struct FrameDescriptionEntry [src]

Fields

cie_length_offset: u64
pc_begin: u64
pc_range: u64
lsda_pointer: ?u64
aug_data: []const u8
instructions: []const u8
Members

parse (Function)
Source

  pub const FrameDescriptionEntry = struct {
    // Offset into eh_frame where the CIE for this FDE is stored
    cie_length_offset: u64,

    pc_begin: u64,
    pc_range: u64,
    lsda_pointer: ?u64,
    aug_data: []const u8,
    instructions: []const u8,

    /// This function expects to read the FDE starting at the PC Begin field.
    /// The returned struct references memory backed by `fde_bytes`.
    ///
    /// `pc_rel_offset` specifies an offset to be applied to pc_rel_base values
    /// used when decoding pointers. This should be set to zero if fde_bytes is
    /// backed by the memory of a .eh_frame / .debug_frame section in the running executable.
    /// Otherwise, it should be the relative offset to translate addresses from
    /// where the section is currently stored in memory, to where it *would* be
    /// stored at runtime: section base addr - backing data base ptr.
    ///
    /// Similarly, `is_runtime` specifies this function is being called on a runtime
    /// section, and so indirect pointers can be followed.
    pub fn parse(
        fde_bytes: []const u8,
        pc_rel_offset: i64,
        is_runtime: bool,
        cie: CommonInformationEntry,
        addr_size_bytes: u8,
        endian: std.builtin.Endian,
    ) !FrameDescriptionEntry {
        if (addr_size_bytes > 8) return error.InvalidAddrSize;

        var fbr: FixedBufferReader = .{ .buf = fde_bytes, .endian = endian };

        const pc_begin = try readEhPointer(&fbr, cie.fde_pointer_enc, addr_size_bytes, .{
            .pc_rel_base = try pcRelBase(@intFromPtr(&fde_bytes[fbr.pos]), pc_rel_offset),
            .follow_indirect = is_runtime,
        }) orelse return bad();

        const pc_range = try readEhPointer(&fbr, cie.fde_pointer_enc, addr_size_bytes, .{
            .pc_rel_base = 0,
            .follow_indirect = false,
        }) orelse return bad();

        var aug_data: []const u8 = &[_]u8{};
        const lsda_pointer = if (cie.aug_str.len > 0) blk: {
            const aug_data_len = try fbr.readUleb128(usize);
            const aug_data_start = fbr.pos;
            aug_data = fde_bytes[aug_data_start..][0..aug_data_len];

            const lsda_pointer = if (cie.lsda_pointer_enc != EH.PE.omit)
                try readEhPointer(&fbr, cie.lsda_pointer_enc, addr_size_bytes, .{
                    .pc_rel_base = try pcRelBase(@intFromPtr(&fde_bytes[fbr.pos]), pc_rel_offset),
                    .follow_indirect = is_runtime,
                })
            else
                null;

            fbr.pos = aug_data_start + aug_data_len;
            break :blk lsda_pointer;
        } else null;

        const instructions = fde_bytes[fbr.pos..];
        return .{
            .cie_length_offset = cie.length_offset,
            .pc_begin = pc_begin,
            .pc_range = pc_range,
            .lsda_pointer = lsda_pointer,
            .aug_data = aug_data,
            .instructions = instructions,
        };
    }
}  