/*
* xsave/xrstor support.
*
* Author: Suresh Siddha <suresh.b.siddha@intel.com>
*/
#include <linux/bootmem.h>
#include <linux/compat.h>
#include <asm/i387.h>
#ifdef CONFIG_IA32_EMULATION
#include <asm/sigcontext32.h>
#endif
#include <asm/xcr.h>
/*
* Supported feature mask by the CPU and the kernel.
*/
u64 pcntxt_mask;
/*
* Represents init state for the supported extended state.
*/
static struct xsave_struct *init_xstate_buf;
struct _fpx_sw_bytes fx_sw_reserved;
#ifdef CONFIG_IA32_EMULATION
struct _fpx_sw_bytes fx_sw_reserved_ia32;
#endif
static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;
/*
* If a processor implementation discern that a processor state component is
* in its initialized state it may modify the corresponding bit in the
* xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory
* layout in the case of xsaveopt. While presenting the xstate information to
* the user, we always ensure that the memory layout of a feature will be in
* the init state if the corresponding header bit is zero. This is to ensure
* that the user doesn't see some stale state in the memory layout during
* signal handling, debugging etc.
*/
void __sanitize_i387_state(struct task_struct *tsk)
{
u64 xstate_bv;
int feature_bit = 0x2;
struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
if (!fx)
return;
BUG_ON(task_thread_info(tsk)->status & TS_USEDFPU);
xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv;
/*
* None of the feature bits are in init state. So nothing else
* to do for us, as the memory layout is up to date.
*/
if ((xstate_bv & pcntxt_mask) == pcntxt_mask)
return;
/*
* FP is in init state
*/
if (!(xstate_bv & XSTATE_FP)) {
fx->cwd = 0x37f;
fx->swd = 0;
fx->twd = 0;
fx->fop = 0;
fx->rip = 0;
fx->rdp = 0;
memset(&fx->st_space[0], 0, 128);
}
/*
* SSE is in init state
*/
if (!(xstate_bv & XSTATE_SSE))
memset(&fx->xmm_space[0], 0, 256);
xstate_bv = (pcntxt_mask & ~xstate_bv) >> 2;
/*
* Update all the other memory layouts for which the corresponding
* header bit is in the init state.
*/
while (xstate_bv) {
if (xstate_bv & 0x1) {
int offset = xstate_offsets[feature_bit];
int size = xstate_sizes[feature_bit];
memcpy(((void *) fx) + offset,
((void *) init_xstate_buf) + offset,
size);
}
xstate_bv >>= 1;
feature_bit++;
}
}
/*
* Check for the presence of extended state information in the
* user fpstate pointer in the sigcontext.
*/
int check_for_xstate(struct i387_fxsave_struct __user *buf,
void __user *fpstate,
struct _fpx_sw_bytes *fx_sw_user)
{
int min_xstate_size = sizeof(struct i387_fxsave_struct) +
sizeof(struct xsave_hdr_struct);
unsigned int magic2;
int err;
err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0],
sizeof(struct _fpx_sw_bytes));
if (err)
return -EFAULT;
/*
* First Magic check failed.
*/
if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
return -EINVAL;
/*
* Check for error scenarios.
*/
if (fx_sw_user->xstate_size < min_xstate_size ||
fx_sw_user->xstate_size > xstate_size ||
fx_sw_user->xstate_size > fx_sw_user->extended_size)
return -EINVAL;
err = __get_user(magic2, (__u32 *) (((void *)fpstate) +
fx_sw_user->extended_size -
FP_XSTATE_MAGIC2_SIZE));
if (err)
return err;
/*
* Check for the presence of second magic word at the end of memory
* layout. This detects the case where the user just copied the legacy
* fpstate layout with out copying the extended state information
* in the memory layout.
*/
if (magic2 != FP_XSTATE_MAGIC2)
return -EFAULT;
return 0;
}
#ifdef CONFIG_X86_64
/*
* Signal frame handlers.
*/
int save_i387_xstate(void __user *buf)
{
struct task_struct *tsk = current;
int err = 0;
if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
return -EACCES;
BUG_ON(sig_xstate_size < xstate_size);
if ((unsigned long)buf % 64)
printk("save_i387_xstate: bad fpstate %p\n", buf);
if (!used_math())
return 0;
if (task_thread_info(tsk)->status & TS_USEDFPU) {
if (use_xsave())
err = xsave_user(buf);
else
err = fxsave_user(buf);
if (err)
return err;
task_thread_info(tsk)->status &= ~TS_USEDFPU;
stts();
} else {
sanitize_i387_state(tsk);
if (__copy_to_user(buf, &tsk->thread.fpu.state->fxsave,
xstate_size))
return -1;
}
clear_used_math(); /* trigger finit */
if (use_xsave()) {
struct _fpstate __user *fx = buf;
struct _xstate __user *x = buf;
u64 xstate_bv;
err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
sizeof(struct _fpx_sw_bytes));
err |= __put_user(FP_XSTATE_MAGIC2,
(__u32 __user *) (buf + sig_xstate_size
- FP_XSTATE_MAGIC2_SIZE));
/*
* Read the xstate_bv which we copied (directly from the cpu or
* from the state in task struct) to the user buffers and
* set the FP/SSE bits.
*/
err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);
/*
* For legacy compatible, we always set FP/SSE bits in the bit
* vector while saving the state to the user context. This will
* enable us capturing any changes(during sigreturn) to
* the FP/SSE bits by the legacy applications which don't touch
* xstate_bv in the xsave header.
*
* xsave aware apps can change the xstate_bv in the xsave
* header as well as change any contents in the memory layout.
* xrestore as part of sigreturn will capture all the changes.
*/
xstate_bv |= XSTATE_FPSSE;
err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);
if (err)
return err;
}
return 1;
}
/*
* Restore the extended state if present. Otherwise, restore the FP/SSE
* state.
*/
static int restore_user_xstate(void __user *buf)
{
struct _fpx_sw_bytes fx_sw_user;
u64 mask;
int err;
if (((unsigned long)buf % 64) ||
check_for_xstate(buf, buf, &fx_sw_user))
goto fx_only;
mask = fx_sw_user.xstate_bv;
/*
* restore the state passed by the user.
*/
err = xrestore_user(buf, mask);
if (err)
return err;
/*
* init the state skipped by the user.
*/
mask = pcntxt_mask & ~mask;
if (unlikely(mask))
xrstor_state(init_xstate_buf, mask);
return 0;
fx_only:
/*
* couldn't find the extended state information in the
* memory layout. Restore just the FP/SSE and init all
* the other extended state.
*/
xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
}
/*
* This restores directly out of user space. Exceptions are handled.
*/
int restore_i387_xstate(void __user *buf)
{
struct task_struct *tsk = current;
int err = 0;
if (!buf) {
if (used_math())
goto clear;
return 0;
} else
if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
return -EACCES;
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;
}
if (use_xsave())
err = restore_user_xstate(buf);
else
err = fxrstor_checking((__force struct i387_fxsave_struct *)
buf);
if (unlikely(err)) {
/*
* Encountered an error while doing the restore from the
* user buffer, clear the fpu state.
*/
clear:
clear_fpu(tsk);
clear_used_math();
}
return err;
}
#endif
/*
* Prepare the SW reserved portion of the fxsave memory layout, indicating
* the presence of the extended state information in the memory layout
* pointed by the fpstate pointer in the sigcontext.
* This will be saved when ever the FP and extended state context is
* saved on the user stack during the signal handler delivery to the user.
*/
static void prepare_fx_sw_frame(void)
{
int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
FP_XSTATE_MAGIC2_SIZE;
sig_xstate_size = sizeof(struct _fpstate) + size_extended;
#ifdef CONFIG_IA32_EMULATION
sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
#endif
memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));
fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
fx_sw_reserved.extended_size = sig_xstate_size;
fx_sw_reserved.xstate_bv = pcntxt_mask;
fx_sw_reserved.xstate_size = xstate_size;
#ifdef CONFIG_IA32_EMULATION
memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
sizeof(struct _fpx_sw_bytes));
fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
#endif
}
#ifdef CONFIG_X86_64
unsigned int sig_xstate_size = sizeof(struct _fpstate);
#endif
/*
* Enable the extended processor state save/restore feature
*/
static inline void xstate_enable(void)
{
set_in_cr4(X86_CR4_OSXSAVE);
xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
}
/*
* Record the offsets and sizes of different state managed by the xsave
* memory layout.
*/
static void __init setup_xstate_features(void)
{
int eax, ebx, ecx, edx, leaf = 0x2;
xstate_features = fls64(pcntxt_mask);
xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));
do {
cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);
if (eax == 0)
break;
xstate_offsets[leaf] = ebx;
xstate_sizes[leaf] = eax;
leaf++;
} while (1);
}
/*
* setup the xstate image representing the init state
*/
static void __init setup_xstate_init(void)
{
setup_xstate_features();
/*
* Setup init_xstate_buf to represent the init state of
* all the features managed by the xsave
*/
init_xstate_buf = alloc_bootmem_align(xstate_size,
__alignof__(struct xsave_struct));
init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
clts();
/*
* Init all the features state with header_bv being 0x0
*/
xrstor_state(init_xstate_buf, -1);
/*
* Dump the init state again. This is to identify the init state
* of any feature which is not represented by all zero's.
*/
xsave_state(init_xstate_buf, -1);
stts();
}
/*
* Enable and initialize the xsave feature.
*/
static void __init xstate_enable_boot_cpu(void)
{
unsigned int eax, ebx, ecx, edx;
if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
WARN(1, KERN_ERR "XSTATE_CPUID missing\n");
return;
}
cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
pcntxt_mask = eax + ((u64)edx << 32);
if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
pcntxt_mask);
BUG();
}
/*
* Support only the state known to OS.
*/
pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
xstate_enable();
/*
* Recompute the context size for enabled features
*/
cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
xstate_size = ebx;
update_regset_xstate_info(xstate_size, pcntxt_mask);
prepare_fx_sw_frame();
setup_xstate_init();
printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
"cntxt size 0x%x\n",
pcntxt_mask, xstate_size);
}
/*
* For the very first instance, this calls xstate_enable_boot_cpu();
* for all subsequent instances, this calls xstate_enable().
*
* This is somewhat obfuscated due to the lack of powerful enough
* overrides for the section checks.
*/
void __cpuinit xsave_init(void)
{
static __refdata void (*next_func)(void) = xstate_enable_boot_cpu;
void (*this_func)(void);
if (!cpu_has_xsave)
return;
this_func = next_func;
next_func = xstate_enable;
this_func();
}
