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diff --git a/static/freebsd/man9/DEFINE_IFUNC.9 3.html b/static/freebsd/man9/DEFINE_IFUNC.9 3.html deleted file mode 100644 index d7bc4b82..00000000 --- a/static/freebsd/man9/DEFINE_IFUNC.9 3.html +++ /dev/null @@ -1,118 +0,0 @@ -<table class="head"> - <tr> - <td class="head-ltitle">DEFINE_IFUNC(9)</td> - <td class="head-vol">Kernel Developer's Manual</td> - <td class="head-rtitle">DEFINE_IFUNC(9)</td> - </tr> -</table> -<div class="manual-text"> -<section class="Sh"> -<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1> -<p class="Pp"><code class="Nm">DEFINE_IFUNC</code> — - <span class="Nd">define a kernel function with an implementation selected at - run-time</span></p> -</section> -<section class="Sh"> -<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1> -<p class="Pp"><code class="In">#include - <<a class="In">machine/ifunc.h</a>></code></p> -<p class="Pp"><code class="Fn">DEFINE_IFUNC</code>(<var class="Fa" style="white-space: nowrap;">qual</var>, - <var class="Fa" style="white-space: nowrap;">ret_type</var>, - <var class="Fa" style="white-space: nowrap;">name</var>, - <var class="Fa" style="white-space: nowrap;">args</var>);</p> -</section> -<section class="Sh"> -<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1> -<p class="Pp">ifuncs are a linker feature which allows the programmer to define - functions whose implementation is selected at boot-time or module load-time. - The <code class="Nm">DEFINE_IFUNC</code> macro can be used to define an - ifunc. The selection is performed by a resolver function, which returns a - pointer to the selected function. ifunc resolvers are invoked very early - during the machine-dependent initialization routine, or at load time for - dynamically loaded modules. Resolution must occur before the first call to - an ifunc. ifunc resolution is performed after CPU features are enumerated - and after the kernel's environment is initialized. The typical use-case for - an ifunc is a routine whose behavior depends on optional CPU features. For - example, newer generations of a given CPU architecture may provide an - instruction to optimize a common operation. To avoid the overhead of testing - for the CPU feature each time the operation is performed, an ifunc can be - used to provide two implementations for the operation: one targeting - platforms with the extra instruction, and one for older platforms.</p> -<p class="Pp">Because <code class="Nm">DEFINE_IFUNC</code> is a macro that - defines a dynamically typed function, its usage looks somewhat unusual. The - <var class="Ar">qual</var> parameter is a list of zero or more C function - qualifiers to be applied to the ifunc. This parameter is typically empty or - the <code class="Dv">static</code> qualifier. <var class="Ar">ret_type</var> - is the return type of the ifunc. <var class="Ar">name</var> is the name of - the ifunc. <var class="Ar">args</var> is a parenthesized, comma-separated - list of the parameter types of the function, as they would appear in a C - function declaration.</p> -<p class="Pp">The <code class="Nm">DEFINE_IFUNC</code> usage must be followed by - the resolver function body. The resolver must return a function with return - type <var class="Ar">ret_type</var> and parameter types - <var class="Ar">args</var>. The resolver function is defined with the - ‘<code class="Li">resolver</code>’ gcc-style function - attribute, causing the corresponding <a class="Xr">elf(5)</a> function - symbol to be of type <code class="Dv">STT_GNU_IFUNC</code> instead of - <code class="Dv">STT_FUNC</code>. The kernel linker invokes the resolver to - process relocations targeting ifunc calls and PLT entries referencing such - symbols.</p> -</section> -<section class="Sh"> -<h1 class="Sh" id="EXAMPLES"><a class="permalink" href="#EXAMPLES">EXAMPLES</a></h1> -<p class="Pp">ifunc resolvers are executed early during boot, before most kernel - facilities are available. They are effectively limited to checking CPU - feature flags and tunables.</p> -<div class="Bd Pp Li"> -<pre>static size_t -fast_strlen(const char *s __unused) -{ - size_t len; - - /* Fast, but may not be correct in all cases. */ - __asm("movq $42,%0\n" : "=r" (len)); - return (len); -} - -static size_t -slow_strlen(const char *s) -{ - const char *t; - - for (t = s; *t != '\0'; t++); - return (t - s); -} - -DEFINE_IFUNC(, size_t, strlen, (const char *)) -{ - int enabled; - - enabled = 1; - TUNABLE_INT_FETCH("debug.use_fast_strlen", &enabled); - if (enabled && (cpu_features & CPUID_FAST_STRLEN) != 0) - return (fast_strlen); - else - return (slow_strlen); -}</pre> -</div> -<p class="Pp">This defines a <code class="Fn">strlen</code>() function with an - optimized implementation for CPUs that advertise support.</p> -</section> -<section class="Sh"> -<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE - ALSO</a></h1> -<p class="Pp"><a class="Xr">elf(5)</a></p> -</section> -<section class="Sh"> -<h1 class="Sh" id="NOTES"><a class="permalink" href="#NOTES">NOTES</a></h1> -<p class="Pp">ifuncs require both toolchain support, to emit function symbols of - type <code class="Dv">STT_GNU_IFUNC</code>, and kernel linker support, to - invoke ifunc resolvers during boot or during module load.</p> -</section> -</div> -<table class="foot"> - <tr> - <td class="foot-date">March 10, 2026</td> - <td class="foot-os">FreeBSD 15.0</td> - </tr> -</table> |