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EDIT :: psx_syscall.h

/* * Copyright (c) 2019 Andrew G. Morgan <morgan@kernel.org> * * This header, and the -lpsx library, provide a number of things to * support POSIX semantics for syscalls associated with the pthread * library. Linking this code is tricky and is done as follows: * * ld ... -lpsx -lpthread --wrap=pthread_create * or, gcc ... -lpsx -lpthread -Wl,-wrap,pthread_create * * glibc provides a subset of this functionality natively through the * nptl:setxid mechanism and could implement psx_syscall() directly * using that style of functionality but, as of 2019-11-30, the setxid * mechanism is limited to 9 specific set*() syscalls that do not * support the syscall6 API (needed for prctl functions and the ambient * capabilities set for example). */ #ifndef _SYS_PSX_SYSCALL_H #define _SYS_PSX_SYSCALL_H #ifdef __cplusplus extern "C" { #endif #include <pthread.h> /* * psx_syscall performs the specified syscall on all psx registered * threads. The mechanism by which this occurs is much less efficient * than a standard system call on Linux, so it should only be used * when POSIX semantics are required to change process relevant * security state. * * Glibc has native support for POSIX semantics on setgroups() and the * 8 set*[gu]id() functions. So, there is no need to use psx_syscall() * for these calls. This call exists for all the other system calls * that need to maintain parity on all pthreads of a program. * * Some macrology is used to allow the caller to provide only as many * arguments as needed, thus psx_syscall() cannot be used as a * function pointer. For those situations, we define psx_syscall3() * and psx_syscall6(). */ #define psx_syscall(syscall_nr, ...) \ __psx_syscall(syscall_nr, __VA_ARGS__, (long int) 6, (long int) 5, \ (long int) 4, (long int) 3, (long int) 2, \ (long int) 1, (long int) 0) long int __psx_syscall(long int syscall_nr, ...); long int psx_syscall3(long int syscall_nr, long int arg1, long int arg2, long int arg3); long int psx_syscall6(long int syscall_nr, long int arg1, long int arg2, long int arg3, long int arg4, long int arg5, long int arg6); /* * This function should be used by systems to obtain pointers to the * two syscall functions provided by the PSX library. A linkage trick * is to define this function as weak in a library that can optionally * use libpsx and then, should the caller link -lpsx, that library can * implicitly use these POSIX semantics syscalls. See libcap for an * example of this useage. */ void psx_load_syscalls(long int (**syscall_fn)(long int, long int, long int, long int), long int (**syscall6_fn)(long int, long int, long int, long int, long int, long int, long int)); #ifdef __cplusplus } #endif #endif /* _SYS_PSX_SYSCALL_H */

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