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Merge branch 'WIP.x86/fpu' into x86/fpu, because it's ready 

Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2017-09-26 10:17:43 +02:00
parent e365806ac2 738f48cb5f
commit 8474c532b5
15 changed files with 385 additions and 325 deletions
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2
arch/x86/ia32/ia32_signal.c
View File

@ -231,7 +231,7 @@ static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
ksig->ka.sa.sa_restorer)
sp = (unsigned long) ksig->ka.sa.sa_restorer;
if (fpu->fpstate_active) {
if (fpu->initialized) {
unsigned long fx_aligned, math_size;
sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);

90
arch/x86/include/asm/fpu/internal.h
View File

@ -23,11 +23,9 @@
/*
* High level FPU state handling functions:
*/
extern void fpu__activate_curr(struct fpu *fpu);
extern void fpu__activate_fpstate_read(struct fpu *fpu);
extern void fpu__activate_fpstate_write(struct fpu *fpu);
extern void fpu__current_fpstate_write_begin(void);
extern void fpu__current_fpstate_write_end(void);
extern void fpu__initialize(struct fpu *fpu);
extern void fpu__prepare_read(struct fpu *fpu);
extern void fpu__prepare_write(struct fpu *fpu);
extern void fpu__save(struct fpu *fpu);
extern void fpu__restore(struct fpu *fpu);
extern int fpu__restore_sig(void __user *buf, int ia32_frame);
@ -120,20 +118,11 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu);
err; \
})
#define check_insn(insn, output, input...) \
({ \
int err; \
#define kernel_insn(insn, output, input...) \
asm volatile("1:" #insn "\n\t" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"3: movl $-1,%[err]\n" \
" jmp 2b\n" \
".previous\n" \
_ASM_EXTABLE(1b, 3b) \
: [err] "=r" (err), output \
: "0"(0), input); \
err; \
})
_ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_fprestore) \
: output : input)
static inline int copy_fregs_to_user(struct fregs_state __user *fx)
{
@ -153,20 +142,16 @@ static inline int copy_fxregs_to_user(struct fxregs_state __user *fx)
static inline void copy_kernel_to_fxregs(struct fxregs_state *fx)
{
int err;
if (IS_ENABLED(CONFIG_X86_32)) {
err = check_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
kernel_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
} else {
if (IS_ENABLED(CONFIG_AS_FXSAVEQ)) {
err = check_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
kernel_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
} else {
/* See comment in copy_fxregs_to_kernel() below. */
err = check_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx), "m" (*fx));
kernel_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx), "m" (*fx));
}
}
/* Copying from a kernel buffer to FPU registers should never fail: */
WARN_ON_FPU(err);
}
static inline int copy_user_to_fxregs(struct fxregs_state __user *fx)
@ -183,9 +168,7 @@ static inline int copy_user_to_fxregs(struct fxregs_state __user *fx)
static inline void copy_kernel_to_fregs(struct fregs_state *fx)
{
int err = check_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
WARN_ON_FPU(err);
kernel_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
}
static inline int copy_user_to_fregs(struct fregs_state __user *fx)
@ -281,18 +264,13 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu)
* Use XRSTORS to restore context if it is enabled. XRSTORS supports compact
* XSAVE area format.
*/
#define XSTATE_XRESTORE(st, lmask, hmask, err) \
#define XSTATE_XRESTORE(st, lmask, hmask) \
asm volatile(ALTERNATIVE(XRSTOR, \
XRSTORS, X86_FEATURE_XSAVES) \
"\n" \
"xor %[err], %[err]\n" \
"3:\n" \
".pushsection .fixup,\"ax\"\n" \
"4: movl $-2, %[err]\n" \
"jmp 3b\n" \
".popsection\n" \
_ASM_EXTABLE(661b, 4b) \
: [err] "=r" (err) \
_ASM_EXTABLE_HANDLE(661b, 3b, ex_handler_fprestore)\
: \
: "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \
: "memory")
@ -336,7 +314,10 @@ static inline void copy_kernel_to_xregs_booting(struct xregs_state *xstate)
else
XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);
/* We should never fault when copying from a kernel buffer: */
/*
* We should never fault when copying from a kernel buffer, and the FPU
* state we set at boot time should be valid.
*/
WARN_ON_FPU(err);
}
@ -350,7 +331,7 @@ static inline void copy_xregs_to_kernel(struct xregs_state *xstate)
u32 hmask = mask >> 32;
int err;
WARN_ON(!alternatives_patched);
WARN_ON_FPU(!alternatives_patched);
XSTATE_XSAVE(xstate, lmask, hmask, err);
@ -365,12 +346,8 @@ static inline void copy_kernel_to_xregs(struct xregs_state *xstate, u64 mask)
{
u32 lmask = mask;
u32 hmask = mask >> 32;
int err;
XSTATE_XRESTORE(xstate, lmask, hmask, err);
/* We should never fault when copying from a kernel buffer: */
WARN_ON_FPU(err);
XSTATE_XRESTORE(xstate, lmask, hmask);
}
/*
@ -526,37 +503,16 @@ static inline int fpregs_state_valid(struct fpu *fpu, unsigned int cpu)
*/
static inline void fpregs_deactivate(struct fpu *fpu)
{
WARN_ON_FPU(!fpu->fpregs_active);
fpu->fpregs_active = 0;
this_cpu_write(fpu_fpregs_owner_ctx, NULL);
trace_x86_fpu_regs_deactivated(fpu);
}
static inline void fpregs_activate(struct fpu *fpu)
{
WARN_ON_FPU(fpu->fpregs_active);
fpu->fpregs_active = 1;
this_cpu_write(fpu_fpregs_owner_ctx, fpu);
trace_x86_fpu_regs_activated(fpu);
}
/*
* The question "does this thread have fpu access?"
* is slightly racy, since preemption could come in
* and revoke it immediately after the test.
*
* However, even in that very unlikely scenario,
* we can just assume we have FPU access - typically
* to save the FP state - we'll just take a #NM
* fault and get the FPU access back.
*/
static inline int fpregs_active(void)
{
return current->thread.fpu.fpregs_active;
}
/*
* FPU state switching for scheduling.
*
@ -571,14 +527,13 @@ static inline int fpregs_active(void)
static inline void
switch_fpu_prepare(struct fpu *old_fpu, int cpu)
{
if (old_fpu->fpregs_active) {
if (old_fpu->initialized) {
if (!copy_fpregs_to_fpstate(old_fpu))
old_fpu->last_cpu = -1;
else
old_fpu->last_cpu = cpu;
/* But leave fpu_fpregs_owner_ctx! */
old_fpu->fpregs_active = 0;
trace_x86_fpu_regs_deactivated(old_fpu);
} else
old_fpu->last_cpu = -1;
@ -595,7 +550,7 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu)
static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
{
bool preload = static_cpu_has(X86_FEATURE_FPU) &&
new_fpu->fpstate_active;
new_fpu->initialized;
if (preload) {
if (!fpregs_state_valid(new_fpu, cpu))
@ -617,8 +572,7 @@ static inline void user_fpu_begin(void)
struct fpu *fpu = &current->thread.fpu;
preempt_disable();
if (!fpregs_active())
fpregs_activate(fpu);
fpregs_activate(fpu);
preempt_enable();
}

32
arch/x86/include/asm/fpu/types.h
View File

@ -68,6 +68,9 @@ struct fxregs_state {
/* Default value for fxregs_state.mxcsr: */
#define MXCSR_DEFAULT 0x1f80
/* Copy both mxcsr & mxcsr_flags with a single u64 memcpy: */
#define MXCSR_AND_FLAGS_SIZE sizeof(u64)
/*
* Software based FPU emulation state. This is arbitrary really,
* it matches the x87 format to make it easier to understand:
@ -290,36 +293,13 @@ struct fpu {
unsigned int last_cpu;
/*
* @fpstate_active:
* @initialized:
*
* This flag indicates whether this context is active: if the task
* This flag indicates whether this context is initialized: if the task
* is not running then we can restore from this context, if the task
* is running then we should save into this context.
*/
unsigned char fpstate_active;
/*
* @fpregs_active:
*
* This flag determines whether a given context is actively
* loaded into the FPU's registers and that those registers
* represent the task's current FPU state.
*
* Note the interaction with fpstate_active:
*
* # task does not use the FPU:
* fpstate_active == 0
*
* # task uses the FPU and regs are active:
* fpstate_active == 1 && fpregs_active == 1
*
* # the regs are inactive but still match fpstate:
* fpstate_active == 1 && fpregs_active == 0 && fpregs_owner == fpu
*
* The third state is what we use for the lazy restore optimization
* on lazy-switching CPUs.
*/
unsigned char fpregs_active;
unsigned char initialized;
/*
* @state:

12
arch/x86/include/asm/fpu/xstate.h
View File

@ -48,8 +48,12 @@ void fpu__xstate_clear_all_cpu_caps(void);
void *get_xsave_addr(struct xregs_state *xsave, int xstate);
const void *get_xsave_field_ptr(int xstate_field);
int using_compacted_format(void);
int copyout_from_xsaves(unsigned int pos, unsigned int count, void *kbuf,
void __user *ubuf, struct xregs_state *xsave);
int copyin_to_xsaves(const void *kbuf, const void __user *ubuf,
struct xregs_state *xsave);
int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int offset, unsigned int size);
int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned int offset, unsigned int size);
int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf);
int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf);
/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */
extern int validate_xstate_header(const struct xstate_header *hdr);
#endif

11
arch/x86/include/asm/trace/fpu.h
View File

@ -12,25 +12,22 @@ DECLARE_EVENT_CLASS(x86_fpu,
TP_STRUCT__entry(
__field(struct fpu *, fpu)
__field(bool, fpregs_active)
__field(bool, fpstate_active)
__field(bool, initialized)
__field(u64, xfeatures)
__field(u64, xcomp_bv)
),
TP_fast_assign(
__entry->fpu = fpu;
__entry->fpregs_active = fpu->fpregs_active;
__entry->fpstate_active = fpu->fpstate_active;
__entry->initialized = fpu->initialized;
if (boot_cpu_has(X86_FEATURE_OSXSAVE)) {
__entry->xfeatures = fpu->state.xsave.header.xfeatures;
__entry->xcomp_bv = fpu->state.xsave.header.xcomp_bv;
}
),
TP_printk("x86/fpu: %p fpregs_active: %d fpstate_active: %d xfeatures: %llx xcomp_bv: %llx",
TP_printk("x86/fpu: %p initialized: %d xfeatures: %llx xcomp_bv: %llx",
__entry->fpu,
__entry->fpregs_active,
__entry->fpstate_active,
__entry->initialized,
__entry->xfeatures,
__entry->xcomp_bv
)

155
arch/x86/kernel/fpu/core.c
View File

@ -100,7 +100,7 @@ void __kernel_fpu_begin(void)
kernel_fpu_disable();
if (fpu->fpregs_active) {
if (fpu->initialized) {
/*
* Ignore return value -- we don't care if reg state
* is clobbered.
@ -116,7 +116,7 @@ void __kernel_fpu_end(void)
{
struct fpu *fpu = &current->thread.fpu;
if (fpu->fpregs_active)
if (fpu->initialized)
copy_kernel_to_fpregs(&fpu->state);
kernel_fpu_enable();
@ -148,7 +148,7 @@ void fpu__save(struct fpu *fpu)
preempt_disable();
trace_x86_fpu_before_save(fpu);
if (fpu->fpregs_active) {
if (fpu->initialized) {
if (!copy_fpregs_to_fpstate(fpu)) {
copy_kernel_to_fpregs(&fpu->state);
}
@ -189,10 +189,9 @@ EXPORT_SYMBOL_GPL(fpstate_init);
int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
{
dst_fpu->fpregs_active = 0;
dst_fpu->last_cpu = -1;
if (!src_fpu->fpstate_active || !static_cpu_has(X86_FEATURE_FPU))
if (!src_fpu->initialized || !static_cpu_has(X86_FEATURE_FPU))
return 0;
WARN_ON_FPU(src_fpu != &current->thread.fpu);
@ -206,26 +205,14 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
/*
* Save current FPU registers directly into the child
* FPU context, without any memory-to-memory copying.
* In lazy mode, if the FPU context isn't loaded into
* fpregs, CR0.TS will be set and do_device_not_available
* will load the FPU context.
*
* We have to do all this with preemption disabled,
* mostly because of the FNSAVE case, because in that
* case we must not allow preemption in the window
* between the FNSAVE and us marking the context lazy.
*
* It shouldn't be an issue as even FNSAVE is plenty
* fast in terms of critical section length.
* ( The function 'fails' in the FNSAVE case, which destroys
* register contents so we have to copy them back. )
*/
preempt_disable();
if (!copy_fpregs_to_fpstate(dst_fpu)) {
memcpy(&src_fpu->state, &dst_fpu->state,
fpu_kernel_xstate_size);
memcpy(&src_fpu->state, &dst_fpu->state, fpu_kernel_xstate_size);
copy_kernel_to_fpregs(&src_fpu->state);
}
preempt_enable();
trace_x86_fpu_copy_src(src_fpu);
trace_x86_fpu_copy_dst(dst_fpu);
@ -237,45 +224,48 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
* Activate the current task's in-memory FPU context,
* if it has not been used before:
*/
void fpu__activate_curr(struct fpu *fpu)
void fpu__initialize(struct fpu *fpu)
{
WARN_ON_FPU(fpu != &current->thread.fpu);
if (!fpu->fpstate_active) {
if (!fpu->initialized) {
fpstate_init(&fpu->state);
trace_x86_fpu_init_state(fpu);
trace_x86_fpu_activate_state(fpu);
/* Safe to do for the current task: */
fpu->fpstate_active = 1;
fpu->initialized = 1;
}
}
EXPORT_SYMBOL_GPL(fpu__activate_curr);
EXPORT_SYMBOL_GPL(fpu__initialize);
/*
* This function must be called before we read a task's fpstate.
*
* If the task has not used the FPU before then initialize its
* fpstate.
* There's two cases where this gets called:
*
* - for the current task (when coredumping), in which case we have
* to save the latest FPU registers into the fpstate,
*
* - or it's called for stopped tasks (ptrace), in which case the
* registers were already saved by the context-switch code when
* the task scheduled out - we only have to initialize the registers
* if they've never been initialized.
*
* If the task has used the FPU before then save it.
*/
void fpu__activate_fpstate_read(struct fpu *fpu)
void fpu__prepare_read(struct fpu *fpu)
{
/*
* If fpregs are active (in the current CPU), then
* copy them to the fpstate:
*/
if (fpu->fpregs_active) {
if (fpu == &current->thread.fpu) {
fpu__save(fpu);
} else {
if (!fpu->fpstate_active) {
if (!fpu->initialized) {
fpstate_init(&fpu->state);
trace_x86_fpu_init_state(fpu);
trace_x86_fpu_activate_state(fpu);
/* Safe to do for current and for stopped child tasks: */
fpu->fpstate_active = 1;
fpu->initialized = 1;
}
}
}
@ -283,17 +273,17 @@ void fpu__activate_fpstate_read(struct fpu *fpu)
/*
* This function must be called before we write a task's fpstate.
*
* If the task has used the FPU before then unlazy it.
* If the task has used the FPU before then invalidate any cached FPU registers.
* If the task has not used the FPU before then initialize its fpstate.
*
* 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 lazy status here then the lazy in-registers
* 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__activate_fpstate_write(struct fpu *fpu)
void fpu__prepare_write(struct fpu *fpu)
{
/*
* Only stopped child tasks can be used to modify the FPU
@ -301,8 +291,8 @@ void fpu__activate_fpstate_write(struct fpu *fpu)
*/
WARN_ON_FPU(fpu == &current->thread.fpu);
if (fpu->fpstate_active) {
/* Invalidate any lazy state: */
if (fpu->initialized) {
/* Invalidate any cached state: */
__fpu_invalidate_fpregs_state(fpu);
} else {
fpstate_init(&fpu->state);
@ -310,73 +300,10 @@ void fpu__activate_fpstate_write(struct fpu *fpu)
trace_x86_fpu_activate_state(fpu);
/* Safe to do for stopped child tasks: */
fpu->fpstate_active = 1;
fpu->initialized = 1;
}
}
/*
* This function must be called before we write the current
* task's fpstate.
*
* This call gets the current FPU register state and moves
* it in to the 'fpstate'. Preemption is disabled so that
* no writes to the 'fpstate' can occur from context
* swiches.
*
* Must be followed by a fpu__current_fpstate_write_end().
*/
void fpu__current_fpstate_write_begin(void)
{
struct fpu *fpu = &current->thread.fpu;
/*
* Ensure that the context-switching code does not write
* over the fpstate while we are doing our update.
*/
preempt_disable();
/*
* Move the fpregs in to the fpu's 'fpstate'.
*/
fpu__activate_fpstate_read(fpu);
/*
* The caller is about to write to 'fpu'. Ensure that no
* CPU thinks that its fpregs match the fpstate. This
* ensures we will not be lazy and skip a XRSTOR in the
* future.
*/
__fpu_invalidate_fpregs_state(fpu);
}
/*
* This function must be paired with fpu__current_fpstate_write_begin()
*
* This will ensure that the modified fpstate gets placed back in
* the fpregs if necessary.
*
* Note: This function may be called whether or not an _actual_
* write to the fpstate occurred.
*/
void fpu__current_fpstate_write_end(void)
{
struct fpu *fpu = &current->thread.fpu;
/*
* 'fpu' now has an updated copy of the state, but the
* registers may still be out of date. Update them with
* an XRSTOR if they are active.
*/
if (fpregs_active())
copy_kernel_to_fpregs(&fpu->state);
/*
* Our update is done and the fpregs/fpstate are in sync
* if necessary. Context switches can happen again.
*/
preempt_enable();
}
/*
* 'fpu__restore()' is called to copy FPU registers from
* the FPU fpstate to the live hw registers and to activate
@ -389,7 +316,7 @@ void fpu__current_fpstate_write_end(void)
*/
void fpu__restore(struct fpu *fpu)
{
fpu__activate_curr(fpu);
fpu__initialize(fpu);
/* Avoid __kernel_fpu_begin() right after fpregs_activate() */
kernel_fpu_disable();
@ -414,15 +341,17 @@ void fpu__drop(struct fpu *fpu)
{
preempt_disable();
if (fpu->fpregs_active) {
/* Ignore delayed exceptions from user space */
asm volatile("1: fwait\n"
"2:\n"
_ASM_EXTABLE(1b, 2b));
fpregs_deactivate(fpu);
if (fpu == &current->thread.fpu) {
if (fpu->initialized) {
/* Ignore delayed exceptions from user space */
asm volatile("1: fwait\n"
"2:\n"
_ASM_EXTABLE(1b, 2b));
fpregs_deactivate(fpu);
}
}
fpu->fpstate_active = 0;
fpu->initialized = 0;
trace_x86_fpu_dropped(fpu);
@ -462,9 +391,11 @@ void fpu__clear(struct fpu *fpu)
* Make sure fpstate is cleared and initialized.
*/
if (static_cpu_has(X86_FEATURE_FPU)) {
fpu__activate_curr(fpu);
preempt_disable();
fpu__initialize(fpu);
user_fpu_begin();
copy_init_fpstate_to_fpregs();
preempt_enable();
}
}

2
arch/x86/kernel/fpu/init.c
View File

@ -240,7 +240,7 @@ static void __init fpu__init_system_ctx_switch(void)
WARN_ON_FPU(!on_boot_cpu);
on_boot_cpu = 0;
WARN_ON_FPU(current->thread.fpu.fpstate_active);
WARN_ON_FPU(current->thread.fpu.initialized);
}
/*

50
arch/x86/kernel/fpu/regset.c
View File

@ -16,14 +16,14 @@ int regset_fpregs_active(struct task_struct *target, const struct user_regset *r
{
struct fpu *target_fpu = &target->thread.fpu;
return target_fpu->fpstate_active ? regset->n : 0;
return target_fpu->initialized ? regset->n : 0;
}
int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
{
struct fpu *target_fpu = &target->thread.fpu;
if (boot_cpu_has(X86_FEATURE_FXSR) && target_fpu->fpstate_active)
if (boot_cpu_has(X86_FEATURE_FXSR) && target_fpu->initialized)
return regset->n;
else
return 0;
@ -38,7 +38,7 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
if (!boot_cpu_has(X86_FEATURE_FXSR))
return -ENODEV;
fpu__activate_fpstate_read(fpu);
fpu__prepare_read(fpu);
fpstate_sanitize_xstate(fpu);
return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
@ -55,7 +55,7 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
if (!boot_cpu_has(X86_FEATURE_FXSR))
return -ENODEV;
fpu__activate_fpstate_write(fpu);
fpu__prepare_write(fpu);
fpstate_sanitize_xstate(fpu);
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
@ -89,10 +89,13 @@ int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
xsave = &fpu->state.xsave;
fpu__activate_fpstate_read(fpu);
fpu__prepare_read(fpu);
if (using_compacted_format()) {
ret = copyout_from_xsaves(pos, count, kbuf, ubuf, xsave);
if (kbuf)
ret = copy_xstate_to_kernel(kbuf, xsave, pos, count);
else
ret = copy_xstate_to_user(ubuf, xsave, pos, count);
} else {
fpstate_sanitize_xstate(fpu);
/*
@ -129,12 +132,23 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
xsave = &fpu->state.xsave;
fpu__activate_fpstate_write(fpu);
fpu__prepare_write(fpu);
if (boot_cpu_has(X86_FEATURE_XSAVES))
ret = copyin_to_xsaves(kbuf, ubuf, xsave);
else
if (using_compacted_format()) {
if (kbuf)
ret = copy_kernel_to_xstate(xsave, kbuf);
else
ret = copy_user_to_xstate(xsave, ubuf);
} else {
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, xsave, 0, -1);
if (!ret)
ret = validate_xstate_header(&xsave->header);
}
/*
* mxcsr reserved bits must be masked to zero for security reasons.
*/
xsave->i387.mxcsr &= mxcsr_feature_mask;
/*
* In case of failure, mark all states as init:
@ -142,16 +156,6 @@ int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
if (ret)
fpstate_init(&fpu->state);
/*
* mxcsr reserved bits must be masked to zero for security reasons.
*/
xsave->i387.mxcsr &= mxcsr_feature_mask;
xsave->header.xfeatures &= xfeatures_mask;
/*
* These bits must be zero.
*/
memset(&xsave->header.reserved, 0, 48);
return ret;
}
@ -299,7 +303,7 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset,
struct fpu *fpu = &target->thread.fpu;
struct user_i387_ia32_struct env;
fpu__activate_fpstate_read(fpu);
fpu__prepare_read(fpu);
if (!boot_cpu_has(X86_FEATURE_FPU))
return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
@ -329,7 +333,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
struct user_i387_ia32_struct env;
int ret;
fpu__activate_fpstate_write(fpu);
fpu__prepare_write(fpu);
fpstate_sanitize_xstate(fpu);
if (!boot_cpu_has(X86_FEATURE_FPU))
@ -369,7 +373,7 @@ int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
struct fpu *fpu = &tsk->thread.fpu;
int fpvalid;
fpvalid = fpu->fpstate_active;
fpvalid = fpu->initialized;
if (fpvalid)
fpvalid = !fpregs_get(tsk, NULL,
0, sizeof(struct user_i387_ia32_struct),

37
arch/x86/kernel/fpu/signal.c
View File

@ -155,7 +155,8 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
*/
int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
{
struct xregs_state *xsave = &current->thread.fpu.state.xsave;
struct fpu *fpu = &current->thread.fpu;
struct xregs_state *xsave = &fpu->state.xsave;
struct task_struct *tsk = current;
int ia32_fxstate = (buf != buf_fx);
@ -170,13 +171,13 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
sizeof(struct user_i387_ia32_struct), NULL,
(struct _fpstate_32 __user *) buf) ? -1 : 1;
if (fpregs_active() || using_compacted_format()) {
if (fpu->initialized || using_compacted_format()) {
/* Save the live register state to the user directly. */
if (copy_fpregs_to_sigframe(buf_fx))
return -1;
/* Update the thread's fxstate to save the fsave header. */
if (ia32_fxstate)
copy_fxregs_to_kernel(&tsk->thread.fpu);
copy_fxregs_to_kernel(fpu);
} else {
/*
* It is a *bug* if kernel uses compacted-format for xsave
@ -189,7 +190,7 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
return -1;
}
fpstate_sanitize_xstate(&tsk->thread.fpu);
fpstate_sanitize_xstate(fpu);
if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size))
return -1;
}
@ -213,8 +214,11 @@ sanitize_restored_xstate(struct task_struct *tsk,
struct xstate_header *header = &xsave->header;
if (use_xsave()) {
/* These bits must be zero. */
memset(header->reserved, 0, 48);
/*
* Note: we don't need to zero the reserved bits in the
* xstate_header here because we either didn't copy them at all,
* or we checked earlier that they aren't set.
*/
/*
* Init the state that is not present in the memory
@ -223,7 +227,7 @@ sanitize_restored_xstate(struct task_struct *tsk,
if (fx_only)
header->xfeatures = XFEATURE_MASK_FPSSE;
else
header->xfeatures &= (xfeatures_mask & xfeatures);
header->xfeatures &= xfeatures;
}
if (use_fxsr()) {
@ -279,7 +283,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
if (!access_ok(VERIFY_READ, buf, size))
return -EACCES;
fpu__activate_curr(fpu);
fpu__initialize(fpu);
if (!static_cpu_has(X86_FEATURE_FPU))
return fpregs_soft_set(current, NULL,
@ -307,28 +311,29 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
/*
* 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.
* header. Validate and sanitize the copied state.
*/
struct fpu *fpu = &tsk->thread.fpu;
struct user_i387_ia32_struct env;
int err = 0;
/*
* Drop the current fpu which clears fpu->fpstate_active. This ensures
* Drop the current fpu which clears fpu->initialized. 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
* fpu->fpstate_active is again set.
* fpu->initialized is again set.
*/
fpu__drop(fpu);
if (using_compacted_format()) {
err = copyin_to_xsaves(NULL, buf_fx,
&fpu->state.xsave);
err = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
} else {
err = __copy_from_user(&fpu->state.xsave,
buf_fx, state_size);
err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
if (!err && state_size > offsetof(struct xregs_state, header))
err = validate_xstate_header(&fpu->state.xsave.header);
}
if (err || __copy_from_user(&env, buf, sizeof(env))) {
@ -339,7 +344,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
}
fpu->fpstate_active = 1;
fpu->initialized = 1;
preempt_disable();
fpu__restore(fpu);
preempt_enable();

282
arch/x86/kernel/fpu/xstate.c
View File

@ -483,6 +483,30 @@ int using_compacted_format(void)
return boot_cpu_has(X86_FEATURE_XSAVES);
}
/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */
int validate_xstate_header(const struct xstate_header *hdr)
{
/* No unknown or supervisor features may be set */
if (hdr->xfeatures & (~xfeatures_mask | XFEATURE_MASK_SUPERVISOR))
return -EINVAL;
/* Userspace must use the uncompacted format */
if (hdr->xcomp_bv)
return -EINVAL;
/*
* If 'reserved' is shrunken to add a new field, make sure to validate
* that new field here!
*/
BUILD_BUG_ON(sizeof(hdr->reserved) != 48);
/* No reserved bits may be set */
if (memchr_inv(hdr->reserved, 0, sizeof(hdr->reserved)))
return -EINVAL;
return 0;
}
static void __xstate_dump_leaves(void)
{
int i;
@ -867,7 +891,7 @@ const void *get_xsave_field_ptr(int xsave_state)
{
struct fpu *fpu = &current->thread.fpu;
if (!fpu->fpstate_active)
if (!fpu->initialized)
return NULL;
/*
* fpu__save() takes the CPU's xstate registers
@ -920,48 +944,55 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
}
#endif /* ! CONFIG_ARCH_HAS_PKEYS */
/*
* Weird legacy quirk: SSE and YMM states store information in the
* MXCSR and MXCSR_FLAGS fields of the FP area. That means if the FP
* area is marked as unused in the xfeatures header, we need to copy
* MXCSR and MXCSR_FLAGS if either SSE or YMM are in use.
*/
static inline bool xfeatures_mxcsr_quirk(u64 xfeatures)
{
if (!(xfeatures & (XFEATURE_MASK_SSE|XFEATURE_MASK_YMM)))
return false;
if (xfeatures & XFEATURE_MASK_FP)
return false;
return true;
}
/*
* This is similar to user_regset_copyout(), but will not add offset to
* the source data pointer or increment pos, count, kbuf, and ubuf.
*/
static inline int xstate_copyout(unsigned int pos, unsigned int count,
void *kbuf, void __user *ubuf,
const void *data, const int start_pos,
const int end_pos)
static inline void
__copy_xstate_to_kernel(void *kbuf, const void *data,
unsigned int offset, unsigned int size, unsigned int size_total)
{
if ((count == 0) || (pos < start_pos))
return 0;
if (offset < size_total) {
unsigned int copy = min(size, size_total - offset);
if (end_pos < 0 || pos < end_pos) {
unsigned int copy = (end_pos < 0 ? count : min(count, end_pos - pos));
if (kbuf) {
memcpy(kbuf + pos, data, copy);
} else {
if (__copy_to_user(ubuf + pos, data, copy))
return -EFAULT;
}
memcpy(kbuf + offset, data, copy);
}
return 0;
}
/*
* Convert from kernel XSAVES compacted format to standard format and copy
* to a ptrace buffer. It supports partial copy but pos always starts from
* zero. This is called from xstateregs_get() and there we check the CPU
* has XSAVES.
* to a kernel-space ptrace buffer.
*
* It supports partial copy but pos always starts from zero. This is called
* from xstateregs_get() and there we check the CPU has XSAVES.
*/
int copyout_from_xsaves(unsigned int pos, unsigned int count, void *kbuf,
void __user *ubuf, struct xregs_state *xsave)
int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int offset_start, unsigned int size_total)
{
unsigned int offset, size;
int ret, i;
struct xstate_header header;
int i;
/*
* Currently copy_regset_to_user() starts from pos 0:
*/
if (unlikely(pos != 0))
if (unlikely(offset_start != 0))
return -EFAULT;
/*
@ -977,8 +1008,91 @@ int copyout_from_xsaves(unsigned int pos, unsigned int count, void *kbuf,
offset = offsetof(struct xregs_state, header);
size = sizeof(header);
ret = xstate_copyout(offset, size, kbuf, ubuf, &header, 0, count);
__copy_xstate_to_kernel(kbuf, &header, offset, size, size_total);
for (i = 0; i < XFEATURE_MAX; i++) {
/*
* Copy only in-use xstates:
*/
if ((header.xfeatures >> i) & 1) {
void *src = __raw_xsave_addr(xsave, 1 << i);
offset = xstate_offsets[i];
size = xstate_sizes[i];
/* The next component has to fit fully into the output buffer: */
if (offset + size > size_total)
break;
__copy_xstate_to_kernel(kbuf, src, offset, size, size_total);
}
}
if (xfeatures_mxcsr_quirk(header.xfeatures)) {
offset = offsetof(struct fxregs_state, mxcsr);
size = MXCSR_AND_FLAGS_SIZE;
__copy_xstate_to_kernel(kbuf, &xsave->i387.mxcsr, offset, size, size_total);
}
/*
* Fill xsave->i387.sw_reserved value for ptrace frame:
*/
offset = offsetof(struct fxregs_state, sw_reserved);
size = sizeof(xstate_fx_sw_bytes);
__copy_xstate_to_kernel(kbuf, xstate_fx_sw_bytes, offset, size, size_total);
return 0;
}
static inline int
__copy_xstate_to_user(void __user *ubuf, const void *data, unsigned int offset, unsigned int size, unsigned int size_total)
{
if (!size)
return 0;
if (offset < size_total) {
unsigned int copy = min(size, size_total - offset);
if (__copy_to_user(ubuf + offset, data, copy))
return -EFAULT;
}
return 0;
}
/*
* Convert from kernel XSAVES compacted format to standard format and copy
* to a user-space buffer. It supports partial copy but pos always starts from
* zero. This is called from xstateregs_get() and there we check the CPU
* has XSAVES.
*/
int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned int offset_start, unsigned int size_total)
{
unsigned int offset, size;
int ret, i;
struct xstate_header header;
/*
* Currently copy_regset_to_user() starts from pos 0:
*/
if (unlikely(offset_start != 0))
return -EFAULT;
/*
* The destination is a ptrace buffer; we put in only user xstates:
*/
memset(&header, 0, sizeof(header));
header.xfeatures = xsave->header.xfeatures;
header.xfeatures &= ~XFEATURE_MASK_SUPERVISOR;
/*
* Copy xregs_state->header:
*/
offset = offsetof(struct xregs_state, header);
size = sizeof(header);
ret = __copy_xstate_to_user(ubuf, &header, offset, size, size_total);
if (ret)
return ret;
@ -992,25 +1106,30 @@ int copyout_from_xsaves(unsigned int pos, unsigned int count, void *kbuf,
offset = xstate_offsets[i];
size = xstate_sizes[i];
ret = xstate_copyout(offset, size, kbuf, ubuf, src, 0, count);
/* The next component has to fit fully into the output buffer: */
if (offset + size > size_total)
break;
ret = __copy_xstate_to_user(ubuf, src, offset, size, size_total);
if (ret)
return ret;
if (offset + size >= count)
break;
}
}
if (xfeatures_mxcsr_quirk(header.xfeatures)) {
offset = offsetof(struct fxregs_state, mxcsr);
size = MXCSR_AND_FLAGS_SIZE;
__copy_xstate_to_user(ubuf, &xsave->i387.mxcsr, offset, size, size_total);
}
/*
* Fill xsave->i387.sw_reserved value for ptrace frame:
*/
offset = offsetof(struct fxregs_state, sw_reserved);
size = sizeof(xstate_fx_sw_bytes);
ret = xstate_copyout(offset, size, kbuf, ubuf, xstate_fx_sw_bytes, 0, count);
ret = __copy_xstate_to_user(ubuf, xstate_fx_sw_bytes, offset, size, size_total);
if (ret)
return ret;
@ -1018,55 +1137,42 @@ int copyout_from_xsaves(unsigned int pos, unsigned int count, void *kbuf,
}
/*
* Convert from a ptrace standard-format buffer to kernel XSAVES format
* and copy to the target thread. This is called from xstateregs_set() and
* there we check the CPU has XSAVES and a whole standard-sized buffer
* exists.
* Convert from a ptrace standard-format kernel buffer to kernel XSAVES format
* and copy to the target thread. This is called from xstateregs_set().
*/
int copyin_to_xsaves(const void *kbuf, const void __user *ubuf,
struct xregs_state *xsave)
int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
{
unsigned int offset, size;
int i;
u64 xfeatures;
u64 allowed_features;
struct xstate_header hdr;
offset = offsetof(struct xregs_state, header);
size = sizeof(xfeatures);
size = sizeof(hdr);
if (kbuf) {
memcpy(&xfeatures, kbuf + offset, size);
} else {
if (__copy_from_user(&xfeatures, ubuf + offset, size))
return -EFAULT;
}
memcpy(&hdr, kbuf + offset, size);
/*
* Reject if the user sets any disabled or supervisor features:
*/
allowed_features = xfeatures_mask & ~XFEATURE_MASK_SUPERVISOR;
if (xfeatures & ~allowed_features)
if (validate_xstate_header(&hdr))
return -EINVAL;
for (i = 0; i < XFEATURE_MAX; i++) {
u64 mask = ((u64)1 << i);
if (xfeatures & mask) {
if (hdr.xfeatures & mask) {
void *dst = __raw_xsave_addr(xsave, 1 << i);
offset = xstate_offsets[i];
size = xstate_sizes[i];
if (kbuf) {
memcpy(dst, kbuf + offset, size);
} else {
if (__copy_from_user(dst, ubuf + offset, size))
return -EFAULT;
}
memcpy(dst, kbuf + offset, size);
}
}
if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
offset = offsetof(struct fxregs_state, mxcsr);
size = MXCSR_AND_FLAGS_SIZE;
memcpy(&xsave->i387.mxcsr, kbuf + offset, size);
}
/*
* The state that came in from userspace was user-state only.
* Mask all the user states out of 'xfeatures':
@ -1076,7 +1182,63 @@ int copyin_to_xsaves(const void *kbuf, const void __user *ubuf,
/*
* Add back in the features that came in from userspace:
*/
xsave->header.xfeatures |= xfeatures;
xsave->header.xfeatures |= hdr.xfeatures;
return 0;
}
/*
* Convert from a ptrace or sigreturn standard-format user-space buffer to
* kernel XSAVES format and copy to the target thread. This is called from
* xstateregs_set(), as well as potentially from the sigreturn() and
* rt_sigreturn() system calls.
*/
int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
{
unsigned int offset, size;
int i;
struct xstate_header hdr;
offset = offsetof(struct xregs_state, header);
size = sizeof(hdr);
if (__copy_from_user(&hdr, ubuf + offset, size))
return -EFAULT;
if (validate_xstate_header(&hdr))
return -EINVAL;
for (i = 0; i < XFEATURE_MAX; i++) {
u64 mask = ((u64)1 << i);
if (hdr.xfeatures & mask) {
void *dst = __raw_xsave_addr(xsave, 1 << i);
offset = xstate_offsets[i];
size = xstate_sizes[i];
if (__copy_from_user(dst, ubuf + offset, size))
return -EFAULT;
}
}
if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
offset = offsetof(struct fxregs_state, mxcsr);
size = MXCSR_AND_FLAGS_SIZE;
if (__copy_from_user(&xsave->i387.mxcsr, ubuf + offset, size))
return -EFAULT;
}
/*
* The state that came in from userspace was user-state only.
* Mask all the user states out of 'xfeatures':
*/
xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR;
/*
* Add back in the features that came in from userspace:
*/
xsave->header.xfeatures |= hdr.xfeatures;
return 0;
}

6
arch/x86/kernel/signal.c
View File

@ -263,7 +263,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
sp = (unsigned long) ka->sa.sa_restorer;
}
if (fpu->fpstate_active) {
if (fpu->initialized) {
sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
&buf_fx, &math_size);
*fpstate = (void __user *)sp;
@ -279,7 +279,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
return (void __user *)-1L;
/* save i387 and extended state */
if (fpu->fpstate_active &&
if (fpu->initialized &&
copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0)
return (void __user *)-1L;
@ -755,7 +755,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
/*
* Ensure the signal handler starts with the new fpu state.
*/
if (fpu->fpstate_active)
if (fpu->initialized)
fpu__clear(fpu);
}
signal_setup_done(failed, ksig, stepping);

2
arch/x86/kvm/x86.c
View File

@ -7225,7 +7225,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
int r;
sigset_t sigsaved;
fpu__activate_curr(fpu);
fpu__initialize(fpu);
if (vcpu->sigset_active)
sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved);

2
arch/x86/math-emu/fpu_entry.c
View File

@ -114,7 +114,7 @@ void math_emulate(struct math_emu_info *info)
struct desc_struct code_descriptor;
struct fpu *fpu = &current->thread.fpu;
fpu__activate_curr(fpu);
fpu__initialize(fpu);
#ifdef RE_ENTRANT_CHECKING
if (emulating) {

24
arch/x86/mm/extable.c
View File

@ -2,6 +2,7 @@
#include <linux/uaccess.h>
#include <linux/sched/debug.h>
#include <asm/fpu/internal.h>
#include <asm/traps.h>
#include <asm/kdebug.h>
@ -78,6 +79,29 @@ bool ex_handler_refcount(const struct exception_table_entry *fixup,
}
EXPORT_SYMBOL_GPL(ex_handler_refcount);
/*
* 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)
* 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
* registers of the task previously executing on the CPU. Mitigate this class
* of vulnerability by restoring from the initial state (essentially, zeroing
* out all the FPU registers) if we can't restore from the task's FPU state.
*/
bool ex_handler_fprestore(const struct exception_table_entry *fixup,
struct pt_regs *regs, int trapnr)
{
regs->ip = ex_fixup_addr(fixup);
WARN_ONCE(1, "Bad FPU state detected at %pB, reinitializing FPU registers.",
(void *)instruction_pointer(regs));
__copy_kernel_to_fpregs(&init_fpstate, -1);
return true;
}
EXPORT_SYMBOL_GPL(ex_handler_fprestore);
bool ex_handler_ext(const struct exception_table_entry *fixup,
struct pt_regs *regs, int trapnr)
{

3
arch/x86/mm/pkeys.c
View File

@ -18,7 +18,6 @@
#include <asm/cpufeature.h> /* boot_cpu_has, ... */
#include <asm/mmu_context.h> /* vma_pkey() */
#include <asm/fpu/internal.h> /* fpregs_active() */
int __execute_only_pkey(struct mm_struct *mm)
{
@ -45,7 +44,7 @@ int __execute_only_pkey(struct mm_struct *mm)
*/
preempt_disable();
if (!need_to_set_mm_pkey &&
fpregs_active() &&
current->thread.fpu.initialized &&
!__pkru_allows_read(read_pkru(), execute_only_pkey)) {
preempt_enable();
return execute_only_pkey;