/*
* High level FPU state handling functions:
*/
-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);
extern void fpu__drop(struct fpu *fpu);
trace_x86_fpu_init_state(fpu);
}
-/*
- * This function must be called before we write a task's fpstate.
- *
- * Invalidate any cached FPU registers.
- *
- * After this function call, after registers in the fpstate are
- * modified and the child task has woken up, the child task will
- * restore the modified FPU state from the modified context. If we
- * didn't clear its cached status here then the cached in-registers
- * state pending on its former CPU could be restored, corrupting
- * the modifications.
- */
-void fpu__prepare_write(struct fpu *fpu)
-{
- /*
- * Only stopped child tasks can be used to modify the FPU
- * state in the fpstate buffer:
- */
- WARN_ON_FPU(fpu == ¤t->thread.fpu);
-
- /* Invalidate any cached state: */
- __fpu_invalidate_fpregs_state(fpu);
-}
-
/*
* Drops current FPU state: deactivates the fpregs and
* the fpstate. NOTE: it still leaves previous contents
fpu__save(fpu);
}
+/*
+ * Invalidate cached FPU registers before modifying the stopped target
+ * task's fpstate.
+ *
+ * This forces the target task on resume to restore the FPU registers from
+ * modified fpstate. Otherwise the task might skip the restore and operate
+ * with the cached FPU registers which discards the modifications.
+ */
+static void fpu_force_restore(struct fpu *fpu)
+{
+ /*
+ * Only stopped child tasks can be used to modify the FPU
+ * state in the fpstate buffer:
+ */
+ WARN_ON_FPU(fpu == ¤t->thread.fpu);
+
+ __fpu_invalidate_fpregs_state(fpu);
+}
+
int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
struct membuf to)
{
if (newstate.mxcsr & ~mxcsr_feature_mask)
return -EINVAL;
- fpu__prepare_write(fpu);
+ fpu_force_restore(fpu);
/* Copy the state */
memcpy(&fpu->state.fxsave, &newstate, sizeof(newstate));
}
}
- fpu__prepare_write(fpu);
+ fpu_force_restore(fpu);
ret = copy_kernel_to_xstate(&fpu->state.xsave, kbuf ?: tmpbuf);
out:
if (ret)
return ret;
- fpu__prepare_write(fpu);
+ fpu_force_restore(fpu);
if (cpu_feature_enabled(X86_FEATURE_FXSR))
convert_to_fxsr(&fpu->state.fxsave, &env);