linux-kernel - Re: [PATCH] tools/power turbostat: call pread64 in kernel directly

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Message-ID: <CAJvTdKm9WHgQuP38Y2o1zQ-VgLKMMDup4crAPrW3pexoWft+6Q@mail.gmail.com>
Date:   Thu, 13 Aug 2020 17:43:25 -0400
From:   Len Brown <lenb@...nel.org>
To:     Liwei Song <liwei.song@...driver.com>
Cc:     Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tools/power turbostat: call pread64 in kernel directly

Huh?

On Fri, Jul 17, 2020 at 2:09 AM Liwei Song <liwei.song@...driver.com> wrote:
>
> with 32-bit rootfs, the offset may out of range when set it
> to 0xc0010299, define it as "unsigned long long" type and
> call pread64 directly in kernel.
>
> Signed-off-by: Liwei Song <liwei.song@...driver.com>
> ---
>  tools/power/x86/turbostat/turbostat.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
> index 33b370865d16..4c5cdfcb5721 100644
> --- a/tools/power/x86/turbostat/turbostat.c
> +++ b/tools/power/x86/turbostat/turbostat.c
> @@ -33,6 +33,7 @@
>  #include <sys/capability.h>
>  #include <errno.h>
>  #include <math.h>
> +#include <sys/syscall.h>
>
>  char *proc_stat = "/proc/stat";
>  FILE *outf;
> @@ -381,11 +382,11 @@ int get_msr_fd(int cpu)
>         return fd;
>  }
>
> -int get_msr(int cpu, off_t offset, unsigned long long *msr)
> +int get_msr(int cpu, unsigned long long offset, unsigned long long *msr)
>  {
>         ssize_t retval;
>
> -       retval = pread(get_msr_fd(cpu), msr, sizeof(*msr), offset);
> +       retval = syscall(SYS_pread64, get_msr_fd(cpu), msr, sizeof(*msr), offset);
>
>         if (retval != sizeof *msr)
>                 err(-1, "cpu%d: msr offset 0x%llx read failed", cpu, (unsigned long long)offset);
> --
> 2.17.1
>


-- 
Len Brown, Intel Open Source Technology Center