On Mon, Jul 01, 2024 at 10:04:18AM +0530, Athira Rajeev wrote:
> Add support to capture and parse raw instruction in powerpc.
> Currently, the perf tool infrastructure uses two ways to disassemble
> and understand the instruction. One is objdump and other option is
> via libcapstone.
>
> 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:
>
> 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 for powerpc. Approach used is to read the raw instruction
> directly from the DSO file using "dso__data_read_offset" utility which
> is already implemented in perf infrastructure in "util/dso.c".
>
> Example:
>
> 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 "symbol__disassemble_dso" is updated to read raw instruction
> directly from DSO using dso__data_read_offset utility. In case of
> above example, this captures:
> line: 38 01 81 e8
>
> The above works well when perf report is invoked with only sort keys for
> data type ie type and typeoff. Because there is no instruction level
> annotation needed if only data type information is requested for. For
> annotating sample, along with type and typeoff sort key, "sym" sort key
> is also needed. And by default invoking just "perf report" uses sort key
> "sym" that displays the symbol information.
>
> With approach changes in powerpc which first reads DSO for raw
> instruction, "perf annotate" and "perf report" + a key breaks since
> it doesn't do the instruction level disassembly.
>
> Snippet of result from perf report:
>
> Samples: 1K of event 'mem-loads', 4000 Hz, Event count (approx.): 937238
> do_work /usr/bin/pmlogger [Percent: local period]
> Percent│ ea230010
> │ 3a550010
> │ 3a600000
>
> │ 38f60001
> │ 39490008
> │ 42400438
> 51.44 │ 81290008
> │ 7d485378
>
> Here, raw instruction is displayed in the output instead of human
> readable annotated form.
>
> One way to get the appropriate data is to specify "--objdump path", by
> which code annotation will be done. But the default behaviour will be
> changed. To fix this breakage, check if "sym" sort key is set. If so
> fallback and use the libcapstone/objdump way of disassmbling the sample.
>
> With the changes and "perf report"
>
> Samples: 1K of event 'mem-loads', 4000 Hz, Event count (approx.): 937238
> do_work /usr/bin/pmlogger [Percent: local period]
> Percent│ ld r17,16(r3)
> │ addi r18,r21,16
> │ li r19,0
>
> │ 8b0: rldicl r10,r10,63,33
> │ addi r10,r10,1
> │ mtctr r10
> │ ↓ b 8e4
> │ 8c0: addi r7,r22,1
> │ addi r10,r9,8
> │ ↓ bdz d00
> 51.44 │ lwz r9,8(r9)
> │ mr r8,r10
> │ cmpw r20,r9
>
> Signed-off-by: Athira Rajeev <atraj...@linux.vnet.ibm.com>
> ---
> tools/perf/util/disasm.c | 101 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 101 insertions(+)
>
> diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
> index ddb861a0b043..e400dcab4029 100644
> --- a/tools/perf/util/disasm.c
> +++ b/tools/perf/util/disasm.c
> @@ -25,6 +25,7 @@
> #include "srcline.h"
> #include "symbol.h"
> #include "util.h"
> +#include "sort.h"
>
> static regex_t file_lineno;
>
> @@ -1645,6 +1646,91 @@ static int symbol__disassemble_capstone(char
> *filename, struct symbol *sym,
> }
> #endif
>
> +static int symbol__disassemble_dso(char *filename, struct symbol *sym,
Again, I still think this should be named to symbol__disassemble_raw()
because it only uses the raw binary codes. Using dso__data_read_offset
is not important here and it's just a way of implementing it.
Thanks,
Namhyung
> + struct annotate_args *args)
> +{
> + struct annotation *notes = symbol__annotation(sym);
> + struct map *map = args->ms.map;
> + struct dso *dso = map__dso(map);
> + u64 start = map__rip_2objdump(map, sym->start);
> + u64 end = map__rip_2objdump(map, sym->end);
> + u64 len = end - start;
> + u64 offset;
> + int i, count;
> + u8 *buf = NULL;
> + char disasm_buf[512];
> + struct disasm_line *dl;
> + u32 *line;
> +
> + /* Return if objdump is specified explicitly */
> + if (args->options->objdump_path)
> + return -1;
> +
> + pr_debug("Reading raw instruction from : %s using
> dso__data_read_offset\n", filename);
> +
> + buf = malloc(len);
> + if (buf == NULL)
> + goto err;
> +
> + count = dso__data_read_offset(dso, NULL, sym->start, buf, len);
> +
> + line = (u32 *)buf;
> +
> + if ((u64)count != len)
> + goto err;
> +
> + /* 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, ¬es->src->source);
> +
> + /* Each raw instruction is 4 byte */
> + 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, ¬es->src->source);
> + offset += 4;
> + }
> +
> + /* It failed in the middle */
> + if (offset != len) {
> + struct list_head *list = ¬es->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:
> + free(buf);
> + return count < 0 ? count : 0;
> +
> +err:
> + count = -1;
> + goto out;
> +}
> /*
> * Possibly create a new version of line with tabs expanded. Returns the
> * existing or new line, storage is updated if a new line is allocated. If
> @@ -1769,6 +1855,21 @@ int symbol__disassemble(struct symbol *sym, struct
> annotate_args *args)
> strcpy(symfs_filename, tmp);
> }
>
> + /*
> + * For powerpc data type profiling, use the dso__data_read_offset
> + * to read raw instruction directly and interpret the binary code
> + * to understand instructions and register fields. For sort keys as
> + * type and typeoff, disassemble to mnemonic notation is
> + * not required in case of powerpc.
> + */
> + if (arch__is(args->arch, "powerpc")) {
> + if (sort_order && !strstr(sort_order, "sym")) {
> + err = symbol__disassemble_dso(symfs_filename, sym,
> args);
> + if (err == 0)
> + goto out_remove_tmp;
> + }
> + }
> +
> #ifdef HAVE_LIBCAPSTONE_SUPPORT
> err = symbol__disassemble_capstone(symfs_filename, sym, args);
> if (err == 0)
> --
> 2.43.0
>
