perf probe: Fix to support libdwfl older than 0.148

Since the libdwfl library before 0.148 fails to analyze live kernel debuginfo,
'perf probe --list' compiled with those old libdwfl sometimes crashes.

To avoid that bug, perf probe does not use libdwfl's live kernel analysis
routine when it is compiled with older libdwfl.

Side effect: perf with older libdwfl doesn't support listing probe in modules
with source code line. Those could be shown by symbol+offset.

Cc: 2nddept-manager@sdl.hitachi.co.jp
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20101217131218.24123.62424.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 3991d73d1cff9164cb23fb4aae3169af97abfe77..ddf4d45563218ad9e2d8971d32f2a8f25097c502 100644 (file)
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -117,28 +117,6 @@ static void line_list__free(struct list_head *head)
 }
 
 /* Dwarf FL wrappers */
-
-static int __linux_kernel_find_elf(Dwfl_Module *mod,
-                                  void **userdata,
-                                  const char *module_name,
-                                  Dwarf_Addr base,
-                                  char **file_name, Elf **elfp)
-{
-       int fd;
-       const char *path = kernel_get_module_path(module_name);
-
-       if (path) {
-               fd = open(path, O_RDONLY);
-               if (fd >= 0) {
-                       *file_name = strdup(path);
-                       return fd;
-               }
-       }
-       /* If failed, try to call standard method */
-       return dwfl_linux_kernel_find_elf(mod, userdata, module_name, base,
-                                         file_name, elfp);
-}
-
 static char *debuginfo_path;   /* Currently dummy */
 
 static const Dwfl_Callbacks offline_callbacks = {
@@ -151,14 +129,6 @@ static const Dwfl_Callbacks offline_callbacks = {
        .find_elf = dwfl_build_id_find_elf,
 };
 
-static const Dwfl_Callbacks kernel_callbacks = {
-       .find_debuginfo = dwfl_standard_find_debuginfo,
-       .debuginfo_path = &debuginfo_path,
-
-       .find_elf = __linux_kernel_find_elf,
-       .section_address = dwfl_linux_kernel_module_section_address,
-};
-
 /* Get a Dwarf from offline image */
 static Dwarf *dwfl_init_offline_dwarf(int fd, Dwfl **dwflp, Dwarf_Addr *bias)
 {
@@ -185,6 +155,38 @@ error:
        return dbg;
 }
 
+#if _ELFUTILS_PREREQ(0, 148)
+/* This method is buggy if elfutils is older than 0.148 */
+static int __linux_kernel_find_elf(Dwfl_Module *mod,
+                                  void **userdata,
+                                  const char *module_name,
+                                  Dwarf_Addr base,
+                                  char **file_name, Elf **elfp)
+{
+       int fd;
+       const char *path = kernel_get_module_path(module_name);
+
+       pr_debug2("Use file %s for %s\n", path, module_name);
+       if (path) {
+               fd = open(path, O_RDONLY);
+               if (fd >= 0) {
+                       *file_name = strdup(path);
+                       return fd;
+               }
+       }
+       /* If failed, try to call standard method */
+       return dwfl_linux_kernel_find_elf(mod, userdata, module_name, base,
+                                         file_name, elfp);
+}
+
+static const Dwfl_Callbacks kernel_callbacks = {
+       .find_debuginfo = dwfl_standard_find_debuginfo,
+       .debuginfo_path = &debuginfo_path,
+
+       .find_elf = __linux_kernel_find_elf,
+       .section_address = dwfl_linux_kernel_module_section_address,
+};
+
 /* Get a Dwarf from live kernel image */
 static Dwarf *dwfl_init_live_kernel_dwarf(Dwarf_Addr addr, Dwfl **dwflp,
                                          Dwarf_Addr *bias)
@@ -205,11 +207,34 @@ static Dwarf *dwfl_init_live_kernel_dwarf(Dwarf_Addr addr, Dwfl **dwflp,
        dbg = dwfl_addrdwarf(*dwflp, addr, bias);
        /* Here, check whether we could get a real dwarf */
        if (!dbg) {
+               pr_debug("Failed to find kernel dwarf at %lx\n",
+                        (unsigned long)addr);
                dwfl_end(*dwflp);
                *dwflp = NULL;
        }
        return dbg;
 }
+#else
+/* With older elfutils, this just support kernel module... */
+static Dwarf *dwfl_init_live_kernel_dwarf(Dwarf_Addr addr __used, Dwfl **dwflp,
+                                         Dwarf_Addr *bias)
+{
+       int fd;
+       const char *path = kernel_get_module_path("kernel");
+
+       if (!path) {
+               pr_err("Failed to find vmlinux path\n");
+               return NULL;
+       }
+
+       pr_debug2("Use file %s for debuginfo\n", path);
+       fd = open(path, O_RDONLY);
+       if (fd < 0)
+               return NULL;
+
+       return dwfl_init_offline_dwarf(fd, dwflp, bias);
+}
+#endif
 
 /* Dwarf wrappers */