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Assembly seems to be broken on riscv #2452

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TethysSvensson opened this issue Sep 5, 2024 · 4 comments · May be fixed by #2419
Open

Assembly seems to be broken on riscv #2452

TethysSvensson opened this issue Sep 5, 2024 · 4 comments · May be fixed by #2419
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backport-required bug

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@TethysSvensson
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I've tried using the asm tool for riscv32 and riscv64 and it doesn't seem to work correctly.

Example:

$ asm -c riscv32 'nop'
[!] Could not find system include headers for riscv32-linux
0100
$ asm -c riscv32 'addi x0, x0, 0'
[!] Could not find system include headers for riscv32-linux
0100
$ asm -c riscv32 'addi x0, x0, 1'
[!] Could not find system include headers for riscv32-linux
13001000
$ asm -c riscv64 'nop'
[!] Could not find system include headers for riscv64-linux
0100
$ asm -c riscv64 'addi x0, x0, 0'
[!] Could not find system include headers for riscv64-linux
0100
$ asm -c riscv64 'addi x0, x0, 1'
[!] Could not find system include headers for riscv64-linux
13001000

Instructions in riscv cannot be only two bytes long.
@Arusekk
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Arusekk commented Sep 5, 2024

See #2419

@Arusekk Arusekk linked a pull request Sep 5, 2024 that will close this issue
riscv: avoid compressed instructions #2419
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@TethysSvensson
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My bad, it seems like I don't know riscv very well at all.

Still, I don't think asm produce assembly that only works on processors with the C extension, unless explicitly enabled.

@Xeonacid
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Still, I don't think asm produce assembly that only works on processors with the C extension, unless explicitly enabled.

All existing riscv64 chips designed to run Linux have the C extension, and main Linux distributions (Debian, Ubuntu, Fedora, Arch Linux...) all use rv64gc as their baseline. I think including the C extension by default is reasonable.

@TethysSvensson
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As far as I remember, I was not targeting a Linux system at the time.

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riscv: avoid compressed instructions Arusekk/pwntools
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@TethysSvensson @Xeonacid @Arusekk