arch/x86/include/asm/syscall_wrapper.h

   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 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 #define __SYS_NI(abi, name)                                             \
  90         SYSCALL_ALIAS(__##abi##_##name, sys_ni_posix_timers);
  91
  92 #ifdef CONFIG_X86_64
  93 #define __X64_SYS_STUB0(name)                                           \
  94         __SYS_STUB0(x64, sys_##name)
  95
  96 #define __X64_SYS_STUBx(x, name, ...)                                   \
  97         __SYS_STUBx(x64, sys##name,                                     \
  98                     SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))
  99
 100 #define __X64_COND_SYSCALL(name)                                        \
 101         __COND_SYSCALL(x64, sys_##name)
 102
 103 #define __X64_SYS_NI(name)                                              \
 104         __SYS_NI(x64, sys_##name)
 105 #else /* CONFIG_X86_64 */
 106 #define __X64_SYS_STUB0(name)
 107 #define __X64_SYS_STUBx(x, name, ...)
 108 #define __X64_COND_SYSCALL(name)
 109 #define __X64_SYS_NI(name)
 110 #endif /* CONFIG_X86_64 */
 111
 112 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 113 #define __IA32_SYS_STUB0(name)                                          \
 114         __SYS_STUB0(ia32, sys_##name)
 115
 116 #define __IA32_SYS_STUBx(x, name, ...)                                  \
 117         __SYS_STUBx(ia32, sys##name,                                    \
 118                     SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
 119
 120 #define __IA32_COND_SYSCALL(name)                                       \
 121         __COND_SYSCALL(ia32, sys_##name)
 122
 123 #define __IA32_SYS_NI(name)                                             \
 124         __SYS_NI(ia32, sys_##name)
 125 #else /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
 126 #define __IA32_SYS_STUB0(name)
 127 #define __IA32_SYS_STUBx(x, name, ...)
 128 #define __IA32_COND_SYSCALL(name)
 129 #define __IA32_SYS_NI(name)
 130 #endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
 131
 132 #ifdef CONFIG_IA32_EMULATION
 133 /*
 134  * For IA32 emulation, we need to handle "compat" syscalls *and* create
 135  * additional wrappers (aptly named __ia32_sys_xyzzy) which decode the
 136  * ia32 regs in the proper order for shared or "common" syscalls. As some
 137  * syscalls may not be implemented, we need to expand COND_SYSCALL in
 138  * kernel/sys_ni.c and SYS_NI in kernel/time/posix-stubs.c to cover this
 139  * case as well.
 140  */
 141 #define __IA32_COMPAT_SYS_STUB0(name)                                   \
 142         __SYS_STUB0(ia32, compat_sys_##name)
 143
 144 #define __IA32_COMPAT_SYS_STUBx(x, name, ...)                           \
 145         __SYS_STUBx(ia32, compat_sys##name,                             \
 146                     SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
 147
 148 #define __IA32_COMPAT_COND_SYSCALL(name)                                \
 149         __COND_SYSCALL(ia32, compat_sys_##name)
 150
 151 #define __IA32_COMPAT_SYS_NI(name)                                      \
 152         __SYS_NI(ia32, compat_sys_##name)
 153
 154 #else /* CONFIG_IA32_EMULATION */
 155 #define __IA32_COMPAT_SYS_STUB0(name)
 156 #define __IA32_COMPAT_SYS_STUBx(x, name, ...)
 157 #define __IA32_COMPAT_COND_SYSCALL(name)
 158 #define __IA32_COMPAT_SYS_NI(name)
 159 #endif /* CONFIG_IA32_EMULATION */
 160
 161
 162 #ifdef CONFIG_X86_X32
 163 /*
 164  * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware
 165  * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common
 166  * with x86_64 obviously do not need such care.
 167  */
 168 #define __X32_COMPAT_SYS_STUB0(name)                                    \
 169         __SYS_STUB0(x64, compat_sys_##name)
 170
 171 #define __X32_COMPAT_SYS_STUBx(x, name, ...)                            \
 172         __SYS_STUBx(x64, compat_sys##name,                              \
 173                     SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))
 174
 175 #define __X32_COMPAT_COND_SYSCALL(name)                                 \
 176         __COND_SYSCALL(x64, compat_sys_##name)
 177
 178 #define __X32_COMPAT_SYS_NI(name)                                       \
 179         __SYS_NI(x64, compat_sys_##name)
 180 #else /* CONFIG_X86_X32 */
 181 #define __X32_COMPAT_SYS_STUB0(name)
 182 #define __X32_COMPAT_SYS_STUBx(x, name, ...)
 183 #define __X32_COMPAT_COND_SYSCALL(name)
 184 #define __X32_COMPAT_SYS_NI(name)
 185 #endif /* CONFIG_X86_X32 */
 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 and COMPAT_SYS_NI in
 216  * kernel/time/posix-stubs.c to cover this case as well.
 217  */
 218 #define COND_SYSCALL_COMPAT(name)                                       \
 219         __IA32_COMPAT_COND_SYSCALL(name)                                \
 220         __X32_COMPAT_COND_SYSCALL(name)
 221
 222 #define COMPAT_SYS_NI(name)                                             \
 223         __IA32_COMPAT_SYS_NI(name)                                      \
 224         __X32_COMPAT_SYS_NI(name)
 225
 226 #endif /* CONFIG_COMPAT */
 227
 228 #define __SYSCALL_DEFINEx(x, name, ...)                                 \
 229         static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));     \
 230         static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
 231         __X64_SYS_STUBx(x, name, __VA_ARGS__)                           \
 232         __IA32_SYS_STUBx(x, name, __VA_ARGS__)                          \
 233         static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))      \
 234         {                                                               \
 235                 long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
 236                 __MAP(x,__SC_TEST,__VA_ARGS__);                         \
 237                 __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));       \
 238                 return ret;                                             \
 239         }                                                               \
 240         static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 241
 242 /*
 243  * As the generic SYSCALL_DEFINE0() macro does not decode any parameters for
 244  * obvious reasons, and passing struct pt_regs *regs to it in %rdi does not
 245  * hurt, we only need to re-define it here to keep the naming congruent to
 246  * SYSCALL_DEFINEx() -- which is essential for the COND_SYSCALL() and SYS_NI()
 247  * macros to work correctly.
 248  */
 249 #define SYSCALL_DEFINE0(sname)                                          \
 250         SYSCALL_METADATA(_##sname, 0);                                  \
 251         static long __do_sys_##sname(const struct pt_regs *__unused);   \
 252         __X64_SYS_STUB0(sname)                                          \
 253         __IA32_SYS_STUB0(sname)                                         \
 254         static long __do_sys_##sname(const struct pt_regs *__unused)
 255
 256 #define COND_SYSCALL(name)                                              \
 257         __X64_COND_SYSCALL(name)                                        \
 258         __IA32_COND_SYSCALL(name)
 259
 260 #define SYS_NI(name)                                                    \
 261         __X64_SYS_NI(name)                                              \
 262         __IA32_SYS_NI(name)
 263
 264
 265 /*
 266  * For VSYSCALLS, we need to declare these three syscalls with the new
 267  * pt_regs-based calling convention for in-kernel use.
 268  */
 269 long __x64_sys_getcpu(const struct pt_regs *regs);
 270 long __x64_sys_gettimeofday(const struct pt_regs *regs);
 271 long __x64_sys_time(const struct pt_regs *regs);
 272
 273 #endif /* _ASM_X86_SYSCALL_WRAPPER_H */