/*
* xsave/xrstor support.
*
* Author: Suresh Siddha <suresh.b.siddha@intel.com>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/bootmem.h>
#include <linux/compat.h>
#include <asm/i387.h>
#include <asm/fpu-internal.h>
#include <asm/sigframe.h>
#include <asm/xcr.h>
/*
* Supported feature mask by the CPU and the kernel.
*/
u64 pcntxt_mask;
/*
* Represents init state for the supported extended state.
*/
struct xsave_struct *init_xstate_buf;
static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
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)
{
struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
int feature_bit = 0x2;
u64 xstate_bv;
if (!fx)
return;
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.
*/
static inline int check_for_xstate(struct i387_fxsave_struct __user *buf,
void __user *fpstate,
struct _fpx_sw_bytes *fx_sw)
{
int min_xstate_size = sizeof(struct i387_fxsave_struct) +
sizeof(struct xsave_hdr_struct);
unsigned int magic2;
if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
return -1;
/* Check for the first magic field and other error scenarios. */
if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
fx_sw->xstate_size < min_xstate_size ||
fx_sw->xstate_size > xstate_size ||
fx_sw->xstate_size > fx_sw->extended_size)
return -1;
/*
* 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 (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
|| magic2 != FP_XSTATE_MAGIC2)
return -1;
return 0;
}
/*
* Signal frame handlers.
*/
static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
{
if (use_fxsr()) {
struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
struct user_i387_ia32_struct env;
struct _fpstate_ia32 __user *fp = buf;
convert_from_fxsr(&env, tsk);
if (__copy_to_user(buf, &env, sizeof(env)) ||
__put_user(xsave->i387.swd, &fp->status) ||
__put_user(X86_FXSR_MAGIC, &fp->magic))
return -1;
} else {
struct i387_fsave_struct __user *fp = buf;
u32 swd;
if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
return -1;
}
return 0;
}
static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
{
struct xsave_struct __user *x = buf;
struct _fpx_sw_bytes *sw_bytes;
u32 xstate_bv;
int err;
/* Setup the bytes not touched by the [f]xsave and reserved for SW. */
sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
if (!use_xsave())
return err;
err |= __put_user(FP_XSTATE_MAGIC2, (__u32 *)(buf + xstate_size));
/*
* Read the xstate_bv which we copied (directly from the cpu or
* from the state in task struct) to the user buffers.
*/
err |= __get_user(xstate_bv, (__u32 *)&x->xsave_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, (__u32 *)&x->xsave_hdr.xstate_bv);
return err;
}
static inline int save_user_xstate(struct xsave_struct __user *buf)
{
int err;
if (use_xsave())
err = xsave_user(buf);
else if (use_fxsr())
err = fxsave_user((struct i387_fxsave_struct __user *) buf);
else
err = fsave_user((struct i387_fsave_struct __user *) buf);
if (unlikely(err) && __clear_user(buf, xstate_size))
err = -EFAULT;
return err;
}
/*
* Save the fpu, extended register state to the user signal frame.
*
* 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
* state is copied.
* 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
*
* buf == buf_fx for 64-bit frames and 32-bit fsave frame.
* buf != buf_fx for 32-bit frames with fxstate.
*
* If the fpu, extended register state is live, save the state directly
* to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise,
* copy the thread's fpu state to the user frame starting at 'buf_fx'.
*
* If this is a 32-bit frame with fxstate, put a fsave header before
* the aligned state at 'buf_fx'.
*
* For [f]xsave state, update the SW reserved fields in the [f]xsave frame
* indicating the absence/presence of the extended state to the user.
*/
int save_xstate_sig(void __user *buf, void __user *buf_fx, int size)
{
struct xsave_struct *xsave = ¤t->thread.fpu.state->xsave;
struct task_struct *tsk = current;
int ia32_fxstate = (buf != buf_fx);
ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
config_enabled(CONFIG_IA32_EMULATION));
if (!access_ok(VERIFY_WRITE, buf, size))
return -EACCES;
if (!HAVE_HWFP)
return fpregs_soft_get(current, NULL, 0,
sizeof(struct user_i387_ia32_struct), NULL,
(struct _fpstate_ia32 __user *) buf) ? -1 : 1;
if (user_has_fpu()) {
/* Save the live register state to the user directly. */
if (save_user_xstate(buf_fx))
return -1;
/* Update the thread's fxstate to save the fsave header. */
if (ia32_fxstate)
fpu_fxsave(&tsk->thread.fpu);
} else {
sanitize_i387_state(tsk);
if (__copy_to_user(buf_fx, xsave, xstate_size))
return -1;
}
/* Save the fsave header for the 32-bit frames. */
if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
return -1;
if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
return -1;
drop_init_fpu(tsk); /* trigger finit */
return 0;
}
static inline void
sanitize_restored_xstate(struct task_struct *tsk,
struct user_i387_ia32_struct *ia32_env,
u64 xstate_bv, int fx_only)
{
struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
struct xsave_hdr_struct *xsave_hdr = &xsave->xsave_hdr;
if (use_xsave()) {
/* These bits must be zero. */
xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
/*
* Init the state that is not present in the memory
* layout and not enabled by the OS.
*/
if (fx_only)
xsave_hdr->xstate_bv = XSTATE_FPSSE;
else
xsave_hdr->xstate_bv &= (pcntxt_mask & xstate_bv);
}
if (use_fxsr()) {
/*
* mscsr reserved bits must be masked to zero for security
* reasons.
*/
xsave->i387.mxcsr &= mxcsr_feature_mask;
convert_to_fxsr(tsk, ia32_env);
}
}
/*
* Restore the extended state if present. Otherwise, restore the FP/SSE state.
*/
static inline int restore_user_xstate(void __user *buf, u64 xbv, int fx_only)
{
if (use_xsave()) {
if ((unsigned long)buf % 64 || fx_only) {
u64 init_bv = pcntxt_mask & ~XSTATE_FPSSE;
xrstor_state(init_xstate_buf, init_bv);
return fxrstor_user(buf);
} else {
u64 init_bv = pcntxt_mask & ~xbv;
if (unlikely(init_bv))
xrstor_state(init_xstate_buf, init_bv);
return xrestore_user(buf, xbv);
}
} else if (use_fxsr()) {
return fxrstor_user(buf);
} else
return frstor_user(buf);
}
int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
{
int ia32_fxstate = (buf != buf_fx);
struct task_struct *tsk = current;
int state_size = xstate_size;
u64 xstate_bv = 0;
int fx_only = 0;
ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
config_enabled(CONFIG_IA32_EMULATION));
if (!buf) {
drop_init_fpu(tsk);
return 0;
}
if (!access_ok(VERIFY_READ, buf, size))
return -EACCES;
if (!used_math() && init_fpu(tsk))
return -1;
if (!HAVE_HWFP) {
return fpregs_soft_set(current, NULL,
0, sizeof(struct user_i387_ia32_struct),
NULL, buf) != 0;
}
if (use_xsave()) {
struct _fpx_sw_bytes fx_sw_user;
if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
/*
* Couldn't find the extended state information in the
* memory layout. Restore just the FP/SSE and init all
* the other extended state.
*/
state_size = sizeof(struct i387_fxsave_struct);
fx_only = 1;
} else {
state_size = fx_sw_user.xstate_size;
xstate_bv = fx_sw_user.xstate_bv;
}
}
if (ia32_fxstate) {
/*
* For 32-bit frames with fxstate, copy the user state to the
* thread's fpu state, reconstruct fxstate from the fsave
* header. Sanitize the copied state etc.
*/
struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
struct user_i387_ia32_struct env;
int err = 0;
/*
* Drop the current fpu which clears used_math(). This ensures
* that any context-switch during the copy of the new state,
* avoids the intermediate state from getting restored/saved.
* Thus avoiding the new restored state from getting corrupted.
* We will be ready to restore/save the state only after
* set_used_math() is again set.
*/
drop_fpu(tsk);
if (__copy_from_user(xsave, buf_fx, state_size) ||
__copy_from_user(&env, buf, sizeof(env))) {
err = -1;
} else {
sanitize_restored_xstate(tsk, &env, xstate_bv, fx_only);
set_used_math();
}
if (use_eager_fpu())
math_state_restore();
return err;
} else {
/*
* For 64-bit frames and 32-bit fsave frames, restore the user
* state to the registers directly (with exceptions handled).
*/
user_fpu_begin();
if (restore_user_xstate(buf_fx, xstate_bv, fx_only)) {
drop_init_fpu(tsk);
return -1;
}
}
return 0;
}
/*
* 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 fsave_header_size = sizeof(struct i387_fsave_struct);
int size = xstate_size + FP_XSTATE_MAGIC2_SIZE;
if (config_enabled(CONFIG_X86_32))
size += fsave_header_size;
fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
fx_sw_reserved.extended_size = size;
fx_sw_reserved.xstate_bv = pcntxt_mask;
fx_sw_reserved.xstate_size = xstate_size;
if (config_enabled(CONFIG_IA32_EMULATION)) {
fx_sw_reserved_ia32 = fx_sw_reserved;
fx_sw_reserved_ia32.extended_size += fsave_header_size;
}
}
/*
* 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_init_fpu_buf(void)
{
/*
* 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));
fx_finit(&init_xstate_buf->i387);
if (!cpu_has_xsave)
return;
setup_xstate_features();
/*
* 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);
}
static enum { AUTO, ENABLE, DISABLE } eagerfpu = AUTO;
static int __init eager_fpu_setup(char *s)
{
if (!strcmp(s, "on"))
eagerfpu = ENABLE;
else if (!strcmp(s, "off"))
eagerfpu = DISABLE;
else if (!strcmp(s, "auto"))
eagerfpu = AUTO;
return 1;
}
__setup("eagerfpu=", eager_fpu_setup);
/*
* 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) {
pr_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_init_fpu_buf();
/* Auto enable eagerfpu for xsaveopt */
if (cpu_has_xsaveopt && eagerfpu != DISABLE)
eagerfpu = ENABLE;
pr_info("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();
}
static inline void __init eager_fpu_init_bp(void)
{
current->thread.fpu.state =
alloc_bootmem_align(xstate_size, __alignof__(struct xsave_struct));
if (!init_xstate_buf)
setup_init_fpu_buf();
}
void __cpuinit eager_fpu_init(void)
{
static __refdata void (*boot_func)(void) = eager_fpu_init_bp;
clear_used_math();
current_thread_info()->status = 0;
if (eagerfpu == ENABLE)
setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);
if (!cpu_has_eager_fpu) {
stts();
return;
}
if (boot_func) {
boot_func();
boot_func = NULL;
}
/*
* This is same as math_state_restore(). But use_xsave() is
* not yet patched to use math_state_restore().
*/
init_fpu(current);
__thread_fpu_begin(current);
if (cpu_has_xsave)
xrstor_state(init_xstate_buf, -1);
else
fxrstor_checking(&init_xstate_buf->i387);
}