1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * syscall_wrapper.h - x86 specific wrappers to syscall definitions
4 */
5
6#ifndef _ASM_X86_SYSCALL_WRAPPER_H
7#define _ASM_X86_SYSCALL_WRAPPER_H
8
9#include <asm/ptrace.h>
10
11extern long __x64_sys_ni_syscall(const struct pt_regs *regs);
12extern long __ia32_sys_ni_syscall(const struct pt_regs *regs);
13
14/*
15 * Instead of the generic __SYSCALL_DEFINEx() definition, the x86 version takes
16 * struct pt_regs *regs as the only argument of the syscall stub(s) named as:
17 * __x64_sys_*() - 64-bit native syscall
18 * __ia32_sys_*() - 32-bit native syscall or common compat syscall
19 * __ia32_compat_sys_*() - 32-bit compat syscall
20 * __x64_compat_sys_*() - 64-bit X32 compat syscall
21 *
22 * The registers are decoded according to the ABI:
23 * 64-bit: RDI, RSI, RDX, R10, R8, R9
24 * 32-bit: EBX, ECX, EDX, ESI, EDI, EBP
25 *
26 * The stub then passes the decoded arguments to the __se_sys_*() wrapper to
27 * perform sign-extension (omitted for zero-argument syscalls). Finally the
28 * arguments are passed to the __do_sys_*() function which is the actual
29 * syscall. These wrappers are marked as inline so the compiler can optimize
30 * the functions where appropriate.
31 *
32 * Example assembly (slightly re-ordered for better readability):
33 *
34 * <__x64_sys_recv>: <-- syscall with 4 parameters
35 * callq <__fentry__>
36 *
37 * mov 0x70(%rdi),%rdi <-- decode regs->di
38 * mov 0x68(%rdi),%rsi <-- decode regs->si
39 * mov 0x60(%rdi),%rdx <-- decode regs->dx
40 * mov 0x38(%rdi),%rcx <-- decode regs->r10
41 *
42 * xor %r9d,%r9d <-- clear %r9
43 * xor %r8d,%r8d <-- clear %r8
44 *
45 * callq __sys_recvfrom <-- do the actual work in __sys_recvfrom()
46 * which takes 6 arguments
47 *
48 * cltq <-- extend return value to 64-bit
49 * retq <-- return
50 *
51 * This approach avoids leaking random user-provided register content down
52 * the call chain.
53 */
54
55/* Mapping of registers to parameters for syscalls on x86-64 and x32 */
56#define SC_X86_64_REGS_TO_ARGS(x, ...) \
57 __MAP(x,__SC_ARGS \
58 ,,regs->di,,regs->si,,regs->dx \
59 ,,regs->r10,,regs->r8,,regs->r9) \
60
61/* Mapping of registers to parameters for syscalls on i386 */
62#define SC_IA32_REGS_TO_ARGS(x, ...) \
63 __MAP(x,__SC_ARGS \
64 ,,(unsigned int)regs->bx,,(unsigned int)regs->cx \
65 ,,(unsigned int)regs->dx,,(unsigned int)regs->si \
66 ,,(unsigned int)regs->di,,(unsigned int)regs->bp)
67
68#define __SYS_STUB0(abi, name) \
69 long __##abi##_##name(const struct pt_regs *regs); \
70 ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO); \
71 long __##abi##_##name(const struct pt_regs *regs) \
72 __alias(__do_##name);
73
74#define __SYS_STUBx(abi, name, ...) \
75 long __##abi##_##name(const struct pt_regs *regs); \
76 ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO); \
77 long __##abi##_##name(const struct pt_regs *regs) \
78 { \
79 return __se_##name(__VA_ARGS__); \
80 }
81
82#define __COND_SYSCALL(abi, name) \
83 __weak long __##abi##_##name(const struct pt_regs *__unused); \
84 __weak long __##abi##_##name(const struct pt_regs *__unused) \
85 { \
86 return sys_ni_syscall(); \
87 }
88
89#define __SYS_NI(abi, name) \
90 SYSCALL_ALIAS(__##abi##_##name, sys_ni_posix_timers);
91
92#ifdef CONFIG_X86_64
93#define __X64_SYS_STUB0(name) \
94 __SYS_STUB0(x64, sys_##name)
95
96#define __X64_SYS_STUBx(x, name, ...) \
97 __SYS_STUBx(x64, sys##name, \
98 SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))
99
100#define __X64_COND_SYSCALL(name) \
101 __COND_SYSCALL(x64, sys_##name)
102
103#define __X64_SYS_NI(name) \
104 __SYS_NI(x64, sys_##name)
105#else /* CONFIG_X86_64 */
106#define __X64_SYS_STUB0(name)
107#define __X64_SYS_STUBx(x, name, ...)
108#define __X64_COND_SYSCALL(name)
109#define __X64_SYS_NI(name)
110#endif /* CONFIG_X86_64 */
111
112#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
113#define __IA32_SYS_STUB0(name) \
114 __SYS_STUB0(ia32, sys_##name)
115
116#define __IA32_SYS_STUBx(x, name, ...) \
117 __SYS_STUBx(ia32, sys##name, \
118 SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
119
120#define __IA32_COND_SYSCALL(name) \
121 __COND_SYSCALL(ia32, sys_##name)
122
123#define __IA32_SYS_NI(name) \
124 __SYS_NI(ia32, sys_##name)
125#else /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
126#define __IA32_SYS_STUB0(name)
127#define __IA32_SYS_STUBx(x, name, ...)
128#define __IA32_COND_SYSCALL(name)
129#define __IA32_SYS_NI(name)
130#endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
131
132#ifdef CONFIG_IA32_EMULATION
133/*
134 * For IA32 emulation, we need to handle "compat" syscalls *and* create
135 * additional wrappers (aptly named __ia32_sys_xyzzy) which decode the
136 * ia32 regs in the proper order for shared or "common" syscalls. As some
137 * syscalls may not be implemented, we need to expand COND_SYSCALL in
138 * kernel/sys_ni.c and SYS_NI in kernel/time/posix-stubs.c to cover this
139 * case as well.
140 */
141#define __IA32_COMPAT_SYS_STUB0(name) \
142 __SYS_STUB0(ia32, compat_sys_##name)
143
144#define __IA32_COMPAT_SYS_STUBx(x, name, ...) \
145 __SYS_STUBx(ia32, compat_sys##name, \
146 SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
147
148#define __IA32_COMPAT_COND_SYSCALL(name) \
149 __COND_SYSCALL(ia32, compat_sys_##name)
150
151#define __IA32_COMPAT_SYS_NI(name) \
152 __SYS_NI(ia32, compat_sys_##name)
153
154#else /* CONFIG_IA32_EMULATION */
155#define __IA32_COMPAT_SYS_STUB0(name)
156#define __IA32_COMPAT_SYS_STUBx(x, name, ...)
157#define __IA32_COMPAT_COND_SYSCALL(name)
158#define __IA32_COMPAT_SYS_NI(name)
159#endif /* CONFIG_IA32_EMULATION */
160
161
162#ifdef CONFIG_X86_X32_ABI
163/*
164 * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware
165 * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common
166 * with x86_64 obviously do not need such care.
167 */
168#define __X32_COMPAT_SYS_STUB0(name) \
169 __SYS_STUB0(x64, compat_sys_##name)
170
171#define __X32_COMPAT_SYS_STUBx(x, name, ...) \
172 __SYS_STUBx(x64, compat_sys##name, \
173 SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))
174
175#define __X32_COMPAT_COND_SYSCALL(name) \
176 __COND_SYSCALL(x64, compat_sys_##name)
177
178#define __X32_COMPAT_SYS_NI(name) \
179 __SYS_NI(x64, compat_sys_##name)
180#else /* CONFIG_X86_X32_ABI */
181#define __X32_COMPAT_SYS_STUB0(name)
182#define __X32_COMPAT_SYS_STUBx(x, name, ...)
183#define __X32_COMPAT_COND_SYSCALL(name)
184#define __X32_COMPAT_SYS_NI(name)
185#endif /* CONFIG_X86_X32_ABI */
186
187
188#ifdef CONFIG_COMPAT
189/*
190 * Compat means IA32_EMULATION and/or X86_X32. As they use a different
191 * mapping of registers to parameters, we need to generate stubs for each
192 * of them.
193 */
194#define COMPAT_SYSCALL_DEFINE0(name) \
195 static long \
196 __do_compat_sys_##name(const struct pt_regs *__unused); \
197 __IA32_COMPAT_SYS_STUB0(name) \
198 __X32_COMPAT_SYS_STUB0(name) \
199 static long \
200 __do_compat_sys_##name(const struct pt_regs *__unused)
201
202#define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
203 static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
204 static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
205 __IA32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__) \
206 __X32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__) \
207 static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
208 { \
209 return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
210 } \
211 static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
212
213/*
214 * As some compat syscalls may not be implemented, we need to expand
215 * COND_SYSCALL_COMPAT in kernel/sys_ni.c and COMPAT_SYS_NI in
216 * kernel/time/posix-stubs.c to cover this case as well.
217 */
218#define COND_SYSCALL_COMPAT(name) \
219 __IA32_COMPAT_COND_SYSCALL(name) \
220 __X32_COMPAT_COND_SYSCALL(name)
221
222#define COMPAT_SYS_NI(name) \
223 __IA32_COMPAT_SYS_NI(name) \
224 __X32_COMPAT_SYS_NI(name)
225
226#endif /* CONFIG_COMPAT */
227
228#define __SYSCALL_DEFINEx(x, name, ...) \
229 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
230 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
231 __X64_SYS_STUBx(x, name, __VA_ARGS__) \
232 __IA32_SYS_STUBx(x, name, __VA_ARGS__) \
233 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
234 { \
235 long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
236 __MAP(x,__SC_TEST,__VA_ARGS__); \
237 __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
238 return ret; \
239 } \
240 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
241
242/*
243 * As the generic SYSCALL_DEFINE0() macro does not decode any parameters for
244 * obvious reasons, and passing struct pt_regs *regs to it in %rdi does not
245 * hurt, we only need to re-define it here to keep the naming congruent to
246 * SYSCALL_DEFINEx() -- which is essential for the COND_SYSCALL() and SYS_NI()
247 * macros to work correctly.
248 */
249#define SYSCALL_DEFINE0(sname) \
250 SYSCALL_METADATA(_##sname, 0); \
251 static long __do_sys_##sname(const struct pt_regs *__unused); \
252 __X64_SYS_STUB0(sname) \
253 __IA32_SYS_STUB0(sname) \
254 static long __do_sys_##sname(const struct pt_regs *__unused)
255
256#define COND_SYSCALL(name) \
257 __X64_COND_SYSCALL(name) \
258 __IA32_COND_SYSCALL(name)
259
260#define SYS_NI(name) \
261 __X64_SYS_NI(name) \
262 __IA32_SYS_NI(name)
263
264
265/*
266 * For VSYSCALLS, we need to declare these three syscalls with the new
267 * pt_regs-based calling convention for in-kernel use.
268 */
269long __x64_sys_getcpu(const struct pt_regs *regs);
270long __x64_sys_gettimeofday(const struct pt_regs *regs);
271long __x64_sys_time(const struct pt_regs *regs);
272
273#endif /* _ASM_X86_SYSCALL_WRAPPER_H */
274

source code of linux/arch/x86/include/asm/syscall_wrapper.h