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

Athira Rajeev
2024-06-08T07:05:50Z

> On 3 Jun 2024, at 10:00 PM, Ian Rogers <irogers@google.com> wrote:
>
> 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

Hi Ian,

Thanks for checking the patch.

Yes, that’s good change to have. I will have this change in V4

Thanks
Athira

>
>> 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