[PATCH V3 03/14] tools/perf: Add support to capture and parse raw instruction in powerpc using dso__data_read_offset utility

Athira Rajeev
2024-06-01T06:10:25Z

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= --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. 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

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
---
tools/perf/util/disasm.c | 98 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 98 insertions(+)

diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
index b5fe3a7508bb..89a9e4136c09 100644
--- a/tools/perf/util/disasm.c
+++ b/tools/perf/util/disasm.c
@@ -1586,6 +1586,91 @@ static int symbol__disassemble_capstone(char *filename, struct symbol *sym,
}
#endif

+static int symbol__disassemble_dso(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);
+ 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, &notes->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, &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:
+ 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
@@ -1710,6 +1795,19 @@ 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")) {
+ 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