Merge branch 'for-linus-4.5' of git://git.kernel.org/pub/scm/linux/kernel/git/mason...

[mirror_ubuntu-artful-kernel.git] / arch / x86 / include / asm / fpu / internal.h

/*
 * Copyright (C) 1994 Linus Torvalds
 *
 * Pentium III FXSR, SSE support
 * General FPU state handling cleanups
 *      Gareth Hughes <gareth@valinux.com>, May 2000
 * x86-64 work by Andi Kleen 2002
 */

#ifndef _ASM_X86_FPU_INTERNAL_H
#define _ASM_X86_FPU_INTERNAL_H

#include <linux/compat.h>
#include <linux/sched.h>
#include <linux/slab.h>

#include <asm/user.h>
#include <asm/fpu/api.h>
#include <asm/fpu/xstate.h>

/*
 * High level FPU state handling functions:
 */
extern void fpu__activate_curr(struct fpu *fpu);
extern void fpu__activate_fpstate_read(struct fpu *fpu);
extern void fpu__activate_fpstate_write(struct fpu *fpu);
extern void fpu__save(struct fpu *fpu);
extern void fpu__restore(struct fpu *fpu);
extern int  fpu__restore_sig(void __user *buf, int ia32_frame);
extern void fpu__drop(struct fpu *fpu);
extern int  fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu);
extern void fpu__clear(struct fpu *fpu);
extern int  fpu__exception_code(struct fpu *fpu, int trap_nr);
extern int  dump_fpu(struct pt_regs *ptregs, struct user_i387_struct *fpstate);

/*
 * Boot time FPU initialization functions:
 */
extern void fpu__init_cpu(void);
extern void fpu__init_system_xstate(void);
extern void fpu__init_cpu_xstate(void);
extern void fpu__init_system(struct cpuinfo_x86 *c);
extern void fpu__init_check_bugs(void);
extern void fpu__resume_cpu(void);
extern u64 fpu__get_supported_xfeatures_mask(void);

/*
 * Debugging facility:
 */
#ifdef CONFIG_X86_DEBUG_FPU
# define WARN_ON_FPU(x) WARN_ON_ONCE(x)
#else
# define WARN_ON_FPU(x) ({ (void)(x); 0; })
#endif

/*
 * FPU related CPU feature flag helper routines:
 */
static __always_inline __pure bool use_eager_fpu(void)
{
        return static_cpu_has_safe(X86_FEATURE_EAGER_FPU);
}

static __always_inline __pure bool use_xsaveopt(void)
{
        return static_cpu_has_safe(X86_FEATURE_XSAVEOPT);
}

static __always_inline __pure bool use_xsave(void)
{
        return static_cpu_has_safe(X86_FEATURE_XSAVE);
}

static __always_inline __pure bool use_fxsr(void)
{
        return static_cpu_has_safe(X86_FEATURE_FXSR);
}

/*
 * fpstate handling functions:
 */

extern union fpregs_state init_fpstate;

extern void fpstate_init(union fpregs_state *state);
#ifdef CONFIG_MATH_EMULATION
extern void fpstate_init_soft(struct swregs_state *soft);
#else
static inline void fpstate_init_soft(struct swregs_state *soft) {}
#endif
static inline void fpstate_init_fxstate(struct fxregs_state *fx)
{
        fx->cwd = 0x37f;
        fx->mxcsr = MXCSR_DEFAULT;
}
extern void fpstate_sanitize_xstate(struct fpu *fpu);

#define user_insn(insn, output, input...)                               \
({                                                                      \
        int err;                                                        \
        asm volatile(ASM_STAC "\n"                                      \
                     "1:" #insn "\n\t"                                  \
                     "2: " ASM_CLAC "\n"                                \
                     ".section .fixup,\"ax\"\n"                         \
                     "3:  movl $-1,%[err]\n"                            \
                     "    jmp  2b\n"                                    \
                     ".previous\n"                                      \
                     _ASM_EXTABLE(1b, 3b)                               \
                     : [err] "=r" (err), output                         \
                     : "0"(0), input);                                  \
        err;                                                            \
})

#define check_insn(insn, output, input...)                              \
({                                                                      \
        int err;                                                        \
        asm volatile("1:" #insn "\n\t"                                  \
                     "2:\n"                                             \
                     ".section .fixup,\"ax\"\n"                         \
                     "3:  movl $-1,%[err]\n"                            \
                     "    jmp  2b\n"                                    \
                     ".previous\n"                                      \
                     _ASM_EXTABLE(1b, 3b)                               \
                     : [err] "=r" (err), output                         \
                     : "0"(0), input);                                  \
        err;                                                            \
})

static inline int copy_fregs_to_user(struct fregs_state __user *fx)
{
        return user_insn(fnsave %[fx]; fwait,  [fx] "=m" (*fx), "m" (*fx));
}

static inline int copy_fxregs_to_user(struct fxregs_state __user *fx)
{
        if (config_enabled(CONFIG_X86_32))
                return user_insn(fxsave %[fx], [fx] "=m" (*fx), "m" (*fx));
        else if (config_enabled(CONFIG_AS_FXSAVEQ))
                return user_insn(fxsaveq %[fx], [fx] "=m" (*fx), "m" (*fx));

        /* See comment in copy_fxregs_to_kernel() below. */
        return user_insn(rex64/fxsave (%[fx]), "=m" (*fx), [fx] "R" (fx));
}

static inline void copy_kernel_to_fxregs(struct fxregs_state *fx)
{
        int err;

        if (config_enabled(CONFIG_X86_32)) {
                err = check_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
        } else {
                if (config_enabled(CONFIG_AS_FXSAVEQ)) {
                        err = check_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
                } else {
                        /* See comment in copy_fxregs_to_kernel() below. */
                        err = check_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx), "m" (*fx));
                }
        }
        /* Copying from a kernel buffer to FPU registers should never fail: */
        WARN_ON_FPU(err);
}

static inline int copy_user_to_fxregs(struct fxregs_state __user *fx)
{
        if (config_enabled(CONFIG_X86_32))
                return user_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
        else if (config_enabled(CONFIG_AS_FXSAVEQ))
                return user_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));

        /* See comment in copy_fxregs_to_kernel() below. */
        return user_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
                          "m" (*fx));
}

static inline void copy_kernel_to_fregs(struct fregs_state *fx)
{
        int err = check_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));

        WARN_ON_FPU(err);
}

static inline int copy_user_to_fregs(struct fregs_state __user *fx)
{
        return user_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
}

static inline void copy_fxregs_to_kernel(struct fpu *fpu)
{
        if (config_enabled(CONFIG_X86_32))
                asm volatile( "fxsave %[fx]" : [fx] "=m" (fpu->state.fxsave));
        else if (config_enabled(CONFIG_AS_FXSAVEQ))
                asm volatile("fxsaveq %[fx]" : [fx] "=m" (fpu->state.fxsave));
        else {
                /* Using "rex64; fxsave %0" is broken because, if the memory
                 * operand uses any extended registers for addressing, a second
                 * REX prefix will be generated (to the assembler, rex64
                 * followed by semicolon is a separate instruction), and hence
                 * the 64-bitness is lost.
                 *
                 * Using "fxsaveq %0" would be the ideal choice, but is only
                 * supported starting with gas 2.16.
                 *
                 * Using, as a workaround, the properly prefixed form below
                 * isn't accepted by any binutils version so far released,
                 * complaining that the same type of prefix is used twice if
                 * an extended register is needed for addressing (fix submitted
                 * to mainline 2005-11-21).
                 *
                 *  asm volatile("rex64/fxsave %0" : "=m" (fpu->state.fxsave));
                 *
                 * This, however, we can work around by forcing the compiler to
                 * select an addressing mode that doesn't require extended
                 * registers.
                 */
                asm volatile( "rex64/fxsave (%[fx])"
                             : "=m" (fpu->state.fxsave)
                             : [fx] "R" (&fpu->state.fxsave));
        }
}

/* These macros all use (%edi)/(%rdi) as the single memory argument. */
#define XSAVE           ".byte " REX_PREFIX "0x0f,0xae,0x27"
#define XSAVEOPT        ".byte " REX_PREFIX "0x0f,0xae,0x37"
#define XSAVES          ".byte " REX_PREFIX "0x0f,0xc7,0x2f"
#define XRSTOR          ".byte " REX_PREFIX "0x0f,0xae,0x2f"
#define XRSTORS         ".byte " REX_PREFIX "0x0f,0xc7,0x1f"

#define XSTATE_OP(op, st, lmask, hmask, err)                            \
        asm volatile("1:" op "\n\t"                                     \
                     "xor %[err], %[err]\n"                             \
                     "2:\n\t"                                           \
                     ".pushsection .fixup,\"ax\"\n\t"                   \
                     "3: movl $-2,%[err]\n\t"                           \
                     "jmp 2b\n\t"                                       \
                     ".popsection\n\t"                                  \
                     _ASM_EXTABLE(1b, 3b)                               \
                     : [err] "=r" (err)                                 \
                     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)    \
                     : "memory")

/*
 * If XSAVES is enabled, it replaces XSAVEOPT because it supports a compact
 * format and supervisor states in addition to modified optimization in
 * XSAVEOPT.
 *
 * Otherwise, if XSAVEOPT is enabled, XSAVEOPT replaces XSAVE because XSAVEOPT
 * supports modified optimization which is not supported by XSAVE.
 *
 * We use XSAVE as a fallback.
 *
 * The 661 label is defined in the ALTERNATIVE* macros as the address of the
 * original instruction which gets replaced. We need to use it here as the
 * address of the instruction where we might get an exception at.
 */
#define XSTATE_XSAVE(st, lmask, hmask, err)                             \
        asm volatile(ALTERNATIVE_2(XSAVE,                               \
                                   XSAVEOPT, X86_FEATURE_XSAVEOPT,      \
                                   XSAVES,   X86_FEATURE_XSAVES)        \
                     "\n"                                               \
                     "xor %[err], %[err]\n"                             \
                     "3:\n"                                             \
                     ".pushsection .fixup,\"ax\"\n"                     \
                     "4: movl $-2, %[err]\n"                            \
                     "jmp 3b\n"                                         \
                     ".popsection\n"                                    \
                     _ASM_EXTABLE(661b, 4b)                             \
                     : [err] "=r" (err)                                 \
                     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)    \
                     : "memory")

/*
 * Use XRSTORS to restore context if it is enabled. XRSTORS supports compact
 * XSAVE area format.
 */
#define XSTATE_XRESTORE(st, lmask, hmask, err)                          \
        asm volatile(ALTERNATIVE(XRSTOR,                                \
                                 XRSTORS, X86_FEATURE_XSAVES)           \
                     "\n"                                               \
                     "xor %[err], %[err]\n"                             \
                     "3:\n"                                             \
                     ".pushsection .fixup,\"ax\"\n"                     \
                     "4: movl $-2, %[err]\n"                            \
                     "jmp 3b\n"                                         \
                     ".popsection\n"                                    \
                     _ASM_EXTABLE(661b, 4b)                             \
                     : [err] "=r" (err)                                 \
                     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)    \
                     : "memory")

/*
 * This function is called only during boot time when x86 caps are not set
 * up and alternative can not be used yet.
 */
static inline void copy_xregs_to_kernel_booting(struct xregs_state *xstate)
{
        u64 mask = -1;
        u32 lmask = mask;
        u32 hmask = mask >> 32;
        int err;

        WARN_ON(system_state != SYSTEM_BOOTING);

        if (static_cpu_has_safe(X86_FEATURE_XSAVES))
                XSTATE_OP(XSAVES, xstate, lmask, hmask, err);
        else
                XSTATE_OP(XSAVE, xstate, lmask, hmask, err);

        /* We should never fault when copying to a kernel buffer: */
        WARN_ON_FPU(err);
}

/*
 * This function is called only during boot time when x86 caps are not set
 * up and alternative can not be used yet.
 */
static inline void copy_kernel_to_xregs_booting(struct xregs_state *xstate)
{
        u64 mask = -1;
        u32 lmask = mask;
        u32 hmask = mask >> 32;
        int err;

        WARN_ON(system_state != SYSTEM_BOOTING);

        if (static_cpu_has_safe(X86_FEATURE_XSAVES))
                XSTATE_OP(XRSTORS, xstate, lmask, hmask, err);
        else
                XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);

        /* We should never fault when copying from a kernel buffer: */
        WARN_ON_FPU(err);
}

/*
 * Save processor xstate to xsave area.
 */
static inline void copy_xregs_to_kernel(struct xregs_state *xstate)
{
        u64 mask = -1;
        u32 lmask = mask;
        u32 hmask = mask >> 32;
        int err;

        WARN_ON(!alternatives_patched);

        XSTATE_XSAVE(xstate, lmask, hmask, err);

        /* We should never fault when copying to a kernel buffer: */
        WARN_ON_FPU(err);
}

/*
 * Restore processor xstate from xsave area.
 */
static inline void copy_kernel_to_xregs(struct xregs_state *xstate, u64 mask)
{
        u32 lmask = mask;
        u32 hmask = mask >> 32;
        int err;

        XSTATE_XRESTORE(xstate, lmask, hmask, err);

        /* We should never fault when copying from a kernel buffer: */
        WARN_ON_FPU(err);
}

/*
 * Save xstate to user space xsave area.
 *
 * We don't use modified optimization because xrstor/xrstors might track
 * a different application.
 *
 * We don't use compacted format xsave area for
 * backward compatibility for old applications which don't understand
 * compacted format of xsave area.
 */
static inline int copy_xregs_to_user(struct xregs_state __user *buf)
{
        int err;

        /*
         * Clear the xsave header first, so that reserved fields are
         * initialized to zero.
         */
        err = __clear_user(&buf->header, sizeof(buf->header));
        if (unlikely(err))
                return -EFAULT;

        stac();
        XSTATE_OP(XSAVE, buf, -1, -1, err);
        clac();

        return err;
}

/*
 * Restore xstate from user space xsave area.
 */
static inline int copy_user_to_xregs(struct xregs_state __user *buf, u64 mask)
{
        struct xregs_state *xstate = ((__force struct xregs_state *)buf);
        u32 lmask = mask;
        u32 hmask = mask >> 32;
        int err;

        stac();
        XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);
        clac();

        return err;
}

/*
 * These must be called with preempt disabled. Returns
 * 'true' if the FPU state is still intact and we can
 * keep registers active.
 *
 * The legacy FNSAVE instruction cleared all FPU state
 * unconditionally, so registers are essentially destroyed.
 * Modern FPU state can be kept in registers, if there are
 * no pending FP exceptions.
 */
static inline int copy_fpregs_to_fpstate(struct fpu *fpu)
{
        if (likely(use_xsave())) {
                copy_xregs_to_kernel(&fpu->state.xsave);
                return 1;
        }

        if (likely(use_fxsr())) {
                copy_fxregs_to_kernel(fpu);
                return 1;
        }

        /*
         * Legacy FPU register saving, FNSAVE always clears FPU registers,
         * so we have to mark them inactive:
         */
        asm volatile("fnsave %[fp]; fwait" : [fp] "=m" (fpu->state.fsave));

        return 0;
}

static inline void __copy_kernel_to_fpregs(union fpregs_state *fpstate)
{
        if (use_xsave()) {
                copy_kernel_to_xregs(&fpstate->xsave, -1);
        } else {
                if (use_fxsr())
                        copy_kernel_to_fxregs(&fpstate->fxsave);
                else
                        copy_kernel_to_fregs(&fpstate->fsave);
        }
}

static inline void copy_kernel_to_fpregs(union fpregs_state *fpstate)
{
        /*
         * AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception is
         * pending. Clear the x87 state here by setting it to fixed values.
         * "m" is a random variable that should be in L1.
         */
        if (unlikely(static_cpu_has_bug_safe(X86_BUG_FXSAVE_LEAK))) {
                asm volatile(
                        "fnclex\n\t"
                        "emms\n\t"
                        "fildl %P[addr]"        /* set F?P to defined value */
                        : : [addr] "m" (fpstate));
        }

        __copy_kernel_to_fpregs(fpstate);
}

extern int copy_fpstate_to_sigframe(void __user *buf, void __user *fp, int size);

/*
 * FPU context switch related helper methods:
 */

DECLARE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);

/*
 * Must be run with preemption disabled: this clears the fpu_fpregs_owner_ctx,
 * on this CPU.
 *
 * This will disable any lazy FPU state restore of the current FPU state,
 * but if the current thread owns the FPU, it will still be saved by.
 */
static inline void __cpu_disable_lazy_restore(unsigned int cpu)
{
        per_cpu(fpu_fpregs_owner_ctx, cpu) = NULL;
}

static inline int fpu_want_lazy_restore(struct fpu *fpu, unsigned int cpu)
{
        return fpu == this_cpu_read_stable(fpu_fpregs_owner_ctx) && cpu == fpu->last_cpu;
}


/*
 * Wrap lazy FPU TS handling in a 'hw fpregs activation/deactivation'
 * idiom, which is then paired with the sw-flag (fpregs_active) later on:
 */

static inline void __fpregs_activate_hw(void)
{
        if (!use_eager_fpu())
                clts();
}

static inline void __fpregs_deactivate_hw(void)
{
        if (!use_eager_fpu())
                stts();
}

/* Must be paired with an 'stts' (fpregs_deactivate_hw()) after! */
static inline void __fpregs_deactivate(struct fpu *fpu)
{
        WARN_ON_FPU(!fpu->fpregs_active);

        fpu->fpregs_active = 0;
        this_cpu_write(fpu_fpregs_owner_ctx, NULL);
}

/* Must be paired with a 'clts' (fpregs_activate_hw()) before! */
static inline void __fpregs_activate(struct fpu *fpu)
{
        WARN_ON_FPU(fpu->fpregs_active);

        fpu->fpregs_active = 1;
        this_cpu_write(fpu_fpregs_owner_ctx, fpu);
}

/*
 * The question "does this thread have fpu access?"
 * is slightly racy, since preemption could come in
 * and revoke it immediately after the test.
 *
 * However, even in that very unlikely scenario,
 * we can just assume we have FPU access - typically
 * to save the FP state - we'll just take a #NM
 * fault and get the FPU access back.
 */
static inline int fpregs_active(void)
{
        return current->thread.fpu.fpregs_active;
}

/*
 * Encapsulate the CR0.TS handling together with the
 * software flag.
 *
 * These generally need preemption protection to work,
 * do try to avoid using these on their own.
 */
static inline void fpregs_activate(struct fpu *fpu)
{
        __fpregs_activate_hw();
        __fpregs_activate(fpu);
}

static inline void fpregs_deactivate(struct fpu *fpu)
{
        __fpregs_deactivate(fpu);
        __fpregs_deactivate_hw();
}

/*
 * FPU state switching for scheduling.
 *
 * This is a two-stage process:
 *
 *  - switch_fpu_prepare() saves the old state and
 *    sets the new state of the CR0.TS bit. This is
 *    done within the context of the old process.
 *
 *  - switch_fpu_finish() restores the new state as
 *    necessary.
 */
typedef struct { int preload; } fpu_switch_t;

static inline fpu_switch_t
switch_fpu_prepare(struct fpu *old_fpu, struct fpu *new_fpu, int cpu)
{
        fpu_switch_t fpu;

        /*
         * If the task has used the math, pre-load the FPU on xsave processors
         * or if the past 5 consecutive context-switches used math.
         */
        fpu.preload = new_fpu->fpstate_active &&
                      (use_eager_fpu() || new_fpu->counter > 5);

        if (old_fpu->fpregs_active) {
                if (!copy_fpregs_to_fpstate(old_fpu))
                        old_fpu->last_cpu = -1;
                else
                        old_fpu->last_cpu = cpu;

                /* But leave fpu_fpregs_owner_ctx! */
                old_fpu->fpregs_active = 0;

                /* Don't change CR0.TS if we just switch! */
                if (fpu.preload) {
                        new_fpu->counter++;
                        __fpregs_activate(new_fpu);
                        prefetch(&new_fpu->state);
                } else {
                        __fpregs_deactivate_hw();
                }
        } else {
                old_fpu->counter = 0;
                old_fpu->last_cpu = -1;
                if (fpu.preload) {
                        new_fpu->counter++;
                        if (fpu_want_lazy_restore(new_fpu, cpu))
                                fpu.preload = 0;
                        else
                                prefetch(&new_fpu->state);
                        fpregs_activate(new_fpu);
                }
        }
        return fpu;
}

/*
 * Misc helper functions:
 */

/*
 * By the time this gets called, we've already cleared CR0.TS and
 * given the process the FPU if we are going to preload the FPU
 * state - all we need to do is to conditionally restore the register
 * state itself.
 */
static inline void switch_fpu_finish(struct fpu *new_fpu, fpu_switch_t fpu_switch)
{
        if (fpu_switch.preload)
                copy_kernel_to_fpregs(&new_fpu->state);
}

/*
 * Needs to be preemption-safe.
 *
 * NOTE! user_fpu_begin() must be used only immediately before restoring
 * the save state. It does not do any saving/restoring on its own. In
 * lazy FPU mode, it is just an optimization to avoid a #NM exception,
 * the task can lose the FPU right after preempt_enable().
 */
static inline void user_fpu_begin(void)
{
        struct fpu *fpu = &current->thread.fpu;

        preempt_disable();
        if (!fpregs_active())
                fpregs_activate(fpu);
        preempt_enable();
}

/*
 * MXCSR and XCR definitions:
 */

extern unsigned int mxcsr_feature_mask;

#define XCR_XFEATURE_ENABLED_MASK       0x00000000

static inline u64 xgetbv(u32 index)
{
        u32 eax, edx;

        asm volatile(".byte 0x0f,0x01,0xd0" /* xgetbv */
                     : "=a" (eax), "=d" (edx)
                     : "c" (index));
        return eax + ((u64)edx << 32);
}

static inline void xsetbv(u32 index, u64 value)
{
        u32 eax = value;
        u32 edx = value >> 32;

        asm volatile(".byte 0x0f,0x01,0xd1" /* xsetbv */
                     : : "a" (eax), "d" (edx), "c" (index));
}

#endif /* _ASM_X86_FPU_INTERNAL_H */