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RISC-V: Cannot invoke Varnode.getAddress because the return value of VariableStorage.getFirstVarnode is null
See original GitHub issueDescribe the bug I’m reverse engineering rv32imafc binary, and for some functions, decompiler shows this error:
Cannot invoke "ghidra.program.model.pcode.Varnode.getAddress()" because the return value of
"ghidra.program.model.listing.VariableStorage.getFirstVarnode()" is null
To Reproduce Steps to reproduce the behavior:
- Open
firmware.binattached, select RV32IMC language, and set base address to0x23000000 - Go to
0x23000daeand check decompile panel - (Optional) Go to similar function (but smaller) at
0x23000d68, this decompiles nicely.
Expected behavior Decompiler should be able to decompile the function.
Screenshots
Stacktrace:
Attachments firmware.bin.zip
(In show log, there wasn’t anything useful)
Environment
- OS: Linux 6.0.8
- Java Version: 19.0.1
- Ghidra Version: 10.2.2 DEV 2022-Nov-15 2224 CET
- Ghidra Origin: ArchLinux Packages
Additional context Let me know if any other information will be needed. Thanks
Issue Analytics
- State:
- Created 10 months ago
- Reactions:1
- Comments:5 (3 by maintainers)
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Hi @mumbel , thanks for all the help. (For anyone struggling with this) Since I applied mumbel’s recommendation, I got memory reads on memory areas, which didn’t gave any sense, generally having GP at
0x1F0164F0didn’t gave any sense in context of real MCU memory map. After a bit thinking, I find out, this GP is wrong.The first instruction is AUIPC, which add upper immediate to PC. This instruction adds a 20-bit immediate value to the upper 20 bits of the program counter and set it to register. This means for:
23000000 97 61 01 1f auipc gp,0x1f016:0x23000000 + (0x1F016 << 12)=0x4201600023000004 93 81 01 4f addi gp,gp,0x4f0:0x42016000 + 0x4F0=0x420164F0So correct GP is
0x420164F0.You might be able to close the code browser and right click firmware.bin in the frontend window and “choose language” (I think, AFK now) and see if it lets yous choose a new language.
Id leave open for now just track if there’s something that could be fixed for gp detection