forked from Minki/linux
f94edacf99
This moves the bit that indicates whether a thread has ownership of the FPU from the TS_USEDFPU bit in thread_info->status to a word of its own (called 'has_fpu') in task_struct->thread.has_fpu. This fixes two independent bugs at the same time: - changing 'thread_info->status' from the scheduler causes nasty problems for the other users of that variable, since it is defined to be thread-synchronous (that's what the "TS_" part of the naming was supposed to indicate). So perfectly valid code could (and did) do ti->status |= TS_RESTORE_SIGMASK; and the compiler was free to do that as separate load, or and store instructions. Which can cause problems with preemption, since a task switch could happen in between, and change the TS_USEDFPU bit. The change to TS_USEDFPU would be overwritten by the final store. In practice, this seldom happened, though, because the 'status' field was seldom used more than once, so gcc would generally tend to generate code that used a read-modify-write instruction and thus happened to avoid this problem - RMW instructions are naturally low fat and preemption-safe. - On x86-32, the current_thread_info() pointer would, during interrupts and softirqs, point to a *copy* of the real thread_info, because x86-32 uses %esp to calculate the thread_info address, and thus the separate irq (and softirq) stacks would cause these kinds of odd thread_info copy aliases. This is normally not a problem, since interrupts aren't supposed to look at thread information anyway (what thread is running at interrupt time really isn't very well-defined), but it confused the heck out of irq_fpu_usable() and the code that tried to squirrel away the FPU state. (It also caused untold confusion for us poor kernel developers). It also turns out that using 'task_struct' is actually much more natural for most of the call sites that care about the FPU state, since they tend to work with the task struct for other reasons anyway (ie scheduling). And the FPU data that we are going to save/restore is found there too. Thanks to Arjan Van De Ven <arjan@linux.intel.com> for pointing us to the %esp issue. Cc: Arjan van de Ven <arjan@linux.intel.com> Reported-and-tested-by: Raphael Prevost <raphael@buro.asia> Acked-and-tested-by: Suresh Siddha <suresh.b.siddha@intel.com> Tested-by: Peter Anvin <hpa@zytor.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
552 lines
13 KiB
C
552 lines
13 KiB
C
/*
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* Copyright (C) 1994 Linus Torvalds
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*
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* Pentium III FXSR, SSE support
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* General FPU state handling cleanups
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* Gareth Hughes <gareth@valinux.com>, May 2000
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* x86-64 work by Andi Kleen 2002
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*/
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#ifndef _ASM_X86_I387_H
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#define _ASM_X86_I387_H
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#ifndef __ASSEMBLY__
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#include <linux/sched.h>
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#include <linux/kernel_stat.h>
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#include <linux/regset.h>
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#include <linux/hardirq.h>
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#include <linux/slab.h>
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#include <asm/asm.h>
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#include <asm/cpufeature.h>
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#include <asm/processor.h>
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#include <asm/sigcontext.h>
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#include <asm/user.h>
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#include <asm/uaccess.h>
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#include <asm/xsave.h>
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extern unsigned int sig_xstate_size;
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extern void fpu_init(void);
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extern void mxcsr_feature_mask_init(void);
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extern int init_fpu(struct task_struct *child);
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extern void math_state_restore(void);
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extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
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extern user_regset_active_fn fpregs_active, xfpregs_active;
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extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get,
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xstateregs_get;
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extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set,
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xstateregs_set;
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/*
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* xstateregs_active == fpregs_active. Please refer to the comment
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* at the definition of fpregs_active.
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*/
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#define xstateregs_active fpregs_active
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extern struct _fpx_sw_bytes fx_sw_reserved;
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#ifdef CONFIG_IA32_EMULATION
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extern unsigned int sig_xstate_ia32_size;
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extern struct _fpx_sw_bytes fx_sw_reserved_ia32;
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struct _fpstate_ia32;
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struct _xstate_ia32;
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extern int save_i387_xstate_ia32(void __user *buf);
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extern int restore_i387_xstate_ia32(void __user *buf);
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#endif
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#ifdef CONFIG_MATH_EMULATION
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extern void finit_soft_fpu(struct i387_soft_struct *soft);
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#else
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static inline void finit_soft_fpu(struct i387_soft_struct *soft) {}
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#endif
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#define X87_FSW_ES (1 << 7) /* Exception Summary */
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static __always_inline __pure bool use_xsaveopt(void)
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{
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return static_cpu_has(X86_FEATURE_XSAVEOPT);
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}
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static __always_inline __pure bool use_xsave(void)
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{
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return static_cpu_has(X86_FEATURE_XSAVE);
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}
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static __always_inline __pure bool use_fxsr(void)
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{
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return static_cpu_has(X86_FEATURE_FXSR);
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}
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extern void __sanitize_i387_state(struct task_struct *);
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static inline void sanitize_i387_state(struct task_struct *tsk)
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{
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if (!use_xsaveopt())
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return;
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__sanitize_i387_state(tsk);
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}
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#ifdef CONFIG_X86_64
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static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
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{
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int err;
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/* See comment in fxsave() below. */
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#ifdef CONFIG_AS_FXSAVEQ
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asm volatile("1: fxrstorq %[fx]\n\t"
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"2:\n"
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".section .fixup,\"ax\"\n"
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"3: movl $-1,%[err]\n"
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" jmp 2b\n"
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".previous\n"
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_ASM_EXTABLE(1b, 3b)
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: [err] "=r" (err)
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: [fx] "m" (*fx), "0" (0));
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#else
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asm volatile("1: rex64/fxrstor (%[fx])\n\t"
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"2:\n"
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".section .fixup,\"ax\"\n"
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"3: movl $-1,%[err]\n"
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" jmp 2b\n"
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".previous\n"
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_ASM_EXTABLE(1b, 3b)
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: [err] "=r" (err)
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: [fx] "R" (fx), "m" (*fx), "0" (0));
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#endif
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return err;
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}
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static inline int fxsave_user(struct i387_fxsave_struct __user *fx)
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{
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int err;
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/*
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* Clear the bytes not touched by the fxsave and reserved
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* for the SW usage.
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*/
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err = __clear_user(&fx->sw_reserved,
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sizeof(struct _fpx_sw_bytes));
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if (unlikely(err))
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return -EFAULT;
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/* See comment in fxsave() below. */
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#ifdef CONFIG_AS_FXSAVEQ
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asm volatile("1: fxsaveq %[fx]\n\t"
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"2:\n"
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".section .fixup,\"ax\"\n"
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"3: movl $-1,%[err]\n"
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" jmp 2b\n"
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".previous\n"
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_ASM_EXTABLE(1b, 3b)
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: [err] "=r" (err), [fx] "=m" (*fx)
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: "0" (0));
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#else
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asm volatile("1: rex64/fxsave (%[fx])\n\t"
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"2:\n"
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".section .fixup,\"ax\"\n"
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"3: movl $-1,%[err]\n"
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" jmp 2b\n"
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".previous\n"
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_ASM_EXTABLE(1b, 3b)
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: [err] "=r" (err), "=m" (*fx)
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: [fx] "R" (fx), "0" (0));
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#endif
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if (unlikely(err) &&
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__clear_user(fx, sizeof(struct i387_fxsave_struct)))
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err = -EFAULT;
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/* No need to clear here because the caller clears USED_MATH */
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return err;
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}
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static inline void fpu_fxsave(struct fpu *fpu)
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{
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/* Using "rex64; fxsave %0" is broken because, if the memory operand
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uses any extended registers for addressing, a second REX prefix
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will be generated (to the assembler, rex64 followed by semicolon
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is a separate instruction), and hence the 64-bitness is lost. */
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#ifdef CONFIG_AS_FXSAVEQ
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/* Using "fxsaveq %0" would be the ideal choice, but is only supported
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starting with gas 2.16. */
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__asm__ __volatile__("fxsaveq %0"
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: "=m" (fpu->state->fxsave));
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#else
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/* Using, as a workaround, the properly prefixed form below isn't
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accepted by any binutils version so far released, complaining that
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the same type of prefix is used twice if an extended register is
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needed for addressing (fix submitted to mainline 2005-11-21).
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asm volatile("rex64/fxsave %0"
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: "=m" (fpu->state->fxsave));
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This, however, we can work around by forcing the compiler to select
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an addressing mode that doesn't require extended registers. */
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asm volatile("rex64/fxsave (%[fx])"
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: "=m" (fpu->state->fxsave)
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: [fx] "R" (&fpu->state->fxsave));
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#endif
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}
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#else /* CONFIG_X86_32 */
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/* perform fxrstor iff the processor has extended states, otherwise frstor */
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static inline int fxrstor_checking(struct i387_fxsave_struct *fx)
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{
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/*
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* The "nop" is needed to make the instructions the same
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* length.
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*/
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alternative_input(
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"nop ; frstor %1",
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"fxrstor %1",
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X86_FEATURE_FXSR,
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"m" (*fx));
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return 0;
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}
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static inline void fpu_fxsave(struct fpu *fpu)
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{
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asm volatile("fxsave %[fx]"
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: [fx] "=m" (fpu->state->fxsave));
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}
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#endif /* CONFIG_X86_64 */
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/*
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* These must be called with preempt disabled
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*/
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static inline void fpu_save_init(struct fpu *fpu)
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{
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if (use_xsave()) {
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fpu_xsave(fpu);
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/*
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* xsave header may indicate the init state of the FP.
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*/
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if (!(fpu->state->xsave.xsave_hdr.xstate_bv & XSTATE_FP))
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return;
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} else if (use_fxsr()) {
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fpu_fxsave(fpu);
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} else {
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asm volatile("fnsave %[fx]; fwait"
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: [fx] "=m" (fpu->state->fsave));
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return;
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}
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if (unlikely(fpu->state->fxsave.swd & X87_FSW_ES))
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asm volatile("fnclex");
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}
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static inline void __save_init_fpu(struct task_struct *tsk)
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{
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fpu_save_init(&tsk->thread.fpu);
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}
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static inline int fpu_fxrstor_checking(struct fpu *fpu)
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{
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return fxrstor_checking(&fpu->state->fxsave);
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}
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static inline int fpu_restore_checking(struct fpu *fpu)
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{
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if (use_xsave())
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return fpu_xrstor_checking(fpu);
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else
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return fpu_fxrstor_checking(fpu);
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}
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static inline int restore_fpu_checking(struct task_struct *tsk)
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{
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return fpu_restore_checking(&tsk->thread.fpu);
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}
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/*
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* Software FPU state helpers. Careful: these need to
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* be preemption protection *and* they need to be
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* properly paired with the CR0.TS changes!
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*/
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static inline int __thread_has_fpu(struct task_struct *tsk)
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{
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return tsk->thread.has_fpu;
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}
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/* Must be paired with an 'stts' after! */
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static inline void __thread_clear_has_fpu(struct task_struct *tsk)
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{
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tsk->thread.has_fpu = 0;
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}
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/* Must be paired with a 'clts' before! */
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static inline void __thread_set_has_fpu(struct task_struct *tsk)
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{
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tsk->thread.has_fpu = 1;
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}
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/*
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* Encapsulate the CR0.TS handling together with the
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* software flag.
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*
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* These generally need preemption protection to work,
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* do try to avoid using these on their own.
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*/
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static inline void __thread_fpu_end(struct task_struct *tsk)
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{
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__thread_clear_has_fpu(tsk);
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stts();
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}
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static inline void __thread_fpu_begin(struct task_struct *tsk)
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{
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clts();
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__thread_set_has_fpu(tsk);
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}
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/*
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* Signal frame handlers...
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*/
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extern int save_i387_xstate(void __user *buf);
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extern int restore_i387_xstate(void __user *buf);
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static inline void __unlazy_fpu(struct task_struct *tsk)
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{
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if (__thread_has_fpu(tsk)) {
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__save_init_fpu(tsk);
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__thread_fpu_end(tsk);
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} else
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tsk->fpu_counter = 0;
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}
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static inline void __clear_fpu(struct task_struct *tsk)
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{
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if (__thread_has_fpu(tsk)) {
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/* Ignore delayed exceptions from user space */
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asm volatile("1: fwait\n"
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"2:\n"
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_ASM_EXTABLE(1b, 2b));
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__thread_fpu_end(tsk);
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}
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}
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/*
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* Were we in an interrupt that interrupted kernel mode?
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*
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* We can do a kernel_fpu_begin/end() pair *ONLY* if that
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* pair does nothing at all: the thread must not have fpu (so
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* that we don't try to save the FPU state), and TS must
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* be set (so that the clts/stts pair does nothing that is
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* visible in the interrupted kernel thread).
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*/
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static inline bool interrupted_kernel_fpu_idle(void)
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{
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return !__thread_has_fpu(current) &&
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(read_cr0() & X86_CR0_TS);
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}
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/*
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* Were we in user mode (or vm86 mode) when we were
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* interrupted?
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*
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* Doing kernel_fpu_begin/end() is ok if we are running
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* in an interrupt context from user mode - we'll just
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* save the FPU state as required.
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*/
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static inline bool interrupted_user_mode(void)
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{
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struct pt_regs *regs = get_irq_regs();
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return regs && user_mode_vm(regs);
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}
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/*
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* Can we use the FPU in kernel mode with the
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* whole "kernel_fpu_begin/end()" sequence?
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*
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* It's always ok in process context (ie "not interrupt")
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* but it is sometimes ok even from an irq.
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*/
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static inline bool irq_fpu_usable(void)
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{
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return !in_interrupt() ||
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interrupted_user_mode() ||
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interrupted_kernel_fpu_idle();
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}
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static inline void kernel_fpu_begin(void)
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{
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struct task_struct *me = current;
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WARN_ON_ONCE(!irq_fpu_usable());
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preempt_disable();
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if (__thread_has_fpu(me)) {
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__save_init_fpu(me);
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__thread_clear_has_fpu(me);
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/* We do 'stts()' in kernel_fpu_end() */
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} else
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clts();
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}
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static inline void kernel_fpu_end(void)
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{
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stts();
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preempt_enable();
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}
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/*
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* Some instructions like VIA's padlock instructions generate a spurious
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* DNA fault but don't modify SSE registers. And these instructions
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* get used from interrupt context as well. To prevent these kernel instructions
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* in interrupt context interacting wrongly with other user/kernel fpu usage, we
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* should use them only in the context of irq_ts_save/restore()
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*/
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static inline int irq_ts_save(void)
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{
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/*
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* If in process context and not atomic, we can take a spurious DNA fault.
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* Otherwise, doing clts() in process context requires disabling preemption
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* or some heavy lifting like kernel_fpu_begin()
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*/
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if (!in_atomic())
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return 0;
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if (read_cr0() & X86_CR0_TS) {
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clts();
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return 1;
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}
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return 0;
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}
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static inline void irq_ts_restore(int TS_state)
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{
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if (TS_state)
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stts();
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}
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/*
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* The question "does this thread have fpu access?"
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* is slightly racy, since preemption could come in
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* and revoke it immediately after the test.
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*
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* However, even in that very unlikely scenario,
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* we can just assume we have FPU access - typically
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* to save the FP state - we'll just take a #NM
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* fault and get the FPU access back.
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*
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* The actual user_fpu_begin/end() functions
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* need to be preemption-safe, though.
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*
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* NOTE! user_fpu_end() must be used only after you
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* have saved the FP state, and user_fpu_begin() must
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* be used only immediately before restoring it.
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* These functions do not do any save/restore on
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* their own.
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*/
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static inline int user_has_fpu(void)
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{
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return __thread_has_fpu(current);
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}
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static inline void user_fpu_end(void)
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{
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preempt_disable();
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__thread_fpu_end(current);
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preempt_enable();
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}
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static inline void user_fpu_begin(void)
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{
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preempt_disable();
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if (!user_has_fpu())
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__thread_fpu_begin(current);
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preempt_enable();
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}
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/*
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* These disable preemption on their own and are safe
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*/
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static inline void save_init_fpu(struct task_struct *tsk)
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{
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WARN_ON_ONCE(!__thread_has_fpu(tsk));
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preempt_disable();
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__save_init_fpu(tsk);
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__thread_fpu_end(tsk);
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preempt_enable();
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}
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static inline void unlazy_fpu(struct task_struct *tsk)
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{
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preempt_disable();
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__unlazy_fpu(tsk);
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preempt_enable();
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}
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static inline void clear_fpu(struct task_struct *tsk)
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{
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preempt_disable();
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__clear_fpu(tsk);
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preempt_enable();
|
|
}
|
|
|
|
/*
|
|
* i387 state interaction
|
|
*/
|
|
static inline unsigned short get_fpu_cwd(struct task_struct *tsk)
|
|
{
|
|
if (cpu_has_fxsr) {
|
|
return tsk->thread.fpu.state->fxsave.cwd;
|
|
} else {
|
|
return (unsigned short)tsk->thread.fpu.state->fsave.cwd;
|
|
}
|
|
}
|
|
|
|
static inline unsigned short get_fpu_swd(struct task_struct *tsk)
|
|
{
|
|
if (cpu_has_fxsr) {
|
|
return tsk->thread.fpu.state->fxsave.swd;
|
|
} else {
|
|
return (unsigned short)tsk->thread.fpu.state->fsave.swd;
|
|
}
|
|
}
|
|
|
|
static inline unsigned short get_fpu_mxcsr(struct task_struct *tsk)
|
|
{
|
|
if (cpu_has_xmm) {
|
|
return tsk->thread.fpu.state->fxsave.mxcsr;
|
|
} else {
|
|
return MXCSR_DEFAULT;
|
|
}
|
|
}
|
|
|
|
static bool fpu_allocated(struct fpu *fpu)
|
|
{
|
|
return fpu->state != NULL;
|
|
}
|
|
|
|
static inline int fpu_alloc(struct fpu *fpu)
|
|
{
|
|
if (fpu_allocated(fpu))
|
|
return 0;
|
|
fpu->state = kmem_cache_alloc(task_xstate_cachep, GFP_KERNEL);
|
|
if (!fpu->state)
|
|
return -ENOMEM;
|
|
WARN_ON((unsigned long)fpu->state & 15);
|
|
return 0;
|
|
}
|
|
|
|
static inline void fpu_free(struct fpu *fpu)
|
|
{
|
|
if (fpu->state) {
|
|
kmem_cache_free(task_xstate_cachep, fpu->state);
|
|
fpu->state = NULL;
|
|
}
|
|
}
|
|
|
|
static inline void fpu_copy(struct fpu *dst, struct fpu *src)
|
|
{
|
|
memcpy(dst->state, src->state, xstate_size);
|
|
}
|
|
|
|
extern void fpu_finit(struct fpu *fpu);
|
|
|
|
#endif /* __ASSEMBLY__ */
|
|
|
|
#endif /* _ASM_X86_I387_H */
|