[PATCH 1/3] x86/fpu: Make task_struct::thread constant size

From: Ingo Molnar
Date: Wed Jun 05 2024 - 04:37:07 EST

Turn thread.fpu into a pointer. Since most FPU code internals work by passing
around the FPU pointer already, the code generation impact is small.

This allows us to remove the old kludge of task_struct being variable size:

struct task_struct {

...
/*
* New fields for task_struct should be added above here, so that
* they are included in the randomized portion of task_struct.
*/
randomized_struct_fields_end

/* CPU-specific state of this task: */
struct thread_struct thread;

/*
* WARNING: on x86, 'thread_struct' contains a variable-sized
* structure. It *MUST* be at the end of 'task_struct'.
*
* Do not put anything below here!
*/
};

... which creates a number of problems, such as requiring thread_struct to be
the last member of the struct - not allowing it to be struct-randomized, etc.

But the primary motivation is to allow the decoupling of task_struct from
hardware details (<asm/processor.h> in particular), and to eventually allow
the per-task infrastructure:

DECLARE_PER_TASK(type, name);
...
per_task(current, name) = val;

... which requires task_struct to be a constant size struct.

The fpu_thread_struct_whitelist() quirk to hardened usercopy can be removed,
now that the FPU structure is not embedded in the task struct anymore, which
reduces text footprint a bit.

Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Uros Bizjak <ubizjak@xxxxxxxxx>
Link: https://lore.kernel.org/r/ZgMeX+lFNgwYdOJF@xxxxxxxxx
---
arch/x86/include/asm/fpu/sched.h | 2 +-
arch/x86/include/asm/processor.h | 14 ++++++--------
arch/x86/kernel/fpu/context.h | 4 ++--
arch/x86/kernel/fpu/core.c | 51 ++++++++++++++++++++++++++-------------------------
arch/x86/kernel/fpu/init.c | 25 +++++++++++++++----------
arch/x86/kernel/fpu/regset.c | 22 +++++++++++-----------
arch/x86/kernel/fpu/signal.c | 18 +++++++++---------
arch/x86/kernel/fpu/xstate.c | 22 +++++++++++-----------
arch/x86/kernel/fpu/xstate.h | 6 +++---
arch/x86/kernel/process.c | 6 +++---
arch/x86/kernel/signal.c | 6 +++---
arch/x86/kernel/traps.c | 2 +-
arch/x86/math-emu/fpu_aux.c | 2 +-
arch/x86/math-emu/fpu_entry.c | 4 ++--
arch/x86/math-emu/fpu_system.h | 2 +-
arch/x86/mm/extable.c | 2 +-
include/linux/sched.h | 13 +++----------
17 files changed, 99 insertions(+), 102 deletions(-)

diff --git a/arch/x86/include/asm/fpu/sched.h b/arch/x86/include/asm/fpu/sched.h
index c485f1944c5f..3cf20ab49b5f 100644
--- a/arch/x86/include/asm/fpu/sched.h
+++ b/arch/x86/include/asm/fpu/sched.h
@@ -41,7 +41,7 @@ static inline void switch_fpu_prepare(struct task_struct *old, int cpu)
{
if (cpu_feature_enabled(X86_FEATURE_FPU) &&
!(old->flags & (PF_KTHREAD | PF_USER_WORKER))) {
- struct fpu *old_fpu = &old->thread.fpu;
+ struct fpu *old_fpu = old->thread.fpu;

save_fpregs_to_fpstate(old_fpu);
/*
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index cb4f6c513c48..920b0beebd11 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -504,19 +504,17 @@ struct thread_struct {
#endif

/* Floating point and extended processor state */
- struct fpu fpu;
- /*
- * WARNING: 'fpu' is dynamically-sized. It *MUST* be at
- * the end.
- */
+ struct fpu *fpu;
};

-extern void fpu_thread_struct_whitelist(unsigned long *offset, unsigned long *size);
-
+/*
+ * X86 doesn't need any embedded-FPU-struct quirks:
+ */
static inline void arch_thread_struct_whitelist(unsigned long *offset,
unsigned long *size)
{
- fpu_thread_struct_whitelist(offset, size);
+ *offset = 0;
+ *size = 0;
}

static inline void
diff --git a/arch/x86/kernel/fpu/context.h b/arch/x86/kernel/fpu/context.h
index f6d856bd50bc..96d1f34179b3 100644
--- a/arch/x86/kernel/fpu/context.h
+++ b/arch/x86/kernel/fpu/context.h
@@ -53,7 +53,7 @@ static inline void fpregs_activate(struct fpu *fpu)
/* Internal helper for switch_fpu_return() and signal frame setup */
static inline void fpregs_restore_userregs(void)
{
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = current->thread.fpu;
int cpu = smp_processor_id();

if (WARN_ON_ONCE(current->flags & (PF_KTHREAD | PF_USER_WORKER)))
@@ -67,7 +67,7 @@ static inline void fpregs_restore_userregs(void)
* If PKRU is enabled, then the PKRU value is already
* correct because it was either set in switch_to() or in
* flush_thread(). So it is excluded because it might be
- * not up to date in current->thread.fpu.xsave state.
+ * not up to date in current->thread.fpu->xsave state.
*
* XFD state is handled in restore_fpregs_from_fpstate().
*/
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 1209c7aebb21..816d48978da4 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -204,7 +204,7 @@ static void fpu_init_guest_permissions(struct fpu_guest *gfpu)
return;

spin_lock_irq(&current->sighand->siglock);
- fpuperm = &current->group_leader->thread.fpu.guest_perm;
+ fpuperm = &current->group_leader->thread.fpu->guest_perm;
perm = fpuperm->__state_perm;

/* First fpstate allocation locks down permissions. */
@@ -316,7 +316,7 @@ EXPORT_SYMBOL_GPL(fpu_update_guest_xfd);
*/
void fpu_sync_guest_vmexit_xfd_state(void)
{
- struct fpstate *fps = current->thread.fpu.fpstate;
+ struct fpstate *fps = current->thread.fpu->fpstate;

lockdep_assert_irqs_disabled();
if (fpu_state_size_dynamic()) {
@@ -330,7 +330,7 @@ EXPORT_SYMBOL_GPL(fpu_sync_guest_vmexit_xfd_state);
int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest)
{
struct fpstate *guest_fps = guest_fpu->fpstate;
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = current->thread.fpu;
struct fpstate *cur_fps = fpu->fpstate;

fpregs_lock();
@@ -430,7 +430,7 @@ void kernel_fpu_begin_mask(unsigned int kfpu_mask)
if (!(current->flags & (PF_KTHREAD | PF_USER_WORKER)) &&
!test_thread_flag(TIF_NEED_FPU_LOAD)) {
set_thread_flag(TIF_NEED_FPU_LOAD);
- save_fpregs_to_fpstate(&current->thread.fpu);
+ save_fpregs_to_fpstate(current->thread.fpu);
}
__cpu_invalidate_fpregs_state();

@@ -458,7 +458,7 @@ EXPORT_SYMBOL_GPL(kernel_fpu_end);
*/
void fpu_sync_fpstate(struct fpu *fpu)
{
- WARN_ON_FPU(fpu != &current->thread.fpu);
+ WARN_ON_FPU(fpu != current->thread.fpu);

fpregs_lock();
trace_x86_fpu_before_save(fpu);
@@ -543,7 +543,7 @@ void fpstate_reset(struct fpu *fpu)
static inline void fpu_inherit_perms(struct fpu *dst_fpu)
{
if (fpu_state_size_dynamic()) {
- struct fpu *src_fpu = &current->group_leader->thread.fpu;
+ struct fpu *src_fpu = current->group_leader->thread.fpu;

spin_lock_irq(&current->sighand->siglock);
/* Fork also inherits the permissions of the parent */
@@ -563,7 +563,7 @@ static int update_fpu_shstk(struct task_struct *dst, unsigned long ssp)
if (!ssp)
return 0;

- xstate = get_xsave_addr(&dst->thread.fpu.fpstate->regs.xsave,
+ xstate = get_xsave_addr(&dst->thread.fpu->fpstate->regs.xsave,
XFEATURE_CET_USER);

/*
@@ -584,8 +584,19 @@ static int update_fpu_shstk(struct task_struct *dst, unsigned long ssp)
int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal,
unsigned long ssp)
{
- struct fpu *src_fpu = &current->thread.fpu;
- struct fpu *dst_fpu = &dst->thread.fpu;
+ /*
+ * We allocate the new FPU structure right after the end of the task struct.
+ * task allocation size already took this into account.
+ *
+ * This is safe because task_struct size is a multiple of cacheline size.
+ */
+ struct fpu *dst_fpu = (void *)dst + sizeof(*dst);
+ struct fpu *src_fpu = current->thread.fpu;
+
+ BUILD_BUG_ON(sizeof(*dst) % SMP_CACHE_BYTES != 0);
+ BUG_ON(!src_fpu);
+
+ dst->thread.fpu = dst_fpu;

/* The new task's FPU state cannot be valid in the hardware. */
dst_fpu->last_cpu = -1;
@@ -654,16 +665,6 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal,
return 0;
}

-/*
- * Whitelist the FPU register state embedded into task_struct for hardened
- * usercopy.
- */
-void fpu_thread_struct_whitelist(unsigned long *offset, unsigned long *size)
-{
- *offset = offsetof(struct thread_struct, fpu.__fpstate.regs);
- *size = fpu_kernel_cfg.default_size;
-}
-
/*
* Drops current FPU state: deactivates the fpregs and
* the fpstate. NOTE: it still leaves previous contents
@@ -677,7 +678,7 @@ void fpu__drop(struct fpu *fpu)
{
preempt_disable();

- if (fpu == &current->thread.fpu) {
+ if (fpu == current->thread.fpu) {
/* Ignore delayed exceptions from user space */
asm volatile("1: fwait\n"
"2:\n"
@@ -711,7 +712,7 @@ static inline void restore_fpregs_from_init_fpstate(u64 features_mask)
*/
static void fpu_reset_fpregs(void)
{
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = current->thread.fpu;

fpregs_lock();
__fpu_invalidate_fpregs_state(fpu);
@@ -740,7 +741,7 @@ static void fpu_reset_fpregs(void)
*/
void fpu__clear_user_states(struct fpu *fpu)
{
- WARN_ON_FPU(fpu != &current->thread.fpu);
+ WARN_ON_FPU(fpu != current->thread.fpu);

fpregs_lock();
if (!cpu_feature_enabled(X86_FEATURE_FPU)) {
@@ -773,7 +774,7 @@ void fpu__clear_user_states(struct fpu *fpu)

void fpu_flush_thread(void)
{
- fpstate_reset(&current->thread.fpu);
+ fpstate_reset(current->thread.fpu);
fpu_reset_fpregs();
}
/*
@@ -814,7 +815,7 @@ void fpregs_lock_and_load(void)
*/
void fpregs_assert_state_consistent(void)
{
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = current->thread.fpu;

if (test_thread_flag(TIF_NEED_FPU_LOAD))
return;
@@ -826,7 +827,7 @@ EXPORT_SYMBOL_GPL(fpregs_assert_state_consistent);

void fpregs_mark_activate(void)
{
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = current->thread.fpu;

fpregs_activate(fpu);
fpu->last_cpu = smp_processor_id();
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 998a08f17e33..de618ec509aa 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -38,7 +38,7 @@ static void fpu__init_cpu_generic(void)
/* Flush out any pending x87 state: */
#ifdef CONFIG_MATH_EMULATION
if (!boot_cpu_has(X86_FEATURE_FPU))
- fpstate_init_soft(&current->thread.fpu.fpstate->regs.soft);
+ fpstate_init_soft(&current->thread.fpu->fpstate->regs.soft);
else
#endif
asm volatile ("fninit");
@@ -71,8 +71,17 @@ static bool __init fpu__probe_without_cpuid(void)
return fsw == 0 && (fcw & 0x103f) == 0x003f;
}

+static struct fpu x86_init_fpu __read_mostly;
+
static void __init fpu__init_system_early_generic(void)
{
+ int this_cpu = smp_processor_id();
+
+ fpstate_reset(&x86_init_fpu);
+ current->thread.fpu = &x86_init_fpu;
+ per_cpu(fpu_fpregs_owner_ctx, this_cpu) = &x86_init_fpu;
+ x86_init_fpu.last_cpu = this_cpu;
+
if (!boot_cpu_has(X86_FEATURE_CPUID) &&
!test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) {
if (fpu__probe_without_cpuid())
@@ -150,11 +159,13 @@ static void __init fpu__init_task_struct_size(void)
{
int task_size = sizeof(struct task_struct);

+ task_size += sizeof(struct fpu);
+
/*
* Subtract off the static size of the register state.
* It potentially has a bunch of padding.
*/
- task_size -= sizeof(current->thread.fpu.__fpstate.regs);
+ task_size -= sizeof(current->thread.fpu->__fpstate.regs);

/*
* Add back the dynamically-calculated register state
@@ -164,14 +175,9 @@ static void __init fpu__init_task_struct_size(void)

/*
* We dynamically size 'struct fpu', so we require that
- * it be at the end of 'thread_struct' and that
- * 'thread_struct' be at the end of 'task_struct'. If
- * you hit a compile error here, check the structure to
- * see if something got added to the end.
+ * 'state' be at the end of 'it:
*/
CHECK_MEMBER_AT_END_OF(struct fpu, __fpstate);
- CHECK_MEMBER_AT_END_OF(struct thread_struct, fpu);
- CHECK_MEMBER_AT_END_OF(struct task_struct, thread);

arch_task_struct_size = task_size;
}
@@ -204,7 +210,7 @@ static void __init fpu__init_system_xstate_size_legacy(void)
fpu_kernel_cfg.default_size = size;
fpu_user_cfg.max_size = size;
fpu_user_cfg.default_size = size;
- fpstate_reset(&current->thread.fpu);
+ fpstate_reset(current->thread.fpu);
}

/*
@@ -213,7 +219,6 @@ static void __init fpu__init_system_xstate_size_legacy(void)
*/
void __init fpu__init_system(void)
{
- fpstate_reset(&current->thread.fpu);
fpu__init_system_early_generic();

/*
diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c
index 6bc1eb2a21bd..38bc0b390d02 100644
--- a/arch/x86/kernel/fpu/regset.c
+++ b/arch/x86/kernel/fpu/regset.c
@@ -45,7 +45,7 @@ int regset_xregset_fpregs_active(struct task_struct *target, const struct user_r
*/
static void sync_fpstate(struct fpu *fpu)
{
- if (fpu == &current->thread.fpu)
+ if (fpu == current->thread.fpu)
fpu_sync_fpstate(fpu);
}

@@ -63,7 +63,7 @@ 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 == &current->thread.fpu);
+ WARN_ON_FPU(fpu == current->thread.fpu);

__fpu_invalidate_fpregs_state(fpu);
}
@@ -71,7 +71,7 @@ static void fpu_force_restore(struct fpu *fpu)
int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
struct membuf to)
{
- struct fpu *fpu = &target->thread.fpu;
+ struct fpu *fpu = target->thread.fpu;

if (!cpu_feature_enabled(X86_FEATURE_FXSR))
return -ENODEV;
@@ -91,7 +91,7 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
- struct fpu *fpu = &target->thread.fpu;
+ struct fpu *fpu = target->thread.fpu;
struct fxregs_state newstate;
int ret;

@@ -133,7 +133,7 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
if (!cpu_feature_enabled(X86_FEATURE_XSAVE))
return -ENODEV;

- sync_fpstate(&target->thread.fpu);
+ sync_fpstate(target->thread.fpu);

copy_xstate_to_uabi_buf(to, target, XSTATE_COPY_XSAVE);
return 0;
@@ -143,7 +143,7 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
- struct fpu *fpu = &target->thread.fpu;
+ struct fpu *fpu = target->thread.fpu;
struct xregs_state *tmpbuf = NULL;
int ret;

@@ -187,7 +187,7 @@ int ssp_active(struct task_struct *target, const struct user_regset *regset)
int ssp_get(struct task_struct *target, const struct user_regset *regset,
struct membuf to)
{
- struct fpu *fpu = &target->thread.fpu;
+ struct fpu *fpu = target->thread.fpu;
struct cet_user_state *cetregs;

if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK))
@@ -213,7 +213,7 @@ int ssp_set(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
- struct fpu *fpu = &target->thread.fpu;
+ struct fpu *fpu = target->thread.fpu;
struct xregs_state *xsave = &fpu->fpstate->regs.xsave;
struct cet_user_state *cetregs;
unsigned long user_ssp;
@@ -367,7 +367,7 @@ static void __convert_from_fxsr(struct user_i387_ia32_struct *env,
void
convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
{
- __convert_from_fxsr(env, tsk, &tsk->thread.fpu.fpstate->regs.fxsave);
+ __convert_from_fxsr(env, tsk, &tsk->thread.fpu->fpstate->regs.fxsave);
}

void convert_to_fxsr(struct fxregs_state *fxsave,
@@ -400,7 +400,7 @@ void convert_to_fxsr(struct fxregs_state *fxsave,
int fpregs_get(struct task_struct *target, const struct user_regset *regset,
struct membuf to)
{
- struct fpu *fpu = &target->thread.fpu;
+ struct fpu *fpu = target->thread.fpu;
struct user_i387_ia32_struct env;
struct fxregs_state fxsave, *fx;

@@ -432,7 +432,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
- struct fpu *fpu = &target->thread.fpu;
+ struct fpu *fpu = target->thread.fpu;
struct user_i387_ia32_struct env;
int ret;

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 247f2225aa9f..6b262d0b8fc1 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -38,7 +38,7 @@ static inline bool check_xstate_in_sigframe(struct fxregs_state __user *fxbuf,
/* 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 > current->thread.fpu.fpstate->user_size ||
+ fx_sw->xstate_size > current->thread.fpu->fpstate->user_size ||
fx_sw->xstate_size > fx_sw->extended_size)
goto setfx;

@@ -54,7 +54,7 @@ static inline bool check_xstate_in_sigframe(struct fxregs_state __user *fxbuf,
if (likely(magic2 == FP_XSTATE_MAGIC2))
return true;
setfx:
- trace_x86_fpu_xstate_check_failed(&current->thread.fpu);
+ trace_x86_fpu_xstate_check_failed(current->thread.fpu);

/* Set the parameters for fx only state */
fx_sw->magic1 = 0;
@@ -69,13 +69,13 @@ static inline bool check_xstate_in_sigframe(struct fxregs_state __user *fxbuf,
static inline bool save_fsave_header(struct task_struct *tsk, void __user *buf)
{
if (use_fxsr()) {
- struct xregs_state *xsave = &tsk->thread.fpu.fpstate->regs.xsave;
+ struct xregs_state *xsave = &tsk->thread.fpu->fpstate->regs.xsave;
struct user_i387_ia32_struct env;
struct _fpstate_32 __user *fp = buf;

fpregs_lock();
if (!test_thread_flag(TIF_NEED_FPU_LOAD))
- fxsave(&tsk->thread.fpu.fpstate->regs.fxsave);
+ fxsave(&tsk->thread.fpu->fpstate->regs.fxsave);
fpregs_unlock();

convert_from_fxsr(&env, tsk);
@@ -188,7 +188,7 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
bool copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
{
struct task_struct *tsk = current;
- struct fpstate *fpstate = tsk->thread.fpu.fpstate;
+ struct fpstate *fpstate = tsk->thread.fpu->fpstate;
bool ia32_fxstate = (buf != buf_fx);
int ret;

@@ -276,7 +276,7 @@ static int __restore_fpregs_from_user(void __user *buf, u64 ufeatures,
*/
static bool restore_fpregs_from_user(void __user *buf, u64 xrestore, bool fx_only)
{
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = current->thread.fpu;
int ret;

/* Restore enabled features only. */
@@ -336,7 +336,7 @@ static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx,
bool ia32_fxstate)
{
struct task_struct *tsk = current;
- struct fpu *fpu = &tsk->thread.fpu;
+ struct fpu *fpu = tsk->thread.fpu;
struct user_i387_ia32_struct env;
bool success, fx_only = false;
union fpregs_state *fpregs;
@@ -456,7 +456,7 @@ static inline unsigned int xstate_sigframe_size(struct fpstate *fpstate)
*/
bool fpu__restore_sig(void __user *buf, int ia32_frame)
{
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = current->thread.fpu;
void __user *buf_fx = buf;
bool ia32_fxstate = false;
bool success = false;
@@ -503,7 +503,7 @@ unsigned long
fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
unsigned long *buf_fx, unsigned long *size)
{
- unsigned long frame_size = xstate_sigframe_size(current->thread.fpu.fpstate);
+ unsigned long frame_size = xstate_sigframe_size(current->thread.fpu->fpstate);

*buf_fx = sp = round_down(sp - frame_size, 64);
if (ia32_frame && use_fxsr()) {
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index c5a026fee5e0..1d1f6599731b 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -735,7 +735,7 @@ static void __init fpu__init_disable_system_xstate(unsigned int legacy_size)
*/
init_fpstate.xfd = 0;

- fpstate_reset(&current->thread.fpu);
+ fpstate_reset(current->thread.fpu);
}

/*
@@ -845,7 +845,7 @@ void __init fpu__init_system_xstate(unsigned int legacy_size)
goto out_disable;

/* Reset the state for the current task */
- fpstate_reset(&current->thread.fpu);
+ fpstate_reset(current->thread.fpu);

/*
* Update info used for ptrace frames; use standard-format size and no
@@ -919,7 +919,7 @@ void fpu__resume_cpu(void)
}

if (fpu_state_size_dynamic())
- wrmsrl(MSR_IA32_XFD, current->thread.fpu.fpstate->xfd);
+ wrmsrl(MSR_IA32_XFD, current->thread.fpu->fpstate->xfd);
}

/*
@@ -1188,8 +1188,8 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
enum xstate_copy_mode copy_mode)
{
- __copy_xstate_to_uabi_buf(to, tsk->thread.fpu.fpstate,
- tsk->thread.fpu.fpstate->user_xfeatures,
+ __copy_xstate_to_uabi_buf(to, tsk->thread.fpu->fpstate,
+ tsk->thread.fpu->fpstate->user_xfeatures,
tsk->thread.pkru, copy_mode);
}

@@ -1329,7 +1329,7 @@ int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf, u
int copy_sigframe_from_user_to_xstate(struct task_struct *tsk,
const void __user *ubuf)
{
- return copy_uabi_to_xstate(tsk->thread.fpu.fpstate, NULL, ubuf, &tsk->thread.pkru);
+ return copy_uabi_to_xstate(tsk->thread.fpu->fpstate, NULL, ubuf, &tsk->thread.pkru);
}

static bool validate_independent_components(u64 mask)
@@ -1423,7 +1423,7 @@ static bool xstate_op_valid(struct fpstate *fpstate, u64 mask, bool rstor)
* The XFD MSR does not match fpstate->xfd. That's invalid when
* the passed in fpstate is current's fpstate.
*/
- if (fpstate->xfd == current->thread.fpu.fpstate->xfd)
+ if (fpstate->xfd == current->thread.fpu->fpstate->xfd)
return false;

/*
@@ -1500,7 +1500,7 @@ void fpstate_free(struct fpu *fpu)
static int fpstate_realloc(u64 xfeatures, unsigned int ksize,
unsigned int usize, struct fpu_guest *guest_fpu)
{
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = current->thread.fpu;
struct fpstate *curfps, *newfps = NULL;
unsigned int fpsize;
bool in_use;
@@ -1593,7 +1593,7 @@ static int __xstate_request_perm(u64 permitted, u64 requested, bool guest)
* AVX512.
*/
bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED);
- struct fpu *fpu = &current->group_leader->thread.fpu;
+ struct fpu *fpu = current->group_leader->thread.fpu;
struct fpu_state_perm *perm;
unsigned int ksize, usize;
u64 mask;
@@ -1696,7 +1696,7 @@ int __xfd_enable_feature(u64 xfd_err, struct fpu_guest *guest_fpu)
return -EPERM;
}

- fpu = &current->group_leader->thread.fpu;
+ fpu = current->group_leader->thread.fpu;
perm = guest_fpu ? &fpu->guest_perm : &fpu->perm;
ksize = perm->__state_size;
usize = perm->__user_state_size;
@@ -1801,7 +1801,7 @@ long fpu_xstate_prctl(int option, unsigned long arg2)
*/
static void avx512_status(struct seq_file *m, struct task_struct *task)
{
- unsigned long timestamp = READ_ONCE(task->thread.fpu.avx512_timestamp);
+ unsigned long timestamp = READ_ONCE(task->thread.fpu->avx512_timestamp);
long delta;

if (!timestamp) {
diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
index 05df04f39628..1c720c376a69 100644
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -22,7 +22,7 @@ static inline void xstate_init_xcomp_bv(struct xregs_state *xsave, u64 mask)

static inline u64 xstate_get_group_perm(bool guest)
{
- struct fpu *fpu = &current->group_leader->thread.fpu;
+ struct fpu *fpu = current->group_leader->thread.fpu;
struct fpu_state_perm *perm;

/* Pairs with WRITE_ONCE() in xstate_request_perm() */
@@ -265,7 +265,7 @@ static inline int xsave_to_user_sigframe(struct xregs_state __user *buf)
* internally, e.g. PKRU. That's user space ABI and also required
* to allow the signal handler to modify PKRU.
*/
- struct fpstate *fpstate = current->thread.fpu.fpstate;
+ struct fpstate *fpstate = current->thread.fpu->fpstate;
u64 mask = fpstate->user_xfeatures;
u32 lmask;
u32 hmask;
@@ -296,7 +296,7 @@ static inline int xrstor_from_user_sigframe(struct xregs_state __user *buf, u64
u32 hmask = mask >> 32;
int err;

- xfd_validate_state(current->thread.fpu.fpstate, mask, true);
+ xfd_validate_state(current->thread.fpu->fpstate, mask, true);

stac();
XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index b8441147eb5e..5f3f48713870 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -97,7 +97,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
dst->thread.vm86 = NULL;
#endif
/* Drop the copied pointer to current's fpstate */
- dst->thread.fpu.fpstate = NULL;
+ dst->thread.fpu = NULL;

return 0;
}
@@ -106,7 +106,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
void arch_release_task_struct(struct task_struct *tsk)
{
if (fpu_state_size_dynamic())
- fpstate_free(&tsk->thread.fpu);
+ fpstate_free(tsk->thread.fpu);
}
#endif

@@ -116,7 +116,7 @@ void arch_release_task_struct(struct task_struct *tsk)
void exit_thread(struct task_struct *tsk)
{
struct thread_struct *t = &tsk->thread;
- struct fpu *fpu = &t->fpu;
+ struct fpu *fpu = t->fpu;

if (test_thread_flag(TIF_IO_BITMAP))
io_bitmap_exit(tsk);
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 31b6f5dddfc2..7e709ae8e99a 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -228,7 +228,7 @@ static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
bool stepping, failed;
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = current->thread.fpu;

if (v8086_mode(regs))
save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
@@ -396,14 +396,14 @@ bool sigaltstack_size_valid(size_t ss_size)
if (!fpu_state_size_dynamic() && !strict_sigaltstack_size)
return true;

- fsize += current->group_leader->thread.fpu.perm.__user_state_size;
+ fsize += current->group_leader->thread.fpu->perm.__user_state_size;
if (likely(ss_size > fsize))
return true;

if (strict_sigaltstack_size)
return ss_size > fsize;

- mask = current->group_leader->thread.fpu.perm.__state_perm;
+ mask = current->group_leader->thread.fpu->perm.__state_perm;
if (mask & XFEATURE_MASK_USER_DYNAMIC)
return ss_size > fsize;

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 4fa0b17e5043..c79e36c4071b 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1148,7 +1148,7 @@ DEFINE_IDTENTRY_RAW(exc_debug)
static void math_error(struct pt_regs *regs, int trapnr)
{
struct task_struct *task = current;
- struct fpu *fpu = &task->thread.fpu;
+ struct fpu *fpu = task->thread.fpu;
int si_code;
char *str = (trapnr == X86_TRAP_MF) ? "fpu exception" :
"simd exception";
diff --git a/arch/x86/math-emu/fpu_aux.c b/arch/x86/math-emu/fpu_aux.c
index d62662bdd460..8087953164fc 100644
--- a/arch/x86/math-emu/fpu_aux.c
+++ b/arch/x86/math-emu/fpu_aux.c
@@ -53,7 +53,7 @@ void fpstate_init_soft(struct swregs_state *soft)

void finit(void)
{
- fpstate_init_soft(&current->thread.fpu.fpstate->regs.soft);
+ fpstate_init_soft(&current->thread.fpu->fpstate->regs.soft);
}

/*
diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
index 91c52ead1226..30400d95d9d0 100644
--- a/arch/x86/math-emu/fpu_entry.c
+++ b/arch/x86/math-emu/fpu_entry.c
@@ -641,7 +641,7 @@ int fpregs_soft_set(struct task_struct *target,
unsigned int pos, unsigned int count,
const void *kbuf, const void __user *ubuf)
{
- struct swregs_state *s387 = &target->thread.fpu.fpstate->regs.soft;
+ struct swregs_state *s387 = &target->thread.fpu->fpstate->regs.soft;
void *space = s387->st_space;
int ret;
int offset, other, i, tags, regnr, tag, newtop;
@@ -692,7 +692,7 @@ int fpregs_soft_get(struct task_struct *target,
const struct user_regset *regset,
struct membuf to)
{
- struct swregs_state *s387 = &target->thread.fpu.fpstate->regs.soft;
+ struct swregs_state *s387 = &target->thread.fpu->fpstate->regs.soft;
const void *space = s387->st_space;
int offset = (S387->ftop & 7) * 10, other = 80 - offset;

diff --git a/arch/x86/math-emu/fpu_system.h b/arch/x86/math-emu/fpu_system.h
index eec3e4805c75..3417337e7d99 100644
--- a/arch/x86/math-emu/fpu_system.h
+++ b/arch/x86/math-emu/fpu_system.h
@@ -73,7 +73,7 @@ static inline bool seg_writable(struct desc_struct *d)
return (d->type & SEG_TYPE_EXECUTE_MASK) == SEG_TYPE_WRITABLE;
}

-#define I387 (&current->thread.fpu.fpstate->regs)
+#define I387 (&current->thread.fpu->fpstate->regs)
#define FPU_info (I387->soft.info)

#define FPU_CS (*(unsigned short *) &(FPU_info->regs->cs))
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 51986e8a9d35..9400c1c29fc8 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -111,7 +111,7 @@ static bool ex_handler_sgx(const struct exception_table_entry *fixup,

/*
* Handler for when we fail to restore a task's FPU state. We should never get
- * here because the FPU state of a task using the FPU (task->thread.fpu.state)
+ * here because the FPU state of a task using the FPU (task->thread.fpu->state)
* should always be valid. However, past bugs have allowed userspace to set
* reserved bits in the XSAVE area using PTRACE_SETREGSET or sys_rt_sigreturn().
* These caused XRSTOR to fail when switching to the task, leaking the FPU
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 61591ac6eab6..215a7380e41c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1554,21 +1554,14 @@ struct task_struct {
struct user_event_mm *user_event_mm;
#endif

+ /* CPU-specific state of this task: */
+ struct thread_struct thread;
+
/*
* New fields for task_struct should be added above here, so that
* they are included in the randomized portion of task_struct.
*/
randomized_struct_fields_end
-
- /* CPU-specific state of this task: */
- struct thread_struct thread;
-
- /*
- * WARNING: on x86, 'thread_struct' contains a variable-sized
- * structure. It *MUST* be at the end of 'task_struct'.
- *
- * Do not put anything below here!
- */
};

#define TASK_REPORT_IDLE (TASK_REPORT + 1)
--
2.43.0