Linux Kernel中的系统调用分析

(kernel-4.19/arch/arm64/kernel/sys.c)#undef __SYSCALL#define __SYSCALL(nr, sym)  [nr] = __arm64_##sym,const syscall_fn_t sys_call_table[__NR_syscalls] = {   [0 ... __NR_syscalls - 1] = __arm64_sys_ni_syscall,#include<asm/unistd.h> };

(kernel-4.19/arch/arm64/kernel/sys.c)const syscall_fn_t sys_call_table[__NR_syscalls] = {   [0 ... __NR_syscalls - 1] = __arm64_sys_ni_syscall,__arm64_compat_sys_io_setup,__arm64_sys_io_destroy,__arm64_compat_sys_io_submit...... };

SYSCALL_DEFINE1(arm64_personality, unsignedint, personality){if (personality(personality) == PER_LINUX32 &&    !system_supports_32bit_el0())return -EINVAL;return ksys_personality(personality);}#define SYSCALL_DEFINE1(name, ...) SYSCALL_DEFINEx(1, _##name, __VA_ARGS__)#define SYSCALL_DEFINE2(name, ...) SYSCALL_DEFINEx(2, _##name, __VA_ARGS__)#define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)#define SYSCALL_DEFINE4(name, ...) SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)#define SYSCALL_DEFINE5(name, ...) SYSCALL_DEFINEx(5, _##name, __VA_ARGS__)#define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)#define SYSCALL_DEFINEx(x, sname, ...)        \   SYSCALL_METADATA(sname, x, __VA_ARGS__)      \   __SYSCALL_DEFINEx(x, sname, __VA_ARGS__)

 SYSCALL_DEFINE1(setgid, gid_t, gid) {return __sys_setgid(gid); }

(kernel-4.19/arch/arm64/kernel/entry.S)el0_svc:movx0, spblel0_svc_handlerbret_to_userENDPROC(el0_svc)

(kernel-4.19/arch/arm64/kernel/syscall.c)asmlinkage voidel0_svc_handler(struct pt_regs *regs){  sve_user_discard();  el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);}staticvoidel0_svc_common(struct pt_regs *regs, int scno, int sc_nr,constsyscall_fn_t syscall_table[]){unsignedlong flags = current_thread_info()->flags;  regs->orig_x0 = regs->regs[0];  regs->syscallno = scno;  cortex_a76_erratum_1463225_svc_handler();  local_daif_restore(DAIF_PROCCTX);  user_exit();if (has_syscall_work(flags)) {/* set default errno for user-issued syscall(-1) */if (scno == NO_SYSCALL)      regs->regs[0] = -ENOSYS;    scno = syscall_trace_enter(regs);if (scno == NO_SYSCALL)goto trace_exit;  }  invoke_syscall(regs, scno, sc_nr, syscall_table);/*   * The tracing status may have changed under our feet, so we have to   * check again. However, if we were tracing entry, then we always trace   * exit regardless, as the old entry assembly did.   */if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {    local_daif_mask();    flags = current_thread_info()->flags;if (!has_syscall_work(flags)) {/*       * We're off to userspace, where interrupts are       * always enabled after we restore the flags from       * the SPSR.       */      trace_hardirqs_on();return;    }    local_daif_restore(DAIF_PROCCTX);  }trace_exit:  syscall_trace_exit(regs);}staticvoidinvoke_syscall(struct pt_regs *regs, unsignedint scno,unsignedint sc_nr,constsyscall_fn_t syscall_table[]){long ret;if (scno < sc_nr) {syscall_fn_t syscall_fn;    syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];    ret = __invoke_syscall(regs, syscall_fn);    //syscall_fn 就是tab表中的函数  } else {    ret = do_ni_syscall(regs, scno);  }  regs->regs[0] = ret;}staticlong __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn){return syscall_fn(regs);  //调用tab表中的函数}

#define __NR_io_setup 0__SC_COMP(__NR_io_setup, sys_io_setup, compat_sys_io_setup)#define __NR_io_destroy 1__SYSCALL(__NR_io_destroy, sys_io_destroy)#define __NR_io_submit 2__SC_COMP(__NR_io_submit, sys_io_submit, compat_sys_io_submit)#define __NR_io_cancel 3__SYSCALL(__NR_io_cancel, sys_io_cancel)#define __NR_io_getevents 4__SC_COMP(__NR_io_getevents, sys_io_getevents, compat_sys_io_getevents)/* fs/xattr.c */#define __NR_setxattr 5__SYSCALL(__NR_setxattr, sys_setxattr)#define __NR_lsetxattr 6__SYSCALL(__NR_lsetxattr, sys_lsetxattr)#define __NR_fsetxattr 7__SYSCALL(__NR_fsetxattr, sys_fsetxattr)#define __NR_getxattr 8__SYSCALL(__NR_getxattr, sys_getxattr)#define __NR_lgetxattr 9__SYSCALL(__NR_lgetxattr, sys_lgetxattr)

SYSCALL_DEFINE1(setgid, gid_t, gid){return __sys_setgid(gid);}SYSCALL_DEFINE1(sysctl, struct __sysctl_args __user *, args){struct __sysctl_argstmp;size_t oldlen = 0;ssize_t result;if (copy_from_user(&tmp, args, sizeof(tmp)))return -EFAULT;if (tmp.oldval && !tmp.oldlenp)return -EFAULT;if (tmp.oldlenp && get_user(oldlen, tmp.oldlenp))return -EFAULT;  result = do_sysctl(tmp.name, tmp.nlen, tmp.oldval, oldlen,         tmp.newval, tmp.newlen);if (result >= 0) {    oldlen = result;    result = 0;  }if (tmp.oldlenp && put_user(oldlen, tmp.oldlenp))return -EFAULT;return result;}