LXR linux/arch/x86/include/asm/syscall

   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
   9struct pt_regs;
  10
  11extern long __x64_sys_ni_syscall(const struct pt_regs *regs);
  12extern 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 */
 269long __x64_sys_getcpu(const struct pt_regs *regs);
 270long __x64_sys_gettimeofday(const struct pt_regs *regs);
 271long __x64_sys_time(const struct pt_regs *regs);
 272
 273#endif /* _ASM_X86_SYSCALL_WRAPPER_H */
 274