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 /* 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 */