linux-kernel - Re: [PATCH v3 2/2] scripts/decodecode: Add support for RISC-V

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Message-ID: <e8b16a7b-8221-2e36-bc8f-92059d083b6b@ghiti.fr>
Date:   Tue, 21 Feb 2023 16:18:35 +0100
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Björn Töpel <bjorn@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org
Cc:     Björn Töpel <bjorn@...osinc.com>,
        Andreas Schwab <schwab@...ux-m68k.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] scripts/decodecode: Add support for RISC-V

Hi Björn,

On 1/19/23 08:47, Björn Töpel wrote:
> From: Björn Töpel <bjorn@...osinc.com>
>
> RISC-V has some GNU disassembly quirks, e.g. it requires '-D' to
> properly disassemble .2byte directives similar to Arm [1]. Further,
> GNU objdump groups RISC-V instruction by 2 or 4 byte chunks, instead
> doing byte-for-byte.
>
> Add the required switches, and translate from short/word to bytes when
> ARCH is "riscv".
>
> An example how to invoke decodecode for RISC-V:
>    $ echo 'Code: bf45 f793 1007 f7d9 50ef 37af d541 b7d9 7097 00c8 (80e7)
>    6140' | AFLAGS="-march=rv64imac_zicbom_zihintpause"  \
>    ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- ./scripts/decodecode
>    Code: bf45 f793 1007 f7d9 50ef 37af d541 b7d9 7097 00c8 (80e7) 6140
>    All code
>    ========
>       0:   bf45                    c.j     0xffffffffffffffb0
>       2:   1007f793                andi    a5,a5,256
>       6:   f7d9                    c.bnez  a5,0xffffffffffffff94
>       8:   37af50ef                jal     ra,0xf5382
>       c:   d541                    c.beqz  a0,0xffffffffffffff94
>       e:   b7d9                    c.j     0xffffffffffffffd4
>      10:   00c87097                auipc   ra,0xc87
>      14:*  614080e7                jalr    ra,1556(ra) # 0xc87624          <-- trapping instruction
>
>    Code starting with the faulting instruction
>    ===========================================
>       0:   614080e7                jalr    ra,1556(ra)
>
> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=10263
>
> Signed-off-by: Björn Töpel <bjorn@...osinc.com>
> ---
>   scripts/decodecode | 12 +++++++++++-
>   1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/decodecode b/scripts/decodecode
> index b28fd2686561..8fe71c292381 100755
> --- a/scripts/decodecode
> +++ b/scripts/decodecode
> @@ -93,6 +93,11 @@ disas() {
>   		${CROSS_COMPILE}strip $t.o
>   	fi
>   
> +	if [ "$ARCH" = "riscv" ]; then
> +		OBJDUMPFLAGS="-M no-aliases --section=.text -D"
> +		${CROSS_COMPILE}strip $t.o
> +	fi
> +
>   	if [ $pc_sub -ne 0 ]; then
>   		if [ $PC ]; then
>   			adj_vma=$(( $PC - $pc_sub ))
> @@ -126,8 +131,13 @@ get_substr_opcode_bytes_num()
>   	do
>   		substr+="$opc"
>   
> +		opcode="$substr"
> +		if [ "$ARCH" = "riscv" ]; then
> +			opcode=$(echo $opcode | tr ' ' '\n' | tac | tr -d '\n')
> +		fi
> +
>   		# return if opcode bytes do not match @opline anymore
> -		if ! echo $opline | grep -q "$substr";
> +		if ! echo $opline | grep -q "$opcode";
>   		then
>   			break
>   		fi


Tested-by: Alexandre Ghiti <alexghiti@...osinc.com>

Thanks, that's very useful!

Alex