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Commit 2a8d41b4 authored by Milian Wolff's avatar Milian Wolff Committed by Arnaldo Carvalho de Melo
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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: default avatarMilian Wolff <milian.wolff@kdab.com>
LPU-Reference: 20160830114102.30863-1-milian.wolff@kdab.com
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent fd227598

tools/perf/util/symbol-elf.c

+52 −29
Original line number Diff line number Diff line
@@ -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;

		}



		f = symbol__new(sym.st_value, sym.st_size,

				GELF_ST_BIND(sym.st_info), elf_name);

		free(demangled);