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