linux-kernel - Re: [PATCH 8/9] perf tools: add kcore to the object code reading test

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Date:	Tue, 30 Jul 2013 14:24:56 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel@...r.kernel.org, David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 8/9] perf tools: add kcore to the object code reading test

On Thu, 25 Jul 2013 17:01:29 +0300, Adrian Hunter wrote:
> Make the "object code reading" test attempt to read from
> kcore.
>
> The test uses objdump which struggles with kcore. i.e.
> doesn't always work, sometimes takes a long time.
> The test has been made to work around those issues.
>
[SNIP]

> -	if (al.map->dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS) {
> +	if (al.map->dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS &&
> +	    !dso__is_kcore(al.map->dso)) {

I was confused.  So this means that the symbols came from the kallsyms
but actual binary data came from the kcore, right?


>  		pr_debug("Unexpected kernel address - skipping\n");
>  		return 0;
>  	}

[SNIP]
> +
> +	/* 2nd time through we just try kcore */
> +	if (try_kcore && !have_kcore)
> +		return TEST_CODE_READING_NO_KCORE;
> +
> +	/* No point getting kernel events if there is no kernel object */
> +	if (!have_vmlinux && !have_kcore)
>  		excl_kernel = true;
>  
>  	threads = thread_map__new_by_tid(pid);
> @@ -457,8 +502,12 @@ static int do_test_code_reading(void)
>  	if (ret < 0)
>  		goto out_err;
>  
> -	if (!have_vmlinux)
> +	if (!have_vmlinux && !have_kcore && !try_kcore)
> +		err = TEST_CODE_READING_NO_KERNEL_OBJ;
> +	else if (!have_vmlinux && !try_kcore)
>  		err = TEST_CODE_READING_NO_VMLINUX;
> +	else if (!have_kcore && try_kcore)
> +		err = TEST_CODE_READING_NO_KCORE;

It seems that the above line is not reachable since we already bailed
out the second test if we don't have kcore.


>  	else if (excl_kernel)
>  		err = TEST_CODE_READING_NO_ACCESS;
>  	else
> @@ -485,7 +534,9 @@ int test__code_reading(void)
>  {
>  	int ret;
>  
> -	ret = do_test_code_reading();
> +	ret = do_test_code_reading(false);
> +	if (!ret)

Shouldn't it be

	if (ret)
?

Thanks,
Namhyung


> +		ret = do_test_code_reading(true);
>  
>  	switch (ret) {
>  	case TEST_CODE_READING_OK:
> @@ -493,9 +544,15 @@ int test__code_reading(void)
>  	case TEST_CODE_READING_NO_VMLINUX:
>  		fprintf(stderr, " (no vmlinux)");
>  		return 0;
> +	case TEST_CODE_READING_NO_KCORE:
> +		fprintf(stderr, " (no kcore)");
> +		return 0;
>  	case TEST_CODE_READING_NO_ACCESS:
>  		fprintf(stderr, " (no access)");
>  		return 0;
> +	case TEST_CODE_READING_NO_KERNEL_OBJ:
> +		fprintf(stderr, " (no kernel obj)");
> +		return 0;
>  	default:
>  		return -1;
>  	};
--
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