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/*
* Copyright (C) 1994 Linus Torvalds
*
* Pentium III FXSR, SSE support
* General FPU state handling cleanups
* Gareth Hughes <gareth@valinux.com>, May 2000
*/
#include <linux/module.h>
#include <linux/regset.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <asm/sigcontext.h>
#include <asm/processor.h>
#include <asm/math_emu.h>
#include <asm/uaccess.h>
#include <asm/ptrace.h>
#include <asm/i387.h>
#include <asm/fpu-internal.h>
#include <asm/user.h>
static DEFINE_PER_CPU(bool, in_kernel_fpu);
void kernel_fpu_disable(void)
{
WARN_ON(this_cpu_read(in_kernel_fpu));
this_cpu_write(in_kernel_fpu, true);
}
void kernel_fpu_enable(void)
{
this_cpu_write(in_kernel_fpu, false);
}
/*
* Were we in an interrupt that interrupted kernel mode?
*
* On others, we can do a kernel_fpu_begin/end() pair *ONLY* if that
* pair does nothing at all: the thread must not have fpu (so
* that we don't try to save the FPU state), and TS must
* be set (so that the clts/stts pair does nothing that is
* visible in the interrupted kernel thread).
*
* Except for the eagerfpu case when we return 1 unless we've already
* been eager and saved the state in kernel_fpu_begin().
*/
static inline bool interrupted_kernel_fpu_idle(void)
{
if (this_cpu_read(in_kernel_fpu))
return false;
if (use_eager_fpu())
return __thread_has_fpu(current);
return !__thread_has_fpu(current) &&
(read_cr0() & X86_CR0_TS);
}
/*
* Were we in user mode (or vm86 mode) when we were
* interrupted?
*
* Doing kernel_fpu_begin/end() is ok if we are running
* in an interrupt context from user mode - we'll just
* save the FPU state as required.
*/
static inline bool interrupted_user_mode(void)
{
struct pt_regs *regs = get_irq_regs();
return regs && user_mode_vm(regs);
}
/*
* Can we use the FPU in kernel mode with the
* whole "kernel_fpu_begin/end()" sequence?
*
* It's always ok in process context (ie "not interrupt")
* but it is sometimes ok even from an irq.
*/
bool irq_fpu_usable(void)
{
return !in_interrupt() ||
interrupted_user_mode() ||
interrupted_kernel_fpu_idle();
}
EXPORT_SYMBOL(irq_fpu_usable);
void __kernel_fpu_begin(void)
{
struct task_struct *me = current;
this_cpu_write(in_kernel_fpu, true);
if (__thread_has_fpu(me)) {
__save_init_fpu(me);
} else if (!use_eager_fpu()) {
this_cpu_write(fpu_owner_task, NULL);
clts();
}
}
EXPORT_SYMBOL(__kernel_fpu_begin);
void __kernel_fpu_end(void)
{
struct task_struct *me = current;
if (__thread_has_fpu(me)) {
if (WARN_ON(restore_fpu_checking(me)))
drop_init_fpu(me);
} else if (!use_eager_fpu()) {
stts();
}
this_cpu_write(in_kernel_fpu, false);
}
EXPORT_SYMBOL(__kernel_fpu_end);
void unlazy_fpu(struct task_struct *tsk)
{
preempt_disable();
if (__thread_has_fpu(tsk)) {
__save_init_fpu(tsk);
__thread_fpu_end(tsk);
} else
tsk->thread.fpu_counter = 0;
preempt_enable();
}
EXPORT_SYMBOL(unlazy_fpu);
unsigned int mxcsr_feature_mask __read_mostly = 0xffffffffu;
unsigned int xstate_size;
EXPORT_SYMBOL_GPL(xstate_size);
static struct i387_fxsave_struct fx_scratch;
static void mxcsr_feature_mask_init(void)
{
unsigned long mask = 0;
if (cpu_has_fxsr) {
memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
asm volatile("fxsave %0" : "+m" (fx_scratch));
mask = fx_scratch.mxcsr_mask;
if (mask == 0)
mask = 0x0000ffbf;
}
mxcsr_feature_mask &= mask;
}
static void init_thread_xstate(void)
{
/*
* Note that xstate_size might be overwriten later during
* xsave_init().
*/
if (!cpu_has_fpu) {
/*
* Disable xsave as we do not support it if i387
* emulation is enabled.
*/
setup_clear_cpu_cap(X86_FEATURE_XSAVE);
setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
xstate_size = sizeof(struct i387_soft_struct);
return;
}
if (cpu_has_fxsr)
xstate_size = sizeof(struct i387_fxsave_struct);
else
xstate_size = sizeof(struct i387_fsave_struct);
}
/*
* Called at bootup to set up the initial FPU state that is later cloned
* into all processes.
*/
void fpu_init(void)
{
unsigned long cr0;
unsigned long cr4_mask = 0;
#ifndef CONFIG_MATH_EMULATION
if (!cpu_has_fpu) {
pr_emerg("No FPU found and no math emulation present\n");
pr_emerg("Giving up\n");
for (;;)
asm volatile("hlt");
}
#endif
if (cpu_has_fxsr)
cr4_mask |= X86_CR4_OSFXSR;
if (cpu_has_xmm)
cr4_mask |= X86_CR4_OSXMMEXCPT;
if (cr4_mask)
set_in_cr4(cr4_mask);
cr0 = read_cr0();
cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */
if (!cpu_has_fpu)
cr0 |= X86_CR0_EM;
write_cr0(cr0);
/*
* init_thread_xstate is only called once to avoid overriding
* xstate_size during boot time or during CPU hotplug.
*/
if (xstate_size == 0)
init_thread_xstate();
mxcsr_feature_mask_init();
xsave_init();
eager_fpu_init();
}
void fpu_finit(struct fpu *fpu)
{
if (!cpu_has_fpu) {
finit_soft_fpu(&fpu->state->soft);
return;
}
if (cpu_has_fxsr) {
fx_finit(&fpu->state->fxsave);
} else {
struct i387_fsave_struct *fp = &fpu->state->fsave;
memset(fp, 0, xstate_size);
fp->cwd = 0xffff037fu;
fp->swd = 0xffff0000u;
fp->twd = 0xffffffffu;
fp->fos = 0xffff0000u;
}
}
EXPORT_SYMBOL_GPL(fpu_finit);
/*
* The _current_ task is using the FPU for the first time
* so initialize it and set the mxcsr to its default
* value at reset if we support XMM instructions and then
* remember the current task has used the FPU.
*/
int init_fpu(struct task_struct *tsk)
{
int ret;
if (tsk_used_math(tsk)) {
if (cpu_has_fpu && tsk == current)
unlazy_fpu(tsk);
tsk->thread.fpu.last_cpu = ~0;
return 0;
}
/*
* Memory allocation at the first usage of the FPU and other state.
*/
ret = fpu_alloc(&tsk->thread.fpu);
if (ret)
return ret;
fpu_finit(&tsk->thread.fpu);
set_stopped_child_used_math(tsk);
return 0;
}
EXPORT_SYMBOL_GPL(init_fpu);
/*
* The xstateregs_active() routine is the same as the fpregs_active() routine,
* as the "regset->n" for the xstate regset will be updated based on the feature
* capabilites supported by the xsave.
*/
int fpregs_active(struct task_struct *target, const struct user_regset *regset)
{
return tsk_used_math(target) ? regset->n : 0;
}
int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
{
return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
}
int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
void
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