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Subject[PATCH 2/2] scripts/decodecode: Add support for RISC-V
Date
From: Björn Töpel <bjorn@rivosinc.com>

RISC-V has some GNU disassembly quirks, e.g. it requires '-D' to
properly disassemble .byte 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: 64 c9 29 a0 17 d4 1f 01 13 04 44
b8 93 92 38 00 16 94 00 60 <02> 94 aa e8' | \
AFLAGS="-march=rv64imac_zicbom_zihintpause" \
ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- ./scripts/decodecode
Code: 64 c9 29 a0 17 d4 1f 01 13 04 44 b8 93 92 38 00 16 94 00 60 <02> 94 aa e8
All code
========
0: c964 c.sw s1,84(a0)
2: a029 c.j c <.text+0xc>
4: 011fd417 auipc s0,0x11fd
8: b8440413 addi s0,s0,-1148 # 11fcb88 <.text+0x11fcb88>
c: 00389293 slli t0,a7,0x3
10: 9416 c.add s0,t0
12: 6000 c.ld s0,0(s0)
14:* 9402 c.jalr s0 <-- trapping instruction
16: e8aa c.sdsp a0,80(sp)

Code starting with the faulting instruction
===========================================
0: 9402 c.jalr s0
2: e8aa c.sdsp a0,80(sp)

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=10263

Signed-off-by: Björn Töpel <bjorn@rivosinc.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
--
2.37.2
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