arch/x86/include/asm/thread_info.h

   1 /* thread_info.h: low-level thread information
   2  *
   3  * Copyright (C) 2002  David Howells (dhowells@redhat.com)
   4  * - Incorporating suggestions made by Linus Torvalds and Dave Miller
   5  */
   6
   7 #ifndef _ASM_X86_THREAD_INFO_H
   8 #define _ASM_X86_THREAD_INFO_H
   9
  10 #include <linux/compiler.h>
  11 #include <asm/page.h>
  12 #include <asm/percpu.h>
  13 #include <asm/types.h>
  14
  15 /*
  16  * TOP_OF_KERNEL_STACK_PADDING is a number of unused bytes that we
  17  * reserve at the top of the kernel stack.  We do it because of a nasty
  18  * 32-bit corner case.  On x86_32, the hardware stack frame is
  19  * variable-length.  Except for vm86 mode, struct pt_regs assumes a
  20  * maximum-length frame.  If we enter from CPL 0, the top 8 bytes of
  21  * pt_regs don't actually exist.  Ordinarily this doesn't matter, but it
  22  * does in at least one case:
  23  *
  24  * If we take an NMI early enough in SYSENTER, then we can end up with
  25  * pt_regs that extends above sp0.  On the way out, in the espfix code,
  26  * we can read the saved SS value, but that value will be above sp0.
  27  * Without this offset, that can result in a page fault.  (We are
  28  * careful that, in this case, the value we read doesn't matter.)
  29  *
  30  * In vm86 mode, the hardware frame is much longer still, so add 16
  31  * bytes to make room for the real-mode segments.
  32  *
  33  * x86_64 has a fixed-length stack frame.
  34  */
  35 #ifdef CONFIG_X86_32
  36 # ifdef CONFIG_VM86
  37 #  define TOP_OF_KERNEL_STACK_PADDING 16
  38 # else
  39 #  define TOP_OF_KERNEL_STACK_PADDING 8
  40 # endif
  41 #else
  42 # define TOP_OF_KERNEL_STACK_PADDING 0
  43 #endif
  44
  45 /*
  46  * low level task data that entry.S needs immediate access to
  47  * - this struct should fit entirely inside of one cache line
  48  * - this struct shares the supervisor stack pages
  49  */
  50 #ifndef __ASSEMBLY__
  51 struct task_struct;
  52 #include <asm/cpufeature.h>
  53 #include <linux/atomic.h>
  54
  55 struct thread_info {
  56         struct task_struct      *task;          /* main task structure */
  57         __u32                   flags;          /* low level flags */
  58         __u32                   status;         /* thread synchronous flags */
  59         __u32                   cpu;            /* current CPU */
  60 };
  61
  62 #define INIT_THREAD_INFO(tsk)                   \
  63 {                                               \
  64         .task           = &tsk,                 \
  65         .flags          = 0,                    \
  66         .cpu            = 0,                    \
  67 }
  68
  69 #define init_thread_info        (init_thread_union.thread_info)
  70 #define init_stack              (init_thread_union.stack)
  71
  72 #else /* !__ASSEMBLY__ */
  73
  74 #include <asm/asm-offsets.h>
  75
  76 #endif
  77
  78 /*
  79  * thread information flags
  80  * - these are process state flags that various assembly files
  81  *   may need to access
  82  * - pending work-to-be-done flags are in LSW
  83  * - other flags in MSW
  84  * Warning: layout of LSW is hardcoded in entry.S
  85  */
  86 #define TIF_SYSCALL_TRACE       0       /* syscall trace active */
  87 #define TIF_NOTIFY_RESUME       1       /* callback before returning to user */
  88 #define TIF_SIGPENDING          2       /* signal pending */
  89 #define TIF_NEED_RESCHED        3       /* rescheduling necessary */
  90 #define TIF_SINGLESTEP          4       /* reenable singlestep on user return*/
  91 #define TIF_SYSCALL_EMU         6       /* syscall emulation active */
  92 #define TIF_SYSCALL_AUDIT       7       /* syscall auditing active */
  93 #define TIF_SECCOMP             8       /* secure computing */
  94 #define TIF_USER_RETURN_NOTIFY  11      /* notify kernel of userspace return */
  95 #define TIF_UPROBE              12      /* breakpointed or singlestepping */
  96 #define TIF_NOTSC               16      /* TSC is not accessible in userland */
  97 #define TIF_IA32                17      /* IA32 compatibility process */
  98 #define TIF_FORK                18      /* ret_from_fork */
  99 #define TIF_NOHZ                19      /* in adaptive nohz mode */
 100 #define TIF_MEMDIE              20      /* is terminating due to OOM killer */
 101 #define TIF_POLLING_NRFLAG      21      /* idle is polling for TIF_NEED_RESCHED */
 102 #define TIF_IO_BITMAP           22      /* uses I/O bitmap */
 103 #define TIF_FORCED_TF           24      /* true if TF in eflags artificially */
 104 #define TIF_BLOCKSTEP           25      /* set when we want DEBUGCTLMSR_BTF */
 105 #define TIF_LAZY_MMU_UPDATES    27      /* task is updating the mmu lazily */
 106 #define TIF_SYSCALL_TRACEPOINT  28      /* syscall tracepoint instrumentation */
 107 #define TIF_ADDR32              29      /* 32-bit address space on 64 bits */
 108 #define TIF_X32                 30      /* 32-bit native x86-64 binary */
 109
 110 #define _TIF_SYSCALL_TRACE      (1 << TIF_SYSCALL_TRACE)
 111 #define _TIF_NOTIFY_RESUME      (1 << TIF_NOTIFY_RESUME)
 112 #define _TIF_SIGPENDING         (1 << TIF_SIGPENDING)
 113 #define _TIF_SINGLESTEP         (1 << TIF_SINGLESTEP)
 114 #define _TIF_NEED_RESCHED       (1 << TIF_NEED_RESCHED)
 115 #define _TIF_SYSCALL_EMU        (1 << TIF_SYSCALL_EMU)
 116 #define _TIF_SYSCALL_AUDIT      (1 << TIF_SYSCALL_AUDIT)
 117 #define _TIF_SECCOMP            (1 << TIF_SECCOMP)
 118 #define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY)
 119 #define _TIF_UPROBE             (1 << TIF_UPROBE)
 120 #define _TIF_NOTSC              (1 << TIF_NOTSC)
 121 #define _TIF_IA32               (1 << TIF_IA32)
 122 #define _TIF_FORK               (1 << TIF_FORK)
 123 #define _TIF_NOHZ               (1 << TIF_NOHZ)
 124 #define _TIF_POLLING_NRFLAG     (1 << TIF_POLLING_NRFLAG)
 125 #define _TIF_IO_BITMAP          (1 << TIF_IO_BITMAP)
 126 #define _TIF_FORCED_TF          (1 << TIF_FORCED_TF)
 127 #define _TIF_BLOCKSTEP          (1 << TIF_BLOCKSTEP)
 128 #define _TIF_LAZY_MMU_UPDATES   (1 << TIF_LAZY_MMU_UPDATES)
 129 #define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
 130 #define _TIF_ADDR32             (1 << TIF_ADDR32)
 131 #define _TIF_X32                (1 << TIF_X32)
 132
 133 /*
 134  * work to do in syscall_trace_enter().  Also includes TIF_NOHZ for
 135  * enter_from_user_mode()
 136  */
 137 #define _TIF_WORK_SYSCALL_ENTRY \
 138         (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT |   \
 139          _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT |       \
 140          _TIF_NOHZ)
 141
 142 /* work to do on any return to user space */
 143 #define _TIF_ALLWORK_MASK                                               \
 144         ((0x0000FFFF & ~_TIF_SECCOMP) | _TIF_SYSCALL_TRACEPOINT |       \
 145         _TIF_NOHZ)
 146
 147 /* flags to check in __switch_to() */
 148 #define _TIF_WORK_CTXSW                                                 \
 149         (_TIF_IO_BITMAP|_TIF_NOTSC|_TIF_BLOCKSTEP)
 150
 151 #define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
 152 #define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
 153
 154 #define STACK_WARN              (THREAD_SIZE/8)
 155
 156 /*
 157  * macros/functions for gaining access to the thread information structure
 158  *
 159  * preempt_count needs to be 1 initially, until the scheduler is functional.
 160  */
 161 #ifndef __ASSEMBLY__
 162
 163 static inline struct thread_info *current_thread_info(void)
 164 {
 165         return (struct thread_info *)(current_top_of_stack() - THREAD_SIZE);
 166 }
 167
 168 static inline unsigned long current_stack_pointer(void)
 169 {
 170         unsigned long sp;
 171 #ifdef CONFIG_X86_64
 172         asm("mov %%rsp,%0" : "=g" (sp));
 173 #else
 174         asm("mov %%esp,%0" : "=g" (sp));
 175 #endif
 176         return sp;
 177 }
 178
 179 #else /* !__ASSEMBLY__ */
 180
 181 #ifdef CONFIG_X86_64
 182 # define cpu_current_top_of_stack (cpu_tss + TSS_sp0)
 183 #endif
 184
 185 /*
 186  * ASM operand which evaluates to a 'thread_info' address of
 187  * the current task, if it is known that "reg" is exactly "off"
 188  * bytes below the top of the stack currently.
 189  *
 190  * ( The kernel stack's size is known at build time, it is usually
 191  *   2 or 4 pages, and the bottom  of the kernel stack contains
 192  *   the thread_info structure. So to access the thread_info very
 193  *   quickly from assembly code we can calculate down from the
 194  *   top of the kernel stack to the bottom, using constant,
 195  *   build-time calculations only. )
 196  *
 197  * For example, to fetch the current thread_info->flags value into %eax
 198  * on x86-64 defconfig kernels, in syscall entry code where RSP is
 199  * currently at exactly SIZEOF_PTREGS bytes away from the top of the
 200  * stack:
 201  *
 202  *      mov ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS), %eax
 203  *
 204  * will translate to:
 205  *
 206  *      8b 84 24 b8 c0 ff ff      mov    -0x3f48(%rsp), %eax
 207  *
 208  * which is below the current RSP by almost 16K.
 209  */
 210 #define ASM_THREAD_INFO(field, reg, off) ((field)+(off)-THREAD_SIZE)(reg)
 211
 212 #endif
 213
 214 /*
 215  * Thread-synchronous status.
 216  *
 217  * This is different from the flags in that nobody else
 218  * ever touches our thread-synchronous status, so we don't
 219  * have to worry about atomic accesses.
 220  */
 221 #define TS_COMPAT               0x0002  /* 32bit syscall active (64BIT)*/
 222 #ifdef CONFIG_COMPAT
 223 #define TS_I386_REGS_POKED      0x0004  /* regs poked by 32-bit ptracer */
 224 #endif
 225
 226 #ifndef __ASSEMBLY__
 227
 228 static inline bool in_ia32_syscall(void)
 229 {
 230 #ifdef CONFIG_X86_32
 231         return true;
 232 #endif
 233 #ifdef CONFIG_IA32_EMULATION
 234         if (current_thread_info()->status & TS_COMPAT)
 235                 return true;
 236 #endif
 237         return false;
 238 }
 239
 240 /*
 241  * Force syscall return via IRET by making it look as if there was
 242  * some work pending. IRET is our most capable (but slowest) syscall
 243  * return path, which is able to restore modified SS, CS and certain
 244  * EFLAGS values that other (fast) syscall return instructions
 245  * are not able to restore properly.
 246  */
 247 #define force_iret() set_thread_flag(TIF_NOTIFY_RESUME)
 248
 249 extern void arch_task_cache_init(void);
 250 extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
 251 extern void arch_release_task_struct(struct task_struct *tsk);
 252 #endif  /* !__ASSEMBLY__ */
 253
 254 #endif /* _ASM_X86_THREAD_INFO_H */