linux-kernel - Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86

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Date:   Tue, 15 May 2018 13:40:12 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86_64
 KPTI entry trampolines

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.