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

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Date:	Tue, 10 May 2016 11:08:05 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	He Kuang <hekuang@...wei.com>, peterz@...radead.org,
	mingo@...hat.com, acme@...nel.org,
	alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
	wangnan0@...wei.com, jpoimboe@...hat.com, ak@...ux.intel.com,
	eranian@...gle.com, namhyung@...nel.org,
	sukadev@...ux.vnet.ibm.com, masami.hiramatsu.pt@...achi.com,
	tumanova@...ux.vnet.ibm.com, kan.liang@...el.com,
	penberg@...nel.org, dsahern@...il.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/9] perf tools: Add methods to test dso is 64-bit or
 32-bit

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() ?

> 
> Signed-off-by: He Kuang <hekuang@...wei.com>
> ---
>  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);
>