Re: [PATCH V8 04/15] tools/perf: Add disasm_line__parse to parse raw instruction for powerpc

Arnaldo Carvalho de Melo
2024-07-23T19:14:36Z

On Thu, Jul 18, 2024 at 02:13:47PM +0530, Athira Rajeev wrote:
> Currently, the perf tool infrastructure disasm_line__parse function to
> parse disassembled line.
>
> Example snippet from objdump:
> objdump --start-address= --stop-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. In powerpc, the approach for data type
> profiling uses raw instruction instead of result from objdump to identify
> the instruction category and extract the source/target registers.
>
> Example: 38 01 81 e8 ld r4,312(r1)
>
> Here "38 01 81 e8" is the raw instruction representation. Add function
> "disasm_line__parse_powerpc" to handle parsing of raw instruction.
> Also update "struct disasm_line" to save the binary code/
> With the change, function captures:
>
> line -> "38 01 81 e8 ld r4,312(r1)"
> raw instruction "38 01 81 e8"
>
> Raw instruction is used later to extract the reg/offset fields. Macros
> are added to extract opcode and register fields. "struct disasm_line"
> is updated to carry union of "bytes" and "raw_insn" of 32 bit to carry raw
> code (raw). Function "disasm_line__parse_powerpc fills the raw
> instruction hex value and can use macros to get opcode. There is no
> changes in existing code paths, which parses the disassembled code.
> The size of raw instruction depends on architecture. In case of powerpc,
> the parsing the disasm line needs to handle cases for reading binary code
> directly from DSO as well as parsing the objdump result. Hence adding
> the logic into separate function instead of updating "disasm_line__parse".
> 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.
>
> Since the disasm_line__parse is used in other cases (perf annotate) and
> not only data tye profiling, the powerpc callback includes changes to
> work with binary code as well as mneumonic representation. Also in case
> if the DSO read fails and libcapstone is not supported, the approach
> fallback to use objdump as option. Hence as option, patch has changes to
> ensure objdump option also works well.
>
> Reviewed-and-tested-by: Kajol Jain <kjain@linux.ibm.com>
> Reviewed-by: Namhyung Kim <namhyung@kernel.org>
> Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
> ---
> tools/include/linux/string.h | 2 +
> tools/lib/string.c | 13 +++++
> .../perf/arch/powerpc/annotate/instructions.c | 1 +
> tools/perf/arch/powerpc/util/dwarf-regs.c | 9 ++++
> tools/perf/util/annotate.h | 5 +-
> tools/perf/util/disasm.c | 48 ++++++++++++++++++-
> 6 files changed, 76 insertions(+), 2 deletions(-)
>
> diff --git a/tools/include/linux/string.h b/tools/include/linux/string.h
> index db5c99318c79..0acb1fc14e19 100644
> --- a/tools/include/linux/string.h
> +++ b/tools/include/linux/string.h
> @@ -46,5 +46,7 @@ extern char * __must_check skip_spaces(const char *);
>
> extern char *strim(char *);
>
> +extern void remove_spaces(char *s);
> +
> extern void *memchr_inv(const void *start, int c, size_t bytes);
> #endif /* _TOOLS_LINUX_STRING_H_ */
> diff --git a/tools/lib/string.c b/tools/lib/string.c
> index 8b6892f959ab..3126d2cff716 100644
> --- a/tools/lib/string.c
> +++ b/tools/lib/string.c
> @@ -153,6 +153,19 @@ char *strim(char *s)
> return skip_spaces(s);
> }
>
> +/*
> + * remove_spaces - Removes whitespaces from @s
> + */
> +void remove_spaces(char *s)
> +{
> + char *d = s;
> +
> + do {
> + while (*d == ' ')
> + ++d;
> + } while ((*s++ = *d++));
> +}
> +
> /**
> * strreplace - Replace all occurrences of character in string.
> * @s: The string to operate on.
> diff --git a/tools/perf/arch/powerpc/annotate/instructions.c b/tools/perf/arch/powerpc/annotate/instructions.c
> index a3f423c27cae..d57fd023ef9c 100644
> --- a/tools/perf/arch/powerpc/annotate/instructions.c
> +++ b/tools/perf/arch/powerpc/annotate/instructions.c
> @@ -55,6 +55,7 @@ static int powerpc__annotate_init(struct arch *arch, char *cpuid __maybe_unused)
> arch->initialized = true;
> arch->associate_instruction_ops = powerpc__associate_instruction_ops;
> arch->objdump.comment_char = '#';
> + annotate_opts.show_asm_raw = true;
> }
>
> return 0;
> diff --git a/tools/perf/arch/powerpc/util/dwarf-regs.c b/tools/perf/arch/powerpc/util/dwarf-regs.c
> index 0c4f4caf53ac..430623ca5612 100644
> --- a/tools/perf/arch/powerpc/util/dwarf-regs.c
> +++ b/tools/perf/arch/powerpc/util/dwarf-regs.c
> @@ -98,3 +98,12 @@ int regs_query_register_offset(const char *name)
> return roff->ptregs_offset;
> return -EINVAL;
> }
> +
> +#define PPC_OP(op) (((op) >> 26) & 0x3F)
> +#define PPC_RA(a) (((a) >> 16) & 0x1f)
> +#define PPC_RT(t) (((t) >> 21) & 0x1f)
> +#define PPC_RB(b) (((b) >> 11) & 0x1f)
> +#define PPC_D(D) ((D) & 0xfffe)
> +#define PPC_DS(DS) ((DS) & 0xfffc)
> +#define OP_LD 58
> +#define OP_STD 62
> diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h
> index d5c821c22f79..9ba772f46270 100644
> --- a/tools/perf/util/annotate.h
> +++ b/tools/perf/util/annotate.h
> @@ -113,7 +113,10 @@ struct annotation_line {
> struct disasm_line {
> struct ins ins;
> struct ins_operands ops;
> -
> + union {
> + u8 bytes[4];
> + u32 raw_insn;
> + } raw;
> /* This needs to be at the end. */
> struct annotation_line al;
> };
> diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
> index d2723ba024bf..a53591a6111e 100644
> --- a/tools/perf/util/disasm.c
> +++ b/tools/perf/util/disasm.c
> @@ -44,6 +44,7 @@ static int call__scnprintf(struct ins *ins, char *bf, size_t size,
>
> static void ins__sort(struct arch *arch);
> static int disasm_line__parse(char *line, const char **namep, char **rawp);
> +static int disasm_line__parse_powerpc(struct disasm_line *dl);
>
> static __attribute__((constructor)) void symbol__init_regexpr(void)
> {
> @@ -845,6 +846,48 @@ static int disasm_line__parse(char *line, const char **namep, char **rawp)
> return -1;
> }
>
> +/*
> + * Parses the result captured from symbol__disassemble_*
> + * Example, line read from DSO file in powerpc:
> + * line: 38 01 81 e8
> + * opcode: fetched from arch specific get_opcode_insn
> + * rawp_insn: e8810138
> + *
> + * rawp_insn is used later to extract the reg/offset fields
> + */
> +#define PPC_OP(op) (((op) >> 26) & 0x3F)
> +#define RAW_BYTES 11
> +
> +static int disasm_line__parse_powerpc(struct disasm_line *dl)
> +{
> + char *line = dl->al.line;
> + const char **namep = &dl->ins.name;
> + char **rawp = &dl->ops.raw;
> + char *tmp_raw_insn, *name_raw_insn = skip_spaces(line);
> + char *name = skip_spaces(name_raw_insn + RAW_BYTES);
> + int objdump = 0;
> +
> + if (strlen(line) > RAW_BYTES)
> + objdump = 1;
> +
> + if (name_raw_insn[0] == '\0')
> + return -1;
> +
> + if (objdump) {
> + disasm_line__parse(name, namep, rawp);
> + } else
> + *namep = "";
> +
> + tmp_raw_insn = strndup(name_raw_insn, 11);

Not checking the result of strndup(), I'll try to add the check on an
extra pass after I read the patches.

- Arnaldo

> + remove_spaces(tmp_raw_insn);
> +
> + sscanf(tmp_raw_insn, "%x", &dl->raw.raw_insn);
> + if (objdump)
> + dl->raw.raw_insn = be32_to_cpu(dl->raw.raw_insn);
> +
> + return 0;
> +}
> +
> static void annotation_line__init(struct annotation_line *al,
> struct annotate_args *args,
> int nr)
> @@ -898,7 +941,10 @@ struct disasm_line *disasm_line__new(struct annotate_args *args)
> goto out_delete;
>
> if (args->offset != -1) {
> - if (disasm_line__parse(dl->al.line, &dl->ins.name, &dl->ops.raw) < 0)
> + if (arch__is(args->arch, "powerpc")) {
> + if (disasm_line__parse_powerpc(dl) < 0)
> + goto out_free_line;
> + } else if (disasm_line__parse(dl->al.line, &dl->ins.name, &dl->ops.raw) < 0)
> goto out_free_line;

When the if has {}, the else should as well.
Documentation/process/coding-style.rst has this documented.

This is minor, I'm pointing out so that you take into account for the
future.

- Arnaldo

>
> disasm_line__init_ins(dl, args->arch, &args->ms);
> --
> 2.43.0