linux-kernel - Re: [PATCH v4 10/11] perf env: Set flag for kernel is 64-bit mode

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Message-ID: <2df0e179-6302-ac7e-b41c-4f91bfc103de@intel.com>
Date:   Mon, 12 Jul 2021 17:37:21 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 10/11] perf env: Set flag for kernel is 64-bit mode

On 11/07/21 1:41 pm, Leo Yan wrote:
> It's useful to know that the kernel is running in 32-bit or 64-bit
> mode.  E.g. We can decide if perf tool is running in compat mode
> from this info.
> 
> This patch adds a global variable "kernel_is_64_bit", it's initialized
> when a session setups environment, its value is decided by checking the
> architecture string.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/util/env.c | 17 ++++++++++++++++-
>  tools/perf/util/env.h |  1 +
>  2 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
> index ebc5e9ad35db..345635a2e842 100644
> --- a/tools/perf/util/env.c
> +++ b/tools/perf/util/env.c
> @@ -11,6 +11,7 @@
>  #include <stdlib.h>
>  #include <string.h>
>  
> +int kernel_is_64_bit;
>  struct perf_env perf_env;
>  
>  #ifdef HAVE_LIBBPF_SUPPORT
> @@ -172,6 +173,19 @@ static void perf_env__purge_bpf(struct perf_env *env __maybe_unused)
>  }
>  #endif // HAVE_LIBBPF_SUPPORT
>  
> +static void perf_env__init_kernel_mode(struct perf_env *env)
> +{
> +	const char *arch = perf_env__raw_arch(env);
> +
> +	if (!strncmp(arch, "x86_64", 6) || !strncmp(arch, "aarch64", 7) ||
> +	    !strncmp(arch, "arm64", 5) || !strncmp(arch, "mips64", 6) ||
> +	    !strncmp(arch, "parisc64", 8) || !strncmp(arch, "riscv64", 7) ||
> +	    !strncmp(arch, "s390x", 5) || !strncmp(arch, "sparc64", 7))
> +		kernel_is_64_bit = 1;
> +	else
> +		kernel_is_64_bit = 0;
> +}
> +
>  void perf_env__exit(struct perf_env *env)
>  {
>  	int i;
> @@ -217,13 +231,14 @@ void perf_env__exit(struct perf_env *env)
>  	zfree(&env->hybrid_cpc_nodes);
>  }
>  
> -void perf_env__init(struct perf_env *env __maybe_unused)
> +void perf_env__init(struct perf_env *env)
>  {
>  #ifdef HAVE_LIBBPF_SUPPORT
>  	env->bpf_progs.infos = RB_ROOT;
>  	env->bpf_progs.btfs = RB_ROOT;
>  	init_rwsem(&env->bpf_progs.lock);
>  #endif
> +	perf_env__init_kernel_mode(env);

perf_env__init() is also used for session->header.env which is not
necessarily the current machine.  So this initialization could be
separate from perf_env__init() to avoid confusion.

>  }
>  
>  int perf_env__set_cmdline(struct perf_env *env, int argc, const char *argv[])
> diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h
> index 6824a7423a2d..cc989ff49740 100644
> --- a/tools/perf/util/env.h
> +++ b/tools/perf/util/env.h
> @@ -139,6 +139,7 @@ enum perf_compress_type {
>  struct bpf_prog_info_node;
>  struct btf_node;
>  
> +extern int kernel_is_64_bit;
>  extern struct perf_env perf_env;
>  
>  void perf_env__exit(struct perf_env *env);
>