Zig 0.17.0-dev (Split by item)

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prepareArea

Initializes all the fields of the static TLS area and returns the computed architecture-specific value of the TP register.

tls.prepareArea

pub fn prepareArea(area: []u8) usize

File

lib/std/os/linux/tls.zig:616

Code

pub fn prepareArea(area: []u8) usize {
    @setRuntimeSafety(false);
    @disableInstrumentation();

    // Clear the area we're going to use, just to be safe.
    @memset(area, 0);

    // Prepare the ABI TCB.
    const abi_tcb = alignPtrCast(AbiTcb, area.ptr + area_desc.abi_tcb.offset);
    switch (current_variant) {
        .I_original, .I_modified => abi_tcb.dtv = @intFromPtr(area.ptr + area_desc.dtv.offset),
        .II => abi_tcb.self = abi_tcb,
    }

    // Prepare the DTV.
    const dtv = alignPtrCast(Dtv, area.ptr + area_desc.dtv.offset);
    dtv.len = 1;
    dtv.tls_block = area.ptr + current_dtv_offset + area_desc.block.offset;

    // Copy the initial data.
    @memcpy(area[area_desc.block.offset..][0..area_desc.block.init.len], area_desc.block.init);

    // Return the corrected value (if needed) for the TP register. Overflow here is not a problem;
    // the pointer arithmetic involving the TP is done with wrapping semantics.
    return @intFromPtr(area.ptr) +% switch (current_variant) {
        .I_original, .II => area_desc.abi_tcb.offset,
        .I_modified => area_desc.block.offset +% current_tp_offset,
    };
}