[ktap] [PATCH] add new symbol module to search symbols in DSO (for uprobes)
- From: Azat Khuzhin <a3at.mail@xxxxxxxxx>
- To: ktap@xxxxxxxxxxxxx
- Date: Tue, 5 Nov 2013 08:16:21 +0400
This will allow to don't hardcoding addresses of functions in ktap
scripts, that use uprobes, but instead, use normal function names.
Before this patch:
$ ktap -e 'trace probe:/path/to/bin:0xDEADBEAF' # instead some real address
After this path:
$ ktap -e 'trace probe:/path/to/bin:foo'
Works also for ret probes (%return)
Requires libelf.
Signed-off-by: Azat Khuzhin <a3at.mail@xxxxxxxxx>
---
v2: make it more pretty
v3: make it faster (thanks to Yicheng)
Makefile | 5 ++-
include/ktap_types.h | 2 +
userspace/eventdef.c | 43 ++++++++++++++++++-
userspace/symbol.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++++++
userspace/symbol.h | 32 +++++++++++++++
5 files changed, 194 insertions(+), 2 deletions(-)
create mode 100644 userspace/symbol.c
create mode 100644 userspace/symbol.h
diff --git a/Makefile b/Makefile
index 372b41a..344c82a 100644
--- a/Makefile
+++ b/Makefile
@@ -59,6 +59,8 @@ $(UDIR)/tstring.o: $(INTP)/tstring.c $(INC)/*
$(QUIET_CC)$(CC) $(DEBUGINFO_FLAG) $(KTAPC_CFLAGS) -o $@ -c $<
$(UDIR)/object.o: $(INTP)/object.c $(INC)/*
$(QUIET_CC)$(CC) $(DEBUGINFO_FLAG) $(KTAPC_CFLAGS) -o $@ -c $<
+$(UDIR)/symbol.o: $(UDIR)/symbol.c $(INC)/*
+ $(QUIET_CC)$(CC) $(DEBUGINFO_FLAG) $(KTAPC_CFLAGS) -o $@ -c $<
KTAPOBJS =
KTAPOBJS += $(UDIR)/lex.o
@@ -73,9 +75,10 @@ KTAPOBJS += $(UDIR)/opcode.o
KTAPOBJS += $(UDIR)/table.o
KTAPOBJS += $(UDIR)/tstring.o
KTAPOBJS += $(UDIR)/object.o
+KTAPOBJS += $(UDIR)/symbol.o
ktap: $(KTAPOBJS)
- $(QUIET_LINK)$(CC) $(KTAPC_CFLAGS) -o $@ $(KTAPOBJS) -lpthread
+ $(QUIET_LINK)$(CC) $(KTAPC_CFLAGS) -o $@ $(KTAPOBJS) -lpthread -lelf
KMISC := /lib/modules/$(KVERSION)/ktapvm/
diff --git a/include/ktap_types.h b/include/ktap_types.h
index 1dae9d8..4e19f0b 100644
--- a/include/ktap_types.h
+++ b/include/ktap_types.h
@@ -600,5 +600,7 @@ extern ktap_global_state dummy_global_state;
#define KTAP_QL(x) "'" x "'"
#define KTAP_QS KTAP_QL("%s")
+#define STRINGIFY(type) #type
+
#endif /* __KTAP_TYPES_H__ */
diff --git a/userspace/eventdef.c b/userspace/eventdef.c
index 76a68ac..280202d 100644
--- a/userspace/eventdef.c
+++ b/userspace/eventdef.c
@@ -29,6 +29,7 @@
#include "../include/ktap_types.h"
#include "../include/ktap_opcodes.h"
#include "ktapc.h"
+#include "symbol.h"
static char tracing_events_path[] = "/sys/kernel/debug/tracing/events";
@@ -305,6 +306,42 @@ static int parse_events_add_kprobe(char *old_event)
#define UPROBE_EVENTS_PATH "/sys/kernel/debug/tracing/uprobe_events"
+static char* parse_events_resolve_symbol(char *event, char *r)
+{
+ char *colon = strchr(event, ':');
+ vaddr_t symbol_address = strtol(colon + 1 /* skip ":" */, NULL, 0);
+
+ char *binary, *symbol;
+
+ /**
+ * We already have address, no need in resolving.
+ */
+ if (symbol_address) {
+ return event;
+ }
+
+ binary = strndup(event, colon - event);
+ if (r) {
+ symbol = strndup(colon + 1 /* skip ":" */,
+ r - 1 /* skip "%" */ - colon);
+ } else {
+ symbol = strdup(colon + 1);
+ }
+
+ if ((symbol_address = find_symbol(binary, symbol))) {
+ verbose_printf("symbol %s resolved to 0x%lx\n",
+ event, symbol_address);
+
+ event = realloc(event, strlen(event) +
(strlen(STRINGIFY(ULONG_MAX))));
+ sprintf(event, "%s:0x%lx", binary, symbol_address);
+ }
+
+ free(binary);
+ free(symbol);
+
+ return event;
+}
+
static int parse_events_add_uprobe(char *old_event)
{
static int event_seq = 0;
@@ -326,6 +363,10 @@ static int parse_events_add_uprobe(char *old_event)
r = strstr(event, "%return");
if (r) {
memset(r, ' ', 7);
+ }
+ event = parse_events_resolve_symbol(event, r);
+
+ if (r) {
snprintf(probe_event, 128, "r:uprobes/kp%d %s",
event_seq, event);
} else
@@ -541,7 +582,7 @@ ktap_string *ktapc_parse_eventdef(ktap_string *eventdef)
goto parse_next_eventdef;
ts = ktapc_ts_new(g_idstr);
- free(g_idstr);
+ free(g_idstr);
return ts;
error:
diff --git a/userspace/symbol.c b/userspace/symbol.c
new file mode 100644
index 0000000..23333b8
--- /dev/null
+++ b/userspace/symbol.c
@@ -0,0 +1,114 @@
+/*
+ * symbol.c
+ *
+ * This file is part of ktap by Jovi Zhangwei.
+ *
+ * Copyright (C) 2013 Azat Khuzhin <a3at.mail@xxxxxxxxx>.
+ *
+ * ktap is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * ktap is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "symbol.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+
+#include <libelf.h>
+
+
+/**
+ * @return v_addr of "LOAD" program header, that have zero offset.
+ */
+static vaddr_t find_load_address(Elf *elf)
+{
+ GElf_Phdr header;
+ size_t headers;
+ vaddr_t address = 0;
+
+ elf_getphdrnum(elf, &headers);
+ while (headers-- > 0) {
+ gelf_getphdr(elf, headers, &header);
+ if (header.p_type != PT_LOAD || header.p_offset != 0)
+ continue;
+
+ address = header.p_vaddr;
+ break;
+ }
+
+ return address;
+}
+
+static vaddr_t search_symbol(Elf *elf, const char *symbol)
+{
+ Elf_Data *elf_data = NULL;
+ Elf_Scn *scn = NULL;
+ GElf_Sym sym;
+ GElf_Shdr shdr;
+
+ vaddr_t load_address = find_load_address(elf);
+
+ if (!load_address)
+ return 0;
+
+ while ((scn = elf_nextscn(elf, scn))) {
+ int i, symbols;
+ char *current_symbol;
+
+ gelf_getshdr(scn, &shdr);
+
+ if (shdr.sh_type != SHT_SYMTAB)
+ continue;
+
+ elf_data = elf_getdata(scn, elf_data);
+ symbols = shdr.sh_size / shdr.sh_entsize;
+
+ for (i = 0; i < symbols; i++) {
+ gelf_getsym(elf_data, i, &sym);
+
+ if (GELF_ST_TYPE(sym.st_info) != STT_FUNC)
+ continue;
+
+ current_symbol = elf_strptr(elf, shdr.sh_link,
sym.st_name);
+ if (!strcmp(current_symbol, symbol)) {
+ return (sym.st_value - load_address);
+ }
+ }
+ }
+
+ return 0;
+}
+
+vaddr_t find_symbol(const char *exec, const char *symbol)
+{
+ Elf *elf = NULL;
+ int fd = 0;
+ vaddr_t vaddr = 0;
+
+ if (((fd = open(exec, O_RDONLY)) != -1) &&
+ (elf_version(EV_CURRENT) != EV_NONE) &&
+ (elf = elf_begin(fd, ELF_C_READ, NULL)))
+ vaddr = search_symbol(elf, symbol);
+
+ if (elf)
+ elf_end(elf);
+ if (fd)
+ close(fd);
+ return vaddr;
+}
diff --git a/userspace/symbol.h b/userspace/symbol.h
new file mode 100644
index 0000000..478ad2e
--- /dev/null
+++ b/userspace/symbol.h
@@ -0,0 +1,32 @@
+/*
+ * symbol.h
+ *
+ * This file is part of ktap by Jovi Zhangwei.
+ *
+ * Copyright (C) 2013 Azat Khuzhin <a3at.mail@xxxxxxxxx>.
+ *
+ * ktap is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * ktap is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <gelf.h> // GElf_Addr
+
+
+typedef GElf_Addr vaddr_t;
+
+/**
+ * Find symbol in DSO
+ *
+ * @return 0 on failure, otherwise address of symbol.
+ */
+vaddr_t find_symbol(const char *exec, const char *symbol);
--
1.8.4.rc3
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