Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86_64 KPTI entry trampolines

From: Adrian Hunter <adrian.hunter@intel.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@linux.intel.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Joerg Roedel <joro@8bytes.org>,
	linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86_64 KPTI entry trampolines
Date: Tue, 15 May 2018 13:40:12 +0300	[thread overview]
Message-ID: <edb2e6aa-8a99-aa8d-1ff0-a69a9161f170@intel.com> (raw)
In-Reply-To: <20180515103043.GA7425@krava>

On 15/05/18 13:30, Jiri Olsa wrote:
> On Wed, May 09, 2018 at 02:43:36PM +0300, Adrian Hunter wrote:
> 
> SNIP
> 
>> +
>> +	for (i = 0; i < ARRAY_SIZE(syms); i++) {
>> +		if (syms[i].addr)
>> +			return syms[i].addr;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +/*
>> + * These values can be used for kernels that do not have symbols for the entry
>> + * trampolines in kallsyms.
>> + */
>> +#define X86_64_CPU_ENTRY_AREA_PER_CPU	0xfffffe0000000000ULL
>> +#define X86_64_CPU_ENTRY_AREA_SIZE	0x2c000
>> +#define X86_64_ENTRY_TRAMPOLINE		0x6000
>> +
>> +/* Map x86_64 KPTI entry trampolines */
>> +int machine__map_x86_64_entry_trampolines(struct machine *machine,
>> +					  struct dso *kernel)
>> +{
> 
> would it make sense to put all this under arch/x86/util/machine.c ?

In this case, machine__map_x86_64_entry_trampolines() is specific to the
arch in the perf.data file, not the arch perf is currently running on.