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Linux/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 */
285 

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