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Date:   Tue, 15 Dec 2020 09:25:42 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org, Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH] perf callchain: Return directly when use '--call-graph
 dwarf' under !CONFIG_DWARF

On 12/14/2020 09:39 PM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Dec 14, 2020 at 08:56:55PM +0800, Tiezhu Yang escreveu:
>> DWARF register mappings have not been defined for some architectures,
>> at least for mips, so we can print an error message and then return
>> directly when use '--call-graph dwarf'.
>>
>> E.g. without this patch:
>>
>> [root@...ux perf]# ./perf record --call-graph dwarf cd
>> Error:
>> The sys_perf_event_open() syscall returned with 89 (Function not implemented) for event (cycles).
>> /bin/dmesg | grep -i perf may provide additional information.
>>
>> With this patch:
>>
>> [root@...ux perf]# ./perf record --call-graph dwarf cd
>> DWARF is not supported for architecture mips64
> Good improvement on the message! But that .config-detected file isn't
> available at run time, take a look if this isn't a better alternative:

Hi Arnaldo,

Thank you very much, the following code with #ifdef HAVE_DWARF_SUPPORT
looks good and it works well on the x86 and mips arch.

So I will send a v2 patch as soon as possible.

Thanks,
Tiezhu

>
> diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
> index 1b60985690bba313..125178fd17482513 100644
> --- a/tools/perf/util/callchain.c
> +++ b/tools/perf/util/callchain.c
> @@ -276,6 +276,7 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
>   
>   		/* Dwarf style */
>   		} else if (!strncmp(name, "dwarf", sizeof("dwarf"))) {
> +#ifdef HAVE_DWARF_SUPPORT
>   			const unsigned long default_stack_dump_size = 8192;
>   
>   			ret = 0;
> @@ -290,6 +291,15 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
>   				ret = get_stack_size(tok, &size);
>   				param->dump_size = size;
>   			}
> +#else
> +			struct utsname uts;
> +
> +			ret = uname(&uts);
> +			pr_err("DWARF is not supported for architecture %s\n",
> +				ret ? "unknown" : uts.machine);
> +
> +			return -ENOTSUP;
> +#endif
>   		} else if (!strncmp(name, "lbr", sizeof("lbr"))) {
>   			if (!strtok_r(NULL, ",", &saveptr)) {
>   				param->record_mode = CALLCHAIN_LBR;
>
>   
>>   Usage: perf record [<options>] [<command>]
>>      or: perf record [<options>] -- <command> [<options>]
>>
>>          --call-graph <record_mode[,record_size]>
>>                            setup and enables call-graph (stack chain/backtrace):
>>
>> 				record_mode:	call graph recording mode (fp|dwarf|lbr)
>> 				record_size:	if record_mode is 'dwarf', max size of stack recording (<bytes>)
>> 						default: 8192 (bytes)
>>
>> 				Default: fp
>>
>> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
>> ---
>>   tools/perf/util/callchain.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
>> index 1b60985..a8cf456 100644
>> --- a/tools/perf/util/callchain.c
>> +++ b/tools/perf/util/callchain.c
>> @@ -18,6 +18,7 @@
>>   #include <math.h>
>>   #include <linux/string.h>
>>   #include <linux/zalloc.h>
>> +#include <sys/utsname.h>
>>   
>>   #include "asm/bug.h"
>>   
>> @@ -278,6 +279,16 @@ int parse_callchain_record(const char *arg, struct callchain_param *param)
>>   		} else if (!strncmp(name, "dwarf", sizeof("dwarf"))) {
>>   			const unsigned long default_stack_dump_size = 8192;
>>   
>> +			if (system("grep -q 'CONFIG_DWARF=y' .config-detected") != 0) {
>> +				struct utsname uts;
>> +
>> +				ret = uname(&uts);
>> +				pr_err("DWARF is not supported for architecture %s\n",
>> +					ret ? "unknown" : uts.machine);
>> +
>> +				return -ENOTSUP;
>> +			}
>> +
>>   			ret = 0;
>>   			param->record_mode = CALLCHAIN_DWARF;
>>   			param->dump_size = default_stack_dump_size;
>> -- 
>> 2.1.0
>>

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