

    <span class="doccomment">/// Add the block of `code` to the runtime and a get function pointer of type `F`.
    ///
    /// # Panics
    ///
    /// Panics if the `code` does not fit on the `mmap`ed pages or is empty.
    ///
    /// # Safety
    ///
    /// The code added must fulfill the ABI of the specified function `F` and the returned function
    /// pointer is only valid until the [`Runtime`] is dropped.
    ///
    /// # Examples
    ///
    /// ```
    /// let mut rt = juicebox_asm::Runtime::new();
    ///
    /// let code = [ 0x90 /* nop */, 0xc3 /* ret */ ];
    /// let nop = unsafe { rt.add_code::&lt;extern "C" fn()&gt;(&amp;code) };
    ///
    /// nop();
    /// ```
    </span><span class="kw">pub unsafe fn </span>add_code&lt;F&gt;(<span class="kw-2">&amp;mut </span><span class="self">self</span>, code: <span class="kw">impl </span>AsRef&lt;[u8]&gt;) -&gt; F {
        <span class="comment">// Get pointer to start of next free byte.
        </span><span class="macro">assert!</span>(<span class="self">self</span>.idx &lt; <span class="self">self</span>.len, <span class="string">"Runtime code page full"</span>);
        <span class="kw">let </span>fn_start = <span class="self">self</span>.buf.add(<span class="self">self</span>.idx);

        <span class="comment">// Copy over code.
        </span><span class="kw">let </span>code = code.as_ref();
        <span class="macro">assert!</span>(!code.is_empty(), <span class="string">"Adding empty code not supported"</span>);
        <span class="macro">assert!</span>(
            code.len() &lt;= (<span class="self">self</span>.len - <span class="self">self</span>.idx),
            <span class="string">"Code does not fit on the runtime code page"
        </span>);
        <span class="self">self</span>.unprotect();
        <span class="kw">unsafe </span>{ std::ptr::copy_nonoverlapping(code.as_ptr(), fn_start, code.len()) };
        <span class="self">self</span>.protect();

        <span class="comment">// Increment index to next free byte.
        </span><span class="self">self</span>.idx += code.len();

        <span class="comment">// Add perf map entry.
        </span><span class="kw">if let </span><span class="prelude-val">Some</span>(map) = <span class="kw-2">&amp;mut </span><span class="self">self</span>.perf {
            map.add_entry(fn_start <span class="kw">as </span>usize, code.len());
        }

        <span class="comment">// Return function to newly added code.
        </span><span class="kw">unsafe </span>{ <span class="self">Self</span>::as_fn::&lt;F&gt;(fn_start) }
    }

    <span class="doccomment">/// Disassemble the code currently added to the runtime, using
    /// [`ndisasm`](https://nasm.us/index.php) and print it to _stdout_. If
    /// `ndisasm` is not available on the system this prints a warning and
    /// becomes a nop.
    ///
    /// # Panics
    ///
    /// Panics if anything goes wrong with spawning, writing to or reading from
    /// the `ndisasm` child process.
    </span><span class="kw">pub fn </span>disasm(<span class="kw-2">&amp;</span><span class="self">self</span>) {
        <span class="macro">assert!</span>(<span class="self">self</span>.idx &lt;= <span class="self">self</span>.len);
        <span class="kw">crate</span>::disasm::disasm(<span class="kw">unsafe </span>{ core::slice::from_raw_parts(<span class="self">self</span>.buf, <span class="self">self</span>.idx) });
    }

    <span class="doccomment">/// Reinterpret the block of code pointed to by `fn_start` as `F`.
    </span><span class="attr">#[inline]
    </span><span class="kw">unsafe fn </span>as_fn&lt;F&gt;(fn_start: <span class="kw-2">*mut </span>u8) -&gt; F {
        <span class="kw">unsafe </span>{ std::mem::transmute_copy(<span class="kw-2">&amp;</span>fn_start) }
    }

    <span class="doccomment">/// Add write protection the underlying code page(s).
    ///
    /// # Panics
    ///
    /// Panics if the `mprotect` call fails.
    </span><span class="kw">fn </span>protect(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
        <span class="kw">unsafe </span>{
            <span class="comment">// Remove write permissions from code page and allow to read-execute from it.
            </span><span class="kw">let </span>ret = libc::mprotect(<span class="self">self</span>.buf.cast(), <span class="self">self</span>.len, libc::PROT_READ | libc::PROT_EXEC);
            <span class="macro">assert_eq!</span>(ret, <span class="number">0</span>, <span class="string">"Failed to RX mprotect runtime code page"</span>);
        }
    }

    <span class="doccomment">/// Remove write protection the underlying code page(s).
    ///
    /// # Panics
    ///
    /// Panics if the `mprotect` call fails.
    </span><span class="kw">fn </span>unprotect(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
        <span class="kw">unsafe </span>{
            <span class="comment">// Add write permissions to code page.
            </span><span class="kw">let </span>ret = libc::mprotect(<span class="self">self</span>.buf.cast(), <span class="self">self</span>.len, libc::PROT_WRITE);
            <span class="macro">assert_eq!</span>(ret, <span class="number">0</span>, <span class="string">"Failed to W mprotect runtime code page"</span>);
        }
    }
}

<span class="kw">impl </span>Drop <span class="kw">for </span>Runtime {
    <span class="doccomment">/// Unmaps the code page. This invalidates all the function pointer returned by
    /// [`Runtime::add_code`].
    </span><span class="kw">fn </span>drop(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
        <span class="kw">unsafe </span>{
            <span class="kw">let </span>ret = libc::munmap(<span class="self">self</span>.buf.cast(), <span class="self">self</span>.len);
            <span class="macro">assert_eq!</span>(ret, <span class="number">0</span>, <span class="string">"Failed to munmap runtime"</span>);
        }
    }
}

<span class="attr">#[cfg(test)]
</span><span class="kw">mod </span>test {
    <span class="kw">use super</span>::<span class="kw-2">*</span>;

    <span class="attr">#[test]
    </span><span class="kw">fn </span>test_code_max_size() {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">4096</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }
    }

    <span class="attr">#[test]
    #[should_panic]
    </span><span class="kw">fn </span>test_code_max_size_plus_1() {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">4097</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }
    }

    <span class="attr">#[test]
    #[should_panic]
    </span><span class="kw">fn </span>test_code_max_size_plus_1_2() {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">4096</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }

        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">1</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }
    }

    <span class="attr">#[test]
    #[should_panic]
    </span><span class="kw">fn </span>test_empty_code() {
        <span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
        <span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">0</span>];
        <span class="kw">unsafe </span>{
            rt.add_code::&lt;<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()&gt;(code);
        }
    }
}
</code></pre></div></section></main></body></html>