[PATCH 1/2] perf sdt: add scanning of sdt probles arguments

From: Alexis Berlemont
Date: Wed Nov 16 2016 - 19:01:01 EST


During a "perf buildid-cache --add" command, the section
".note.stapsdt" of the "added" binary is scanned in order to list the
available SDT markers available in a binary. The parts containing the
probes arguments were left unscanned.

The whole section is now parsed; the probe arguments are extracted for
later use.

Signed-off-by: Alexis Berlemont <alexis.berlemont@xxxxxxxxx>
---
tools/perf/util/symbol-elf.c | 16 +++++++++++++++-
tools/perf/util/symbol.h | 1 +
2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 99400b0..0fbe0b2 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1822,7 +1822,7 @@ void kcore_extract__delete(struct kcore_extract *kce)
static int populate_sdt_note(Elf **elf, const char *data, size_t len,
struct list_head *sdt_notes)
{
- const char *provider, *name;
+ const char *provider, *name, *args;
struct sdt_note *tmp = NULL;
GElf_Ehdr ehdr;
GElf_Addr base_off = 0;
@@ -1881,6 +1881,20 @@ static int populate_sdt_note(Elf **elf, const char *data, size_t len,
goto out_free_prov;
}

+ args = (const char *)memchr(name, '\0', data + len - name);
+
+ /*
+ * There is no argument if:
+ * - We reached the end of the note;
+ * - There is not enough room to hold a potential string;
+ * - The argument string is empty or just contains ':'.
+ */
+ if (args == NULL || data + len - args < 2 ||
+ args[1] == ':' || args[1] == '\0')
+ tmp->args = NULL;
+ else
+ tmp->args = strdup(++args);
+
if (gelf_getclass(*elf) == ELFCLASS32) {
memcpy(&tmp->addr, &buf, 3 * sizeof(Elf32_Addr));
tmp->bit32 = true;
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 2d0a905..913be07 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -347,6 +347,7 @@ int arch__choose_best_symbol(struct symbol *syma, struct symbol *symb);
struct sdt_note {
char *name; /* name of the note*/
char *provider; /* provider name */
+ char *args;
bool bit32; /* whether the location is 32 bits? */
union { /* location, base and semaphore addrs */
Elf64_Addr a64[3];
--
2.10.2