perf symbols: Demangle symbols for synthesized @plt entries.

The symbols in the synthesized @plt entries where not demangled before,
i.e. we could end up with entries such as:

    $ perf report
    Samples: 7K of event 'cycles:ppp', Event count (approx.): 6223833141
    Children      Self  Command          Shared Object           Symbol
    -   93.63%    28.89%  lab_mandelbrot   lab_mandelbrot        [.] main
        - 73.81% main
            - 33.57% hypot
              27.76% __hypot_finite
              15.97% __muldc3
               2.90% __muldc3@plt
               2.40% _ZNK6QImage6heightEv@plt
             + 2.14% QColor::rgb
               1.94% _ZNK6QImage5widthEv@plt
               1.92% cabs@plt

This patch remedies this issue by also applying demangling to the
synthesized symbols. The output for the above is now:

    $ perf report
    Samples: 7K of event 'cycles:ppp', Event count (approx.): 6223833141
    Children      Self  Command          Shared Object           Symbol
    -   93.63%    28.89%  lab_mandelbrot   lab_mandelbrot        [.] main
        - 73.81% main
            - 33.57% hypot
              27.76% __hypot_finite
              15.97% __muldc3
               2.90% __muldc3@plt
               2.40% QImage::height() const@plt
             + 2.14% QColor::rgb
               1.94% QImage::width() const@plt
               1.92% cabs@plt

Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
LPU-Reference: 20160830114102.30863-1-milian.wolff@kdab.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index a811c13a74d663ac40efdf03333145450e7d7c19..fbe31eff1bebe6cdf097dff8ac112e433065682f 100644 (file)
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -206,6 +206,37 @@ Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
        return NULL;
 }
 
+static bool want_demangle(bool is_kernel_sym)
+{
+       return is_kernel_sym ? symbol_conf.demangle_kernel : symbol_conf.demangle;
+}
+
+static char *demangle_sym(struct dso *dso, int kmodule, const char *elf_name)
+{
+       int demangle_flags = verbose ? (DMGL_PARAMS | DMGL_ANSI) : DMGL_NO_OPTS;
+       char *demangled = NULL;
+
+       /*
+        * We need to figure out if the object was created from C++ sources
+        * DWARF DW_compile_unit has this, but we don't always have access
+        * to it...
+        */
+       if (!want_demangle(dso->kernel || kmodule))
+           return demangled;
+
+       demangled = bfd_demangle(NULL, elf_name, demangle_flags);
+       if (demangled == NULL)
+               demangled = java_demangle_sym(elf_name, JAVA_DEMANGLE_NORET);
+       else if (rust_is_mangled(demangled))
+               /*
+                   * Input to Rust demangling is the BFD-demangled
+                   * name which it Rust-demangles in place.
+                   */
+               rust_demangle_sym(demangled);
+
+       return demangled;
+}
+
 #define elf_section__for_each_rel(reldata, pos, pos_mem, idx, nr_entries) \
        for (idx = 0, pos = gelf_getrel(reldata, 0, &pos_mem); \
             idx < nr_entries; \
@@ -301,11 +332,19 @@ int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss, struct map *
 
                elf_section__for_each_rela(reldata, pos, pos_mem, idx,
                                           nr_rel_entries) {
+                       const char *elf_name = NULL;
+                       char *demangled = NULL;
                        symidx = GELF_R_SYM(pos->r_info);
                        plt_offset += shdr_plt.sh_entsize;
                        gelf_getsym(syms, symidx, &sym);
+
+                       elf_name = elf_sym__name(&sym, symstrs);
+                       demangled = demangle_sym(dso, 0, elf_name);
+                       if (demangled != NULL)
+                               elf_name = demangled;
                        snprintf(sympltname, sizeof(sympltname),
-                                "%s@plt", elf_sym__name(&sym, symstrs));
+                                "%s@plt", elf_name);
+                       free(demangled);
 
                        f = symbol__new(plt_offset, shdr_plt.sh_entsize,
                                        STB_GLOBAL, sympltname);
@@ -323,11 +362,19 @@ int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss, struct map *
                GElf_Rel pos_mem, *pos;
                elf_section__for_each_rel(reldata, pos, pos_mem, idx,
                                          nr_rel_entries) {
+                       const char *elf_name = NULL;
+                       char *demangled = NULL;
                        symidx = GELF_R_SYM(pos->r_info);
                        plt_offset += shdr_plt.sh_entsize;
                        gelf_getsym(syms, symidx, &sym);
+
+                       elf_name = elf_sym__name(&sym, symstrs);
+                       demangled = demangle_sym(dso, 0, elf_name);
+                       if (demangled != NULL)
+                               elf_name = demangled;
                        snprintf(sympltname, sizeof(sympltname),
-                                "%s@plt", elf_sym__name(&sym, symstrs));
+                                "%s@plt", elf_name);
+                       free(demangled);
 
                        f = symbol__new(plt_offset, shdr_plt.sh_entsize,
                                        STB_GLOBAL, sympltname);
@@ -775,11 +822,6 @@ static u64 ref_reloc(struct kmap *kmap)
        return 0;
 }
 
-static bool want_demangle(bool is_kernel_sym)
-{
-       return is_kernel_sym ? symbol_conf.demangle_kernel : symbol_conf.demangle;
-}
-
 void __weak arch__sym_update(struct symbol *s __maybe_unused,
                GElf_Sym *sym __maybe_unused) { }
 
@@ -1070,29 +1112,10 @@ int dso__load_sym(struct dso *dso, struct map *map,
                        sym.st_value -= shdr.sh_addr - shdr.sh_offset;
                }
 new_symbol:
-               /*
-                * We need to figure out if the object was created from C++ sources
-                * DWARF DW_compile_unit has this, but we don't always have access
-                * to it...
-                */
-               if (want_demangle(dso->kernel || kmodule)) {
-                       int demangle_flags = DMGL_NO_OPTS;
-                       if (verbose)
-                               demangle_flags = DMGL_PARAMS | DMGL_ANSI;
-
-                       demangled = bfd_demangle(NULL, elf_name, demangle_flags);
-                       if (demangled == NULL)
-                               demangled = java_demangle_sym(elf_name, JAVA_DEMANGLE_NORET);
-                       else if (rust_is_mangled(demangled))
-                               /*
-                                * Input to Rust demangling is the BFD-demangled
-                                * name which it Rust-demangles in place.
-                                */
-                               rust_demangle_sym(demangled);
+               demangled = demangle_sym(dso, kmodule, elf_name);
+               if (demangled != NULL)
+                       elf_name = demangled;
 
-                       if (demangled != NULL)
-                               elf_name = demangled;
-               }
                f = symbol__new(sym.st_value, sym.st_size,
                                GELF_ST_BIND(sym.st_info), elf_name);
                free(demangled);