Le 06/05/2024 à 14:19, Athira Rajeev a écrit :
> Add support to capture and parse raw instruction in objdump.
What's the purpose of using 'objdump' for reading raw instructions ?
Can't they be read directly without invoking 'objdump' ? It looks odd to
me to use objdump to provide readable text and then parse it back.
> Currently, the perf tool infrastructure uses "--no-show-raw-insn" option
> with "objdump" while disassemble. Example from powerpc with this option
> for an instruction address is:
Yes and that makes sense because the purpose of objdump is to provide
human readable annotations, not to perform automated analysis. Am I
missing something ?
>
> Snippet from:
> objdump --start-address=<address> --stop-address=<address> -d
> --no-show-raw-insn -C <vmlinux>
>
> c0000000010224b4: lwz r10,0(r9)
>
> This line "lwz r10,0(r9)" is parsed to extract instruction name,
> registers names and offset. Also to find whether there is a memory
> reference in the operands, "memory_ref_char" field of objdump is used.
> For x86, "(" is used as memory_ref_char to tackle instructions of the
> form "mov (%rax), %rcx".
>
> In case of powerpc, not all instructions using "(" are the only memory
> instructions. Example, above instruction can also be of extended form (X
> form) "lwzx r10,0,r19". Inorder to easy identify the instruction category
> and extract the source/target registers, patch adds support to use raw
> instruction. With raw instruction, macros are added to extract opcode
> and register fields.
>
> "struct ins_operands" and "struct ins" is updated to carry opcode and
> raw instruction binary code (raw_insn). Function "disasm_line__parse"
> is updated to fill the raw instruction hex value and opcode in newly
> added fields. There is no changes in existing code paths, which parses
> the disassembled code. The architecture using the instruction name and
> present approach is not altered. Since this approach targets powerpc,
> the macro implementation is added for powerpc as of now.
>
> Example:
> representation using --show-raw-insn in objdump gives result:
>
> 38 01 81 e8 ld r4,312(r1)
>
> Here "38 01 81 e8" is the raw instruction representation. In powerpc,
> this translates to instruction form: "ld RT,DS(RA)" and binary code
> as:
> _____________________________________
> | 58 | RT | RA | DS | |
> -------------------------------------
> 0 6 11 16 30 31
>
> Function "disasm_line__parse" is updated to capture:
>
> line: 38 01 81 e8 ld r4,312(r1)
> opcode and raw instruction "38 01 81 e8"
> Raw instruction is used later to extract the reg/offset fields.
>
> Signed-off-by: Athira Rajeev <atraj...@linux.vnet.ibm.com>
> ---
