Find the given address from offline dwarfs instead of
online kernel dwarfs.

On the KASLR enabled kernel, the kernel text section is
loaded with random offset, and the debuginfo__new_online_kernel
can't handle it. So let's move to the offline dwarf
loader instead of using the online dwarf loader.

As a result, since we don't need debuginfo__new_online_kernel
any more, this also removes the functions related that.

Without this change;

  # ./perf probe -l
    probe:t_show         (on _stext+901288 with m v)
    probe:t_show_1       (on _stext+939624 with m v t)
    probe:t_show_2       (on _stext+980296 with m v fmt)
    probe:t_show_3       (on _stext+1014392 with m v file)

With this change;

  # ./perf probe -l
    probe:t_show         (on t_show@linux-3/kernel/trace/ftrace.c with m v)
    probe:t_show_1       (on t_show@linux-3/kernel/trace/trace.c with m v t)
    probe:t_show_2       (on t_show@kernel/trace/trace_printk.c with m v fmt)
    probe:t_show_3       (on t_show@kernel/trace/trace_events.c with m v file)

Changes from v2:
 - Instead of retrying, directly opens offline dwarf.
 - Remove debuginfo__new_online_kernel and related functions.
 - Refer map->reloc to get the correct address of a symbol.
 - Add a special case for handling ref_reloc_sym based address.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
---
 tools/perf/util/probe-event.c  |   40 ++++++++++++-------
 tools/perf/util/probe-finder.c |   86 ----------------------------------------
 tools/perf/util/probe-finder.h |    1 
 3 files changed, 26 insertions(+), 101 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 1ce2cb9..8e34c8d 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -248,6 +248,18 @@ static struct debuginfo *open_debuginfo(const char *module)
        return debuginfo__new(path);
 }
 
+static struct ref_reloc_sym *__kernel_get_ref_reloc_sym(void)
+{
+       /* kmap->ref_reloc_sym should be set if host_machine is initialized */
+       struct kmap *kmap;
+
+       if (map__load(host_machine->vmlinux_maps[MAP__FUNCTION], NULL) < 0)
+               return NULL;
+
+       kmap = map__kmap(host_machine->vmlinux_maps[MAP__FUNCTION]);
+       return kmap->ref_reloc_sym;
+}
+
 /*
  * Convert trace point to probe point with debuginfo
  * Currently only handles kprobes.
@@ -256,18 +268,27 @@ static int kprobe_convert_to_perf_probe(struct 
probe_trace_point *tp,
                                        struct perf_probe_point *pp)
 {
        struct symbol *sym;
+       struct ref_reloc_sym *reloc_sym;
        struct map *map;
-       u64 addr;
+       u64 addr = 0;
        int ret = -ENOENT;
        struct debuginfo *dinfo;
 
-       sym = __find_kernel_function_by_name(tp->symbol, &map);
-       if (sym) {
-               addr = map->unmap_ip(map, sym->start + tp->offset);
+       /* ref_reloc_sym is just a label. Need a special fix*/
+       reloc_sym = __kernel_get_ref_reloc_sym();
+       if (reloc_sym && strcmp(tp->symbol, reloc_sym->name) == 0)
+               addr = reloc_sym->unrelocated_addr + tp->offset;
+       else {
+               sym = __find_kernel_function_by_name(tp->symbol, &map);
+               if (sym)
+                       addr = map->unmap_ip(map, sym->start + tp->offset) -
+                               map->reloc;
+       }
+       if (addr) {
                pr_debug("try to find %s+%ld@%" PRIx64 "\n", tp->symbol,
                         tp->offset, addr);
 
-               dinfo = debuginfo__new_online_kernel(addr);
+               dinfo = open_debuginfo(tp->module);
                if (dinfo) {
                        ret = debuginfo__find_probe_point(dinfo,
                                                 (unsigned long)addr, pp);
@@ -383,15 +404,6 @@ static int add_module_to_probe_trace_events(struct 
probe_trace_event *tevs,
        return ret;
 }
 
-static struct ref_reloc_sym *__kernel_get_ref_reloc_sym(void)
-{
-       /* kmap->ref_reloc_sym should be set if host_machine is initialized */
-       struct kmap *kmap;
-
-       kmap = map__kmap(host_machine->vmlinux_maps[MAP__FUNCTION]);
-       return kmap->ref_reloc_sym;
-}
-
 /* Post processing the probe events */
 static int post_process_probe_trace_events(struct probe_trace_event *tevs,
                                           int ntevs, const char *module,
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index e5e589f..4f6e277 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -89,79 +89,6 @@ error:
        return -ENOENT;
 }
 
-#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 int debuginfo__init_online_kernel_dwarf(struct debuginfo *dbg,
-                                              Dwarf_Addr addr)
-{
-       dbg->dwfl = dwfl_begin(&kernel_callbacks);
-       if (!dbg->dwfl)
-               return -EINVAL;
-
-       /* Load the kernel dwarves: Don't care the result here */
-       dwfl_linux_kernel_report_kernel(dbg->dwfl);
-       dwfl_linux_kernel_report_modules(dbg->dwfl);
-
-       dbg->dbg = dwfl_addrdwarf(dbg->dwfl, addr, &dbg->bias);
-       /* Here, check whether we could get a real dwarf */
-       if (!dbg->dbg) {
-               pr_debug("Failed to find kernel dwarf at %lx\n",
-                        (unsigned long)addr);
-               dwfl_end(dbg->dwfl);
-               memset(dbg, 0, sizeof(*dbg));
-               return -ENOENT;
-       }
-
-       return 0;
-}
-#else
-/* With older elfutils, this just support kernel module... */
-static int debuginfo__init_online_kernel_dwarf(struct debuginfo *dbg,
-                                              Dwarf_Addr addr __maybe_unused)
-{
-       const char *path = kernel_get_module_path("kernel");
-
-       if (!path) {
-               pr_err("Failed to find vmlinux path\n");
-               return -ENOENT;
-       }
-
-       pr_debug2("Use file %s for debuginfo\n", path);
-       return debuginfo__init_offline_dwarf(dbg, path);
-}
-#endif
-
 struct debuginfo *debuginfo__new(const char *path)
 {
        struct debuginfo *dbg = zalloc(sizeof(*dbg));
@@ -174,19 +101,6 @@ struct debuginfo *debuginfo__new(const char *path)
        return dbg;
 }
 
-struct debuginfo *debuginfo__new_online_kernel(unsigned long addr)
-{
-       struct debuginfo *dbg = zalloc(sizeof(*dbg));
-
-       if (!dbg)
-               return NULL;
-
-       if (debuginfo__init_online_kernel_dwarf(dbg, (Dwarf_Addr)addr) < 0)
-               zfree(&dbg);
-
-       return dbg;
-}
-
 void debuginfo__delete(struct debuginfo *dbg)
 {
        if (dbg) {
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index 592c4da..3fc5973 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -31,7 +31,6 @@ struct debuginfo {
 };
 
 extern struct debuginfo *debuginfo__new(const char *path);
-extern struct debuginfo *debuginfo__new_online_kernel(unsigned long addr);
 extern void debuginfo__delete(struct debuginfo *dbg);
 
 /* Find probe_trace_events specified by perf_probe_event from debuginfo */


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