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422 giacomo 1
/*
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 *  include/asm-i386/bugs.h
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 *
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 *  Copyright (C) 1994  Linus Torvalds
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 *
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 *  Cyrix stuff, June 1998 by:
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 *      - Rafael R. Reilova (moved everything from head.S),
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 *        <rreilova@ececs.uc.edu>
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 *      - Channing Corn (tests & fixes),
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 *      - Andrew D. Balsa (code cleanup).
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 *
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 *  Pentium III FXSR, SSE support
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 *      Gareth Hughes <gareth@valinux.com>, May 2000
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 */
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/*
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 * This is included by init/main.c to check for architecture-dependent bugs.
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 *
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 * Needs:
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 *      void check_bugs(void);
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 */
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#include <linux/config.h>
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#include <linux/init.h>
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#include <asm/processor.h>
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#include <asm/i387.h>
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#include <asm/msr.h>
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static int __init no_halt(char *s)
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{
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        boot_cpu_data.hlt_works_ok = 0;
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        return 1;
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}
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__setup("no-hlt", no_halt);
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static int __init mca_pentium(char *s)
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{
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        mca_pentium_flag = 1;
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        return 1;
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}
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__setup("mca-pentium", mca_pentium);
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static int __init no_387(char *s)
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{
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        boot_cpu_data.hard_math = 0;
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        write_cr0(0xE | read_cr0());
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        return 1;
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}
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__setup("no387", no_387);
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static double __initdata x = 4195835.0;
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static double __initdata y = 3145727.0;
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/*
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 * This used to check for exceptions..
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 * However, it turns out that to support that,
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 * the XMM trap handlers basically had to
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 * be buggy. So let's have a correct XMM trap
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 * handler, and forget about printing out
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 * some status at boot.
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 *
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 * We should really only care about bugs here
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 * anyway. Not features.
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 */
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static void __init check_fpu(void)
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{
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        if (!boot_cpu_data.hard_math) {
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#ifndef CONFIG_MATH_EMULATION
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                printk(KERN_EMERG "No coprocessor found and no math emulation present.\n");
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                printk(KERN_EMERG "Giving up.\n");
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                for (;;) ;
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#endif
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                return;
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        }
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/* Enable FXSR and company _before_ testing for FP problems. */
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        /*
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         * Verify that the FXSAVE/FXRSTOR data will be 16-byte aligned.
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         */
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        if (offsetof(struct task_struct, thread.i387.fxsave) & 15) {
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                extern void __buggy_fxsr_alignment(void);
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                __buggy_fxsr_alignment();
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        }
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        if (cpu_has_fxsr) {
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                printk(KERN_INFO "Enabling fast FPU save and restore... ");
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                set_in_cr4(X86_CR4_OSFXSR);
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                printk("done.\n");
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        }
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        if (cpu_has_xmm) {
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                printk(KERN_INFO "Enabling unmasked SIMD FPU exception support... ");
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                set_in_cr4(X86_CR4_OSXMMEXCPT);
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                printk("done.\n");
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        }
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        /* Test for the divl bug.. */
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        __asm__("fninit\n\t"
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                "fldl %1\n\t"
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                "fdivl %2\n\t"
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                "fmull %2\n\t"
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                "fldl %1\n\t"
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                "fsubp %%st,%%st(1)\n\t"
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                "fistpl %0\n\t"
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                "fwait\n\t"
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                "fninit"
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                : "=m" (*&boot_cpu_data.fdiv_bug)
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                : "m" (*&x), "m" (*&y));
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        if (boot_cpu_data.fdiv_bug)
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                printk("Hmm, FPU with FDIV bug.\n");
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}
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static void __init check_hlt(void)
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{
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        printk(KERN_INFO "Checking 'hlt' instruction... ");
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        if (!boot_cpu_data.hlt_works_ok) {
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                printk("disabled\n");
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                return;
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        }
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        __asm__ __volatile__("hlt ; hlt ; hlt ; hlt");
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        printk("OK.\n");
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}
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/*
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 *      Most 386 processors have a bug where a POPAD can lock the
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 *      machine even from user space.
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 */
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static void __init check_popad(void)
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{
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#ifndef CONFIG_X86_POPAD_OK
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        int res, inp = (int) &res;
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        printk(KERN_INFO "Checking for popad bug... ");
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        __asm__ __volatile__(
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          "movl $12345678,%%eax; movl $0,%%edi; pusha; popa; movl (%%edx,%%edi),%%ecx "
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          : "=&a" (res)
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          : "d" (inp)
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          : "ecx", "edi" );
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        /* If this fails, it means that any user program may lock the CPU hard. Too bad. */
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        if (res != 12345678) printk( "Buggy.\n" );
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                        else printk( "OK.\n" );
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#endif
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}
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/*
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 * Check whether we are able to run this kernel safely on SMP.
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 *
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 * - In order to run on a i386, we need to be compiled for i386
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 *   (for due to lack of "invlpg" and working WP on a i386)
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 * - In order to run on anything without a TSC, we need to be
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 *   compiled for a i486.
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 * - In order to support the local APIC on a buggy Pentium machine,
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 *   we need to be compiled with CONFIG_X86_GOOD_APIC disabled,
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 *   which happens implicitly if compiled for a Pentium or lower
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 *   (unless an advanced selection of CPU features is used) as an
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 *   otherwise config implies a properly working local APIC without
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 *   the need to do extra reads from the APIC.
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*/
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static void __init check_config(void)
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{
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/*
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 * We'd better not be a i386 if we're configured to use some
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 * i486+ only features! (WP works in supervisor mode and the
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 * new "invlpg" and "bswap" instructions)
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 */
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#if defined(CONFIG_X86_WP_WORKS_OK) || defined(CONFIG_X86_INVLPG) || defined(CONFIG_X86_BSWAP)
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        if (boot_cpu_data.x86 == 3)
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                panic("Kernel requires i486+ for 'invlpg' and other features");
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#endif
173
 
174
/*
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 * If we configured ourselves for a TSC, we'd better have one!
176
 */
177
#ifdef CONFIG_X86_TSC
178
        if (!cpu_has_tsc)
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                panic("Kernel compiled for Pentium+, requires TSC feature!");
180
#endif
181
 
182
/*
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 * If we were told we had a good local APIC, check for buggy Pentia,
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 * i.e. all B steppings and the C2 stepping of P54C when using their
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 * integrated APIC (see 11AP erratum in "Pentium Processor
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 * Specification Update").
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 */
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#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_GOOD_APIC)
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        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL
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            && cpu_has_apic
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            && boot_cpu_data.x86 == 5
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            && boot_cpu_data.x86_model == 2
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            && (boot_cpu_data.x86_mask < 6 || boot_cpu_data.x86_mask == 11))
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                panic("Kernel compiled for PMMX+, assumes a local APIC without the read-before-write bug!");
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#endif
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}
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198
extern void alternative_instructions(void);
199
 
200
static void __init check_bugs(void)
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{
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        identify_cpu(&boot_cpu_data);
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#ifndef CONFIG_SMP
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        printk("CPU: ");
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        print_cpu_info(&boot_cpu_data);
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#endif
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        check_config();
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        check_fpu();
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        check_hlt();
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        check_popad();
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        system_utsname.machine[1] = '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
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        alternative_instructions();
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}