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 17:49:47 +0800
From:	Hekuang <hekuang@...wei.com>
To:	Adrian Hunter <adrian.hunter@...el.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

hi

在 2016/5/10 16:08, Adrian Hunter 写道:
> 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@...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);
>>
>