austanss / skylight Goto Github PK

i want to know to take a look at the project i think it is skylight but i cant remember i was just messing around with it a bit

Ii'm trying to use skylight as a base for my os,but i was wondering how could i implement a fopen syscall, trying to read a pointer from userspace to kernel space (path string) obviously makes the kernel crash, so how can i read/translate user memory addresses to kernel?
here's my code:

void fopen(vfs_handle_t* out, char* path, vfs_open_flags_t flags) {
    task_context_t* ctx = ((gs_kernel_base_t*)(rdmsr(IA32_GS_BASE)))->ctx;
    uint64_t pid = ((gs_kernel_base_t*)(rdmsr(IA32_GS_BASE)))->pid;
    paging_table_t* kpml4 = paging_get_pml4();
    paging_load_pml4((paging_table_t *)ctx->cr3);

    serial_print_quiet(path);

    paging_load_pml4(kpml4);
}

when trying to print the path in serial the kernel just goes into unknown exception (obviously it can't find the value referred by the pointer).

In frame, when you call a syscall using the syscall instruction, it causes an error interrupt.