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Date:   Thu, 1 Sep 2022 15:34:49 -0700
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Subject: Re: [PATCH 6/6] selftests/sgx: Add a bpftrace script for tracking
 allocation errors
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To:     Jarkko Sakkinen <jarkko@kernel.org>
Cc:     linux-sgx@vger.kernel.org,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Vijay Dhanraj <vijay.dhanraj@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Shuah Khan <shuah@kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>
References: <20220830031206.13449-1-jarkko@kernel.org>
 <20220830031206.13449-7-jarkko@kernel.org>
 <e870df49-77ed-3222-086d-ae929107f33b@intel.com>
 <YxEwGU2bkM272+QA@kernel.org>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <YxEwGU2bkM272+QA@kernel.org>
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On 9/1/22 15:20, Jarkko Sakkinen wrote:
>>> +kr:sgx_alloc_epc_page /(uint64)retval >= (uint64)(-4095)/ {
>>> +		 printf("sgx_alloc_epc_page: retval=%d\n", (int64)retval);
>>> +}
>>> +
>>> +kr:sgx_encl_page_alloc /(uint64)retval >= (uint64)(-4095)/ {
>>> +		 printf("sgx_encl_page_alloc: retval=%d\n", (int64)retval);
>>> +}
>> I guess this doesn't _hurt_, but it's also not exactly the easiest way
>> to get this done.  You need a whole bpf toolchain.  You could also just do:
>>
>> 	perf probe 'sgx_encl_page_alloc%return $retval'
>>
>> Even *that* can be replicated in a few scant lines of shell code echoing
>> into /sys/kernel/debug/tracing.
> Thanks, I have not used perf that much. What if I replace
> this with a shell script using perf? How do you use that
> for two kretprobes?

The manpage is pretty good.

But, I'd proably be doing something along these lines:

	perf probe 'sgx_encl_page_alloc%return ret=$retval'
	perf record -e probe:sgx_encl_page_alloc -aR	\
		--filter='ret >= 0xwhatever' sleep 1
	perf script

There are probably shorter ways to do it, but I'm pretty sure that works.