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, but it depends on whether
35 * or not FRED is enabled. Future versions of FRED might make this
36 * dynamic, but for now it is always 2 words longer.
37 */
38#ifdef CONFIG_X86_32
39# ifdef CONFIG_VM86
40#  define TOP_OF_KERNEL_STACK_PADDING 16
41# else
42#  define TOP_OF_KERNEL_STACK_PADDING 8
43# endif
44#else /* x86-64 */
45# ifdef CONFIG_X86_FRED
46#  define TOP_OF_KERNEL_STACK_PADDING (2 * 8)
47# else
48#  define TOP_OF_KERNEL_STACK_PADDING 0
49# endif
50#endif
51
52/*
53 * low level task data that entry.S needs immediate access to
54 * - this struct should fit entirely inside of one cache line
55 * - this struct shares the supervisor stack pages
56 */
57#ifndef __ASSEMBLY__
58struct task_struct;
59#include <asm/cpufeature.h>
60#include <linux/atomic.h>
61
62struct thread_info {
63	unsigned long		flags;		/* low level flags */
64	unsigned long		syscall_work;	/* SYSCALL_WORK_ flags */
65	u32			status;		/* thread synchronous flags */
66#ifdef CONFIG_SMP
67	u32			cpu;		/* current CPU */
68#endif
69};
70
71#define INIT_THREAD_INFO(tsk)			\
72{						\
73	.flags		= 0,			\
74}
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 */
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_SSBD		5	/* Speculative store bypass disable */
92#define TIF_SPEC_IB		9	/* Indirect branch speculation mitigation */
93#define TIF_SPEC_L1D_FLUSH	10	/* Flush L1D on mm switches (processes) */
94#define TIF_USER_RETURN_NOTIFY	11	/* notify kernel of userspace return */
95#define TIF_UPROBE		12	/* breakpointed or singlestepping */
96#define TIF_PATCH_PENDING	13	/* pending live patching update */
97#define TIF_NEED_FPU_LOAD	14	/* load FPU on return to userspace */
98#define TIF_NOCPUID		15	/* CPUID is not accessible in userland */
99#define TIF_NOTSC		16	/* TSC is not accessible in userland */
100#define TIF_NOTIFY_SIGNAL	17	/* signal notifications exist */
101#define TIF_MEMDIE		20	/* is terminating due to OOM killer */
102#define TIF_POLLING_NRFLAG	21	/* idle is polling for TIF_NEED_RESCHED */
103#define TIF_IO_BITMAP		22	/* uses I/O bitmap */
104#define TIF_SPEC_FORCE_UPDATE	23	/* Force speculation MSR update in context switch */
105#define TIF_FORCED_TF		24	/* true if TF in eflags artificially */
106#define TIF_BLOCKSTEP		25	/* set when we want DEBUGCTLMSR_BTF */
107#define TIF_LAZY_MMU_UPDATES	27	/* task is updating the mmu lazily */
108#define TIF_ADDR32		29	/* 32-bit address space on 64 bits */
109
110#define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
111#define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
112#define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
113#define _TIF_SINGLESTEP		(1 << TIF_SINGLESTEP)
114#define _TIF_SSBD		(1 << TIF_SSBD)
115#define _TIF_SPEC_IB		(1 << TIF_SPEC_IB)
116#define _TIF_SPEC_L1D_FLUSH	(1 << TIF_SPEC_L1D_FLUSH)
117#define _TIF_USER_RETURN_NOTIFY	(1 << TIF_USER_RETURN_NOTIFY)
118#define _TIF_UPROBE		(1 << TIF_UPROBE)
119#define _TIF_PATCH_PENDING	(1 << TIF_PATCH_PENDING)
120#define _TIF_NEED_FPU_LOAD	(1 << TIF_NEED_FPU_LOAD)
121#define _TIF_NOCPUID		(1 << TIF_NOCPUID)
122#define _TIF_NOTSC		(1 << TIF_NOTSC)
123#define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
124#define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
125#define _TIF_IO_BITMAP		(1 << TIF_IO_BITMAP)
126#define _TIF_SPEC_FORCE_UPDATE	(1 << TIF_SPEC_FORCE_UPDATE)
127#define _TIF_FORCED_TF		(1 << TIF_FORCED_TF)
128#define _TIF_BLOCKSTEP		(1 << TIF_BLOCKSTEP)
129#define _TIF_LAZY_MMU_UPDATES	(1 << TIF_LAZY_MMU_UPDATES)
130#define _TIF_ADDR32		(1 << TIF_ADDR32)
131
132/* flags to check in __switch_to() */
133#define _TIF_WORK_CTXSW_BASE					\
134	(_TIF_NOCPUID | _TIF_NOTSC | _TIF_BLOCKSTEP |		\
135	 _TIF_SSBD | _TIF_SPEC_FORCE_UPDATE)
136
137/*
138 * Avoid calls to __switch_to_xtra() on UP as STIBP is not evaluated.
139 */
140#ifdef CONFIG_SMP
141# define _TIF_WORK_CTXSW	(_TIF_WORK_CTXSW_BASE | _TIF_SPEC_IB)
142#else
143# define _TIF_WORK_CTXSW	(_TIF_WORK_CTXSW_BASE)
144#endif
145
146#ifdef CONFIG_X86_IOPL_IOPERM
147# define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
148				 _TIF_IO_BITMAP)
149#else
150# define _TIF_WORK_CTXSW_PREV	(_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY)
151#endif
152
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
164/*
165 * Walks up the stack frames to make sure that the specified object is
166 * entirely contained by a single stack frame.
167 *
168 * Returns:
169 *	GOOD_FRAME	if within a frame
170 *	BAD_STACK	if placed across a frame boundary (or outside stack)
171 *	NOT_STACK	unable to determine (no frame pointers, etc)
172 *
173 * This function reads pointers from the stack and dereferences them. The
174 * pointers may not have their KMSAN shadow set up properly, which may result
175 * in false positive reports. Disable instrumentation to avoid those.
176 */
177__no_kmsan_checks
178static inline int arch_within_stack_frames(const void * const stack,
179					   const void * const stackend,
180					   const void *obj, unsigned long len)
181{
182#if defined(CONFIG_FRAME_POINTER)
183	const void *frame = NULL;
184	const void *oldframe;
185
186	oldframe = __builtin_frame_address(1);
187	if (oldframe)
188		frame = __builtin_frame_address(2);
189	/*
190	 * low ----------------------------------------------> high
191	 * [saved bp][saved ip][args][local vars][saved bp][saved ip]
192	 *                     ^----------------^
193	 *               allow copies only within here
194	 */
195	while (stack <= frame && frame < stackend) {
196		/*
197		 * If obj + len extends past the last frame, this
198		 * check won't pass and the next frame will be 0,
199		 * causing us to bail out and correctly report
200		 * the copy as invalid.
201		 */
202		if (obj + len <= frame)
203			return obj >= oldframe + 2 * sizeof(void *) ?
204				GOOD_FRAME : BAD_STACK;
205		oldframe = frame;
206		frame = *(const void * const *)frame;
207	}
208	return BAD_STACK;
209#else
210	return NOT_STACK;
211#endif
212}
213
214#endif  /* !__ASSEMBLY__ */
215
216/*
217 * Thread-synchronous status.
218 *
219 * This is different from the flags in that nobody else
220 * ever touches our thread-synchronous status, so we don't
221 * have to worry about atomic accesses.
222 */
223#define TS_COMPAT		0x0002	/* 32bit syscall active (64BIT)*/
224
225#ifndef __ASSEMBLY__
226#ifdef CONFIG_COMPAT
227#define TS_I386_REGS_POKED	0x0004	/* regs poked by 32-bit ptracer */
228
229#define arch_set_restart_data(restart)	\
230	do { restart->arch_data = current_thread_info()->status; } while (0)
231
232#endif
233
234#ifdef CONFIG_X86_32
235#define in_ia32_syscall() true
236#else
237#define in_ia32_syscall() (IS_ENABLED(CONFIG_IA32_EMULATION) && \
238			   current_thread_info()->status & TS_COMPAT)
239#endif
240
241extern void arch_setup_new_exec(void);
242#define arch_setup_new_exec arch_setup_new_exec
243#endif	/* !__ASSEMBLY__ */
244
245#endif /* _ASM_X86_THREAD_INFO_H */
246