setThreadPointer

pub fn setThreadPointer(addr: usize) void {
    @setRuntimeSafety(false);
    @disableInstrumentation();

    switch (native_arch) {
        .x86 => {
            var user_desc: linux.user_desc = .{
                .entry_number = area_desc.gdt_entry_number,
                .base_addr = addr,
                .limit = 0xfffff,
                .flags = .{
                    .seg_32bit = 1,
                    .contents = 0, // Data
                    .read_exec_only = 0,
                    .limit_in_pages = 1,
                    .seg_not_present = 0,
                    .useable = 1,
                },
            };
            const rc = @call(.always_inline, linux.syscall1, .{ .set_thread_area, @intFromPtr(&user_desc) });
            assert(rc == 0);

            const gdt_entry_number = user_desc.entry_number;
            // We have to keep track of our slot as it's also needed for clone()
            area_desc.gdt_entry_number = gdt_entry_number;
            // Update the %gs selector
            asm volatile ("movl %[gs_val], %%gs"
                :
                : [gs_val] "r" (gdt_entry_number << 3 | 3),
            );
        },
        .x86_64 => {
            const rc = @call(.always_inline, linux.syscall2, .{ .arch_prctl, linux.ARCH.SET_FS, addr });
            assert(rc == 0);
        },
        .aarch64, .aarch64_be => {
            asm volatile (
                \\ msr tpidr_el0, %[addr]
                :
                : [addr] "r" (addr),
            );
        },
        .arc => {
            // We apparently need to both set r25 (TP) *and* inform the kernel...
            asm volatile (
                \\ mov r25, %[addr]
                :
                : [addr] "r" (addr),
            );
            const rc = @call(.always_inline, linux.syscall1, .{ .arc_settls, addr });
            assert(rc == 0);
        },
        .arm, .armeb, .thumb, .thumbeb => {
            const rc = @call(.always_inline, linux.syscall1, .{ .set_tls, addr });
            assert(rc == 0);
        },
        .m68k => {
            const rc = linux.syscall1(.set_thread_area, addr);
            assert(rc == 0);
        },
        .hexagon => {
            asm volatile (
                \\ ugp = %[addr]
                :
                : [addr] "r" (addr),
            );
        },
        .loongarch32, .loongarch64 => {
            asm volatile (
                \\ move $tp, %[addr]
                :
                : [addr] "r" (addr),
            );
        },
        .riscv32, .riscv64 => {
            asm volatile (
                \\ mv tp, %[addr]
                :
                : [addr] "r" (addr),
            );
        },
        .csky, .mips, .mipsel, .mips64, .mips64el => {
            const rc = @call(.always_inline, linux.syscall1, .{ .set_thread_area, addr });
            assert(rc == 0);
        },
        .powerpc, .powerpcle => {
            asm volatile (
                \\ mr 2, %[addr]
                :
                : [addr] "r" (addr),
            );
        },
        .powerpc64, .powerpc64le => {
            asm volatile (
                \\ mr 13, %[addr]
                :
                : [addr] "r" (addr),
            );
        },
        .s390x => {
            asm volatile (
                \\ lgr %%r0, %[addr]
                \\ sar %%a1, %%r0
                \\ srlg %%r0, %%r0, 32
                \\ sar %%a0, %%r0
                :
                : [addr] "r" (addr),
                : .{ .r0 = true });
        },
        .sparc, .sparc64 => {
            asm volatile (
                \\ mov %[addr], %%g7
                :
                : [addr] "r" (addr),
            );
        },
        else => @compileError("Unsupported architecture"),
    }
}