Thread (40 messages) 40 messages, 2 authors, 2024-06-30

Re: [V4 03/16] tools/perf: Add support to capture and parse raw instruction in powerpc using dso__data_read_offset utility

From: Namhyung Kim <namhyung@kernel.org>
Date: 2024-06-25 05:29:05
Also in: linux-perf-users, lkml

On Fri, Jun 14, 2024 at 10:56:18PM +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)
What about removing --no-show-raw-insn and parse the raw byte code in
the output for powerpc?  I think it's better to support normal
annotation together.
quoted hunk ↗ jump to hunk
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 <redacted>
---
 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..f19496133bf0 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,
Maybe rename to symbol__disassemble_raw() ?
+					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);
You may want to print the actual offset and remove the "using
dso__data_read_offset" part.

Thanks,
Namhyung
quoted hunk ↗ jump to hunk
+
+	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
Keyboard shortcuts
hback out one level
jnext message in thread
kprevious message in thread
ldrill in
Escclose help / fold thread tree
?toggle this help