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 11 extern long __x64_sys_ni_syscall(const struct pt_regs *regs); 12 extern 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 /* Mapping of registers to parameters for syscalls on i386 */ 62 #define SC_IA32_REGS_TO_ARGS(x, ...) \ 63 __MAP(x,__SC_ARGS \ 64 ,,(unsigned int)regs->bx,,(unsigned int)regs->cx \ 65 ,,(unsigned int)regs->dx,,(unsigned int)regs->si \ 66 ,,(unsigned int)regs->di,,(unsigned int)regs->bp) 67 68 #define __SYS_STUB0(abi, name) \ 69 long __##abi##_##name(const struct pt_regs *regs); \ 70 ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO); \ 71 long __##abi##_##name(const struct pt_regs *regs) \ 72 __alias(__do_##name); 73 74 #define __SYS_STUBx(abi, name, ...) \ 75 long __##abi##_##name(const struct pt_regs *regs); \ 76 ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO); \ 77 long __##abi##_##name(const struct pt_regs *regs) \ 78 { \ 79 return __se_##name(__VA_ARGS__); \ 80 } 81 82 #define __COND_SYSCALL(abi, name) \ 83 __weak long __##abi##_##name(const struct pt_regs *__unused); \ 84 __weak long __##abi##_##name(const struct pt_regs *__unused) \ 85 { \ 86 return sys_ni_syscall(); \ 87 } 88 89 #ifdef CONFIG_X86_64 90 #define __X64_SYS_STUB0(name) \ 91 __SYS_STUB0(x64, sys_##name) 92 93 #define __X64_SYS_STUBx(x, name, ...) \ 94 __SYS_STUBx(x64, sys##name, \ 95 SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__)) 96 97 #define __X64_COND_SYSCALL(name) \ 98 __COND_SYSCALL(x64, sys_##name) 99 100 #else /* CONFIG_X86_64 */ 101 #define __X64_SYS_STUB0(name) 102 #define __X64_SYS_STUBx(x, name, ...) 103 #define __X64_COND_SYSCALL(name) 104 #endif /* CONFIG_X86_64 */ 105 106 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) 107 #define __IA32_SYS_STUB0(name) \ 108 __SYS_STUB0(ia32, sys_##name) 109 110 #define __IA32_SYS_STUBx(x, name, ...) \ 111 __SYS_STUBx(ia32, sys##name, \ 112 SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__)) 113 114 #define __IA32_COND_SYSCALL(name) \ 115 __COND_SYSCALL(ia32, sys_##name) 116 117 #else /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */ 118 #define __IA32_SYS_STUB0(name) 119 #define __IA32_SYS_STUBx(x, name, ...) 120 #define __IA32_COND_SYSCALL(name) 121 #endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */ 122 123 #ifdef CONFIG_IA32_EMULATION 124 /* 125 * For IA32 emulation, we need to handle "compat" syscalls *and* create 126 * additional wrappers (aptly named __ia32_sys_xyzzy) which decode the 127 * ia32 regs in the proper order for shared or "common" syscalls. As some 128 * syscalls may not be implemented, we need to expand COND_SYSCALL in 129 * kernel/sys_ni.c to cover this case as well. 130 */ 131 #define __IA32_COMPAT_SYS_STUB0(name) \ 132 __SYS_STUB0(ia32, compat_sys_##name) 133 134 #define __IA32_COMPAT_SYS_STUBx(x, name, ...) \ 135 __SYS_STUBx(ia32, compat_sys##name, \ 136 SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__)) 137 138 #define __IA32_COMPAT_COND_SYSCALL(name) \ 139 __COND_SYSCALL(ia32, compat_sys_##name) 140 141 #else /* CONFIG_IA32_EMULATION */ 142 #define __IA32_COMPAT_SYS_STUB0(name) 143 #define __IA32_COMPAT_SYS_STUBx(x, name, ...) 144 #define __IA32_COMPAT_COND_SYSCALL(name) 145 #endif /* CONFIG_IA32_EMULATION */ 146 147 148 #ifdef CONFIG_X86_X32_ABI 149 /* 150 * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware 151 * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common 152 * with x86_64 obviously do not need such care. 153 */ 154 #define __X32_COMPAT_SYS_STUB0(name) \ 155 __SYS_STUB0(x64, compat_sys_##name) 156 157 #define __X32_COMPAT_SYS_STUBx(x, name, ...) \ 158 __SYS_STUBx(x64, compat_sys##name, \ 159 SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__)) 160 161 #define __X32_COMPAT_COND_SYSCALL(name) \ 162 __COND_SYSCALL(x64, compat_sys_##name) 163 164 #else /* CONFIG_X86_X32_ABI */ 165 #define __X32_COMPAT_SYS_STUB0(name) 166 #define __X32_COMPAT_SYS_STUBx(x, name, ...) 167 #define __X32_COMPAT_COND_SYSCALL(name) 168 #endif /* CONFIG_X86_X32_ABI */ 169 170 171 #ifdef CONFIG_COMPAT 172 /* 173 * Compat means IA32_EMULATION and/or X86_X32. As they use a different 174 * mapping of registers to parameters, we need to generate stubs for each 175 * of them. 176 */ 177 #define COMPAT_SYSCALL_DEFINE0(name) \ 178 static long \ 179 __do_compat_sys_##name(const struct pt_regs *__unused); \ 180 __IA32_COMPAT_SYS_STUB0(name) \ 181 __X32_COMPAT_SYS_STUB0(name) \ 182 static long \ 183 __do_compat_sys_##name(const struct pt_regs *__unused) 184 185 #define COMPAT_SYSCALL_DEFINEx(x, name, ...) \ 186 static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \ 187 static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\ 188 __IA32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__) \ 189 __X32_COMPAT_SYS_STUBx(x, name, __VA_ARGS__) \ 190 static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \ 191 { \ 192 return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\ 193 } \ 194 static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) 195 196 /* 197 * As some compat syscalls may not be implemented, we need to expand 198 * COND_SYSCALL_COMPAT in kernel/sys_ni.c to cover this case as well. 199 */ 200 #define COND_SYSCALL_COMPAT(name) \ 201 __IA32_COMPAT_COND_SYSCALL(name) \ 202 __X32_COMPAT_COND_SYSCALL(name) 203 204 #endif /* CONFIG_COMPAT */ 205 206 #define __SYSCALL_DEFINEx(x, name, ...) \ 207 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \ 208 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\ 209 __X64_SYS_STUBx(x, name, __VA_ARGS__) \ 210 __IA32_SYS_STUBx(x, name, __VA_ARGS__) \ 211 static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \ 212 { \ 213 long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\ 214 __MAP(x,__SC_TEST,__VA_ARGS__); \ 215 __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \ 216 return ret; \ 217 } \ 218 static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) 219 220 /* 221 * As the generic SYSCALL_DEFINE0() macro does not decode any parameters for 222 * obvious reasons, and passing struct pt_regs *regs to it in %rdi does not 223 * hurt, we only need to re-define it here to keep the naming congruent to 224 * SYSCALL_DEFINEx() -- which is essential for the COND_SYSCALL() macro 225 * to work correctly. 226 */ 227 #define SYSCALL_DEFINE0(sname) \ 228 SYSCALL_METADATA(_##sname, 0); \ 229 static long __do_sys_##sname(const struct pt_regs *__unused); \ 230 __X64_SYS_STUB0(sname) \ 231 __IA32_SYS_STUB0(sname) \ 232 static long __do_sys_##sname(const struct pt_regs *__unused) 233 234 #define COND_SYSCALL(name) \ 235 __X64_COND_SYSCALL(name) \ 236 __IA32_COND_SYSCALL(name) 237 238 239 /* 240 * For VSYSCALLS, we need to declare these three syscalls with the new 241 * pt_regs-based calling convention for in-kernel use. 242 */ 243 long __x64_sys_getcpu(const struct pt_regs *regs); 244 long __x64_sys_gettimeofday(const struct pt_regs *regs); 245 long __x64_sys_time(const struct pt_regs *regs); 246 247 #endif /* _ASM_X86_SYSCALL_WRAPPER_H */ 248