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 #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
  62 /* SYSCALL_PT_ARGS is Adapted from s390x */
  63 #define SYSCALL_PT_ARG6(m, t1, t2, t3, t4, t5, t6)                      \
  64         SYSCALL_PT_ARG5(m, t1, t2, t3, t4, t5), m(t6, (regs->bp))
  65 #define SYSCALL_PT_ARG5(m, t1, t2, t3, t4, t5)                          \
  66         SYSCALL_PT_ARG4(m, t1, t2, t3, t4),  m(t5, (regs->di))
  67 #define SYSCALL_PT_ARG4(m, t1, t2, t3, t4)                              \
  68         SYSCALL_PT_ARG3(m, t1, t2, t3),  m(t4, (regs->si))
  69 #define SYSCALL_PT_ARG3(m, t1, t2, t3)                                  \
  70         SYSCALL_PT_ARG2(m, t1, t2), m(t3, (regs->dx))
  71 #define SYSCALL_PT_ARG2(m, t1, t2)                                      \
  72         SYSCALL_PT_ARG1(m, t1), m(t2, (regs->cx))
  73 #define SYSCALL_PT_ARG1(m, t1) m(t1, (regs->bx))
  74 #define SYSCALL_PT_ARGS(x, ...) SYSCALL_PT_ARG##x(__VA_ARGS__)
  75
  76 #define __SC_COMPAT_CAST(t, a)                                          \
  77         (__typeof(__builtin_choose_expr(__TYPE_IS_L(t), 0, 0U)))        \
  78         (unsigned int)a
  79
  80 /* Mapping of registers to parameters for syscalls on i386 */
  81 #define SC_IA32_REGS_TO_ARGS(x, ...)                                    \
  82         SYSCALL_PT_ARGS(x, __SC_COMPAT_CAST,                            \
  83                         __MAP(x, __SC_TYPE, __VA_ARGS__))               \
  84
  85 #define __SYS_STUB0(abi, name)                                          \
  86         long __##abi##_##name(const struct pt_regs *regs);              \
  87         ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO);                 \
  88         long __##abi##_##name(const struct pt_regs *regs)               \
  89                 __alias(__do_##name);
  90
  91 #define __SYS_STUBx(abi, name, ...)                                     \
  92         long __##abi##_##name(const struct pt_regs *regs);              \
  93         ALLOW_ERROR_INJECTION(__##abi##_##name, ERRNO);                 \
  94         long __##abi##_##name(const struct pt_regs *regs)               \
  95         {                                                               \
  96                 return __se_##name(__VA_ARGS__);                        \
  97         }
  98
  99 #define __COND_SYSCALL(abi, name)                                       \
 100         __weak long __##abi##_##name(const struct pt_regs *__unused);   \
 101         __weak long __##abi##_##name(const struct pt_regs *__unused)    \
 102         {                                                               \
 103                 return sys_ni_syscall();                                \
 104         }
 105
 106 #ifdef CONFIG_X86_64
 107 #define __X64_SYS_STUB0(name)                                           \
 108         __SYS_STUB0(x64, sys_##name)
 109
 110 #define __X64_SYS_STUBx(x, name, ...)                                   \
 111         __SYS_STUBx(x64, sys##name,                                     \
 112                     SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))
 113
 114 #define __X64_COND_SYSCALL(name)                                        \
 115         __COND_SYSCALL(x64, sys_##name)
 116
 117 #else /* CONFIG_X86_64 */
 118 #define __X64_SYS_STUB0(name)
 119 #define __X64_SYS_STUBx(x, name, ...)
 120 #define __X64_COND_SYSCALL(name)
 121 #endif /* CONFIG_X86_64 */
 122
 123 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 124 #define __IA32_SYS_STUB0(name)                                          \
 125         __SYS_STUB0(ia32, sys_##name)
 126
 127 #define __IA32_SYS_STUBx(x, name, ...)                                  \
 128         __SYS_STUBx(ia32, sys##name,                                    \
 129                     SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
 130
 131 #define __IA32_COND_SYSCALL(name)                                       \
 132         __COND_SYSCALL(ia32, sys_##name)
 133
 134 #else /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
 135 #define __IA32_SYS_STUB0(name)
 136 #define __IA32_SYS_STUBx(x, name, ...)
 137 #define __IA32_COND_SYSCALL(name)
 138 #endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */
 139
 140 #ifdef CONFIG_IA32_EMULATION
 141 /*
 142  * For IA32 emulation, we need to handle "compat" syscalls *and* create
 143  * additional wrappers (aptly named __ia32_sys_xyzzy) which decode the
 144  * ia32 regs in the proper order for shared or "common" syscalls. As some
 145  * syscalls may not be implemented, we need to expand COND_SYSCALL in
 146  * kernel/sys_ni.c to cover this case as well.
 147  */
 148 #define __IA32_COMPAT_SYS_STUB0(name)                                   \
 149         __SYS_STUB0(ia32, compat_sys_##name)
 150
 151 #define __IA32_COMPAT_SYS_STUBx(x, name, ...)                           \
 152         __SYS_STUBx(ia32, compat_sys##name,                             \
 153                     SC_IA32_REGS_TO_ARGS(x, __VA_ARGS__))
 154
 155 #define __IA32_COMPAT_COND_SYSCALL(name)                                \
 156         __COND_SYSCALL(ia32, compat_sys_##name)
 157
 158 #else /* CONFIG_IA32_EMULATION */
 159 #define __IA32_COMPAT_SYS_STUB0(name)
 160 #define __IA32_COMPAT_SYS_STUBx(x, name, ...)
 161 #define __IA32_COMPAT_COND_SYSCALL(name)
 162 #endif /* CONFIG_IA32_EMULATION */
 163
 164
 165 #ifdef CONFIG_X86_X32_ABI
 166 /*
 167  * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware
 168  * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common
 169  * with x86_64 obviously do not need such care.
 170  */
 171 #define __X32_COMPAT_SYS_STUB0(name)                                    \
 172         __SYS_STUB0(x64, compat_sys_##name)
 173
 174 #define __X32_COMPAT_SYS_STUBx(x, name, ...)                            \
 175         __SYS_STUBx(x64, compat_sys##name,                              \
 176                     SC_X86_64_REGS_TO_ARGS(x, __VA_ARGS__))
 177
 178 #define __X32_COMPAT_COND_SYSCALL(name)                                 \
 179         __COND_SYSCALL(x64, compat_sys_##name)
 180
 181 #else /* CONFIG_X86_X32_ABI */
 182 #define __X32_COMPAT_SYS_STUB0(name)
 183 #define __X32_COMPAT_SYS_STUBx(x, name, ...)
 184 #define __X32_COMPAT_COND_SYSCALL(name)
 185 #endif /* CONFIG_X86_X32_ABI */
 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 to cover this case as well.
 216  */
 217 #define COND_SYSCALL_COMPAT(name)                                       \
 218         __IA32_COMPAT_COND_SYSCALL(name)                                \
 219         __X32_COMPAT_COND_SYSCALL(name)
 220
 221 #endif /* CONFIG_COMPAT */
 222
 223 #define __SYSCALL_DEFINEx(x, name, ...)                                 \
 224         static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));     \
 225         static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
 226         __X64_SYS_STUBx(x, name, __VA_ARGS__)                           \
 227         __IA32_SYS_STUBx(x, name, __VA_ARGS__)                          \
 228         static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))      \
 229         {                                                               \
 230                 long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));\
 231                 __MAP(x,__SC_TEST,__VA_ARGS__);                         \
 232                 __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));       \
 233                 return ret;                                             \
 234         }                                                               \
 235         static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 236
 237 /*
 238  * As the generic SYSCALL_DEFINE0() macro does not decode any parameters for
 239  * obvious reasons, and passing struct pt_regs *regs to it in %rdi does not
 240  * hurt, we only need to re-define it here to keep the naming congruent to
 241  * SYSCALL_DEFINEx() -- which is essential for the COND_SYSCALL() macro
 242  * to work correctly.
 243  */
 244 #define SYSCALL_DEFINE0(sname)                                          \
 245         SYSCALL_METADATA(_##sname, 0);                                  \
 246         static long __do_sys_##sname(const struct pt_regs *__unused);   \
 247         __X64_SYS_STUB0(sname)                                          \
 248         __IA32_SYS_STUB0(sname)                                         \
 249         static long __do_sys_##sname(const struct pt_regs *__unused)
 250
 251 #define COND_SYSCALL(name)                                              \
 252         __X64_COND_SYSCALL(name)                                        \
 253         __IA32_COND_SYSCALL(name)
 254
 255
 256 /*
 257  * For VSYSCALLS, we need to declare these three syscalls with the new
 258  * pt_regs-based calling convention for in-kernel use.
 259  */
 260 long __x64_sys_getcpu(const struct pt_regs *regs);
 261 long __x64_sys_gettimeofday(const struct pt_regs *regs);
 262 long __x64_sys_time(const struct pt_regs *regs);
 263
 264 #endif /* _ASM_X86_SYSCALL_WRAPPER_H */