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
 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_ABI
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_ABI */
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_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 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 */