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core/x86_64: Set up a second stack in the TSS to handle system calls

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This commit is contained in:
Gabriel 2025-02-15 22:40:48 +01:00
parent 56f2c018a7
commit fa04363a51
1 changed files with 6 additions and 4 deletions
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10
core/src/arch/x86_64/gdt.zig
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@ -79,9 +79,8 @@ fn stackTop(begin: usize, size: usize) usize {
return (begin + size) - 16; return (begin + size) - 16;
} }
fn setupTSS(gdt: *GlobalDescriptorTable, tss: *TSS, stack: [*]u8, stack_length: usize) void { fn setupTSS(gdt: *GlobalDescriptorTable, tss: *TSS) void {
tss.iomap_base = @sizeOf(TSS); tss.iomap_base = @sizeOf(TSS);
tss.ist0 = stackTop(@intFromPtr(stack), stack_length);
setTSSBase(&gdt.tss, &gdt.tss2, @intFromPtr(tss)); setTSSBase(&gdt.tss, &gdt.tss2, @intFromPtr(tss));
setLimit(&gdt.tss, @sizeOf(TSS) - 1); setLimit(&gdt.tss, @sizeOf(TSS) - 1);
} }
@ -120,12 +119,15 @@ pub fn setupGDT() void {
var gdt = GlobalDescriptorTable{ .null = std.mem.zeroes(GDTEntry), .kernel_code = createGDTEntry(0xffff, 0x0000, 0x00, 0x9a, 0xaf, 0x00), .kernel_data = createGDTEntry(0xffff, 0x0000, 0x00, 0x92, 0xcf, 0x00), .user_code = createGDTEntry(0xffff, 0x0000, 0x00, 0xfa, 0xaf, 0x00), .user_data = createGDTEntry(0xffff, 0x0000, 0x00, 0xf2, 0xcf, 0x00), .tss = createGDTEntry(0x0000, 0x0000, 0x00, 0xe9, 0x0f, 0x00), .tss2 = HighGDTEntry{ .base_high = 0x00000000, .reserved = 0x00000000 } }; var gdt = GlobalDescriptorTable{ .null = std.mem.zeroes(GDTEntry), .kernel_code = createGDTEntry(0xffff, 0x0000, 0x00, 0x9a, 0xaf, 0x00), .kernel_data = createGDTEntry(0xffff, 0x0000, 0x00, 0x92, 0xcf, 0x00), .user_code = createGDTEntry(0xffff, 0x0000, 0x00, 0xfa, 0xaf, 0x00), .user_data = createGDTEntry(0xffff, 0x0000, 0x00, 0xf2, 0xcf, 0x00), .tss = createGDTEntry(0x0000, 0x0000, 0x00, 0xe9, 0x0f, 0x00), .tss2 = HighGDTEntry{ .base_high = 0x00000000, .reserved = 0x00000000 } };
var gdtr = std.mem.zeroes(GDTR); var gdtr = std.mem.zeroes(GDTR);
var tss = std.mem.zeroes(TSS); var tss = std.mem.zeroes(TSS);
var alternate_stack: [platform.PAGE_SIZE * 4]u8 = std.mem.zeroes([platform.PAGE_SIZE * 4]u8); var interrupt_stack: [platform.PAGE_SIZE * 4]u8 = std.mem.zeroes([platform.PAGE_SIZE * 4]u8);
var syscall_stack: [platform.PAGE_SIZE * 4]u8 = std.mem.zeroes([platform.PAGE_SIZE * 4]u8);
}; };
state.gdtr.offset = @intFromPtr(&state.gdt); state.gdtr.offset = @intFromPtr(&state.gdt);
state.gdtr.size = @sizeOf(GlobalDescriptorTable); state.gdtr.size = @sizeOf(GlobalDescriptorTable);
setupTSS(&state.gdt, &state.tss, @ptrCast(&state.alternate_stack[0]), @sizeOf(@TypeOf(state.alternate_stack))); setupTSS(&state.gdt, &state.tss);
state.tss.ist0 = stackTop(@intFromPtr(&state.interrupt_stack[0]), @sizeOf(@TypeOf(state.interrupt_stack)));
state.tss.rsp0 = stackTop(@intFromPtr(&state.syscall_stack[0]), @sizeOf(@TypeOf(state.syscall_stack)));
// Hackish way to call naked functions which we know conform to SysV ABI. // Hackish way to call naked functions which we know conform to SysV ABI.
const lgdt: *const fn (g: *GDTR) callconv(.C) void = @ptrCast(&loadGDT); const lgdt: *const fn (g: *GDTR) callconv(.C) void = @ptrCast(&loadGDT);