mirror of
https://github.com/JannisHeydemann/BoredOS.git
synced 2026-05-30 02:16:58 +00:00
88 lines
1.7 KiB
NASM
88 lines
1.7 KiB
NASM
; Copyright (c) 2023-2026 Chris (boreddevnl)
|
|
; This software is released under the GNU General Public License v3.0. See LICENSE file for details.
|
|
; This header needs to maintain in any file it is present in, as per the GPL license terms.
|
|
global syscall_entry
|
|
extern syscall_handler_c
|
|
|
|
section .text
|
|
|
|
; Syscall ABI:
|
|
; RAX = syscall_num
|
|
; RDI = arg1
|
|
; RSI = arg2
|
|
; RDX = arg3
|
|
; R10 = arg4
|
|
; R8 = arg5
|
|
; R9 = arg6
|
|
|
|
syscall_entry:
|
|
swapgs
|
|
|
|
mov [gs:40], rsp
|
|
mov rsp, [gs:48]
|
|
|
|
; 2. Build iretq frame
|
|
push 0x1B ; SS (User Data)
|
|
push qword [gs:40] ; RSP
|
|
push r11 ; RFLAGS (captured by syscall)
|
|
push 0x23 ; CS (User Code)
|
|
push rcx ; RIP (return address from syscall)
|
|
|
|
push 0 ; err_code
|
|
push 0 ; int_no (can be used for syscall vector)
|
|
|
|
; 3. Save all registers in registers_t order
|
|
push rax
|
|
push rbx
|
|
push rcx
|
|
push rdx
|
|
push rsi
|
|
push rdi
|
|
push rbp
|
|
push r8
|
|
push r9
|
|
push r10
|
|
push r11
|
|
push r12
|
|
push r13
|
|
push r14
|
|
push r15
|
|
|
|
; Save SSE/FPU state
|
|
sub rsp, 512
|
|
fxsave [rsp]
|
|
|
|
; 4. Call C handler with registers_t*
|
|
mov rdi, rsp
|
|
call syscall_handler_c
|
|
|
|
; 5. Switch to the resulting RSP (might be different if task switched)
|
|
mov rsp, rax
|
|
|
|
; Restore SSE/FPU state
|
|
fxrstor [rsp]
|
|
add rsp, 512
|
|
|
|
; 6. Restore and return via iretq
|
|
pop r15
|
|
pop r14
|
|
pop r13
|
|
pop r12
|
|
pop r11
|
|
pop r10
|
|
pop r9
|
|
pop r8
|
|
pop rbp
|
|
pop rdi
|
|
pop rsi
|
|
pop rdx
|
|
pop rcx
|
|
pop rbx
|
|
pop rax
|
|
add rsp, 16 ; drop int_no/err_code
|
|
|
|
swapgs
|
|
iretq
|
|
|
|
section .bss
|