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 18 /* SYSCALL_PT_ARGS is Adapted from s390x */ 19 #define SYSCALL_PT_ARG6(m, t1, t2, t3, t4, t5, t6) \ 20 SYSCALL_PT_ARG5(m, t1, t2, t3, t4, t5), m(t6, (regs->bp)) 21 #define SYSCALL_PT_ARG5(m, t1, t2, t3, t4, t5) \ 22 SYSCALL_PT_ARG4(m, t1, t2, t3, t4), m(t5, (regs->di)) 23 #define SYSCALL_PT_ARG4(m, t1, t2, t3, t4) \ 24 SYSCALL_PT_ARG3(m, t1, t2, t3), m(t4, (regs->si)) 25 #define SYSCALL_PT_ARG3(m, t1, t2, t3) \ 26 SYSCALL_PT_ARG2(m, t1, t2), m(t3, (regs->dx)) 27 #define SYSCALL_PT_ARG2(m, t1, t2) \ 28 SYSCALL_PT_ARG1(m, t1), m(t2, (regs->cx)) 29 #define SYSCALL_PT_ARG1(m, t1) m(t1, (regs->bx)) 30 #define SYSCALL_PT_ARGS(x, ...) SYSCALL_PT_ARG##x(__VA_ARGS__) 31 32 #define __SC_COMPAT_CAST(t, a) \ 33 (__typeof(__builtin_choose_expr(__TYPE_IS_L(t), 0, 0U))) \ 34 (unsigned int)a 35 36 /* Mapping of registers to parameters for syscalls on i386 */ 37 #define SC_IA32_REGS_TO_ARGS(x, ...) \ 38 SYSCALL_PT_ARGS(x, __SC_COMPAT_CAST, \ 39 __MAP(x, __SC_TYPE, __VA_ARGS__)) \ 40 41 #ifdef CONFIG_IA32_EMULATION 42 /* 43 * For IA32 emulation, we need to handle "compat" syscalls *and* create 44 * additional wrappers (aptly named __ia32_sys_xyzzy) which decode the 45 * ia32 regs in the proper order for shared or "common" syscalls. As some 46 * syscalls may not be implemented, we need to expand COND_SYSCALL in 47 * kernel/sys_ni.c and SYS_NI in kernel/time/posix-stubs.c to cover this 48 * case as well. 49 */ 50 #define __IA32_COMPAT_SYS_STUB0(x, name) \ 51 asmlinkage long __ia32_compat_sys_##name(const struct pt_regs *regs);\ 52 ALLOW_ERROR_INJECTION(__ia32_compat_sys_##name, ERRNO); \ 53 asmlinkage long __ia32_compat_sys_##name(const struct pt_regs *regs)\ 54 { \ 55 return __se_compat_sys_##name(); \ 56 } 57 58 #define __IA32_COMPAT_SYS_STUBx(x, name, ...) \ 59 asmlinkage long __ia32_compat_sys##name(const struct pt_regs *regs);\ 60 ALLOW_ERROR_INJECTION(__ia32_compat_sys##name, ERRNO); \ 61 asmlinkage long __ia32_compat_sys##name(const struct pt_regs *regs)\ 62 { \ 63 return __se_compat_sys##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__));\ 64 } 65 66 #define __IA32_SYS_STUBx(x, name, ...) \ 67 asmlinkage long __ia32_sys##name(const struct pt_regs *regs); \ 68 ALLOW_ERROR_INJECTION(__ia32_sys##name, ERRNO); \ 69 asmlinkage long __ia32_sys##name(const struct pt_regs *regs) \ 70 { \ 71 return __se_sys##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__));\ 72 } 73 74 /* 75 * To keep the naming coherent, re-define SYSCALL_DEFINE0 to create an alias 76 * named __ia32_sys_*() 77 */ 78 79 #define SYSCALL_DEFINE0(sname) \ 80 SYSCALL_METADATA(_##sname, 0); \ 81 asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused);\ 82 ALLOW_ERROR_INJECTION(__x64_sys_##sname, ERRNO); \ 83 SYSCALL_ALIAS(__ia32_sys_##sname, __x64_sys_##sname); \ 84 asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused) 85 86 #define COND_SYSCALL(name) \ 87 asmlinkage __weak long __x64_sys_##name(const struct pt_regs *__unused) \ 88 { \ 89 return sys_ni_syscall(); \ 90 } \ 91 asmlinkage __weak long __ia32_sys_##name(const struct pt_regs *__unused)\ 92 { \ 93 return sys_ni_syscall(); \ 94 } 95 96 #define SYS_NI(name) \ 97 SYSCALL_ALIAS(__x64_sys_##name, sys_ni_posix_timers); \ 98 SYSCALL_ALIAS(__ia32_sys_##name, sys_ni_posix_timers) 99 100 #else /* CONFIG_IA32_EMULATION */ 101 #define __IA32_COMPAT_SYS_STUBx(x, name, ...) 102 #define __IA32_SYS_STUBx(x, fullname, name, ...) 103 #endif /* CONFIG_IA32_EMULATION */ 104 105 106 #ifdef CONFIG_X86_X32 107 /* 108 * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware 109 * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common 110 * with x86_64 obviously do not need such care. 111 */ 112 #define __X32_COMPAT_SYS_STUB0(x, name, ...) \ 113 asmlinkage long __x32_compat_sys_##name(const struct pt_regs *regs);\ 114 ALLOW_ERROR_INJECTION(__x32_compat_sys_##name, ERRNO); \ 115 asmlinkage long __x32_compat_sys_##name(const struct pt_regs *regs)\ 116 { \ 117 return __se_compat_sys_##name();\ 118 } 119 120 #define __X32_COMPAT_SYS_STUBx(x, name, ...) \ 121 asmlinkage long __x32_compat_sys##name(const struct pt_regs *regs);\ 122 ALLOW_ERROR_INJECTION(__x32_compat_sys##name, ERRNO); \ 123 asmlinkage long __x32_compat_sys##name(const struct pt_regs *regs)\ 124 { \ 125 return __se_compat_sys##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\ 126 } 127 128 #else /* CONFIG_X86_X32 */ 129 #define __X32_COMPAT_SYS_STUB0(x, name) 130 #define __X32_COMPAT_SYS_STUBx(x, name, ...) 131 #endif /* CONFIG_X86_X32 */ 132 133 134 #ifdef CONFIG_COMPAT 135 /* 136 * Compat means IA32_EMULATION and/or X86_X32. As they use a different 137 * mapping of registers to parameters, we need to generate stubs for each 138 * of them. 139 */ 140 #define COMPAT_SYSCALL_DEFINE0(name) \ 141 static long __se_compat_sys_##name(void); \ 142 static inline long __do_compat_sys_##name(void); \ 143 __IA32_COMPAT_SYS_STUB0(x, name) \ 144 __X32_COMPAT_SYS_STUB0(x, name) \ 145 static long __se_compat_sys_##name(void) \ 146 { \ 147 return __do_compat_sys_##name(); \ 148 } \ 149 static inline long __do_compat_sys_##name(void) 150 151 #define COMPAT_SYSCALL_DEFINEx(x, name, ...) \ 152 static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \ 153 static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\ 154 __IA32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__) \ 155 __X32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__) \ 156 static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \ 157 { \ 158 return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\ 159 } \ 160 static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) 161 162 /* 163 * As some compat syscalls may not be implemented, we need to expand 164 * COND_SYSCALL_COMPAT in kernel/sys_ni.c and COMPAT_SYS_NI in 165 * kernel/time/posix-stubs.c to cover this case as well. 166 */ 167 #define COND_SYSCALL_COMPAT(name) \ 168 cond_syscall(__ia32_compat_sys_##name); \ 169 cond_syscall(__x32_compat_sys_##name) 170 171 #define COMPAT_SYS_NI(name) \ 172 SYSCALL_ALIAS(__ia32_compat_sys_##name, sys_ni_posix_timers); \ 173 SYSCALL_ALIAS(__x32_compat_sys_##name, sys_ni_posix_timers) 174 175 #endif /* CONFIG_COMPAT */ 176 177 178 /* 179 * Instead of the generic __SYSCALL_DEFINEx() definition, this macro takes 180 * struct pt_regs *regs as the only argument of the syscall stub named 181 * __x64_sys_*(). It decodes just the registers it needs and passes them on to 182 * the __se_sys_*() wrapper performing sign extension and then to the 183 * __do_sys_*() function doing the actual job. These wrappers and functions 184 * are inlined (at least in very most cases), meaning that the assembly looks 185 * as follows (slightly re-ordered for better readability): 186 * 187 * <__x64_sys_recv>: <-- syscall with 4 parameters 188 * callq <__fentry__> 189 * 190 * mov 0x70(%rdi),%rdi <-- decode regs->di 191 * mov 0x68(%rdi),%rsi <-- decode regs->si 192 * mov 0x60(%rdi),%rdx <-- decode regs->dx 193 * mov 0x38(%rdi),%rcx <-- decode regs->r10 194 * 195 * xor %r9d,%r9d <-- clear %r9 196 * xor %r8d,%r8d <-- clear %r8 197 * 198 * callq __sys_recvfrom <-- do the actual work in __sys_recvfrom() 199 * which takes 6 arguments 200 * 201 * cltq <-- extend return value to 64-bit 202 * retq <-- return 203 * 204 * This approach avoids leaking random user-provided register content down 205 * the call chain. 206 * 207 * If IA32_EMULATION is enabled, this macro generates an additional wrapper 208 * named __ia32_sys_*() which decodes the struct pt_regs *regs according 209 * to the i386 calling convention (bx, cx, dx, si, di, bp). 210 */ 211 #define __SYSCALL_DEFINEx(x, name, ...) \ 212 asmlinkage long __x64_sys##name(const struct pt_regs *regs); \ 213 ALLOW_ERROR_INJECTION(__x64_sys##name, ERRNO); \ 214 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \ 215 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\ 216 asmlinkage long __x64_sys##name(const struct pt_regs *regs) \ 217 { \ 218 return __se_sys##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\ 219 } \ 220 __IA32_SYS_STUBx(x, name, __VA_ARGS__) \ 221 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \ 222 { \ 223 long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\ 224 __MAP(x,__SC_TEST,__VA_ARGS__); \ 225 __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \ 226 return ret; \ 227 } \ 228 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) 229 230 /* 231 * As the generic SYSCALL_DEFINE0() macro does not decode any parameters for 232 * obvious reasons, and passing struct pt_regs *regs to it in %rdi does not 233 * hurt, we only need to re-define it here to keep the naming congruent to 234 * SYSCALL_DEFINEx() -- which is essential for the COND_SYSCALL() and SYS_NI() 235 * macros to work correctly. 236 */ 237 #ifndef SYSCALL_DEFINE0 238 #define SYSCALL_DEFINE0(sname) \ 239 SYSCALL_METADATA(_##sname, 0); \ 240 asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused);\ 241 ALLOW_ERROR_INJECTION(__x64_sys_##sname, ERRNO); \ 242 asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused) 243 #endif 244 245 #ifndef COND_SYSCALL 246 #define COND_SYSCALL(name) \ 247 asmlinkage __weak long __x64_sys_##name(const struct pt_regs *__unused) \ 248 { \ 249 return sys_ni_syscall(); \ 250 } 251 #endif 252 253 #ifndef SYS_NI 254 #define SYS_NI(name) SYSCALL_ALIAS(__x64_sys_##name, sys_ni_posix_timers); 255 #endif 256 257 258 /* 259 * For VSYSCALLS, we need to declare these three syscalls with the new 260 * pt_regs-based calling convention for in-kernel use. 261 */ 262 asmlinkage long __x64_sys_getcpu(const struct pt_regs *regs); 263 asmlinkage long __x64_sys_gettimeofday(const struct pt_regs *regs); 264 asmlinkage long __x64_sys_time(const struct pt_regs *regs); 265 266 #endif /* _ASM_X86_SYSCALL_WRAPPER_H */ 267