registers command fails on remote qemu-system-i386 target #829
Description
- Did you use the latest version of GEF from
devbranch? - Is your bug specific to GEF (not GDB)? - Try to reproduce it running
gdb -nx - Did you read the documentation first?
- Did you check issues (including the closed ones) - and the PR?
Step 1: Describe your environment
- Operating System / Distribution: Ubuntu 20.04.3, 5.4.0-100-generic
- Architecture: x64
- GEF version (including the Python library version) run
versionin GEF.
GEF: rev:2b7f31515a3638718b133e0d3b096aedeef5518c (Git - clean)
SHA256(/home/noxwizard/gef/gef.py): 767fcae12cac4cc6dbd3a0b2f51ad6b66f40ed72be199f256ed6c85aed44a70f
GDB: 9.2
GDB-Python: 3.8
Step 2: Describe your problem
Steps to reproduce
- Download "small.ffs" image from here: https://wiki.qemu.org/Testing/System_Images
- Extract .ffs image file
- Run in QEMU:
qemu-system-i386 small.ffs -gdb tcp::1234 - Launch gdb
- Attach to exposed gdb stub:
gef-remote localhost:1234 - Issue step-instruction command
Minimalist test case
See instructions to reproduce
Observed Results
- gdb connects, but GEF is unable to read the registers with error:
[!] Command 'registers' failed to execute properly, reason: max() arg is an empty sequence
gef➤ gef-remote localhost:1234
warning: No executable has been specified and target does not support
determining executable automatically. Try using the "file" command.
0x90216c0f in ?? ()
[+] Connected to 'localhost:1234'
[+] Remote information loaded to temporary path '/tmp/gef/1'
[!] Command 'gef-remote' failed to execute properly, reason: Not a valid ELF file (magic)
gef➤ si
0x90216c12 in ?? ()
[ Legend: Modified register | Code | Heap | Stack | String ]
───────────────────────────────────────────────────────────────── registers ────
[!] Command 'registers' failed to execute properly, reason: max() arg is an empty sequence
───────────────────────────────────────────────────────────────────── stack ────
0x00000090275a64│+0x0000: 0x0000000000f9ef → 0x0000000000f9ef
0x00000090275a64│+0x0000: 0x0000000000f9ef → 0x0000000000f9ef
0x00000090275a64│+0x0000: 0x0000000000f9ef → 0x0000000000f9ef
0x00000090275a64│+0x0000: 0x0000000000f9ef → 0x0000000000f9ef
0x00000090275a64│+0x0000: 0x0000000000f9ef → 0x0000000000f9ef
0x00000090275a64│+0x0000: 0x0000000000f9ef → 0x0000000000f9ef
0x00000090275a64│+0x0000: 0x0000000000f9ef → 0x0000000000f9ef
0x00000090275a64│+0x0000: 0x0000000000f9ef → 0x0000000000f9ef
───────────────────────────────────────────────────────────── code:generic: ────
0x90216c0d push ebx
0x90216c0e popf
0x90216c0f movzx edx, dl
→ 0x90216c12 shl edx, 0x8
0x90216c15 movzx eax, cl
0x90216c18 or edx, eax
0x90216c1a mov eax, edx
0x90216c1c pop ebx
0x90216c1d pop esi
─────────────────────────────────────────────────────────────────── threads ────
[#0] Id 1, stopped 0x90216c12 in ?? (), reason: SINGLE STEP
───────────────────────────────────────────────────────────────────── trace ────
[#0] 0x90216c12 → shl edx, 0x8
[#1] 0x90216c6d → mov edx, eax
[#2] 0x90137768 → add esp, 0xfffffffc
[#3] 0x9020c7a7 → lea esp, [ebp-0x18]
[#4] 0x90193596 → add esp, 0x20
[#5] 0x9020a63c → add esp, 0x10
[#6] 0x90192ed0 → jmp 0x90192f0f
[#7] 0x90193060 → add esp, 0x10
[#8] 0x9020a0c4 → lea esp, [ebp-0x18]
[#9] 0x90193596 → add esp, 0x20
────────────────────────────────────────────────────────────────────────────────
gef➤
Expected results
- Registers are shown like normal
Traces
N/A
Let me know if you need any other information.