Re: [PATCH V3 11/14] tools/perf: Add support to use libcapstone in powerpc

Ian Rogers
2024-06-03T16:30:54Z

On Fri, May 31, 2024 at 11:10 PM 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_args *args, bool is_64bit,
> {
> struct annotation_options *opt = args->options;
> cs_mode mode = 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, "powerpc")))
> return -1;
>
> - if (cs_open(CS_ARCH_X86, mode, handle) != CS_ERR_OK)
> + if (arch__is(args->arch, "x86"))
> + ret = cs_open(CS_ARCH_X86, mode, handle);
> + else
> + ret = cs_open(CS_ARCH_PPC, mode, handle);
> +
> + if (ret != 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/tree/tools/perf/util/print_insn.c?h=perf-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 symbol *sym,
> + struct annotate_args *args)
> +{
> + struct annotation *notes = symbol__annotation(sym);
> + struct map *map = args->ms.map;
> + struct dso *dso = map__dso(map);
> + struct nscookie nsc;
> + u64 start = map__rip_2objdump(map, sym->start);
> + u64 end = map__rip_2objdump(map, sym->end);
> + u64 len = end - start;
> + u64 offset;
> + int i, fd, count;
> + bool is_64bit = false;
> + bool needs_cs_close = false;
> + u8 *buf = NULL;
> + struct find_file_offset_data data = {
> + .ip = 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 = open(filename, O_RDONLY);
> + nsinfo__mountns_exit(&nsc);
> + if (fd < 0)
> + return -1;
> +
> + if (file__read_maps(fd, /*exe=*/true, find_file_offset, &data,
> + &is_64bit) == 0)
> + goto err;
> +
> + if (open_capstone_handle(args, is_64bit, &handle) < 0)
> + goto err;
> +
> + needs_cs_close = true;
> +
> + buf = malloc(len);
> + if (buf == NULL)
> + goto err;
> +
> + count = pread(fd, buf, len, data.offset);
> + close(fd);
> + fd = -1;
> +
> + if ((u64)count != len)
> + goto err;
> +
> + line = (u32 *)buf;
> +
> + /* add the function address and name */
> + scnprintf(disasm_buf, sizeof(disasm_buf), "%#"PRIx64" <%s>:",
> + start, sym->name);
> +
> + args->offset = -1;
> + args->line = disasm_buf;
> + args->line_nr = 0;
> + args->fileloc = NULL;
> + args->ms.sym = sym;
> +
> + dl = disasm_line__new(args);
> + if (dl == NULL)
> + goto err;
> +
> + annotation_line__add(&dl->al, &notes->src->source);
> +
> + /*
> + * TODO: enable disassm for powerpc
> + * count = 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 = len/4;
> +
> + for (i = 0, offset = 0; i < count; i++) {
> + args->offset = offset;
> + sprintf(args->line, "%x", line[i]);
> +
> + dl = disasm_line__new(args);
> + if (dl == NULL)
> + goto err;
> +
> + annotation_line__add(&dl->al, &notes->src->source);
> +
> + offset += 4;
> + }
> +
> + /* It failed in the middle */
> + if (offset != len) {
> + struct list_head *list = &notes->src->source;
> +
> + /* Discard all lines and fallback to objdump */
> + while (!list_empty(list)) {
> + dl = list_first_entry(list, struct disasm_line, al.node);
> +
> + list_del_init(&dl->al.node);
> + disasm_line__free(dl);
> + }
> + count = -1;
> + }
> +
> +out:
> + if (needs_cs_close)
> + cs_close(&handle);
> + free(buf);
> + return count < 0 ? count : 0;
> +
> +err:
> + if (fd >= 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 = -1;
> + goto out;
> +}
> +
> static int symbol__disassemble_capstone(char *filename, struct symbol *sym,
> struct annotate_args *args)
> {
> @@ -1987,6 +2126,11 @@ int symbol__disassemble(struct symbol *sym, struct annotate_args *args)
> err = symbol__disassemble_dso(symfs_filename, sym, args);
> if (err == 0)
> goto out_remove_tmp;
> +#ifdef HAVE_LIBCAPSTONE_SUPPORT
> + err = symbol__disassemble_capstone_powerpc(symfs_filename, sym, args);
> + if (err == 0)
> + goto out_remove_tmp;
> +#endif
> }
> }
>
> --
> 2.43.0
>