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 struct pt_regs;
10
11 /* Mapping of registers to parameters for syscalls on x86-64 and x32 */
12 #define SC_X86_64_REGS_TO_ARGS(x, ...) \
13 __MAP(x,__SC_ARGS \
14 ,,regs->di,,regs->si,,regs->dx \
15 ,,regs->r10,,regs->r8,,regs->r9) \
16
17 /* Mapping of registers to parameters for syscalls on i386 */
18 #define SC_IA32_REGS_TO_ARGS(x, ...) \
19 __MAP(x,__SC_ARGS \
20 ,,(unsigned int)regs->bx,,(unsigned int)regs->cx \
21 ,,(unsigned int)regs->dx,,(unsigned int)regs->si \
22 ,,(unsigned int)regs->di,,(unsigned int)regs->bp)
23
24 #ifdef CONFIG_IA32_EMULATION
25 /*
26 * For IA32 emulation, we need to handle "compat" syscalls *and* create
27 * additional wrappers (aptly named __ia32_sys_xyzzy) which decode the
28 * ia32 regs in the proper order for shared or "common" syscalls. As some
29 * syscalls may not be implemented, we need to expand COND_SYSCALL in
30 * kernel/sys_ni.c and SYS_NI in kernel/time/posix-stubs.c to cover this
31 * case as well.
32 */
33 #define __IA32_COMPAT_SYS_STUB0(x, name) \
34 asmlinkage long __ia32_compat_sys_##name(const struct pt_regs *regs);\
35 ALLOW_ERROR_INJECTION(__ia32_compat_sys_##name, ERRNO); \
36 asmlinkage long __ia32_compat_sys_##name(const struct pt_regs *regs)\
37 { \
38 return __se_compat_sys_##name(); \
39 }
40
41 #define __IA32_COMPAT_SYS_STUBx(x, name, ...) \
42 asmlinkage long __ia32_compat_sys##name(const struct pt_regs *regs);\
43 ALLOW_ERROR_INJECTION(__ia32_compat_sys##name, ERRNO); \
44 asmlinkage long __ia32_compat_sys##name(const struct pt_regs *regs)\
45 { \
46 return __se_compat_sys##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__));\
47 }
48
49 #define __IA32_SYS_STUBx(x, name, ...) \
50 asmlinkage long __ia32_sys##name(const struct pt_regs *regs); \
51 ALLOW_ERROR_INJECTION(__ia32_sys##name, ERRNO); \
52 asmlinkage long __ia32_sys##name(const struct pt_regs *regs) \
53 { \
54 return __se_sys##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__));\
55 }
56
57 /*
58 * To keep the naming coherent, re-define SYSCALL_DEFINE0 to create an alias
59 * named __ia32_sys_*()
60 */
61
62 #define SYSCALL_DEFINE0(sname) \
63 SYSCALL_METADATA(_##sname, 0); \
64 asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused);\
65 ALLOW_ERROR_INJECTION(__x64_sys_##sname, ERRNO); \
66 SYSCALL_ALIAS(__ia32_sys_##sname, __x64_sys_##sname); \
67 asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused)
68
69 #define COND_SYSCALL(name) \
70 asmlinkage __weak long __x64_sys_##name(const struct pt_regs *__unused) \
71 { \
72 return sys_ni_syscall(); \
73 } \
74 asmlinkage __weak long __ia32_sys_##name(const struct pt_regs *__unused)\
75 { \
76 return sys_ni_syscall(); \
77 }
78
79 #define SYS_NI(name) \
80 SYSCALL_ALIAS(__x64_sys_##name, sys_ni_posix_timers); \
81 SYSCALL_ALIAS(__ia32_sys_##name, sys_ni_posix_timers)
82
83 #else /* CONFIG_IA32_EMULATION */
84 #define __IA32_COMPAT_SYS_STUBx(x, name, ...)
85 #define __IA32_SYS_STUBx(x, fullname, name, ...)
86 #endif /* CONFIG_IA32_EMULATION */
87
88
89 #ifdef CONFIG_X86_X32
90 /*
91 * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware
92 * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common
93 * with x86_64 obviously do not need such care.
94 */
95 #define __X32_COMPAT_SYS_STUB0(x, name, ...) \
96 asmlinkage long __x32_compat_sys_##name(const struct pt_regs *regs);\
97 ALLOW_ERROR_INJECTION(__x32_compat_sys_##name, ERRNO); \
98 asmlinkage long __x32_compat_sys_##name(const struct pt_regs *regs)\
99 { \
100 return __se_compat_sys_##name();\
101 }
102
103 #define __X32_COMPAT_SYS_STUBx(x, name, ...) \
104 asmlinkage long __x32_compat_sys##name(const struct pt_regs *regs);\
105 ALLOW_ERROR_INJECTION(__x32_compat_sys##name, ERRNO); \
106 asmlinkage long __x32_compat_sys##name(const struct pt_regs *regs)\
107 { \
108 return __se_compat_sys##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\
109 }
110
111 #else /* CONFIG_X86_X32 */
112 #define __X32_COMPAT_SYS_STUB0(x, name)
113 #define __X32_COMPAT_SYS_STUBx(x, name, ...)
114 #endif /* CONFIG_X86_X32 */
115
116
117 #ifdef CONFIG_COMPAT
118 /*
119 * Compat means IA32_EMULATION and/or X86_X32. As they use a different
120 * mapping of registers to parameters, we need to generate stubs for each
121 * of them.
122 */
123 #define COMPAT_SYSCALL_DEFINE0(name) \
124 static long __se_compat_sys_##name(void); \
125 static inline long __do_compat_sys_##name(void); \
126 __IA32_COMPAT_SYS_STUB0(x, name) \
127 __X32_COMPAT_SYS_STUB0(x, name) \
128 static long __se_compat_sys_##name(void) \
129 { \
130 return __do_compat_sys_##name(); \
131 } \
132 static inline long __do_compat_sys_##name(void)
133
134 #define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
135 static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
136 static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
137 __IA32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__) \
138 __X32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__) \
139 static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
140 { \
141 return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
142 } \
143 static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
144
145 /*
146 * As some compat syscalls may not be implemented, we need to expand
147 * COND_SYSCALL_COMPAT in kernel/sys_ni.c and COMPAT_SYS_NI in
148 * kernel/time/posix-stubs.c to cover this case as well.
149 */
150 #define COND_SYSCALL_COMPAT(name) \
151 cond_syscall(__ia32_compat_sys_##name); \
152 cond_syscall(__x32_compat_sys_##name)
153
154 #define COMPAT_SYS_NI(name) \
155 SYSCALL_ALIAS(__ia32_compat_sys_##name, sys_ni_posix_timers); \
156 SYSCALL_ALIAS(__x32_compat_sys_##name, sys_ni_posix_timers)
157
158 #endif /* CONFIG_COMPAT */
159
160
161 /*
162 * Instead of the generic __SYSCALL_DEFINEx() definition, this macro takes
163 * struct pt_regs *regs as the only argument of the syscall stub named
164 * __x64_sys_*(). It decodes just the registers it needs and passes them on to
165 * the __se_sys_*() wrapper performing sign extension and then to the
166 * __do_sys_*() function doing the actual job. These wrappers and functions
167 * are inlined (at least in very most cases), meaning that the assembly looks
168 * as follows (slightly re-ordered for better readability):
169 *
170 * <__x64_sys_recv>: <-- syscall with 4 parameters
171 * callq <__fentry__>
172 *
173 * mov 0x70(%rdi),%rdi <-- decode regs->di
174 * mov 0x68(%rdi),%rsi <-- decode regs->si
175 * mov 0x60(%rdi),%rdx <-- decode regs->dx
176 * mov 0x38(%rdi),%rcx <-- decode regs->r10
177 *
178 * xor %r9d,%r9d <-- clear %r9
179 * xor %r8d,%r8d <-- clear %r8
180 *
181 * callq __sys_recvfrom <-- do the actual work in __sys_recvfrom()
182 * which takes 6 arguments
183 *
184 * cltq <-- extend return value to 64-bit
185 * retq <-- return
186 *
187 * This approach avoids leaking random user-provided register content down
188 * the call chain.
189 *
190 * If IA32_EMULATION is enabled, this macro generates an additional wrapper
191 * named __ia32_sys_*() which decodes the struct pt_regs *regs according
192 * to the i386 calling convention (bx, cx, dx, si, di, bp).
193 */
194 #define __SYSCALL_DEFINEx(x, name, ...) \
195 asmlinkage long __x64_sys##name(const struct pt_regs *regs); \
196 ALLOW_ERROR_INJECTION(__x64_sys##name, ERRNO); \
197 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
198 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
199 asmlinkage long __x64_sys##name(const struct pt_regs *regs) \
200 { \
201 return __se_sys##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\
202 } \
203 __IA32_SYS_STUBx(x, name, __VA_ARGS__) \
204 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
205 { \
206 long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
207 __MAP(x,__SC_TEST,__VA_ARGS__); \
208 __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
209 return ret; \
210 } \
211 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
212
213 /*
214 * As the generic SYSCALL_DEFINE0() macro does not decode any parameters for
215 * obvious reasons, and passing struct pt_regs *regs to it in %rdi does not
216 * hurt, we only need to re-define it here to keep the naming congruent to
217 * SYSCALL_DEFINEx() -- which is essential for the COND_SYSCALL() and SYS_NI()
218 * macros to work correctly.
219 */
220 #ifndef SYSCALL_DEFINE0
221 #define SYSCALL_DEFINE0(sname) \
222 SYSCALL_METADATA(_##sname, 0); \
223 asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused);\
224 ALLOW_ERROR_INJECTION(__x64_sys_##sname, ERRNO); \
225 asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused)
226 #endif
227
228 #ifndef COND_SYSCALL
229 #define COND_SYSCALL(name) \
230 asmlinkage __weak long __x64_sys_##name(const struct pt_regs *__unused) \
231 { \
232 return sys_ni_syscall(); \
233 }
234 #endif
235
236 #ifndef SYS_NI
237 #define SYS_NI(name) SYSCALL_ALIAS(__x64_sys_##name, sys_ni_posix_timers);
238 #endif
239
240
241 /*
242 * For VSYSCALLS, we need to declare these three syscalls with the new
243 * pt_regs-based calling convention for in-kernel use.
244 */
245 asmlinkage long __x64_sys_getcpu(const struct pt_regs *regs);
246 asmlinkage long __x64_sys_gettimeofday(const struct pt_regs *regs);
247 asmlinkage long __x64_sys_time(const struct pt_regs *regs);
248
249 #endif /* _ASM_X86_SYSCALL_WRAPPER_H */