linux-kernel - Re: [PATCH 6/6] selftests/sgx: Add a bpftrace script for tracking allocation errors

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Message-ID: <e870df49-77ed-3222-086d-ae929107f33b@intel.com>
Date:   Wed, 31 Aug 2022 11:23:55 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>, linux-sgx@...r.kernel.org
Cc:     Haitao Huang <haitao.huang@...ux.intel.com>,
        Vijay Dhanraj <vijay.dhanraj@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Shuah Khan <shuah@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH 6/6] selftests/sgx: Add a bpftrace script for tracking
 allocation errors

On 8/29/22 20:12, Jarkko Sakkinen wrote:
> diff --git a/tools/testing/selftests/sgx/alloc-error.bt b/tools/testing/selftests/sgx/alloc-error.bt
> new file mode 100644
> index 000000000000..9268d50dea29
> --- /dev/null
> +++ b/tools/testing/selftests/sgx/alloc-error.bt
> @@ -0,0 +1,7 @@
> +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.