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         mm_segment_t            addr_limit;
  61         unsigned int            sig_on_uaccess_error:1;
  62         unsigned int            uaccess_err:1;  /* uaccess failed */
  63 };
  64
  65 #define INIT_THREAD_INFO(tsk)                   \
  66 {                                               \
  67         .task           = &tsk,                 \
  68         .flags          = 0,                    \
  69         .cpu            = 0,                    \
  70         .addr_limit     = KERNEL_DS,            \
  71 }
  72
  73 #define init_thread_info        (init_thread_union.thread_info)
  74 #define init_stack              (init_thread_union.stack)
  75
  76 #else /* !__ASSEMBLY__ */
  77
  78 #include <asm/asm-offsets.h>
  79
  80 #endif
  81
  82 /*
  83  * thread information flags
  84  * - these are process state flags that various assembly files
  85  *   may need to access
  86  * - pending work-to-be-done flags are in LSW
  87  * - other flags in MSW
  88  * Warning: layout of LSW is hardcoded in entry.S
  89  */
  90 #define TIF_SYSCALL_TRACE       0       /* syscall trace active */
  91 #define TIF_NOTIFY_RESUME       1       /* callback before returning to user */
  92 #define TIF_SIGPENDING          2       /* signal pending */
  93 #define TIF_NEED_RESCHED        3       /* rescheduling necessary */
  94 #define TIF_SINGLESTEP          4       /* reenable singlestep on user return*/
  95 #define TIF_SYSCALL_EMU         6       /* syscall emulation active */
  96 #define TIF_SYSCALL_AUDIT       7       /* syscall auditing active */
  97 #define TIF_SECCOMP             8       /* secure computing */
  98 #define TIF_USER_RETURN_NOTIFY  11      /* notify kernel of userspace return */
  99 #define TIF_UPROBE              12      /* breakpointed or singlestepping */
 100 #define TIF_NOTSC               16      /* TSC is not accessible in userland */
 101 #define TIF_IA32                17      /* IA32 compatibility process */
 102 #define TIF_FORK                18      /* ret_from_fork */
 103 #define TIF_NOHZ                19      /* in adaptive nohz mode */
 104 #define TIF_MEMDIE              20      /* is terminating due to OOM killer */
 105 #define TIF_POLLING_NRFLAG      21      /* idle is polling for TIF_NEED_RESCHED */
 106 #define TIF_IO_BITMAP           22      /* uses I/O bitmap */
 107 #define TIF_FORCED_TF           24      /* true if TF in eflags artificially */
 108 #define TIF_BLOCKSTEP           25      /* set when we want DEBUGCTLMSR_BTF */
 109 #define TIF_LAZY_MMU_UPDATES    27      /* task is updating the mmu lazily */
 110 #define TIF_SYSCALL_TRACEPOINT  28      /* syscall tracepoint instrumentation */
 111 #define TIF_ADDR32              29      /* 32-bit address space on 64 bits */
 112 #define TIF_X32                 30      /* 32-bit native x86-64 binary */
 113
 114 #define _TIF_SYSCALL_TRACE      (1 << TIF_SYSCALL_TRACE)
 115 #define _TIF_NOTIFY_RESUME      (1 << TIF_NOTIFY_RESUME)
 116 #define _TIF_SIGPENDING         (1 << TIF_SIGPENDING)
 117 #define _TIF_SINGLESTEP         (1 << TIF_SINGLESTEP)
 118 #define _TIF_NEED_RESCHED       (1 << TIF_NEED_RESCHED)
 119 #define _TIF_SYSCALL_EMU        (1 << TIF_SYSCALL_EMU)
 120 #define _TIF_SYSCALL_AUDIT      (1 << TIF_SYSCALL_AUDIT)
 121 #define _TIF_SECCOMP            (1 << TIF_SECCOMP)
 122 #define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY)
 123 #define _TIF_UPROBE             (1 << TIF_UPROBE)
 124 #define _TIF_NOTSC              (1 << TIF_NOTSC)
 125 #define _TIF_IA32               (1 << TIF_IA32)
 126 #define _TIF_FORK               (1 << TIF_FORK)
 127 #define _TIF_NOHZ               (1 << TIF_NOHZ)
 128 #define _TIF_POLLING_NRFLAG     (1 << TIF_POLLING_NRFLAG)
 129 #define _TIF_IO_BITMAP          (1 << TIF_IO_BITMAP)
 130 #define _TIF_FORCED_TF          (1 << TIF_FORCED_TF)
 131 #define _TIF_BLOCKSTEP          (1 << TIF_BLOCKSTEP)
 132 #define _TIF_LAZY_MMU_UPDATES   (1 << TIF_LAZY_MMU_UPDATES)
 133 #define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
 134 #define _TIF_ADDR32             (1 << TIF_ADDR32)
 135 #define _TIF_X32                (1 << TIF_X32)
 136
 137 /*
 138  * work to do in syscall_trace_enter().  Also includes TIF_NOHZ for
 139  * enter_from_user_mode()
 140  */
 141 #define _TIF_WORK_SYSCALL_ENTRY \
 142         (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT |   \
 143          _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT |       \
 144          _TIF_NOHZ)
 145
 146 /* work to do on any return to user space */
 147 #define _TIF_ALLWORK_MASK                                               \
 148         ((0x0000FFFF & ~_TIF_SECCOMP) | _TIF_SYSCALL_TRACEPOINT |       \
 149         _TIF_NOHZ)
 150
 151 /* flags to check in __switch_to() */
 152 #define _TIF_WORK_CTXSW                                                 \
 153         (_TIF_IO_BITMAP|_TIF_NOTSC|_TIF_BLOCKSTEP)
 154
 155 #define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
 156 #define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
 157
 158 #define STACK_WARN              (THREAD_SIZE/8)
 159
 160 /*
 161  * macros/functions for gaining access to the thread information structure
 162  *
 163  * preempt_count needs to be 1 initially, until the scheduler is functional.
 164  */
 165 #ifndef __ASSEMBLY__
 166
 167 static inline struct thread_info *current_thread_info(void)
 168 {
 169         return (struct thread_info *)(current_top_of_stack() - THREAD_SIZE);
 170 }
 171
 172 static inline unsigned long current_stack_pointer(void)
 173 {
 174         unsigned long sp;
 175 #ifdef CONFIG_X86_64
 176         asm("mov %%rsp,%0" : "=g" (sp));
 177 #else
 178         asm("mov %%esp,%0" : "=g" (sp));
 179 #endif
 180         return sp;
 181 }
 182
 183 #else /* !__ASSEMBLY__ */
 184
 185 #ifdef CONFIG_X86_64
 186 # define cpu_current_top_of_stack (cpu_tss + TSS_sp0)
 187 #endif
 188
 189 /* Load thread_info address into "reg" */
 190 #define GET_THREAD_INFO(reg) \
 191         _ASM_MOV PER_CPU_VAR(cpu_current_top_of_stack),reg ; \
 192         _ASM_SUB $(THREAD_SIZE),reg ;
 193
 194 /*
 195  * ASM operand which evaluates to a 'thread_info' address of
 196  * the current task, if it is known that "reg" is exactly "off"
 197  * bytes below the top of the stack currently.
 198  *
 199  * ( The kernel stack's size is known at build time, it is usually
 200  *   2 or 4 pages, and the bottom  of the kernel stack contains
 201  *   the thread_info structure. So to access the thread_info very
 202  *   quickly from assembly code we can calculate down from the
 203  *   top of the kernel stack to the bottom, using constant,
 204  *   build-time calculations only. )
 205  *
 206  * For example, to fetch the current thread_info->flags value into %eax
 207  * on x86-64 defconfig kernels, in syscall entry code where RSP is
 208  * currently at exactly SIZEOF_PTREGS bytes away from the top of the
 209  * stack:
 210  *
 211  *      mov ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS), %eax
 212  *
 213  * will translate to:
 214  *
 215  *      8b 84 24 b8 c0 ff ff      mov    -0x3f48(%rsp), %eax
 216  *
 217  * which is below the current RSP by almost 16K.
 218  */
 219 #define ASM_THREAD_INFO(field, reg, off) ((field)+(off)-THREAD_SIZE)(reg)
 220
 221 #endif
 222
 223 /*
 224  * Thread-synchronous status.
 225  *
 226  * This is different from the flags in that nobody else
 227  * ever touches our thread-synchronous status, so we don't
 228  * have to worry about atomic accesses.
 229  */
 230 #define TS_COMPAT               0x0002  /* 32bit syscall active (64BIT)*/
 231 #define TS_RESTORE_SIGMASK      0x0008  /* restore signal mask in do_signal() */
 232
 233 #ifndef __ASSEMBLY__
 234 #define HAVE_SET_RESTORE_SIGMASK        1
 235 static inline void set_restore_sigmask(void)
 236 {
 237         struct thread_info *ti = current_thread_info();
 238         ti->status |= TS_RESTORE_SIGMASK;
 239         WARN_ON(!test_bit(TIF_SIGPENDING, (unsigned long *)&ti->flags));
 240 }
 241 static inline void clear_restore_sigmask(void)
 242 {
 243         current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
 244 }
 245 static inline bool test_restore_sigmask(void)
 246 {
 247         return current_thread_info()->status & TS_RESTORE_SIGMASK;
 248 }
 249 static inline bool test_and_clear_restore_sigmask(void)
 250 {
 251         struct thread_info *ti = current_thread_info();
 252         if (!(ti->status & TS_RESTORE_SIGMASK))
 253                 return false;
 254         ti->status &= ~TS_RESTORE_SIGMASK;
 255         return true;
 256 }
 257
 258 static inline bool is_ia32_task(void)
 259 {
 260 #ifdef CONFIG_X86_32
 261         return true;
 262 #endif
 263 #ifdef CONFIG_IA32_EMULATION
 264         if (current_thread_info()->status & TS_COMPAT)
 265                 return true;
 266 #endif
 267         return false;
 268 }
 269
 270 /*
 271  * Force syscall return via IRET by making it look as if there was
 272  * some work pending. IRET is our most capable (but slowest) syscall
 273  * return path, which is able to restore modified SS, CS and certain
 274  * EFLAGS values that other (fast) syscall return instructions
 275  * are not able to restore properly.
 276  */
 277 #define force_iret() set_thread_flag(TIF_NOTIFY_RESUME)
 278
 279 extern void arch_task_cache_init(void);
 280 extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
 281 extern void arch_release_task_struct(struct task_struct *tsk);
 282 #endif  /* !__ASSEMBLY__ */
 283
 284 #endif /* _ASM_X86_THREAD_INFO_H */