#LINUX PROGRAMMING LANGUAGE LIST MANUAL#

Otherwise copy args to an allocated area of memory and store the address of the first arg in %ebx.Example: Then the stack pointer should be copied to %ebx. If you are using the stack, args must be pushed onto it backwards, i.e. Syscalls whos number of args is greater than five still expect the syscall number to be in %eax, but the args are arranged in memory and the pointer to the first arg is stored in %ebx. Syscalls such as open or fcntl which have an optional extra arg will know what to use. Just leave the un-used registers unchanged. The same process applies to syscalls which have less than five args. The return value of the syscall is stored in %eax. This is followed by an int $0x80 which executes the syscall. Hence fd goes in %ebx, buf goes in %ecx, count goes in %edx and SYS_write goes in %eax. (Hello world program - it had to be done)ДЄccording to the write(2) man page, write is declared as: ssize_t write(int fd, const void *buf, size_t count) A great list is at These functions can be executed via the linux interrupt service: int $0x80.

They are also listed in: /usr/include/sys/syscall.h.

Syscalls consist of all the functions in the second section of the manual pages located in /usr/man/man2. This section will outline the use of linux syscalls in assembly language. **NOTE: ALL EXAMPLES FROM HERE WILL BE IN AT&T SYNTAX** This is similar to type casting in C but it doesnt seem to be necessary since the size of registers used is the assumed datatype.Example: 'dword' of course corresponding to 'long'. Intel syntax has similar directives for use with memory operands, i.e. 'l' is for long, 'w' is for word, and 'b' is for byte. The significance of this suffix is that of operand size. Suffixes.ДЄs you may have noticed, the AT&T syntax mnemonics have a suffix. makes more sense at a glance than disp(base,index,scale). Immediate data used should not '$' prefixed in AT&T when used for scale/disp.Example:ДЄs you can see, AT&T is very obscure. In real mode it depends on the instruction whereas in pmode its unnecessary. Segreg depends on the instruction and whether the app is being run in real mode or pmode. Scale, if not specified and index is specified, defaults to 1. Index/scale/disp/segreg are all optional and can simply be left out. The AT&T syntax form is %segreg:disp(base,index,scale). The Intel syntax form of these is segreg. The AT&T form for instructions involving complex operations is very obscure compared to Intel syntax. In Intel syntax the base register is enclosed in '' whereas in AT&T syntax it is enclosed in '(' and ')'. Memory operands as seen above are different also. We read from left to right, we write from left to right, so this way is only natural.Example: The advantage of AT&T syntax in this situation is obvious. In Intel syntax the first operand is the destination, and the second operand is the source whereas in AT&T syntax the first operand is the source and the second operand is the destination. The direction of the operands in Intel syntax is opposite from that of AT&T syntax. Also if the first hexadecimal digit is a letter then the value is prefixed by a '0'.Example: Intel syntax hexadecimal or binary immed data are suffixed with 'h' and 'b' respectively. In AT&T however registers are prefixed with a '%' and immed's are prefixed with a '$'. In Intel syntax there are no register prefixes or immed prefixes. Intel and AT&T syntax Assembly language are very different from each other in appearance, and this will lead to confusion when one first comes across AT&T syntax after having learnt Intel syntax first, or vice versa. There is only one prerequisite for reading this article, and thats obviously a basic knowledge of x86 assembly language and C.

Should you find any of these errors on my part, do not hesitate to notify me via email and enlighten me on the given issue. Various parts of this text I have learnt about through experimentation and hence may be prone to error. This article was written due to the lack of (good) info on this field of programming (inline asm section in particular), in which case i should remind thee that this is not a shellcode writing tutorial because there is no lack of info in this field. Contained within the bounds of the article is a comparison between Intel and AT&T syntax asm, a guide to using syscalls and a introductory guide to using inline asm in gcc. This article will describe assembly language programming under Linux.

by Phillip updated: Monday 8th January 2001 РЎС‚Р°С‚СЊСЏ :: Using Assembly Language in Linux.

#LINUX PROGRAMMING LANGUAGE LIST MANUAL#

Linux programming language list