[Ping PATCH] perf record: Add support for arch_sdt_arg_parse_op() on s390

[Thomas Richter]

commit e5e66adfe45a6 ("perf regs: Remove __weak attributive arch_sdt_arg_parse_op() function")
removes arch_sdt_arg_parse_op() function and reveals missing s390 support.
The following warning is printed:

  Unknown ELF machine 22, standard arguments parse will be skipped.

ELF machine 22 is the EM_S390 host. This happens with command
  # ./perf record -v -- stress-ng -t 1s --matrix 0
when the event is not specified.

Add s390 specific __perf_sdt_arg_parse_op_s390() function to support
-architecture calls to arch_sdt_arg_parse_op() for s390.
The warning disappears.

Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
Tested-by: Jan Polensky <japo@xxxxxxxxxxxxx>
Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 .../perf/util/perf-regs-arch/perf_regs_s390.c | 78 +++++++++++++++++++
 tools/perf/util/perf_regs.c                   |  3 +
 tools/perf/util/perf_regs.h                   |  1 +
 3 files changed, 82 insertions(+)

diff --git a/tools/perf/util/perf-regs-arch/perf_regs_s390.c b/tools/perf/util/perf-regs-arch/perf_regs_s390.c
index c61df24edf0f..19f219225183 100644
--- a/tools/perf/util/perf-regs-arch/perf_regs_s390.c
+++ b/tools/perf/util/perf-regs-arch/perf_regs_s390.c
@@ -1,7 +1,13 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include <errno.h>
+#include <regex.h>
 #include "../perf_regs.h"
 #include "../../arch/s390/include/perf_regs.h"
+#include "debug.h"
+
+#include <linux/zalloc.h>
+#include <linux/kernel.h>
 
 uint64_t __perf_reg_mask_s390(bool intr __maybe_unused)
 {
@@ -95,3 +101,75 @@ uint64_t __perf_reg_sp_s390(void)
 {
 	return PERF_REG_S390_R15;
 }
+
+/* %rXX */
+#define SDT_OP_REGEX1  "^(%r([0-9]|1[0-5]))$"
+/* +-###(%rXX) */
+#define SDT_OP_REGEX2  "^([+-]?[0-9]+\\(%r([0-9]|1[0-5])\\))$"
+static regex_t sdt_op_regex1, sdt_op_regex2;
+
+static int sdt_init_op_regex(void)
+{
+	static int initialized;
+	int ret = 0;
+
+	if (initialized)
+		return 0;
+
+	ret = regcomp(&sdt_op_regex1, SDT_OP_REGEX1, REG_EXTENDED);
+	if (ret)
+		goto error;
+	initialized = 1;
+
+	ret = regcomp(&sdt_op_regex2, SDT_OP_REGEX2, REG_EXTENDED);
+	if (ret)
+		goto free_regex1;
+	initialized = 2;
+
+	return 0;
+
+free_regex1:
+	regfree(&sdt_op_regex1);
+error:
+	pr_debug4("Regex compilation error, initialized %d\n", initialized);
+	initialized = 0;
+	return ret;
+}
+
+/*
+ * Parse OP and convert it into uprobe format, which is, +/-NUM(%gprREG).
+ * Possible variants of OP are:
+ *	Format		Example
+ *	-------------------------
+ *	NUM(%rREG)	48(%r1)
+ *	-NUM(%rREG)	-48(%r1)
+ *	+NUM(%rREG)	+48(%r1)
+ *	%rREG		%r1
+ */
+int __perf_sdt_arg_parse_op_s390(char *old_op, char **new_op)
+{
+	int ret, new_len;
+	regmatch_t rm[6];
+
+	*new_op = NULL;
+	ret = sdt_init_op_regex();
+	if (ret)
+		return -EINVAL;
+
+	if (!regexec(&sdt_op_regex1, old_op, ARRAY_SIZE(rm), rm, 0) ||
+	    !regexec(&sdt_op_regex2, old_op, ARRAY_SIZE(rm), rm, 0)) {
+		new_len = 1;    /* NULL byte */
+		new_len += (int)(rm[1].rm_eo - rm[1].rm_so);
+		*new_op = zalloc(new_len);
+		if (!*new_op)
+			return -ENOMEM;
+
+		scnprintf(*new_op, new_len, "%.*s",
+			  (int)(rm[1].rm_eo - rm[1].rm_so), old_op + rm[1].rm_so);
+	} else {
+		pr_debug4("Skipping unsupported SDT argument: %s\n", old_op);
+		return SDT_ARG_SKIP;
+	}
+
+	return SDT_ARG_VALID;
+}
diff --git a/tools/perf/util/perf_regs.c b/tools/perf/util/perf_regs.c
index 5b8f34beb24e..f52b0e1f7fc7 100644
--- a/tools/perf/util/perf_regs.c
+++ b/tools/perf/util/perf_regs.c
@@ -23,6 +23,9 @@ int perf_sdt_arg_parse_op(uint16_t e_machine, char *old_op, char **new_op)
 	case EM_X86_64:
 		ret = __perf_sdt_arg_parse_op_x86(old_op, new_op);
 		break;
+	case EM_S390:
+		ret = __perf_sdt_arg_parse_op_s390(old_op, new_op);
+		break;
 	default:
 		pr_debug("Unknown ELF machine %d, standard arguments parse will be skipped.\n",
 			 e_machine);
diff --git a/tools/perf/util/perf_regs.h b/tools/perf/util/perf_regs.h
index 7c04700bf837..573f0d1dfe04 100644
--- a/tools/perf/util/perf_regs.h
+++ b/tools/perf/util/perf_regs.h
@@ -62,6 +62,7 @@ uint64_t __perf_reg_mask_s390(bool intr);
 const char *__perf_reg_name_s390(int id);
 uint64_t __perf_reg_ip_s390(void);
 uint64_t __perf_reg_sp_s390(void);
+int __perf_sdt_arg_parse_op_s390(char *old_op, char **new_op);
 
 int __perf_sdt_arg_parse_op_x86(char *old_op, char **new_op);
 uint64_t __perf_reg_mask_x86(bool intr);
-- 
2.53.0