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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 };
 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 /*
180  * Walks up the stack frames to make sure that the specified object is
181  * entirely contained by a single stack frame.
182  *
183  * Returns:
184  *               1 if within a frame
185  *              -1 if placed across a frame boundary (or outside stack)
186  *               0 unable to determine (no frame pointers, etc)
187  */
188 static inline int arch_within_stack_frames(const void * const stack,
189                                            const void * const stackend,
190                                            const void *obj, unsigned long len)
191 {
192 #if defined(CONFIG_FRAME_POINTER)
193         const void *frame = NULL;
194         const void *oldframe;
195 
196         oldframe = __builtin_frame_address(1);
197         if (oldframe)
198                 frame = __builtin_frame_address(2);
199         /*
200          * low ----------------------------------------------> high
201          * [saved bp][saved ip][args][local vars][saved bp][saved ip]
202          *                     ^----------------^
203          *               allow copies only within here
204          */
205         while (stack <= frame && frame < stackend) {
206                 /*
207                  * If obj + len extends past the last frame, this
208                  * check won't pass and the next frame will be 0,
209                  * causing us to bail out and correctly report
210                  * the copy as invalid.
211                  */
212                 if (obj + len <= frame)
213                         return obj >= oldframe + 2 * sizeof(void *) ? 1 : -1;
214                 oldframe = frame;
215                 frame = *(const void * const *)frame;
216         }
217         return -1;
218 #else
219         return 0;
220 #endif
221 }
222 
223 #else /* !__ASSEMBLY__ */
224 
225 #ifdef CONFIG_X86_64
226 # define cpu_current_top_of_stack (cpu_tss + TSS_sp0)
227 #endif
228 
229 /*
230  * ASM operand which evaluates to a 'thread_info' address of
231  * the current task, if it is known that "reg" is exactly "off"
232  * bytes below the top of the stack currently.
233  *
234  * ( The kernel stack's size is known at build time, it is usually
235  *   2 or 4 pages, and the bottom  of the kernel stack contains
236  *   the thread_info structure. So to access the thread_info very
237  *   quickly from assembly code we can calculate down from the
238  *   top of the kernel stack to the bottom, using constant,
239  *   build-time calculations only. )
240  *
241  * For example, to fetch the current thread_info->flags value into %eax
242  * on x86-64 defconfig kernels, in syscall entry code where RSP is
243  * currently at exactly SIZEOF_PTREGS bytes away from the top of the
244  * stack:
245  *
246  *      mov ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS), %eax
247  *
248  * will translate to:
249  *
250  *      8b 84 24 b8 c0 ff ff      mov    -0x3f48(%rsp), %eax
251  *
252  * which is below the current RSP by almost 16K.
253  */
254 #define ASM_THREAD_INFO(field, reg, off) ((field)+(off)-THREAD_SIZE)(reg)
255 
256 #endif
257 
258 /*
259  * Thread-synchronous status.
260  *
261  * This is different from the flags in that nobody else
262  * ever touches our thread-synchronous status, so we don't
263  * have to worry about atomic accesses.
264  */
265 #define TS_COMPAT               0x0002  /* 32bit syscall active (64BIT)*/
266 #ifdef CONFIG_COMPAT
267 #define TS_I386_REGS_POKED      0x0004  /* regs poked by 32-bit ptracer */
268 #endif
269 
270 #ifndef __ASSEMBLY__
271 
272 static inline bool in_ia32_syscall(void)
273 {
274 #ifdef CONFIG_X86_32
275         return true;
276 #endif
277 #ifdef CONFIG_IA32_EMULATION
278         if (current_thread_info()->status & TS_COMPAT)
279                 return true;
280 #endif
281         return false;
282 }
283 
284 /*
285  * Force syscall return via IRET by making it look as if there was
286  * some work pending. IRET is our most capable (but slowest) syscall
287  * return path, which is able to restore modified SS, CS and certain
288  * EFLAGS values that other (fast) syscall return instructions
289  * are not able to restore properly.
290  */
291 #define force_iret() set_thread_flag(TIF_NOTIFY_RESUME)
292 
293 extern void arch_task_cache_init(void);
294 extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
295 extern void arch_release_task_struct(struct task_struct *tsk);
296 #endif  /* !__ASSEMBLY__ */
297 
298 #endif /* _ASM_X86_THREAD_INFO_H */
299 

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