C runtime library dictates a structure to any programs that link to it. This include a block of code that runs before your program begins and another block of code after your program ends. Your program is called by the startup code as though it is a procedure with the CALL instruction. Your program returns to C library using the RET instruction.
The C calling convention is as follow:
(1) A procedure must preserve the values of the EBX, ESP, EBP, ESI and EDI. The other GPR can be altered.
(2) A procedure's return value in EAX for 32-bit or less. 64-bit return value is stored in EDX and EAX.
(3) Parameters passed to procedures are pushed onto the stack in reverse order. In other words, given MyFunc(p1, p2, p3), p3 is pushed onto stack first, then followed by p2 and p1.
(4) Parameters are removed by the caller after the procedure returns.
(5) The label name of the the assembly program (or the one generated by gcc) must be called "main:" and must be declared as GLOBAL.
No comments:
Post a Comment