My elf file's sections are as follows
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .text PROGBITS fffffffff7e020b0 000000b0
0000000000074f50 0000000000000000 AX 0 0 16
[ 2] .rodata PROGBITS fffffffff7e77000 00075000
0000000000014000 0000000000000000 AM 0 0 16
[ 3] .eh_frame_hdr PROGBITS fffffffff7e8b000 00089000
000000000000000c 0000000000000000 A 0 0 4
[ 4] .data PROGBITS fffffffff7e8b010 00089010
0000000000001ff0 0000000000000000 WA 0 0 16
[ 5] .bss NOBITS fffffffff7e8d000 0008b000
0000000000014000 0000000000000000 WA 0 0 4096
[ 6] .got PROGBITS fffffffff7ea1000 0009f000
0000000000001000 0000000000000000 WA 0 0 8
[ 7] .tdata PROGBITS fffffffff7ea2000 000a0000
000000000000b000 0000000000000000 WAT 0 0 8
[ 8] .tbss NOBITS fffffffff7ead000 000ab000
000000000000012a 0000000000000000 WAT 0 0 8
[ 9] .debug_abbrev PROGBITS 0000000000000000 000ab000
000000000001a8d4 0000000000000000 0 0 1
[10] .debug_info PROGBITS 0000000000000000 000c58d4
000000000016c624 0000000000000000 0 0 1
[11] .debug_aranges PROGBITS 0000000000000000 00231ef8
0000000000024130 0000000000000000 0 0 1
[12] .debug_ranges PROGBITS 0000000000000000 00256028
000000000004bfa0 0000000000000000 0 0 1
[13] .debug_str PROGBITS 0000000000000000 002a1fc8
0000000000123ecd 0000000000000001 MS 0 0 1
[14] .debug_pubnames PROGBITS 0000000000000000 003c5e95
000000000005da3c 0000000000000000 0 0 1
[15] .debug_pubtypes PROGBITS 0000000000000000 004238d1
00000000000a1e07 0000000000000000 0 0 1
[16] .debug_frame PROGBITS 0000000000000000 004c56d8
0000000000056c10 0000000000000000 0 0 8
[17] .debug_line PROGBITS 0000000000000000 0051c2e8
00000000000b5c55 0000000000000000 0 0 1
[18] .debug_loc PROGBITS 0000000000000000 005d1f3d
000000000000628c 0000000000000000 0 0 1
[19] .symtab SYMTAB 0000000000000000 005d81d0
0000000000015a20 0000000000000018 21 2565 8
[20] .shstrtab STRTAB 0000000000000000 005edbf0
00000000000000da 0000000000000000 0 0 1
[21] .strtab STRTAB 0000000000000000 005edcca
000000000004783e 0000000000000000 0 0 1
and the program headers are
Elf file type is EXEC (Executable file)
Entry point 0xfffffffff7e39be0
There are 2 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0xfffffffff7e02000 0x0000000000000000
0x00000000000ab000 0x00000000000ab12a RWE 0x1000
TLS 0x00000000000a0000 0xfffffffff7ea2000 0x00000000000a0000
0x000000000000b000 0x000000000000b12a RW 0x8
Section to Segment mapping:
Segment Sections...
00 .text .rodata .eh_frame_hdr .data .bss .got .tdata
01 .tdata .tbss
The TLS section's total size is as expected being the size of tdata + tbss sections.
From the TLS handling document, i expect that tdata and tbss sections will be right before the fs register's pointed value and thus the total size would be 0xb12a.
But one of the variables which use thread_local have an offset of fs - 0xb130 which is outside of the expected TLS size.
I am trying to understand why the variable is not offset to at-most 0xb12a but more than that?
Although the size of TLS here is 0xb12a. The alignment of 0x8 will make the TLS pointer move to 0xb130 which is the address of variable observed here.