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__
51struct task_struct;
52#include <asm/processor.h>
53#include <linux/atomic.h>
54
55struct 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/* work to do in syscall_trace_enter() */
138#define _TIF_WORK_SYSCALL_ENTRY	\
139	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT |	\
140	 _TIF_SECCOMP | _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT |	\
141	 _TIF_NOHZ)
142
143/* work to do on any return to user space */
144#define _TIF_ALLWORK_MASK						\
145	((0x0000FFFF & ~_TIF_SECCOMP) | _TIF_SYSCALL_TRACEPOINT |	\
146	_TIF_NOHZ)
147
148/* flags to check in __switch_to() */
149#define _TIF_WORK_CTXSW							\
150	(_TIF_IO_BITMAP|_TIF_NOTSC|_TIF_BLOCKSTEP)
151
152#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
153#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
154
155#define STACK_WARN		(THREAD_SIZE/8)
156
157/*
158 * macros/functions for gaining access to the thread information structure
159 *
160 * preempt_count needs to be 1 initially, until the scheduler is functional.
161 */
162#ifndef __ASSEMBLY__
163
164static inline struct thread_info *current_thread_info(void)
165{
166	return (struct thread_info *)(current_top_of_stack() - THREAD_SIZE);
167}
168
169static inline unsigned long current_stack_pointer(void)
170{
171	unsigned long sp;
172#ifdef CONFIG_X86_64
173	asm("mov %%rsp,%0" : "=g" (sp));
174#else
175	asm("mov %%esp,%0" : "=g" (sp));
176#endif
177	return sp;
178}
179
180#else /* !__ASSEMBLY__ */
181
182#ifdef CONFIG_X86_64
183# define cpu_current_top_of_stack (cpu_tss + TSS_sp0)
184#endif
185
186/* Load thread_info address into "reg" */
187#define GET_THREAD_INFO(reg) \
188	_ASM_MOV PER_CPU_VAR(cpu_current_top_of_stack),reg ; \
189	_ASM_SUB $(THREAD_SIZE),reg ;
190
191/*
192 * ASM operand which evaluates to a 'thread_info' address of
193 * the current task, if it is known that "reg" is exactly "off"
194 * bytes below the top of the stack currently.
195 *
196 * ( The kernel stack's size is known at build time, it is usually
197 *   2 or 4 pages, and the bottom  of the kernel stack contains
198 *   the thread_info structure. So to access the thread_info very
199 *   quickly from assembly code we can calculate down from the
200 *   top of the kernel stack to the bottom, using constant,
201 *   build-time calculations only. )
202 *
203 * For example, to fetch the current thread_info->flags value into %eax
204 * on x86-64 defconfig kernels, in syscall entry code where RSP is
205 * currently at exactly SIZEOF_PTREGS bytes away from the top of the
206 * stack:
207 *
208 *      mov ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS), %eax
209 *
210 * will translate to:
211 *
212 *      8b 84 24 b8 c0 ff ff      mov    -0x3f48(%rsp), %eax
213 *
214 * which is below the current RSP by almost 16K.
215 */
216#define ASM_THREAD_INFO(field, reg, off) ((field)+(off)-THREAD_SIZE)(reg)
217
218#endif
219
220/*
221 * Thread-synchronous status.
222 *
223 * This is different from the flags in that nobody else
224 * ever touches our thread-synchronous status, so we don't
225 * have to worry about atomic accesses.
226 */
227#define TS_COMPAT		0x0002	/* 32bit syscall active (64BIT)*/
228#define TS_RESTORE_SIGMASK	0x0008	/* restore signal mask in do_signal() */
229
230#ifndef __ASSEMBLY__
231#define HAVE_SET_RESTORE_SIGMASK	1
232static inline void set_restore_sigmask(void)
233{
234	struct thread_info *ti = current_thread_info();
235	ti->status |= TS_RESTORE_SIGMASK;
236	WARN_ON(!test_bit(TIF_SIGPENDING, (unsigned long *)&ti->flags));
237}
238static inline void clear_restore_sigmask(void)
239{
240	current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
241}
242static inline bool test_restore_sigmask(void)
243{
244	return current_thread_info()->status & TS_RESTORE_SIGMASK;
245}
246static inline bool test_and_clear_restore_sigmask(void)
247{
248	struct thread_info *ti = current_thread_info();
249	if (!(ti->status & TS_RESTORE_SIGMASK))
250		return false;
251	ti->status &= ~TS_RESTORE_SIGMASK;
252	return true;
253}
254
255static inline bool is_ia32_task(void)
256{
257#ifdef CONFIG_X86_32
258	return true;
259#endif
260#ifdef CONFIG_IA32_EMULATION
261	if (current_thread_info()->status & TS_COMPAT)
262		return true;
263#endif
264	return false;
265}
266
267/*
268 * Force syscall return via IRET by making it look as if there was
269 * some work pending. IRET is our most capable (but slowest) syscall
270 * return path, which is able to restore modified SS, CS and certain
271 * EFLAGS values that other (fast) syscall return instructions
272 * are not able to restore properly.
273 */
274#define force_iret() set_thread_flag(TIF_NOTIFY_RESUME)
275
276#endif	/* !__ASSEMBLY__ */
277
278#ifndef __ASSEMBLY__
279extern void arch_task_cache_init(void);
280extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
281extern void arch_release_task_struct(struct task_struct *tsk);
282#endif
283#endif /* _ASM_X86_THREAD_INFO_H */
284