while debuggung with gdb, custom instructions not showing

[RohanAhmed1]

I added the custom instructions in toolchain. The toolchain works perfectly and my new instructions in also showing in dump file(disasmebly) with their proper naming convention but when I use gdb to debug, the hex is showing instead of the custom instruction name

[TommyMurphyTM1234]

You'll have to provide some detail about how exactly you modified the toolchain to add support for your custom instructions.

[RohanAhmed1]

Adding custom instructions compilation support, to RISCV ... https://medium.com/@viveksgt/adding-custom-instructions-compilation-support-to-riscv-toolchain-78ce1b6efcf4

I followed these steps

[TommyMurphyTM1234]

Adding custom instructions compilation support, to RISCV ... https://medium.com/@viveksgt/adding-custom-instructions-compilation-support-to-riscv-toolchain-78ce1b6efcf4

I followed these steps

Did you do this?

optinally same changes can be done in
riscv-gnu-toolchain/riscv-gdb/opcodes/riscv-opc.c
riscv-gnu-toolchain/riscv-gdb/include/opcode/riscv-opc.h

[TommyMurphyTM1234]

This may also be relevant:

• Adding custom instruction to the elf tool-chain #837 (comment)

[TommyMurphyTM1234]

Did that help at all @RohanAhmed1 ?

[kito-cheng]

Just remind that: gdb and binutils are shared same code base, but they are different folder in riscv-gnu-toolchain, so you need to apply those change for gdb folder as well, generally should be same change, but may facing some minor merge conflict due to the base version mismatch, because binutils and gdb had different release schedule.

[TommyMurphyTM1234]

Thanks @kito-cheng - I always wondered why there were two different copies of binutils-gdb with different branches/tags pulled in by riscv-gnu-toolchain.

• Binutils (binutils @ 49f6117)

  • riscv-gnu-toolchain/.gitmodules

    Lines 1 to 4 in 8c969a9

    	[submodule "binutils"]
    	path = binutils
    	url = https://sourceware.org/git/binutils-gdb.git
    	branch = binutils-2_41-release-point

• GDB (gdb @ 662243d)

  • riscv-gnu-toolchain/.gitmodules

    Lines 20 to 23 in 8c969a9

    	[submodule "gdb"]
    	path = gdb
    	url = https://sourceware.org/git/binutils-gdb.git
    	branch = gdb-13-branch

[TommyMurphyTM1234]

No update from @RohanAhmed1 for over a week so I am assuming that the issue has been explained by the need to make the relevant changes in the two copies of the binutils-gdb sources and, as such, am closing the issue. If it's still a problem then reopen it with further info.

[RohanAhmed1]

Hi, apologies from my side for being late of trying suggestion of adding custom instructions in the gdb folder as well.

Let me give you all of what I have done and what issue I am facing.

Procedure and Explanation

I am adding custom instruction(vgmul.vv) in the toolchain in following path.

At gdb/opcodes/riscv-opc.c and riscv-binutils/opcodes/riscv-opc.c
{"vgmul.vv", 0, INSN_CLASS_V, "Vd,Vt", MATCH_VGMULVV, MASK_VGMULVV, match_opcode, 0 },

At riscv-binutils/include/opcode/riscv-opc.h and gdb/include/opcode/riscv-opc.h
#define MATCH_VGMULVV 0xA208A077
2586 #define MASK_VGMULVV 0xFE0FF07F

Now, I am test this instrucion by making a simple test.
...
li x11, 0x100000000
29 li x12, 0x100000040
30 li x10, 0x100000120
31 li x9, 0x100000080
32
33 vle32.v v2, (x11)
34 vle32.v v4, (x12)
36 vgmul.vv v2, v4
37
38 vse32.v v2, (x10)
39 # test ends here

Now, I build this test with the help of obj_folder of updated toolchain with;

riscv64-unknown-elf-gcc -march=rv64gv -O -g -mcmodel=medany -gdwarf-2 -c -o test.out

and create disassmebly file with

riscv64-unknown-elf-objdump -D test.o > test.dump

This dissassembly file has the vgmul.vv instruction.
...
80000002c: 12050513 addi a0,a0,288
20 800000030: 0010049b addiw s1,zero,1
21 800000034: 02049493 slli s1,s1,0x20
22 800000038: 08048493 addi s1,s1,128
23 80000003c: 0205e107 vle32.v v2,(a1)
24 800000040: 02066207 vle32.v v4,(a2)
25 800000044: a248a177 vgmul.vv v2,v4
26 800000048: 02056127 vse32.v v2,(a0)
...

It means that, my instruction is identifed by the toolchain and my test is running as well.

Issue

Now, I am debugging this with gdb of updated toolchain by:

riscv64-unknown-elf-gdb test.out

and running this command to open the debugger window of dissambly by

tui reg vector
layout next

As you see in this, my custom instruction is showing with .4byte instead of vgmul.vv

Am I missing some files to update?

[TommyMurphyTM1234]

I am adding custom instruction(vgmul.vv) in the toolchain in following path.
...

After making the relevant code changes did you make sure to do a full/clean build?
E.g.

make distclean
rm -rf <toolchain-prefix-dir>
make

BTW - your screenshot is really difficult to read - please use logs rather than screenshots for ease of readability and analysis.

[RohanAhmed1]

Yeah, I have followed this command to build except make distclean and use one more command. Let me write my steps to build.

make clean
rm -rf [toolchain-prefix-dir]
./configure -with-gcc-src=[path-to-gcc] --prefix=[toolchain-prefix-dir] --with-cmodel=medany
make.

-with-gcc-src= is used to save cloning time. Actually, It is a copy of a clone of gcc 13.0. Instead of using riscv RNU toolchain / gcc which I think was gcc 12.3 or something.

I will try this command as well and let you know. Thanks.

[TommyMurphyTM1234]

Yeah, I have followed this command to build except make distclean and use one more command. Let me write my steps to build.

make clean
rm -rf [toolchain-prefix-dir]
./configure -with-gcc-src=[path-to-gcc] --prefix=[toolchain-prefix-dir] --with-cmodel=medany
make

I don't think that make clean is sufficient to do a clean build.

• What's the proper way to re-build? #1196

-with-gcc-src= is used to save cloning time.

Cloning only happens the first time you do the following:

git clone https://github.com/riscv-collab/riscv-gnu-toolchain
cd riscv-gnu-toolchain
./configure ...
make

It doesn't happen thereafter.

Actually, It is a copy of a clone of gcc 13.0. Instead of using riscv RNU toolchain / gcc which I think was gcc 12.3 or something.

I don't know what "riscv RNU toolchain" is.
If you mean this repo - riscv-gnu-toolchain - then it has been GCC 13.2.0 for a while now:

• riscv-gnu-toolchain/.gitmodules

  Lines 5 to 8 in 59ab58e

  	[submodule "gcc"]
  	path = gcc
  	url = https://gcc.gnu.org/git/gcc.git
  	branch = releases/gcc-13

• Bump GCC to 13.2.0 #1341

[RohanAhmed1]

Thanks you for your response. Yeah I mean riscv-gnu-toolchain repo.

Well I tried it out with these steps now,

make distclean
rm -rf [toolchain-prefix-dir]
./configure -with-gcc-src=[path-to-gcc] --prefix=[toolchain-prefix-dir] --with-cmodel=medany
make

The issue is still remain. What can be other thing I can try? can you suggest some?

[TommyMurphyTM1234]

The issue is still remain. What can be other thing I can try? can you suggest some?

Maybe ask about the issue on the GDB mailing list since this is not really a RISC-V specific issue?

• https://www.sourceware.org/gdb/mailing-lists/