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| en:multiasm:papc:chapter_6_8 [2026/02/13 13:31] – [Procedures, Functions and Calls in Windows and Linux] ktokarz | en:multiasm:papc:chapter_6_8 [2026/02/27 01:48] (current) – [Callig Windows system functions] jtokarz | ||
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| Since the parameter passing method has changed in 64-bit operating systems, the **PROC** directive calculates the addresses of local variables and arguments on the stack properly, but if we want to use the stack for argument passing, we need to put parameters on the stack manually before a procedure call. With the use of additional directives, it is possible to provide information about stack utilisation for stack unwinding. | Since the parameter passing method has changed in 64-bit operating systems, the **PROC** directive calculates the addresses of local variables and arguments on the stack properly, but if we want to use the stack for argument passing, we need to put parameters on the stack manually before a procedure call. With the use of additional directives, it is possible to provide information about stack utilisation for stack unwinding. | ||
| - | Procedures can have parameters. In general, parameters can be passed through the stack, registers, common memory or a combination of these. In different operating systems, the rules of passing parameters differ. In 64-bit Windows, the fast call calling convention is used. In this convention, the first four parameters are passed through registers, and each subsequent parameter is passed through the stack. If the parameters are integers, they are passed through general-purpose registers. If parameters are floating-point numbers, they are passed through XMM registers as scalars. If the procedure plays the role of a function, it returns the resulting value. Integers are returned through the accumulator (RAX), and floating-point values are returned through XMM0. Parameters passing in Windows x64 ABI is summarised in a table {{ref> | + | Procedures can have parameters. In general, parameters can be passed through the stack, registers, common memory or a combination of these. In different operating systems, the rules of passing parameters differ. |
| + | |||
| + | **Windows Application Binary Interface.**\\ | ||
| + | In 64-bit Windows, the fast call calling convention is used. In this convention, the first four parameters are passed through registers, and each subsequent parameter is passed through the stack. If the parameters are integers, they are passed through general-purpose registers. If parameters are floating-point numbers, they are passed through XMM registers as scalars. If the procedure plays the role of a function, it returns the resulting value. Integers are returned through the accumulator (RAX), and floating-point values are returned through XMM0. Parameters passing in Windows x64 ABI is summarised in a table {{ref> | ||
| <table masmparampass> | <table masmparampass> | ||
| < | < | ||
| Line 62: | Line 65: | ||
| Certainly, these rules are to be used if there is a need to call a system function or to maintain compatibility with a high-level compiler. If the procedure is written in pure assembly and called from an assembly program, it is the programmer' | Certainly, these rules are to be used if there is a need to call a system function or to maintain compatibility with a high-level compiler. If the procedure is written in pure assembly and called from an assembly program, it is the programmer' | ||
| The rules of passing parameters, stack and registers use, and data storage layout in 64-bit Microsoft Windows are described in the document about x64 Application Binary Interface (ABI)((https:// | The rules of passing parameters, stack and registers use, and data storage layout in 64-bit Microsoft Windows are described in the document about x64 Application Binary Interface (ABI)((https:// | ||
| + | **Linux System V Application Binary Interface.**\\ | ||
| In the Linux x64 Calling Convention, the first six arguments of type integer/ | In the Linux x64 Calling Convention, the first six arguments of type integer/ | ||
| <table linuxparampass> | <table linuxparampass> | ||
| Line 76: | Line 80: | ||
| | subsequent | stack | stack | | | subsequent | stack | stack | | ||
| </ | </ | ||
| + | The non-volatile registers are RBX, RBP, R12, R13, R14, and R15. They should be saved and restored by a function that uses them. | ||
| ===== Calling the system functions ===== | ===== Calling the system functions ===== | ||
| Line 112: | Line 117: | ||
| push rbp ; push rpb to the stack | push rbp ; push rpb to the stack | ||
| mov rbp, rsp ; store rsp to rbp | mov rbp, rsp ; store rsp to rbp | ||
| - | sub rsp, 48 ; shadow space (32 bytes) and stack alignment (additional 8 bytes) | + | sub rsp, 48 ; shadow space (32 bytes) and stack alignment (additional |
| + | ; | ||
| ; we need the handle of the console window | ; we need the handle of the console window | ||
