Invalid store/load AF behaviour - sahf, lahf

[mfaerevaag]

Description

When executing the sahf or lahff instructions, AH should be stored or loaded, but rather AL is used.

Reference:
Ref. Intel 64 and IA-32 Architecture Software Developer's Manual Vol. 2B 4-578
Ref. Intel 64 and IA-32 Architecture Software Developer's Manual Vol. 2A 3-517

Affected instructions:

0x9e    # sahf
0x9f    # lahf

NOTE: All combinations of prefixes are omitted.

Reproduction guide

Instruction:

00000000  9E                sahf

Input:

binsec disasm -decode 9e

Observed output:

     ⎧ 0: SF := eax₍₃₂₎{7}
     ⎪ 1: ZF := eax₍₃₂₎{6}
     ⎪ 2: AF := eax₍₃₂₎{4}
sahf ⎨ 3: PF := eax₍₃₂₎{2}
     ⎪ 4: CF := eax₍₃₂₎{0}
     ⎩ 5: goto ({0x00000001; 32}, 0)

Expected output:
Use AH instead of AL.

System Info

OS:

# uname -a
Linux ubuntu 4.10.0-28-generic #32-Ubuntu SMP Fri Jun 30 05:32:18 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
# cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=17.04
DISTRIB_CODENAME=zesty
DISTRIB_DESCRIPTION="Ubuntu 17.04"

BINSEC: 20170301 0.1