Messages in this thread | | | From | Len Brown <> | Date | Thu, 3 Sep 2020 13:36:14 -0400 | Subject | Re: [PATCH] tools/power turbostat: call pread64 in kernel directly |
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> -D_FILE_OFFSET_BITS=64
Applied.
thanks! -Len
On Mon, Aug 24, 2020 at 12:09 AM Liwei Song <liwei.song@windriver.com> wrote: > > > > On 8/24/20 04:54, Alexander Monakov wrote: > > Hi, > > > > I am not the original submitter, but I have answers and a proper patch :) > > > > On Fri, 21 Aug 2020, Len Brown wrote: > > > >> Re: offset size > >> > >> The offsets on this file are the MSR offsets. > >> What MSR are you trying to access at offset 0xc0010299? > > > > This MSR is particular is part of AMD RAPL (energy measurements) interface. > > > >> Re: pread vs pread64 > >> > >> If I take on faith that you have some kind of 32-bit execution > >> environment that makes pread into pread32 instead of pread64, and that > >> truncates an off_t to 32-bits from 64-bits, and it actually makes > >> sense to request a read at this large offset... > > > > The problem here stems from the backward compatibility in Glibc: off_t is > > 32-bit on 32-bit x86, unless compiled with -D_FILE_OFFSET_BITS=64. This > > macro should be used for all new code. Distros should enable it for all > > builds, but when one builds turbostat 'by hand', they hit the issue. > > > >> would we really have to invoke syscall() directly -- couldn't we > >> invoke pread64() directly? (eg. below) > > > > No, the proper fix is to pass -D_FILE_OFFSET_BITS=64 to the compiler. > > > > Here's the patch: > > This path works with my case. > > Thanks, > Liwei. > > > > > > ---8<--- > > > > From: Alexander Monakov <amonakov@ispras.ru> > > Date: Sun, 23 Aug 2020 23:27:02 +0300 > > Subject: [PATCH] turbostat: build with _FILE_OFFSET_BITS=64 > > > > For compatibility reasons, Glibc off_t is a 32-bit type on 32-bit x86 > > unless _FILE_OFFSET_BITS=64 is defined. Add this define, as otherwise > > reading MSRs with index 0x80000000 and above attempts a pread with a > > negative offset, which fails. > > > > Signed-off-by: Alexander Monakov <amonakov@ispras.ru> > > --- > > tools/power/x86/turbostat/Makefile | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/tools/power/x86/turbostat/Makefile b/tools/power/x86/turbostat/Makefile > > index 2b6551269e43..40ae44402eec 100644 > > --- a/tools/power/x86/turbostat/Makefile > > +++ b/tools/power/x86/turbostat/Makefile > > @@ -12,6 +12,7 @@ turbostat : turbostat.c > > override CFLAGS += -O2 -Wall -I../../../include > > override CFLAGS += -DMSRHEADER='"../../../../arch/x86/include/asm/msr-index.h"' > > override CFLAGS += -DINTEL_FAMILY_HEADER='"../../../../arch/x86/include/asm/intel-family.h"' > > +override CFLAGS += -D_FILE_OFFSET_BITS=64 > > override CFLAGS += -D_FORTIFY_SOURCE=2 > > > > %: %.c > >
-- Len Brown, Intel Open Source Technology Center
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