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References: <20240601060941.13692-1-atrajeev@linux.vnet.ibm.com> <20240601060941.13692-12-atrajeev@linux.vnet.ibm.com>
In-Reply-To: <20240601060941.13692-12-atrajeev@linux.vnet.ibm.com>
From: Ian Rogers <irogers@google.com>
Date: Mon, 3 Jun 2024 09:30:42 -0700
Message-ID: <CAP-5=fXGPHMF+5cUu42ns0=qm9QCPg0LNUveLLnjdGHPCnVg3w@mail.gmail.com>
Subject: Re: [PATCH V3 11/14] tools/perf: Add support to use libcapstone in powerpc
To: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: acme@kernel.org, jolsa@kernel.org, adrian.hunter@intel.com, 
	namhyung@kernel.org, segher@kernel.crashing.org, christophe.leroy@csgroup.eu, 
	linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, 
	linuxppc-dev@lists.ozlabs.org, akanksha@linux.ibm.com, maddy@linux.ibm.com, 
	kjain@linux.ibm.com, disgoel@linux.vnet.ibm.com
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On Fri, May 31, 2024 at 11:10=E2=80=AFPM Athira Rajeev
<atrajeev@linux.vnet.ibm.com> wrote:
>
> Now perf uses the capstone library to disassemble the instructions in
> x86. capstone is used (if available) for perf annotate to speed up.
> Currently it only supports x86 architecture. Patch includes changes to
> enable this in powerpc. For now, only for data type sort keys, this
> method is used and only binary code (raw instruction) is read. This is
> because powerpc approach to understand instructions and reg fields uses
> raw instruction. The "cs_disasm" is currently not enabled. While
> attempting to do cs_disasm, observation is that some of the instructions
> were not identified (ex: extswsli, maddld) and it had to fallback to use
> objdump. Hence enabling "cs_disasm" is added in comment section as a
> TODO for powerpc.
>
> Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
> ---
>  tools/perf/util/disasm.c | 148 ++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 146 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
> index d8b357055302..915508d2e197 100644
> --- a/tools/perf/util/disasm.c
> +++ b/tools/perf/util/disasm.c
> @@ -1540,12 +1540,18 @@ static int open_capstone_handle(struct annotate_a=
rgs *args, bool is_64bit,
>  {
>         struct annotation_options *opt =3D args->options;
>         cs_mode mode =3D is_64bit ? CS_MODE_64 : CS_MODE_32;
> +       int ret;
>
>         /* TODO: support more architectures */
> -       if (!arch__is(args->arch, "x86"))
> +       if ((!arch__is(args->arch, "x86")) && (!arch__is(args->arch, "pow=
erpc")))
>                 return -1;
>
> -       if (cs_open(CS_ARCH_X86, mode, handle) !=3D CS_ERR_OK)
> +       if (arch__is(args->arch, "x86"))
> +               ret =3D cs_open(CS_ARCH_X86, mode, handle);
> +       else
> +               ret =3D cs_open(CS_ARCH_PPC, mode, handle);
> +
> +       if (ret !=3D CS_ERR_OK)
>                 return -1;

There looks to be a pretty/more robust capstone_init function in
print_insn.c, should we factor this code out and recycle:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tr=
ee/tools/perf/util/print_insn.c?h=3Dperf-tools-next#n40

Thanks,
Ian

>         if (!opt->disassembler_style ||
> @@ -1635,6 +1641,139 @@ static void print_capstone_detail(cs_insn *insn, =
char *buf, size_t len,
>         }
>  }
>
> +static int symbol__disassemble_capstone_powerpc(char *filename, struct s=
ymbol *sym,
> +                                       struct annotate_args *args)
> +{
> +       struct annotation *notes =3D symbol__annotation(sym);
> +       struct map *map =3D args->ms.map;
> +       struct dso *dso =3D map__dso(map);
> +       struct nscookie nsc;
> +       u64 start =3D map__rip_2objdump(map, sym->start);
> +       u64 end =3D map__rip_2objdump(map, sym->end);
> +       u64 len =3D end - start;
> +       u64 offset;
> +       int i, fd, count;
> +       bool is_64bit =3D false;
> +       bool needs_cs_close =3D false;
> +       u8 *buf =3D NULL;
> +       struct find_file_offset_data data =3D {
> +               .ip =3D start,
> +       };
> +       csh handle;
> +       char disasm_buf[512];
> +       struct disasm_line *dl;
> +       u32 *line;
> +
> +       if (args->options->objdump_path)
> +               return -1;
> +
> +       nsinfo__mountns_enter(dso->nsinfo, &nsc);
> +       fd =3D open(filename, O_RDONLY);
> +       nsinfo__mountns_exit(&nsc);
> +       if (fd < 0)
> +               return -1;
> +
> +       if (file__read_maps(fd, /*exe=3D*/true, find_file_offset, &data,
> +                           &is_64bit) =3D=3D 0)
> +               goto err;
> +
> +       if (open_capstone_handle(args, is_64bit, &handle) < 0)
> +               goto err;
> +
> +       needs_cs_close =3D true;
> +
> +       buf =3D malloc(len);
> +       if (buf =3D=3D NULL)
> +               goto err;
> +
> +       count =3D pread(fd, buf, len, data.offset);
> +       close(fd);
> +       fd =3D -1;
> +
> +       if ((u64)count !=3D len)
> +               goto err;
> +
> +       line =3D (u32 *)buf;
> +
> +       /* add the function address and name */
> +       scnprintf(disasm_buf, sizeof(disasm_buf), "%#"PRIx64" <%s>:",
> +                 start, sym->name);
> +
> +       args->offset =3D -1;
> +       args->line =3D disasm_buf;
> +       args->line_nr =3D 0;
> +       args->fileloc =3D NULL;
> +       args->ms.sym =3D sym;
> +
> +       dl =3D disasm_line__new(args);
> +       if (dl =3D=3D NULL)
> +               goto err;
> +
> +       annotation_line__add(&dl->al, &notes->src->source);
> +
> +       /*
> +        * TODO: enable disassm for powerpc
> +        * count =3D cs_disasm(handle, buf, len, start, len, &insn);
> +        *
> +        * For now, only binary code is saved in disassembled line
> +        * to be used in "type" and "typeoff" sort keys. Each raw code
> +        * is 32 bit instruction. So use "len/4" to get the number of
> +        * entries.
> +        */
> +       count =3D len/4;
> +
> +       for (i =3D 0, offset =3D 0; i < count; i++) {
> +               args->offset =3D offset;
> +               sprintf(args->line, "%x", line[i]);
> +
> +               dl =3D disasm_line__new(args);
> +               if (dl =3D=3D NULL)
> +                       goto err;
> +
> +               annotation_line__add(&dl->al, &notes->src->source);
> +
> +               offset +=3D 4;
> +       }
> +
> +       /* It failed in the middle */
> +       if (offset !=3D len) {
> +               struct list_head *list =3D &notes->src->source;
> +
> +               /* Discard all lines and fallback to objdump */
> +               while (!list_empty(list)) {
> +                       dl =3D list_first_entry(list, struct disasm_line,=
 al.node);
> +
> +                       list_del_init(&dl->al.node);
> +                       disasm_line__free(dl);
> +               }
> +               count =3D -1;
> +       }
> +
> +out:
> +       if (needs_cs_close)
> +               cs_close(&handle);
> +       free(buf);
> +       return count < 0 ? count : 0;
> +
> +err:
> +       if (fd >=3D 0)
> +               close(fd);
> +       if (needs_cs_close) {
> +               struct disasm_line *tmp;
> +
> +               /*
> +                * It probably failed in the middle of the above loop.
> +                * Release any resources it might add.
> +                */
> +               list_for_each_entry_safe(dl, tmp, &notes->src->source, al=
.node) {
> +                       list_del(&dl->al.node);
> +                       free(dl);
> +               }
> +       }
> +       count =3D -1;
> +       goto out;
> +}
> +
>  static int symbol__disassemble_capstone(char *filename, struct symbol *s=
ym,
>                                         struct annotate_args *args)
>  {
> @@ -1987,6 +2126,11 @@ int symbol__disassemble(struct symbol *sym, struct=
 annotate_args *args)
>                         err =3D symbol__disassemble_dso(symfs_filename, s=
ym, args);
>                         if (err =3D=3D 0)
>                                 goto out_remove_tmp;
> +#ifdef HAVE_LIBCAPSTONE_SUPPORT
> +                       err =3D symbol__disassemble_capstone_powerpc(symf=
s_filename, sym, args);
> +                       if (err =3D=3D 0)
> +                               goto out_remove_tmp;
> +#endif
>                 }
>         }
>
> --
> 2.43.0
>