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 __ASSEMBLER__
58 struct task_struct;
59 #include <asm/cpufeature.h>
60 #include <linux/atomic.h>
61
62 struct 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 /* !__ASSEMBLER__ */
77
78 #include <asm/asm-offsets.h>
79
80 #endif
81
82 /*
83 * Tell the generic TIF infrastructure which bits x86 supports
84 */
85 #define HAVE_TIF_NEED_RESCHED_LAZY
86 #define HAVE_TIF_POLLING_NRFLAG
87 #define HAVE_TIF_SINGLESTEP
88
89 #include <asm-generic/thread_info_tif.h>
90
91 /* Architecture specific TIF space starts at 16 */
92 #define TIF_SSBD 16 /* Speculative store bypass disable */
93 #define TIF_SPEC_IB 17 /* Indirect branch speculation mitigation */
94 #define TIF_SPEC_L1D_FLUSH 18 /* Flush L1D on mm switches (processes) */
95 #define TIF_NEED_FPU_LOAD 19 /* load FPU on return to userspace */
96 #define TIF_NOCPUID 20 /* CPUID is not accessible in userland */
97 #define TIF_NOTSC 21 /* TSC is not accessible in userland */
98 #define TIF_IO_BITMAP 22 /* uses I/O bitmap */
99 #define TIF_SPEC_FORCE_UPDATE 23 /* Force speculation MSR update in context switch */
100 #define TIF_FORCED_TF 24 /* true if TF in eflags artificially */
101 #define TIF_SINGLESTEP 25 /* reenable singlestep on user return*/
102 #define TIF_BLOCKSTEP 26 /* set when we want DEBUGCTLMSR_BTF */
103 #define TIF_ADDR32 27 /* 32-bit address space on 64 bits */
104
105 #define _TIF_SSBD BIT(TIF_SSBD)
106 #define _TIF_SPEC_IB BIT(TIF_SPEC_IB)
107 #define _TIF_SPEC_L1D_FLUSH BIT(TIF_SPEC_L1D_FLUSH)
108 #define _TIF_NEED_FPU_LOAD BIT(TIF_NEED_FPU_LOAD)
109 #define _TIF_NOCPUID BIT(TIF_NOCPUID)
110 #define _TIF_NOTSC BIT(TIF_NOTSC)
111 #define _TIF_IO_BITMAP BIT(TIF_IO_BITMAP)
112 #define _TIF_SPEC_FORCE_UPDATE BIT(TIF_SPEC_FORCE_UPDATE)
113 #define _TIF_FORCED_TF BIT(TIF_FORCED_TF)
114 #define _TIF_BLOCKSTEP BIT(TIF_BLOCKSTEP)
115 #define _TIF_SINGLESTEP BIT(TIF_SINGLESTEP)
116 #define _TIF_ADDR32 BIT(TIF_ADDR32)
117
118 /* flags to check in __switch_to() */
119 #define _TIF_WORK_CTXSW_BASE \
120 (_TIF_NOCPUID | _TIF_NOTSC | _TIF_BLOCKSTEP | \
121 _TIF_SSBD | _TIF_SPEC_FORCE_UPDATE)
122
123 /*
124 * Avoid calls to __switch_to_xtra() on UP as STIBP is not evaluated.
125 */
126 #ifdef CONFIG_SMP
127 # define _TIF_WORK_CTXSW (_TIF_WORK_CTXSW_BASE | _TIF_SPEC_IB)
128 #else
129 # define _TIF_WORK_CTXSW (_TIF_WORK_CTXSW_BASE)
130 #endif
131
132 #ifdef CONFIG_X86_IOPL_IOPERM
133 # define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY | \
134 _TIF_IO_BITMAP)
135 #else
136 # define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW| _TIF_USER_RETURN_NOTIFY)
137 #endif
138
139 #define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
140
141 #define STACK_WARN (THREAD_SIZE/8)
142
143 /*
144 * macros/functions for gaining access to the thread information structure
145 *
146 * preempt_count needs to be 1 initially, until the scheduler is functional.
147 */
148 #ifndef __ASSEMBLER__
149
150 /*
151 * Walks up the stack frames to make sure that the specified object is
152 * entirely contained by a single stack frame.
153 *
154 * Returns:
155 * GOOD_FRAME if within a frame
156 * BAD_STACK if placed across a frame boundary (or outside stack)
157 * NOT_STACK unable to determine (no frame pointers, etc)
158 *
159 * This function reads pointers from the stack and dereferences them. The
160 * pointers may not have their KMSAN shadow set up properly, which may result
161 * in false positive reports. Disable instrumentation to avoid those.
162 */
163 __no_kmsan_checks
arch_within_stack_frames(const void * const stack,const void * const stackend,const void * obj,unsigned long len)164 static inline int arch_within_stack_frames(const void * const stack,
165 const void * const stackend,
166 const void *obj, unsigned long len)
167 {
168 #if defined(CONFIG_FRAME_POINTER)
169 const void *frame = NULL;
170 const void *oldframe;
171
172 oldframe = __builtin_frame_address(1);
173 if (oldframe)
174 frame = __builtin_frame_address(2);
175 /*
176 * low ----------------------------------------------> high
177 * [saved bp][saved ip][args][local vars][saved bp][saved ip]
178 * ^----------------^
179 * allow copies only within here
180 */
181 while (stack <= frame && frame < stackend) {
182 /*
183 * If obj + len extends past the last frame, this
184 * check won't pass and the next frame will be 0,
185 * causing us to bail out and correctly report
186 * the copy as invalid.
187 */
188 if (obj + len <= frame)
189 return obj >= oldframe + 2 * sizeof(void *) ?
190 GOOD_FRAME : BAD_STACK;
191 oldframe = frame;
192 frame = *(const void * const *)frame;
193 }
194 return BAD_STACK;
195 #else
196 return NOT_STACK;
197 #endif
198 }
199
200 #endif /* !__ASSEMBLER__ */
201
202 /*
203 * Thread-synchronous status.
204 *
205 * This is different from the flags in that nobody else
206 * ever touches our thread-synchronous status, so we don't
207 * have to worry about atomic accesses.
208 */
209 #define TS_COMPAT 0x0002 /* 32bit syscall active (64BIT)*/
210
211 #ifndef __ASSEMBLER__
212 #ifdef CONFIG_COMPAT
213 #define TS_I386_REGS_POKED 0x0004 /* regs poked by 32-bit ptracer */
214
215 #define arch_set_restart_data(restart) \
216 do { restart->arch_data = current_thread_info()->status; } while (0)
217
218 #endif
219
220 #ifdef CONFIG_X86_32
221 #define in_ia32_syscall() true
222 #else
223 #define in_ia32_syscall() (IS_ENABLED(CONFIG_IA32_EMULATION) && \
224 current_thread_info()->status & TS_COMPAT)
225 #endif
226
227 extern void arch_setup_new_exec(void);
228 #define arch_setup_new_exec arch_setup_new_exec
229 #endif /* !__ASSEMBLER__ */
230
231 #endif /* _ASM_X86_THREAD_INFO_H */
232