perf probe: Add sdt probes arguments into the uprobe cmd string

An sdt probe can be associated with arguments but they were not passed
to the user probe tracing interface (uprobe_events); this patch adapts
the sdt argument descriptors according to the uprobe input format.

As the uprobe parser does not support scaled address mode, perf will
skip arguments which cannot be adapted to the uprobe format.

Here are the results:

  $ perf buildid-cache -v --add test_sdt
  $ perf probe -x test_sdt sdt_libfoo:table_frob
  $ perf probe -x test_sdt sdt_libfoo:table_diddle
  $ perf record -e sdt_libfoo:table_frob -e sdt_libfoo:table_diddle test_sdt
  $ perf script
  test_sdt  ...   666.255678:   sdt_libfoo:table_frob: (4004d7) arg0=0 arg1=0
  test_sdt  ...   666.255683: sdt_libfoo:table_diddle: (40051a) arg0=0 arg1=0
  test_sdt  ...   666.255686:   sdt_libfoo:table_frob: (4004d7) arg0=1 arg1=2
  test_sdt  ...   666.255689: sdt_libfoo:table_diddle: (40051a) arg0=3 arg1=4
  test_sdt  ...   666.255692:   sdt_libfoo:table_frob: (4004d7) arg0=2 arg1=4
  test_sdt  ...   666.255694: sdt_libfoo:table_diddle: (40051a) arg0=6 arg1=8

Signed-off-by: Alexis Berlemont <alexis.berlemont@gmail.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20161214000732.1710-3-alexis.berlemont@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

3 files changed, 178 insertions, 4 deletions

diff --git a/tools/perf/util/perf_regs.c b/tools/perf/util/perf_regs.c
index c4023f22f287..a37e5934aa2a 100644
--- a/tools/perf/util/perf_regs.c
+++ b/tools/perf/util/perf_regs.c
@@ -6,6 +6,12 @@ const struct sample_reg __weak sample_reg_masks[] = {
 	SMPL_REG_END
 };
 
+int __weak sdt_rename_register(char **pdesc __maybe_unused,
+			char *old_name __maybe_unused)
+{
+	return 0;
+}
+
 #ifdef HAVE_PERF_REGS_SUPPORT
 int perf_reg_value(u64 *valp, struct regs_dump *regs, int id)
 {
diff --git a/tools/perf/util/perf_regs.h b/tools/perf/util/perf_regs.h
index 679d6e493962..7544a157e159 100644
--- a/tools/perf/util/perf_regs.h
+++ b/tools/perf/util/perf_regs.h
@@ -15,6 +15,12 @@ struct sample_reg {
 
 extern const struct sample_reg sample_reg_masks[];
 
+/*
+ * The table sdt_reg_renamings is used for adjusting gcc/gas-generated
+ * registers before filling the uprobe tracer interface.
+ */
+int sdt_rename_register(char **pdesc, char *old_name);
+
 #ifdef HAVE_PERF_REGS_SUPPORT
 #include <perf_regs.h>
 
diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index c3c287125be5..d741634cbfc0 100644
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -27,6 +27,7 @@
 #include "probe-event.h"
 #include "probe-file.h"
 #include "session.h"
+#include "perf_regs.h"
 
 /* 4096 - 2 ('\n' + '\0') */
 #define MAX_CMDLEN 4094
@@ -688,6 +689,166 @@ static unsigned long long sdt_note__get_addr(struct sdt_note *note)
 		 : (unsigned long long)note->addr.a64[0];
 }
 
+static const char * const type_to_suffix[] = {
+	":s64", "", "", "", ":s32", "", ":s16", ":s8",
+	"", ":u8", ":u16", "", ":u32", "", "", "", ":u64"
+};
+
+static int synthesize_sdt_probe_arg(struct strbuf *buf, int i, const char *arg)
+{
+	char *tmp, *desc = strdup(arg);
+	const char *prefix = "", *suffix = "";
+	int ret = -1;
+
+	if (desc == NULL) {
+		pr_debug4("Allocation error\n");
+		return ret;
+	}
+
+	tmp = strchr(desc, '@');
+	if (tmp) {
+		long type_idx;
+		/*
+		 * Isolate the string number and convert it into a
+		 * binary value; this will be an index to get suffix
+		 * of the uprobe name (defining the type)
+		 */
+		tmp[0] = '\0';
+		type_idx = strtol(desc, NULL, 10);
+		/* Check that the conversion went OK */
+		if (type_idx == LONG_MIN || type_idx == LONG_MAX) {
+			pr_debug4("Failed to parse sdt type\n");
+			goto error;
+		}
+		/* Check that the converted value is OK */
+		if (type_idx < -8 || type_idx > 8) {
+			pr_debug4("Failed to get a valid sdt type\n");
+			goto error;
+		}
+		suffix = type_to_suffix[type_idx + 8];
+		/* Get rid of the sdt prefix which is now useless */
+		tmp++;
+		memmove(desc, tmp, strlen(tmp) + 1);
+	}
+
+	/*
+	 * The uprobe tracer format does not support all the
+	 * addressing modes (notably: in x86 the scaled mode); so, we
+	 * detect ',' characters, if there is just one, there is no
+	 * use converting the sdt arg into a uprobe one.
+	 */
+	if (strchr(desc, ',')) {
+		pr_debug4("Skipping unsupported SDT argument; %s\n", desc);
+		goto out;
+	}
+
+	/*
+	 * If the argument addressing mode is indirect, we must check
+	 * a few things...
+	 */
+	tmp = strchr(desc, '(');
+	if (tmp) {
+		int j;
+
+		/*
+		 * ...if the addressing mode is indirect with a
+		 * positive offset (ex.: "1608(%ax)"), we need to add
+		 * a '+' prefix so as to be compliant with uprobe
+		 * format.
+		 */
+		if (desc[0] != '+' && desc[0] != '-')
+			prefix = "+";
+
+		/*
+		 * ...or if the addressing mode is indirect with a symbol
+		 * as offset, the argument will not be supported by
+		 * the uprobe tracer format; so, let's skip this one.
+		 */
+		for (j = 0; j < tmp - desc; j++) {
+			if (desc[j] != '+' && desc[j] != '-' &&
+				!isdigit(desc[j])) {
+				pr_debug4("Skipping unsupported SDT argument; "
+					"%s\n", desc);
+				goto out;
+			}
+		}
+	}
+
+	/*
+	 * The uprobe tracer format does not support constants; if we
+	 * find one in the current argument, let's skip the argument.
+	 */
+	if (strchr(desc, '$')) {
+		pr_debug4("Skipping unsupported SDT argument; %s\n", desc);
+		goto out;
+	}
+
+	/*
+	 * The uprobe parser does not support all gas register names;
+	 * so, we have to replace them (ex. for x86_64: %rax -> %ax);
+	 * the loop below looks for the register names (starting with
+	 * a '%' and tries to perform the needed renamings.
+	 */
+	tmp = strchr(desc, '%');
+	while (tmp) {
+		size_t offset = tmp - desc;
+
+		ret = sdt_rename_register(&desc, desc + offset);
+		if (ret < 0)
+			goto error;
+
+		/*
+		 * The desc pointer might have changed; so, let's not
+		 * try to reuse tmp for next lookup
+		 */
+		tmp = strchr(desc + offset + 1, '%');
+	}
+
+	if (strbuf_addf(buf, " arg%d=%s%s%s", i + 1, prefix, desc, suffix) < 0)
+		goto error;
+
+out:
+	ret = 0;
+error:
+	free(desc);
+	return ret;
+}
+
+static char *synthesize_sdt_probe_command(struct sdt_note *note,
+					const char *pathname,
+					const char *sdtgrp)
+{
+	struct strbuf buf;
+	char *ret = NULL, **args;
+	int i, args_count;
+
+	if (strbuf_init(&buf, 32) < 0)
+		return NULL;
+
+	if (strbuf_addf(&buf, "p:%s/%s %s:0x%llx",
+				sdtgrp, note->name, pathname,
+				sdt_note__get_addr(note)) < 0)
+		goto error;
+
+	if (!note->args)
+		goto out;
+
+	if (note->args) {
+		args = argv_split(note->args, &args_count);
+
+		for (i = 0; i < args_count; ++i) {
+			if (synthesize_sdt_probe_arg(&buf, i, args[i]) < 0)
+				goto error;
+		}
+	}
+
+out:
+	ret = strbuf_detach(&buf, NULL);
+error:
+	strbuf_release(&buf);
+	return ret;
+}
+
 int probe_cache__scan_sdt(struct probe_cache *pcache, const char *pathname)
 {
 	struct probe_cache_entry *entry = NULL;
@@ -724,11 +885,12 @@ int probe_cache__scan_sdt(struct probe_cache *pcache, const char *pathname)
 			entry->pev.group = strdup(sdtgrp);
 			list_add_tail(&entry->node, &pcache->entries);
 		}
-		ret = asprintf(&buf, "p:%s/%s %s:0x%llx",
-				sdtgrp, note->name, pathname,
-				sdt_note__get_addr(note));
-		if (ret < 0)
+		buf = synthesize_sdt_probe_command(note, pathname, sdtgrp);
+		if (!buf) {
+			ret = -ENOMEM;
 			break;
+		}
+
 		strlist__add(entry->tevlist, buf);
 		free(buf);
 		entry = NULL;