G.5.5 i386 Features

The ‘org.gnu.gdb.i386.core’ feature is required for i386/amd64 targets. It should describe the following registers:

• - ‘eax’ through ‘edi’ plus ‘eip’ for i386
• - ‘rax’ through ‘r15’ plus ‘rip’ for amd64
• - ‘eflags’, ‘cs’, ‘ss’, ‘ds’, ‘es’, ‘fs’, ‘gs’
• - ‘st0’ through ‘st7’
• - ‘fctrl’, ‘fstat’, ‘ftag’, ‘fiseg’, ‘fioff’, ‘foseg’, ‘fooff’ and ‘fop’

The register sets may be different, depending on the target.

The ‘org.gnu.gdb.i386.sse’ feature is optional. It should describe registers:

• - ‘xmm0’ through ‘xmm7’ for i386
• - ‘xmm0’ through ‘xmm15’ for amd64
• - ‘mxcsr’

The ‘org.gnu.gdb.i386.avx’ feature is optional and requires the ‘org.gnu.gdb.i386.sse’ feature. It should describe the upper 128 bits of YMM registers:

• - ‘ymm0h’ through ‘ymm7h’ for i386
• - ‘ymm0h’ through ‘ymm15h’ for amd64

The ‘org.gnu.gdb.i386.linux’ feature is optional. If the feature is present, then it should describe the 32 bit register, ‘orig_eax’.

Additionally, the ‘org.gnu.gdb.i386.linux’ feature can optionally contain three 128 bit registers called ‘i386_tls_gdt_0’, ‘i386_tls_gdt_1’, and ‘i386_tls_gdt_2’. Each of these registers contains one 16 byte ‘struct user_desc’ (see man 2 get_thread_area) object which describes one of the three TLS related GDT entries.

The ‘org.gnu.gdb.i386.segments’ feature is optional. It should describe two system registers: ‘fs_base’ and ‘gs_base’.

The ‘org.gnu.gdb.i386.avx512’ feature is optional and requires the ‘org.gnu.gdb.i386.avx’ feature. It should describe additional XMM registers:

• - ‘xmm16’ through ‘xmm31’, only valid for amd64.

It should describe the upper 128 bits of additional YMM registers:

• - ‘ymm16h’ through ‘ymm31h’, only valid for amd64.

It should describe the upper 256 bits of ZMM registers:

• - ‘zmm0h’ through ‘zmm7h’ for i386.
• - ‘zmm0h’ through ‘zmm15h’ for amd64.

It should describe the additional ZMM registers:

• - ‘zmm16h’ through ‘zmm31h’, only valid for amd64.

It should describe the additional 64-bit K registers:

• - ‘k0’ through ‘k7’, valid for amd64 and i386.

The ‘org.gnu.gdb.i386.pkeys’ feature is optional. It should describe a single register, ‘pkru’. It is a 32-bit register valid for i386 and amd64.

The ‘org.gnu.gdb.i386.pl3_ssp’ feature is optional. It should describe the user mode register ‘pl3_ssp’ which has 64 bits on amd64, 32 bits on amd64 with 32-bit pointer size (X32) and 32 bits on i386. Following the restriction of the Linux kernel, only GDB for amd64 targets makes use of this feature for now.