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    Subject[patch V4 19/65] x86/fpu/regset: Move fpu__read_begin() into regset
    The function can only be used from the regset get() callbacks safely. So
    there is no reason to have it globaly exposed.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Borislav Petkov <bp@suse.de>
    ---
    arch/x86/include/asm/fpu/internal.h | 1 -
    arch/x86/kernel/fpu/core.c | 20 --------------------
    arch/x86/kernel/fpu/regset.c | 22 +++++++++++++++++++---
    3 files changed, 19 insertions(+), 24 deletions(-)

    --- a/arch/x86/include/asm/fpu/internal.h
    +++ b/arch/x86/include/asm/fpu/internal.h
    @@ -26,7 +26,6 @@
    /*
    * High level FPU state handling functions:
    */
    -extern void fpu__prepare_read(struct fpu *fpu);
    extern void fpu__prepare_write(struct fpu *fpu);
    extern void fpu__save(struct fpu *fpu);
    extern int fpu__restore_sig(void __user *buf, int ia32_frame);
    --- a/arch/x86/kernel/fpu/core.c
    +++ b/arch/x86/kernel/fpu/core.c
    @@ -282,26 +282,6 @@ static void fpu__initialize(struct fpu *
    }

    /*
    - * This function must be called before we read a task's fpstate.
    - *
    - * There's two cases where this gets called:
    - *
    - * - for the current task (when coredumping), in which case we have
    - * to save the latest FPU registers into the fpstate,
    - *
    - * - or it's called for stopped tasks (ptrace), in which case the
    - * registers were already saved by the context-switch code when
    - * the task scheduled out.
    - *
    - * If the task has used the FPU before then save it.
    - */
    -void fpu__prepare_read(struct fpu *fpu)
    -{
    - if (fpu == &current->thread.fpu)
    - fpu__save(fpu);
    -}
    -
    -/*
    * This function must be called before we write a task's fpstate.
    *
    * Invalidate any cached FPU registers.
    --- a/arch/x86/kernel/fpu/regset.c
    +++ b/arch/x86/kernel/fpu/regset.c
    @@ -28,6 +28,22 @@ int regset_xregset_fpregs_active(struct
    return 0;
    }

    +/*
    + * The regset get() functions are invoked from:
    + *
    + * - coredump to dump the current task's fpstate. If the current task
    + * owns the FPU then the memory state has to be synchronized and the
    + * FPU register state preserved. Otherwise fpstate is already in sync.
    + *
    + * - ptrace to dump fpstate of a stopped task, in which case the registers
    + * have already been saved to fpstate on context switch.
    + */
    +static void sync_fpstate(struct fpu *fpu)
    +{
    + if (fpu == &current->thread.fpu)
    + fpu__save(fpu);
    +}
    +
    int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
    struct membuf to)
    {
    @@ -36,7 +52,7 @@ int xfpregs_get(struct task_struct *targ
    if (!cpu_feature_enabled(X86_FEATURE_FXSR))
    return -ENODEV;

    - fpu__prepare_read(fpu);
    + sync_fpstate(fpu);

    if (!use_xsave()) {
    return membuf_write(&to, &fpu->state.fxsave,
    @@ -96,7 +112,7 @@ int xstateregs_get(struct task_struct *t
    if (!cpu_feature_enabled(X86_FEATURE_XSAVE))
    return -ENODEV;

    - fpu__prepare_read(fpu);
    + sync_fpstate(fpu);

    copy_xstate_to_uabi_buf(to, &fpu->state.xsave, XSTATE_COPY_XSAVE);
    return 0;
    @@ -287,7 +303,7 @@ int fpregs_get(struct task_struct *targe
    struct user_i387_ia32_struct env;
    struct fxregs_state fxsave, *fx;

    - fpu__prepare_read(fpu);
    + sync_fpstate(fpu);

    if (!cpu_feature_enabled(X86_FEATURE_FPU))
    return fpregs_soft_get(target, regset, to);
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