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    SubjectRe: Oops with strace_test
    On Wed, 7 May 2008, Suresh Siddha wrote:
    > On Wed, May 07, 2008 at 07:26:20PM +0200, Thomas Gleixner wrote:
    > >
    > > Ok, we decoded the problem in meantime. Suresh will send a patch soon.
    >
    > Appended patch should fix it. Eric, can you please check if it fixes the issue?
    > I have to fix the math-emu aswell. But I will send a different patch for it.

    Suresh,

    looks good. Applied to x86.git. Waiting for Erics confirmation.

    Thanks,
    tglx

    > thanks,
    > suresh
    > ---
    >
    > [patch] fix fpu restore during sig return
    >
    > If the task never used fpu, initialize the fpu before restoring the FP state
    > from the signal handler context. This will allocate the fpu state,
    > if the task never needed it before.
    >
    > Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
    > ---
    >
    > diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
    > index db6839b..45e19ee 100644
    > --- a/arch/x86/kernel/i387.c
    > +++ b/arch/x86/kernel/i387.c
    > @@ -450,7 +450,6 @@ static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
    > {
    > struct task_struct *tsk = current;
    >
    > - clear_fpu(tsk);
    > return __copy_from_user(&tsk->thread.xstate->fsave, buf,
    > sizeof(struct i387_fsave_struct));
    > }
    > @@ -461,7 +460,6 @@ static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
    > struct user_i387_ia32_struct env;
    > int err;
    >
    > - clear_fpu(tsk);
    > err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
    > sizeof(struct i387_fxsave_struct));
    > /* mxcsr reserved bits must be masked to zero for security reasons */
    > @@ -478,6 +476,16 @@ int restore_i387_ia32(struct _fpstate_ia32 __user *buf)
    > int err;
    >
    > if (HAVE_HWFP) {
    > + struct task_struct *tsk = current;
    > +
    > + clear_fpu(tsk);
    > +
    > + if (!used_math()) {
    > + err = init_fpu(tsk);
    > + if (err)
    > + return err;
    > + }
    > +
    > if (cpu_has_fxsr)
    > err = restore_i387_fxsave(buf);
    > else
    > diff --git a/include/asm-x86/i387.h b/include/asm-x86/i387.h
    > index da2adb4..6b722d3 100644
    > --- a/include/asm-x86/i387.h
    > +++ b/include/asm-x86/i387.h
    > @@ -175,7 +175,15 @@ static inline int save_i387(struct _fpstate __user *buf)
    > */
    > static inline int restore_i387(struct _fpstate __user *buf)
    > {
    > - set_used_math();
    > + struct task_struct *tsk = current;
    > + int err;
    > +
    > + if (!used_math()) {
    > + err = init_fpu(tsk);
    > + if (err)
    > + return err;
    > + }
    > +
    > if (!(task_thread_info(current)->status & TS_USEDFPU)) {
    > clts();
    > task_thread_info(current)->status |= TS_USEDFPU;
    >


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