1/* SPDX-License-Identifier: GPL-2.0 */
2/* thread_info.h: low-level thread information
3 *
4 * Copyright (C) 2002  David Howells (dhowells@redhat.com)
5 * - Incorporating suggestions made by Linus Torvalds and Dave Miller
6 */
7
8#ifndef _ASM_X86_THREAD_INFO_H
9#define _ASM_X86_THREAD_INFO_H
10
11#include <linux/compiler.h>
12#include <asm/page.h>
13#include <asm/percpu.h>
14#include <asm/types.h>
15
16/*
17 * TOP_OF_KERNEL_STACK_PADDING is a number of unused bytes that we
18 * reserve at the top of the kernel stack.  We do it because of a nasty
19 * 32-bit corner case.  On x86_32, the hardware stack frame is
20 * variable-length.  Except for vm86 mode, struct pt_regs assumes a
21 * maximum-length frame.  If we enter from CPL 0, the top 8 bytes of
22 * pt_regs don't actually exist.  Ordinarily this doesn't matter, but it
23 * does in at least one case:
24 *
25 * If we take an NMI early enough in SYSENTER, then we can end up with
26 * pt_regs that extends above sp0.  On the way out, in the espfix code,
27 * we can read the saved SS value, but that value will be above sp0.
28 * Without this offset, that can result in a page fault.  (We are
29 * careful that, in this case, the value we read doesn't matter.)
30 *
31 * In vm86 mode, the hardware frame is much longer still, so add 16
32 * bytes to make room for the real-mode segments.
33 *
34 * x86_64 has a fixed-length stack frame.
35 */
36#ifdef CONFIG_X86_32
37# ifdef CONFIG_VM86
38#  define TOP_OF_KERNEL_STACK_PADDING 16
39# else
40#  define TOP_OF_KERNEL_STACK_PADDING 8
41# endif
42#else
43# define TOP_OF_KERNEL_STACK_PADDING 0
44#endif
45
46/*
47 * low level task data that entry.S needs immediate access to
48 * - this struct should fit entirely inside of one cache line
49 * - this struct shares the supervisor stack pages
50 */
51#ifndef __ASSEMBLY__
52struct task_struct;
53#include <asm/cpufeature.h>
54#include <linux/atomic.h>
55
56struct thread_info {
57	unsigned long		flags;		/* low level flags */
58	unsigned long		syscall_work;	/* SYSCALL_WORK_ flags */
59	u32			status;		/* thread synchronous flags */
60#ifdef CONFIG_SMP
61	u32			cpu;		/* current CPU */
62#endif
63};
64
65#define INIT_THREAD_INFO(tsk)			\
66{						\
67	.flags		= 0,			\
68}
69
70#else /* !__ASSEMBLY__ */
71
72#include <asm/asm-offsets.h>
73
74#endif
75
76/*
77 * thread information flags
78 * - these are process state flags that various assembly files
79 *   may need to access
80 */
81#define TIF_NOTIFY_RESUME	1	/* callback before returning to user */
82#define TIF_SIGPENDING		2	/* signal pending */
83#define TIF_NEED_RESCHED	3	/* rescheduling necessary */
84#define TIF_SINGLESTEP		4	/* reenable singlestep on user return*/
85#define TIF_SSBD		5	/* Speculative store bypass disable */
86#define TIF_SPEC_IB		9	/* Indirect branch speculation mitigation */
87#define TIF_SPEC_L1D_FLUSH	10	/* Flush L1D on mm switches (processes) */
88#define TIF_USER_RETURN_NOTIFY	11	/* notify kernel of userspace return */
89#define TIF_UPROBE		12	/* breakpointed or singlestepping */
90#define TIF_PATCH_PENDING	13	/* pending live patching update */
91#define TIF_NEED_FPU_LOAD	14	/* load FPU on return to userspace */
92#define TIF_NOCPUID		15	/* CPUID is not accessible in userland */
93#define TIF_NOTSC		16	/* TSC is not accessible in userland */
94#define TIF_NOTIFY_SIGNAL	17	/* signal notifications exist */
95#define TIF_MEMDIE		20	/* is terminating due to OOM killer */
96#define TIF_POLLING_NRFLAG	21	/* idle is polling for TIF_NEED_RESCHED */
97#define TIF_IO_BITMAP		22	/* uses I/O bitmap */
98#define TIF_SPEC_FORCE_UPDATE	23	/* Force speculation MSR update in context switch */
99#define TIF_FORCED_TF		24	/* true if TF in eflags artificially */
100#define TIF_BLOCKSTEP		25	/* set when we want DEBUGCTLMSR_BTF */
101#define TIF_LAZY_MMU_UPDATES	27	/* task is updating the mmu lazily */
102#define TIF_ADDR32		29	/* 32-bit address space on 64 bits */
103
104#define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
105#define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
106#define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
107#define _TIF_SINGLESTEP		(1 << TIF_SINGLESTEP)
108#define _TIF_SSBD		(1 << TIF_SSBD)
109#define _TIF_SPEC_IB		(1 << TIF_SPEC_IB)
110#define _TIF_SPEC_L1D_FLUSH	(1 << TIF_SPEC_L1D_FLUSH)
111#define _TIF_USER_RETURN_NOTIFY	(1 << TIF_USER_RETURN_NOTIFY)
112#define _TIF_UPROBE		(1 << TIF_UPROBE)
113#define _TIF_PATCH_PENDING	(1 << TIF_PATCH_PENDING)
114#define _TIF_NEED_FPU_LOAD	(1 << TIF_NEED_FPU_LOAD)
115#define _TIF_NOCPUID		(1 << TIF_NOCPUID)
116#define _TIF_NOTSC		(1 << TIF_NOTSC)
117#define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
118#define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
119#define _TIF_IO_BITMAP		(1 << TIF_IO_BITMAP)
120#define _TIF_SPEC_FORCE_UPDATE	(1 << TIF_SPEC_FORCE_UPDATE)
121#define _TIF_FORCED_TF		(1 << TIF_FORCED_TF)
122#define _TIF_BLOCKSTEP		(1 << TIF_BLOCKSTEP)
123#define _TIF_LAZY_MMU_UPDATES	(1 << TIF_LAZY_MMU_UPDATES)
124#define _TIF_ADDR32		(1 << TIF_ADDR32)
125
126/* flags to check in __switch_to() */
127#define _TIF_WORK_CTXSW_BASE					\
128	(_TIF_NOCPUID | _TIF_NOTSC | _TIF_BLOCKSTEP |		\
129	 _TIF_SSBD | _TIF_SPEC_FORCE_UPDATE)
130
131/*
132 * Avoid calls to __switch_to_xtra() on UP as STIBP is not evaluated.
133 */
134#ifdef CONFIG_SMP
135# define _TIF_WORK_CTXSW	(_TIF_WORK_CTXSW_BASE | _TIF_SPEC_IB)
136#else
137# define _TIF_WORK_CTXSW	(_TIF_WORK_CTXSW_BASE)
138#endif
139
140#ifdef CONFIG_X86_IOPL_IOPERM
141# define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
142				 _TIF_IO_BITMAP)
143#else
144# define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY)
145#endif
146
147#define _TIF_WORK_CTXSW_NEXT	(_TIF_WORK_CTXSW)
148
149#define STACK_WARN		(THREAD_SIZE/8)
150
151/*
152 * macros/functions for gaining access to the thread information structure
153 *
154 * preempt_count needs to be 1 initially, until the scheduler is functional.
155 */
156#ifndef __ASSEMBLY__
157
158/*
159 * Walks up the stack frames to make sure that the specified object is
160 * entirely contained by a single stack frame.
161 *
162 * Returns:
163 *	GOOD_FRAME	if within a frame
164 *	BAD_STACK	if placed across a frame boundary (or outside stack)
165 *	NOT_STACK	unable to determine (no frame pointers, etc)
166 *
167 * This function reads pointers from the stack and dereferences them. The
168 * pointers may not have their KMSAN shadow set up properly, which may result
169 * in false positive reports. Disable instrumentation to avoid those.
170 */
171__no_kmsan_checks
172static inline int arch_within_stack_frames(const void * const stack,
173					   const void * const stackend,
174					   const void *obj, unsigned long len)
175{
176#if defined(CONFIG_FRAME_POINTER)
177	const void *frame = NULL;
178	const void *oldframe;
179
180	oldframe = __builtin_frame_address(1);
181	if (oldframe)
182		frame = __builtin_frame_address(2);
183	/*
184	 * low ----------------------------------------------> high
185	 * [saved bp][saved ip][args][local vars][saved bp][saved ip]
186	 *                     ^----------------^
187	 *               allow copies only within here
188	 */
189	while (stack <= frame && frame < stackend) {
190		/*
191		 * If obj + len extends past the last frame, this
192		 * check won't pass and the next frame will be 0,
193		 * causing us to bail out and correctly report
194		 * the copy as invalid.
195		 */
196		if (obj + len <= frame)
197			return obj >= oldframe + 2 * sizeof(void *) ?
198				GOOD_FRAME : BAD_STACK;
199		oldframe = frame;
200		frame = *(const void * const *)frame;
201	}
202	return BAD_STACK;
203#else
204	return NOT_STACK;
205#endif
206}
207
208#endif  /* !__ASSEMBLY__ */
209
210/*
211 * Thread-synchronous status.
212 *
213 * This is different from the flags in that nobody else
214 * ever touches our thread-synchronous status, so we don't
215 * have to worry about atomic accesses.
216 */
217#define TS_COMPAT		0x0002	/* 32bit syscall active (64BIT)*/
218
219#ifndef __ASSEMBLY__
220#ifdef CONFIG_COMPAT
221#define TS_I386_REGS_POKED	0x0004	/* regs poked by 32-bit ptracer */
222
223#define arch_set_restart_data(restart)	\
224	do { restart->arch_data = current_thread_info()->status; } while (0)
225
226#endif
227
228#ifdef CONFIG_X86_32
229#define in_ia32_syscall() true
230#else
231#define in_ia32_syscall() (IS_ENABLED(CONFIG_IA32_EMULATION) && \
232			   current_thread_info()->status & TS_COMPAT)
233#endif
234
235extern void arch_setup_new_exec(void);
236#define arch_setup_new_exec arch_setup_new_exec
237#endif	/* !__ASSEMBLY__ */
238
239#endif /* _ASM_X86_THREAD_INFO_H */
240