IPC之syscall.c源码解读

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// SPDX-License-Identifier: GPL-2.0 /*  * sys_ipc() is the old de-multiplexer for the SysV IPC calls.  *  * This is really horribly ugly, and new architectures should just wire up  * the individual syscalls instead.  */ #include <linux/unistd.h> #include <linux/syscalls.h> #include <linux/security.h> #include <linux/ipc_namespace.h> #include "util.h"   #ifdef __ARCH_WANT_SYS_IPC #include <linux/errno.h> #include <linux/ipc.h> #include <linux/shm.h> #include <linux/uaccess.h>   int ksys_ipc(unsigned int call, int first, unsigned long second,     unsigned long third, void __user * ptr, long fifth) {     int version, ret;       version = call >> 16; /* hack for backward compatibility */     call &= 0xffff;       switch (call) {     case SEMOP:         return ksys_semtimedop(first, (struct sembuf __user *)ptr,                        second, NULL);     case SEMTIMEDOP:         if (IS_ENABLED(CONFIG_64BIT))             return ksys_semtimedop(first, ptr, second,                     (const struct __kernel_timespec __user *)fifth);         else if (IS_ENABLED(CONFIG_COMPAT_32BIT_TIME))             return compat_ksys_semtimedop(first, ptr, second,                     (const struct old_timespec32 __user *)fifth);         else             return -ENOSYS;       case SEMGET:         return ksys_semget(first, second, third);     case SEMCTL: {         unsigned long arg;         if (!ptr)             return -EINVAL;         if (get_user(arg, (unsigned long __user *) ptr))             return -EFAULT;         return ksys_old_semctl(first, second, third, arg);     }       case MSGSND:         return ksys_msgsnd(first, (struct msgbuf __user *) ptr,                   second, third);     case MSGRCV:         switch (version) {         case 0: {             struct ipc_kludge tmp;             if (!ptr)                 return -EINVAL;               if (copy_from_user(&tmp,                        (struct ipc_kludge __user *) ptr,                        sizeof(tmp)))                 return -EFAULT;             return ksys_msgrcv(first, tmp.msgp, second,                        tmp.msgtyp, third);         }         default:             return ksys_msgrcv(first,                        (struct msgbuf __user *) ptr,                        second, fifth, third);         }     case MSGGET:         return ksys_msgget((key_t) first, second);     case MSGCTL:         return ksys_old_msgctl(first, second,                    (struct msqid_ds __user *)ptr);       case SHMAT:         switch (version) {         default: {             unsigned long raddr;             ret = do_shmat(first, (char __user *)ptr,                        second, &raddr, SHMLBA);             if (ret)                 return ret;             return put_user(raddr, (unsigned long __user *) third);         }         case 1:             /*              * This was the entry point for kernel-originating calls              * from iBCS2 in 2.2 days.              */             return -EINVAL;         }     case SHMDT:         return ksys_shmdt((char __user *)ptr);     case SHMGET:         return ksys_shmget(first, second, third);     case SHMCTL:         return ksys_old_shmctl(first, second,                    (struct shmid_ds __user *) ptr);     default:         return -ENOSYS;     } }   SYSCALL_DEFINE6(ipc, unsigned int, call, int, first, unsigned long, second,         unsigned long, third, void __user *, ptr, long, fifth) {     return ksys_ipc(call, first, second, third, ptr, fifth); } #endif   #ifdef CONFIG_COMPAT #include <linux/compat.h>   #ifndef COMPAT_SHMLBA #define COMPAT_SHMLBA   SHMLBA #endif   struct compat_ipc_kludge {     compat_uptr_t msgp;     compat_long_t msgtyp; };   #ifdef CONFIG_ARCH_WANT_OLD_COMPAT_IPC int compat_ksys_ipc(u32 call, int first, int second,     u32 third, compat_uptr_t ptr, u32 fifth) {     int version;     u32 pad;       version = call >> 16; /* hack for backward compatibility */     call &= 0xffff;       switch (call) {     case SEMOP:         /* struct sembuf is the same on 32 and 64bit :)) */         return ksys_semtimedop(first, compat_ptr(ptr), second, NULL);     case SEMTIMEDOP:         if (!IS_ENABLED(CONFIG_COMPAT_32BIT_TIME))             return -ENOSYS;         return compat_ksys_semtimedop(first, compat_ptr(ptr), second,                         compat_ptr(fifth));     case SEMGET:         return ksys_semget(first, second, third);     case SEMCTL:         if (!ptr)             return -EINVAL;         if (get_user(pad, (u32 __user *) compat_ptr(ptr)))             return -EFAULT;         return compat_ksys_old_semctl(first, second, third, pad);       case MSGSND:         return compat_ksys_msgsnd(first, ptr, second, third);       case MSGRCV: {         void __user *uptr = compat_ptr(ptr);           if (first < 0 || second < 0)             return -EINVAL;           if (!version) {             struct compat_ipc_kludge ipck;             if (!uptr)                 return -EINVAL;             if (copy_from_user(&ipck, uptr, sizeof(ipck)))                 return -EFAULT;             return compat_ksys_msgrcv(first, ipck.msgp, second,                          ipck.msgtyp, third);         }         return compat_ksys_msgrcv(first, ptr, second, fifth, third);     }     case MSGGET:         return ksys_msgget(first, second);     case MSGCTL:         return compat_ksys_old_msgctl(first, second, compat_ptr(ptr));       case SHMAT: {         int err;         unsigned long raddr;           if (version == 1)             return -EINVAL;         err = do_shmat(first, compat_ptr(ptr), second, &raddr,                    COMPAT_SHMLBA);         if (err < 0)             return err;         return put_user(raddr, (compat_ulong_t __user *)compat_ptr(third));     }     case SHMDT:         return ksys_shmdt(compat_ptr(ptr));     case SHMGET:         return ksys_shmget(first, (unsigned int)second, third);     case SHMCTL:         return compat_ksys_old_shmctl(first, second, compat_ptr(ptr));     }       return -ENOSYS; }   COMPAT_SYSCALL_DEFINE6(ipc, u32, call, int, first, int, second,     u32, third, compat_uptr_t, ptr, u32, fifth) {     return compat_ksys_ipc(call, first, second, third, ptr, fifth); } #endif #endif

　　

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本文作者：漫漫程序之路
本文链接：https://www.cnblogs.com/still-smile/p/12040596.html
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