Re: [PATCH v2 5/9] perf tools: Add methods to test dso is 64-bit or 32-bit

[Hekuang]

hi

å 2016/5/10 16:08, Adrian Hunter åé:
> On 10/05/16 10:40, He Kuang wrote:
> > 32-bit programs can be run on 64-bit machines, so we should choose
> > unwind methods according to 'thread->map' instead of the host
> > architecture.
> >
> > This patch adds methods to test whether a dso is 64-bit or 32-bit by
> > the class info in elf.
> What about using dso->is_64_bit set by dso__load_sym() ?

I've noticed this variable, but it's value is not as its name said:

util/dso.c: 1067    dso->is_64_bit = (sizeof(void *) == 8);

This is only related to the host architecture.

A closer one is 'is_64_bit' in 'struct symsrc', but the value is 
assigned after dso
loaded. So I think we should provide individual methods to get that value.

Thanks.

> > Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
> > ---
> >   tools/perf/util/symbol-elf.c | 16 +++++++++++++++
> >   tools/perf/util/symbol.c     | 49 ++++++++++++++++++++++++++++++++++++++++++++
> >   tools/perf/util/symbol.h     |  2 ++
> >   3 files changed, 67 insertions(+)
> >
> > diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> > index 3f9d679..9f290b9 100644
> > --- a/tools/perf/util/symbol-elf.c
> > +++ b/tools/perf/util/symbol-elf.c
> > @@ -636,6 +636,22 @@ bool __weak elf__needs_adjust_symbols(GElf_Ehdr ehdr)
> >   	return ehdr.e_type == ET_EXEC || ehdr.e_type == ET_REL;
> >   }
> >   
> > +int elf_is_64_bit(char *name)
> > +{
> > +	Elf *elf;
> > +	int fd;
> > +
> > +	fd = open(name, O_RDONLY);
> > +	if (fd < 0)
> > +		return -1;
> > +
> > +	elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
> > +	if (elf == NULL)
> > +		return -1;
> > +
> > +	return (gelf_getclass(elf) == ELFCLASS64);
> > +}
> > +
> >   int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
> >   		 enum dso_binary_type type)
> >   {
> > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> > index 4630751..592bf8c 100644
> > --- a/tools/perf/util/symbol.c
> > +++ b/tools/perf/util/symbol.c
> > @@ -1395,6 +1395,55 @@ static bool dso__is_compatible_symtab_type(struct dso *dso, bool kmod,
> >   	}
> >   }
> >   
> > +int dso_is_64_bit(struct dso *dso, struct map *map)
> > +{
> > +	char *name;
> > +	u_int i;
> > +	bool kmod;
> > +	char *root_dir = (char *) "";
> > +	struct machine *machine;
> > +
> > +	if (map->groups && map->groups->machine)
> > +		machine = map->groups->machine;
> > +	else
> > +		machine = NULL;
> > +
> > +	if (machine)
> > +		root_dir = machine->root_dir;
> > +
> > +	name = malloc(PATH_MAX);
> > +	if (!name)
> > +		return -1;
> > +
> > +	kmod = dso->symtab_type == DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE ||
> > +		dso->symtab_type == DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE_COMP ||
> > +		dso->symtab_type == DSO_BINARY_TYPE__GUEST_KMODULE ||
> > +		dso->symtab_type == DSO_BINARY_TYPE__GUEST_KMODULE_COMP;
> > +
> > +	/*
> > +	 * Iterate over candidate debug images.
> > +	 * Keep track of "interesting" ones (those which have a symtab, dynsym,
> > +	 * and/or opd section) for processing.
> > +	 */
> > +	for (i = 0; i < DSO_BINARY_TYPE__SYMTAB_CNT; i++) {
> > +		enum dso_binary_type symtab_type = binary_type_symtab[i];
> > +
> > +		if (!dso__is_compatible_symtab_type(dso, kmod, symtab_type))
> > +			continue;
> > +
> > +		if (dso__read_binary_type_filename(dso, symtab_type,
> > +						   root_dir, name, PATH_MAX))
> > +			continue;
> > +
> > +		if (!is_regular_file(name))
> > +			continue;
> > +
> > +		return elf_is_64_bit(name);
> > +	}
> > +
> > +	return -1;
> > +}
> > +
> >   int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
> >   {
> >   	char *name;
> > diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> > index 4e6910e..d33fbf4 100644
> > --- a/tools/perf/util/symbol.h
> > +++ b/tools/perf/util/symbol.h
> > @@ -308,6 +308,8 @@ int setup_list(struct strlist **list, const char *list_str,
> >   	       const char *list_name);
> >   int setup_intlist(struct intlist **list, const char *list_str,
> >   		  const char *list_name);
> > +int elf_is_64_bit(char *name);
> > +int dso_is_64_bit(struct dso *dso, struct map *map);
> >   
> >   #ifdef HAVE_LIBELF_SUPPORT
> >   bool elf__needs_adjust_symbols(GElf_Ehdr ehdr);