| |
| |
| @@ -28,7 +28,70 @@ |
| #include <asm/intel-family.h> |
| #include <linux/prctl.h> |
| #include <linux/sched/smt.h> |
| + |
| +static int __init no_387(char *s) |
| +{ |
| + boot_cpu_data.hard_math = 0; |
| + write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0()); |
| + return 1; |
| +} |
| + |
| +__setup("no387", no_387); |
| + |
| +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. |
| + */ |
| +static void __init check_fpu(void) |
| +{ |
| + s32 fdiv_bug; |
| + |
| + if (!boot_cpu_data.hard_math) { |
| +#ifndef CONFIG_MATH_EMULATION |
| + pr_emerg("No coprocessor found and no math emulation present\n"); |
| + pr_emerg("Giving up\n"); |
| + for (;;) ; |
| +#endif |
| + 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"); |
| + } |
| +} |
| |
| static void __init spectre_v2_select_mitigation(void); |
| static void __init ssb_parse_cmdline(void); |
| @@ -926,8 +989,10 @@ static ssize_t cpu_show_common(struct de |
| |
| switch (bug) { |
| case X86_BUG_CPU_MELTDOWN: |
| +#ifdef CONFIG_KAISER |
| if (kaiser_enabled) |
| return sprintf(buf, "Mitigation: PTI\n"); |
| +#endif |
| |
| break; |
| |