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

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Date:   Fri, 14 Aug 2020 10:17:06 +0800
From:   Liwei Song <liwei.song@...driver.com>
To:     Len Brown <lenb@...nel.org>
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

with multilib lib32 support, the rootfs will be 32-bit, 
the kernel is still 64-bit, in this case run turbostat
will failed with "out of range" error.

Thanks,
Liwei.

On 8/14/20 05:43, Len Brown wrote:
> 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
>>
> 
>