2017-2018-1 20179219 "Linux kernel Fundamentals and analysis" Fifth week assignment

Lab Operation:

The 64-bit system call function you selected is the socket number 41st.

The function prototype is an int socket (int domain, int type, int protocol); Used to create sockets, commonly used in network programming

Function parameters:

Domain protocol family, commonly used protocol families have af_inet, Af_inet6, af_local, respectively, to create a IPv4 socket, IPv6 socket, local process communication sockets
Type socket types, common with Sock_stream, SOCK_DGRAM, Sock_raw, respectively, for creating streaming sockets, datagram sockets, raw sockets
Protocol protocol, common by Ipproto_tcp, IPPTOTO_UDP, respectively, the use of TCP protocol, UDP protocol

　　

The code for the Experiment program is:

1 #include <sys/types.h>2 #include <sys/socket.h>4int  main ()  5{
int temp; 6     Socket (Af_inet,sock_raw,0);
Temp=socket (2,3,0);
7 printf ("Return temp%d\n", temp); 8     return 0 ; 9 }

Find the Af_inet definition:

Find the SOCK_RAW definition:

The experimental actions are:

The above results indicate that the header file #include<stdio.h> is missing, and no warning is added.

Using the embed assembler code to implement the program, the code is:

#include <sys/types.h> #include <sys/socket.h> #include <stdio.h>int main () {int temp;asm volatile (" int $0x80 ":" =a "(temp):" A "(" a "()," B "(2)," C "(3)," D "(0)//eax The interrupt number, EBX in the parameter 2,ecx put parameter 3,edx in the parameter 0);
printf ("Return temp%d\n", temp); return 0;}

Run as:

Study notes:

Kernel state: At high execution level, code can execute privileged instruction to access any physical address, at which point the CPU execution level corresponds to the kernel state
User status: In low-level state, the code is limited in scope and can only be active within the level allowed
Execution Level 0 maximum indicates kernel state, the higher the number level the lower
Protect the scene: Enter the interrupt procedure to save the data of the register to be used
Resume the scene: Exit the terminal program, restore the data to save the Register
System call: The operating system interacts with the hardware device to provide a set of interfaces for the user-state process
API: Application Programming Interface
The difference between an API and a system call: The API is just a function definition; a system call sends a clear request to the kernel via a soft interrupt
Interrupt vector: The entry address of the Interrupt service program
System invocation: A set of program interfaces or application programming interfaces that comprise all system calls provided by the operating system implementation
Register Pass parameter restriction: the length of the parameter must not exceed the register length and cannot exceed 32 bits; no more than 6 parameters (EBX,ECX,EDX,ESI,EDI,EBP) outside of the system call number (EAX)

C Language inline assembly syntax:
__ASM__VOLATILE__ (
Assembly statement template;
Output part;
Input part;
Destruction of the description section);
Volatile means not to allow the compiler to optimize the code, you can not write
eg.
#include <stdio.h>
{
/*val1+val2=vla3*/
unsigned int val1=1;
unsigned int val2=2;
unsigned int val3=0;
printf ("val1:%d,val2:%d,val3:%d\n", VAL1,VAL2,VLA3);
ASM volatile (
"Movl $0,%%eax\n\t"//clear eax to 0
"Addl%1,%%eax\n\t"//eax+=vla1
"Addl%2,%%eax\n\t"//eax+=vla2
"Movl%%eax,%0\n\t"//val2=eax
: "=m" (VLA3)//Output section. =m to write memory.
: "C" (Val1), "D" (val2)//input section. C means ecx,d represents edx, which is stored val1 with ECX, with edx storage val2
);
printf ("val1:%d+val2:%d=vla3:%d\n", VAL1,VAL2,VAL3);
return 0;
}

2017-2018-1 20179219 "Linux kernel Fundamentals and analysis" Fifth week assignment