Re: [PATCH] perf callchain: Return directly when use '--call-graph dwarf' under !CONFIG_DWARF

[Arnaldo Carvalho de Melo <acme@kernel.org>]

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@linux 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@linux 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:

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@loongson.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
> 

-- 

- Arnaldo