// SPDX-License-Identifier: GPL-2.0
|
/*
|
* x86 FPU bug checks:
|
*/
|
#include <asm/fpu/internal.h>
|
|
/*
|
* Boot time CPU/FPU FDIV bug detection code:
|
*/
|
|
static double __initdata x = 4195835.0;
|
static double __initdata y = 3145727.0;
|
|
/*
|
* This used to check for exceptions..
|
* However, it turns out that to support that,
|
* the XMM trap handlers basically had to
|
* be buggy. So let's have a correct XMM trap
|
* handler, and forget about printing out
|
* some status at boot.
|
*
|
* We should really only care about bugs here
|
* anyway. Not features.
|
*/
|
void __init fpu__init_check_bugs(void)
|
{
|
s32 fdiv_bug;
|
|
/* kernel_fpu_begin/end() relies on patched alternative instructions. */
|
if (!boot_cpu_has(X86_FEATURE_FPU))
|
return;
|
|
kernel_fpu_begin();
|
|
/*
|
* trap_init() enabled FXSR and company _before_ testing for FP
|
* problems here.
|
*
|
* Test for the divl bug: http://en.wikipedia.org/wiki/Fdiv_bug
|
*/
|
__asm__("fninit\n\t"
|
"fldl %1\n\t"
|
"fdivl %2\n\t"
|
"fmull %2\n\t"
|
"fldl %1\n\t"
|
"fsubp %%st,%%st(1)\n\t"
|
"fistpl %0\n\t"
|
"fwait\n\t"
|
"fninit"
|
: "=m" (*&fdiv_bug)
|
: "m" (*&x), "m" (*&y));
|
|
kernel_fpu_end();
|
|
if (fdiv_bug) {
|
set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV);
|
pr_warn("Hmm, FPU with FDIV bug\n");
|
}
|
}
|
