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
62/* SYSCALL_PT_ARGS is Adapted from s390x */
63#define SYSCALL_PT_ARG6(m, t1, t2, t3, t4, t5, t6) \
64 SYSCALL_PT_ARG5(m, t1, t2, t3, t4, t5), m(t6, (regs->bp))
65#define SYSCALL_PT_ARG5(m, t1, t2, t3, t4, t5) \
66 SYSCALL_PT_ARG4(m, t1, t2, t3, t4), m(t5, (regs->di))
67#define SYSCALL_PT_ARG4(m, t1, t2, t3, t4) \
68 SYSCALL_PT_ARG3(m, t1, t2, t3), m(t4, (regs->si))
69#define SYSCALL_PT_ARG3(m, t1, t2, t3) \
70 SYSCALL_PT_ARG2(m, t1, t2), m(t3, (regs->dx))
71#define SYSCALL_PT_ARG2(m, t1, t2) \
72 SYSCALL_PT_ARG1(m, t1), m(t2, (regs->cx))
73#define SYSCALL_PT_ARG1(m, t1) m(t1, (regs->bx))
74#define SYSCALL_PT_ARGS(x, ...) SYSCALL_PT_ARG##x(__VA_ARGS__)
75
76#define __SC_COMPAT_CAST(t, a) \
77 (__typeof(__builtin_choose_expr(__TYPE_IS_L(t), 0, 0U))) \
78 (unsigned int)a
79
80/* Mapping of registers to parameters for syscalls on i386 */
81#define SC_IA32_REGS_TO_ARGS(x, ...) \
82 SYSCALL_PT_ARGS(x, __SC_COMPAT_CAST, \
83 __MAP(x, __SC_TYPE, __VA_ARGS__)) \
84
85#define __SYS_STUB0(abi, name) \
86 long __##abi##_##name(const struct pt_regs *regs); \
87 ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO); \
88 long __##abi##_##name(const struct pt_regs *regs) \
89 __alias(__do_##name);
90
91#define __SYS_STUBx(abi, name, ...) \
92 long __##abi##_##name(const struct pt_regs *regs); \
93 ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO); \
94 long __##abi##_##name(const struct pt_regs *regs) \
95 { \
96 return __se_##name(__VA_ARGS__); \
97 }
98
99#define __COND_SYSCALL(abi, name) \
100 __weak long __##abi##_##name(const struct pt_regs *__unused); \
101 __weak long __##abi##_##name(const struct pt_regs *__unused) \
102 { \
103 return sys_ni_syscall(); \
104 }
105
106#ifdef CONFIG_X86_64
107#define __X64_SYS_STUB0(name) \
108 __SYS_STUB0(x64, sys_##name)
109
110#define __X64_SYS_STUBx(x, name, ...) \
111 __SYS_STUBx(x64, sys##name, \
112 SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))
113
114#define __X64_COND_SYSCALL(name) \
115 __COND_SYSCALL(x64, sys_##name)
116
117#else /* CONFIG_X86_64 */
118#define __X64_SYS_STUB0(name)
119#define __X64_SYS_STUBx(x, name, ...)
120#define __X64_COND_SYSCALL(name)
121#endif /* CONFIG_X86_64 */
122
123#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
124#define __IA32_SYS_STUB0(name) \
125 __SYS_STUB0(ia32, sys_##name)
126
127#define __IA32_SYS_STUBx(x, name, ...) \
128 __SYS_STUBx(ia32, sys##name, \
129 SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
130
131#define __IA32_COND_SYSCALL(name) \
132 __COND_SYSCALL(ia32, sys_##name)
133
134#else /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
135#define __IA32_SYS_STUB0(name)
136#define __IA32_SYS_STUBx(x, name, ...)
137#define __IA32_COND_SYSCALL(name)
138#endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
139
140#ifdef CONFIG_IA32_EMULATION
141/*
142 * For IA32 emulation, we need to handle "compat" syscalls *and* create
143 * additional wrappers (aptly named __ia32_sys_xyzzy) which decode the
144 * ia32 regs in the proper order for shared or "common" syscalls. As some
145 * syscalls may not be implemented, we need to expand COND_SYSCALL in
146 * kernel/sys_ni.c to cover this case as well.
147 */
148#define __IA32_COMPAT_SYS_STUB0(name) \
149 __SYS_STUB0(ia32, compat_sys_##name)
150
151#define __IA32_COMPAT_SYS_STUBx(x, name, ...) \
152 __SYS_STUBx(ia32, compat_sys##name, \
153 SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
154
155#define __IA32_COMPAT_COND_SYSCALL(name) \
156 __COND_SYSCALL(ia32, compat_sys_##name)
157
158#else /* CONFIG_IA32_EMULATION */
159#define __IA32_COMPAT_SYS_STUB0(name)
160#define __IA32_COMPAT_SYS_STUBx(x, name, ...)
161#define __IA32_COMPAT_COND_SYSCALL(name)
162#endif /* CONFIG_IA32_EMULATION */
163
164
165#ifdef CONFIG_X86_X32_ABI
166/*
167 * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware
168 * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common
169 * with x86_64 obviously do not need such care.
170 */
171#define __X32_COMPAT_SYS_STUB0(name) \
172 __SYS_STUB0(x64, compat_sys_##name)
173
174#define __X32_COMPAT_SYS_STUBx(x, name, ...) \
175 __SYS_STUBx(x64, compat_sys##name, \
176 SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))
177
178#define __X32_COMPAT_COND_SYSCALL(name) \
179 __COND_SYSCALL(x64, compat_sys_##name)
180
181#else /* CONFIG_X86_X32_ABI */
182#define __X32_COMPAT_SYS_STUB0(name)
183#define __X32_COMPAT_SYS_STUBx(x, name, ...)
184#define __X32_COMPAT_COND_SYSCALL(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 to cover this case as well.
216 */
217#define COND_SYSCALL_COMPAT(name) \
218 __IA32_COMPAT_COND_SYSCALL(name) \
219 __X32_COMPAT_COND_SYSCALL(name)
220
221#endif /* CONFIG_COMPAT */
222
223#define __SYSCALL_DEFINEx(x, name, ...) \
224 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
225 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
226 __X64_SYS_STUBx(x, name, __VA_ARGS__) \
227 __IA32_SYS_STUBx(x, name, __VA_ARGS__) \
228 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
229 { \
230 long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
231 __MAP(x,__SC_TEST,__VA_ARGS__); \
232 __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
233 return ret; \
234 } \
235 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
236
237/*
238 * As the generic SYSCALL_DEFINE0() macro does not decode any parameters for
239 * obvious reasons, and passing struct pt_regs *regs to it in %rdi does not
240 * hurt, we only need to re-define it here to keep the naming congruent to
241 * SYSCALL_DEFINEx() -- which is essential for the COND_SYSCALL() macro
242 * to work correctly.
243 */
244#define SYSCALL_DEFINE0(sname) \
245 SYSCALL_METADATA(_##sname, 0); \
246 static long __do_sys_##sname(const struct pt_regs *__unused); \
247 __X64_SYS_STUB0(sname) \
248 __IA32_SYS_STUB0(sname) \
249 static long __do_sys_##sname(const struct pt_regs *__unused)
250
251#define COND_SYSCALL(name) \
252 __X64_COND_SYSCALL(name) \
253 __IA32_COND_SYSCALL(name)
254
255
256/*
257 * For VSYSCALLS, we need to declare these three syscalls with the new
258 * pt_regs-based calling convention for in-kernel use.
259 */
260long __x64_sys_getcpu(const struct pt_regs *regs);
261long __x64_sys_gettimeofday(const struct pt_regs *regs);
262long __x64_sys_time(const struct pt_regs *regs);
263
264#endif /* _ASM_X86_SYSCALL_WRAPPER_H */
265