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x86/fpu: Move fpregs_restore_userregs() to core

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Only used internally in the FPU core code.

While at it, convert to the percpu accessors which verify preemption is
disabled.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011539.686806639@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-10-15 03:16:30 +02:00 committed by Borislav Petkov
parent cdcb6fa14e
commit 9848fb9683
5 changed files with 88 additions and 83 deletions
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83
arch/x86/include/asm/fpu/internal.h
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@ -55,89 +55,6 @@ extern void restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask);
extern bool copy_fpstate_to_sigframe(void __user *buf, void __user *fp, int size);
/*
* FPU context switch related helper methods:
*/
DECLARE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
/*
* The in-register FPU state for an FPU context on a CPU is assumed to be
* valid if the fpu->last_cpu matches the CPU, and the fpu_fpregs_owner_ctx
* matches the FPU.
*
* If the FPU register state is valid, the kernel can skip restoring the
* FPU state from memory.
*
* Any code that clobbers the FPU registers or updates the in-memory
* FPU state for a task MUST let the rest of the kernel know that the
* FPU registers are no longer valid for this task.
*
* Either one of these invalidation functions is enough. Invalidate
* a resource you control: CPU if using the CPU for something else
* (with preemption disabled), FPU for the current task, or a task that
* is prevented from running by the current task.
*/
static inline void __cpu_invalidate_fpregs_state(void)
{
__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
}
static inline void __fpu_invalidate_fpregs_state(struct fpu *fpu)
{
fpu->last_cpu = -1;
}
static inline int fpregs_state_valid(struct fpu *fpu, unsigned int cpu)
{
return fpu == this_cpu_read(fpu_fpregs_owner_ctx) && cpu == fpu->last_cpu;
}
/*
* These generally need preemption protection to work,
* do try to avoid using these on their own:
*/
static inline void fpregs_deactivate(struct fpu *fpu)
{
this_cpu_write(fpu_fpregs_owner_ctx, NULL);
trace_x86_fpu_regs_deactivated(fpu);
}
static inline void fpregs_activate(struct fpu *fpu)
{
this_cpu_write(fpu_fpregs_owner_ctx, fpu);
trace_x86_fpu_regs_activated(fpu);
}
/* Internal helper for switch_fpu_return() and signal frame setup */
static inline void fpregs_restore_userregs(void)
{
struct fpu *fpu = &current->thread.fpu;
int cpu = smp_processor_id();
if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
return;
if (!fpregs_state_valid(fpu, cpu)) {
u64 mask;
/*
* This restores _all_ xstate which has not been
* established yet.
*
* 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.
*/
mask = xfeatures_mask_restore_user() |
xfeatures_mask_supervisor();
restore_fpregs_from_fpstate(&fpu->state, mask);
fpregs_activate(fpu);
fpu->last_cpu = cpu;
}
clear_thread_flag(TIF_NEED_FPU_LOAD);
}
#endif /* _ASM_X86_FPU_INTERNAL_H */

85
arch/x86/kernel/fpu/context.h Normal file
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@ -0,0 +1,85 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __X86_KERNEL_FPU_CONTEXT_H
#define __X86_KERNEL_FPU_CONTEXT_H
#include <asm/fpu/xstate.h>
#include <asm/trace/fpu.h>
/* Functions related to FPU context tracking */
/*
* The in-register FPU state for an FPU context on a CPU is assumed to be
* valid if the fpu->last_cpu matches the CPU, and the fpu_fpregs_owner_ctx
* matches the FPU.
*
* If the FPU register state is valid, the kernel can skip restoring the
* FPU state from memory.
*
* Any code that clobbers the FPU registers or updates the in-memory
* FPU state for a task MUST let the rest of the kernel know that the
* FPU registers are no longer valid for this task.
*
* Either one of these invalidation functions is enough. Invalidate
* a resource you control: CPU if using the CPU for something else
* (with preemption disabled), FPU for the current task, or a task that
* is prevented from running by the current task.
*/
static inline void __cpu_invalidate_fpregs_state(void)
{
__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
}
static inline void __fpu_invalidate_fpregs_state(struct fpu *fpu)
{
fpu->last_cpu = -1;
}
static inline int fpregs_state_valid(struct fpu *fpu, unsigned int cpu)
{
return fpu == this_cpu_read(fpu_fpregs_owner_ctx) && cpu == fpu->last_cpu;
}
static inline void fpregs_deactivate(struct fpu *fpu)
{
__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
trace_x86_fpu_regs_deactivated(fpu);
}
static inline void fpregs_activate(struct fpu *fpu)
{
__this_cpu_write(fpu_fpregs_owner_ctx, fpu);
trace_x86_fpu_regs_activated(fpu);
}
/* Internal helper for switch_fpu_return() and signal frame setup */
static inline void fpregs_restore_userregs(void)
{
struct fpu *fpu = &current->thread.fpu;
int cpu = smp_processor_id();
if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
return;
if (!fpregs_state_valid(fpu, cpu)) {
u64 mask;
/*
* This restores _all_ xstate which has not been
* established yet.
*
* 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.
*/
mask = xfeatures_mask_restore_user() |
xfeatures_mask_supervisor();
restore_fpregs_from_fpstate(&fpu->state, mask);
fpregs_activate(fpu);
fpu->last_cpu = cpu;
}
clear_thread_flag(TIF_NEED_FPU_LOAD);
}
#endif

1
arch/x86/kernel/fpu/core.c
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@ -17,6 +17,7 @@
#include <linux/hardirq.h>
#include <linux/pkeys.h>
#include "context.h"
#include "internal.h"
#include "legacy.h"
#include "xstate.h"

1
arch/x86/kernel/fpu/regset.c
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@ -10,6 +10,7 @@
#include <asm/fpu/regset.h>
#include <asm/fpu/xstate.h>
#include "context.h"
#include "internal.h"
/*

1
arch/x86/kernel/fpu/signal.c
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@ -16,6 +16,7 @@
#include <asm/trapnr.h>
#include <asm/trace/fpu.h>
#include "context.h"
#include "internal.h"
#include "legacy.h"
#include "xstate.h"