question about tcb_size in arm

[rain z]

Hi,
   When I read the source code of binutils-2.21.1/bfd/elf32-arm.c, I
found the tcb size defined here is 8,which is:

/* The size of the thread control block. */
#define TCB_SIZE 8

well, in my knowledge, the size of thread control block is larger than
8 bytes,  so why it is defined 8 bytes here?
Thanks in advance.

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