perf symbols: Try reading the symbol table with libbfd

Wine generates PE binaries for its code modules and also generates debug
files in PE or PDB formats, which perf cannot parse either.

Trying to read symbols on non-ELF binaries with libbfd, when supported,
makes it possible for perf to report symbols and annotations for Windows
applications running under Wine.

Because libbfd doesn't provide symbol size (probably because of some
backends not supporting it), we compute it by first sorting the symbols
by addresses and then considering that they are sequential in a given
section.

v3: Also include local and weak bfd symbols and mark them as such, only
global symbols were previously reported, and that caused a very
imprecise address to symbol resolution.

Signed-off-by: Remi Bernon <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Jacek Caban <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/symbol.c

···
 	return -1;
 }
 
+#ifdef HAVE_LIBBFD_SUPPORT
+#define PACKAGE 'perf'
+#include <bfd.h>
+
+static int bfd_symbols__cmpvalue(const void *a, const void *b)
+{
+	const asymbol *as = *(const asymbol **)a, *bs = *(const asymbol **)b;
+
+	if (bfd_asymbol_value(as) != bfd_asymbol_value(bs))
+		return bfd_asymbol_value(as) - bfd_asymbol_value(bs);
+
+	return bfd_asymbol_name(as)[0] - bfd_asymbol_name(bs)[0];
+}
+
+static int bfd2elf_binding(asymbol *symbol)
+{
+	if (symbol->flags & BSF_WEAK)
+		return STB_WEAK;
+	if (symbol->flags & BSF_GLOBAL)
+		return STB_GLOBAL;
+	if (symbol->flags & BSF_LOCAL)
+		return STB_LOCAL;
+	return -1;
+}
+
+int dso__load_bfd_symbols(struct dso *dso, const char *debugfile)
+{
+	int err = -1;
+	long symbols_size, symbols_count;
+	asection *section;
+	asymbol **symbols, *sym;
+	struct symbol *symbol;
+	bfd *abfd;
+	u_int i;
+	u64 start, len;
+
+	abfd = bfd_openr(dso->long_name, NULL);
+	if (!abfd)
+		return -1;
+
+	if (!bfd_check_format(abfd, bfd_object)) {
+		pr_debug2("%s: cannot read %s bfd file.\n", __func__,
+			  dso->long_name);
+		goto out_close;
+	}
+
+	if (bfd_get_flavour(abfd) == bfd_target_elf_flavour)
+		goto out_close;
+
+	section = bfd_get_section_by_name(abfd, ".text");
+	if (section)
+		dso->text_offset = section->vma - section->filepos;
+
+	bfd_close(abfd);
+
+	abfd = bfd_openr(debugfile, NULL);
+	if (!abfd)
+		return -1;
+
+	if (!bfd_check_format(abfd, bfd_object)) {
+		pr_debug2("%s: cannot read %s bfd file.\n", __func__,
+			  debugfile);
+		goto out_close;
+	}
+
+	if (bfd_get_flavour(abfd) == bfd_target_elf_flavour)
+		goto out_close;
+
+	symbols_size = bfd_get_symtab_upper_bound(abfd);
+	if (symbols_size == 0) {
+		bfd_close(abfd);
+		return 0;
+	}
+
+	if (symbols_size < 0)
+		goto out_close;
+
+	symbols = malloc(symbols_size);
+	if (!symbols)
+		goto out_close;
+
+	symbols_count = bfd_canonicalize_symtab(abfd, symbols);
+	if (symbols_count < 0)
+		goto out_free;
+
+	qsort(symbols, symbols_count, sizeof(asymbol *), bfd_symbols__cmpvalue);
+
+#ifdef bfd_get_section
+#define bfd_asymbol_section bfd_get_section
+#endif
+	for (i = 0; i < symbols_count; ++i) {
+		sym = symbols[i];
+		section = bfd_asymbol_section(sym);
+		if (bfd2elf_binding(sym) < 0)
+			continue;
+
+		while (i + 1 < symbols_count &&
+		       bfd_asymbol_section(symbols[i + 1]) == section &&
+		       bfd2elf_binding(symbols[i + 1]) < 0)
+			i++;
+
+		if (i + 1 < symbols_count &&
+		    bfd_asymbol_section(symbols[i + 1]) == section)
+			len = symbols[i + 1]->value - sym->value;
+		else
+			len = section->size - sym->value;
+
+		start = bfd_asymbol_value(sym) - dso->text_offset;
+		symbol = symbol__new(start, len, bfd2elf_binding(sym), STT_FUNC,
+				     bfd_asymbol_name(sym));
+		if (!symbol)
+			goto out_free;
+
+		symbols__insert(&dso->symbols, symbol);
+	}
+#ifdef bfd_get_section
+#undef bfd_asymbol_section
+#endif
+
+	symbols__fixup_end(&dso->symbols);
+	symbols__fixup_duplicate(&dso->symbols);
+	dso->adjust_symbols = 1;
+
+	err = 0;
+out_free:
+	free(symbols);
+out_close:
+	bfd_close(abfd);
+	return err;
+}
+#endif
+
 static bool dso__is_compatible_symtab_type(struct dso *dso, bool kmod,
 					   enum dso_binary_type type)
 {
···
 		bool next_slot = false;
 		bool is_reg;
 		bool nsexit;
+		int bfdrc = -1;
 		int sirc = -1;
 
 		enum dso_binary_type symtab_type = binary_type_symtab[i];
···
 			nsinfo__mountns_exit(&nsc);
 
 		is_reg = is_regular_file(name);
+#ifdef HAVE_LIBBFD_SUPPORT
 		if (is_reg)
+			bfdrc = dso__load_bfd_symbols(dso, name);
+#endif
+		if (is_reg && bfdrc < 0)
 			sirc = symsrc__init(ss, dso, name, symtab_type);
 
 		if (nsexit)
 			nsinfo__mountns_enter(dso->nsinfo, &nsc);
+
+		if (bfdrc == 0)
+			break;
 
 		if (!is_reg || sirc < 0)
 			continue;

tools/perf/util/symbol.h

···
 
 struct symsrc;
 
+#ifdef HAVE_LIBBFD_SUPPORT
+int dso__load_bfd_symbols(struct dso *dso, const char *debugfile);
+#endif
+
 int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss,
 		  struct symsrc *runtime_ss, int kmodule);
 int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss);