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 */ 250