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/* SPDX-License-Identifier: GPL-2.0 */
/*
* syscall_wrapper.h - x86 specific wrappers to syscall definitions
*/
#ifndef _ASM_X86_SYSCALL_WRAPPER_H
#define _ASM_X86_SYSCALL_WRAPPER_H
/*
* Instead of the generic __SYSCALL_DEFINEx() definition, this macro takes
* struct pt_regs *regs as the only argument of the syscall stub named
* sys_*(). It decodes just the registers it needs and passes them on to
* the SyS_*() wrapper and then to the SYSC_*() function doing the actual job.
* These wrappers and functions are inlined, meaning that the assembly looks
* as follows (slightly re-ordered):
*
* <sys_recv>: <-- syscall with 4 parameters
* callq <__fentry__>
*
* mov 0x70(%rdi),%rdi <-- decode regs->di
* mov 0x68(%rdi),%rsi <-- decode regs->si
* mov 0x60(%rdi),%rdx <-- decode regs->dx
* mov 0x38(%rdi),%rcx <-- decode regs->r10
*
* xor %r9d,%r9d <-- clear %r9
* xor %r8d,%r8d <-- clear %r8
*
* callq __sys_recvfrom <-- do the actual work in __sys_recvfrom()
* which takes 6 arguments
*
* cltq <-- extend return value to 64-bit
* retq <-- return
*
* This approach avoids leaking random user-provided register content down
* the call chain.
*
* As the generic SYSCALL_DEFINE0() macro does not decode any parameters for
* obvious reasons, and passing struct pt_regs *regs to it in %rdi does not
* hurt, there is no need to override it.
*/
#define __SYSCALL_DEFINEx(x, name, ...) \
asmlinkage long sys##name(const struct pt_regs *regs); \
ALLOW_ERROR_INJECTION(sys##name, ERRNO); \
static long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
asmlinkage long sys##name(const struct pt_regs *regs) \
{ \
return SyS##name(__MAP(x,__SC_ARGS \
,,regs->di,,regs->si,,regs->dx \
,,regs->r10,,regs->r8,,regs->r9)); \
} \
static long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
{ \
long ret = SYSC##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
__MAP(x,__SC_TEST,__VA_ARGS__); \
__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
return ret; \
} \
static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
/*
* For VSYSCALLS, we need to declare these three syscalls with the new
* pt_regs-based calling convention for in-kernel use.
*/
struct pt_regs;
asmlinkage long sys_getcpu(const struct pt_regs *regs); /* di,si,dx */
asmlinkage long sys_gettimeofday(const struct pt_regs *regs); /* di,si */
asmlinkage long sys_time(const struct pt_regs *regs); /* di */
#endif /* _ASM_X86_SYSCALL_WRAPPER_H */
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