Sorry for the top-post...
Yeah, I've now mixed up the variable attribute:
https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#Common-Variable-Attributes
with the type attribute:
https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#Common-Type-Attributes
Late here, so maybe it will make more sense tomorrow.
-----Original Message-----
From: Arnaldo Carvalho de Melo [mailto:[email protected]]
Sent: Wednesday, June 28, 2017 9:54 PM
To: Hunter, Adrian <[email protected]>
Cc: Andi Kleen <[email protected]>; [email protected]
Subject: Re: [PATCH V2 25/37] perf script: Add synthesized Intel PT power and
ptwrite events
Em Wed, Jun 28, 2017 at 08:40:25PM +0300, Adrian Hunter escreveu:
> On 06/28/2017 04:04 PM, Arnaldo Carvalho de Melo wrote:
> > Em Fri, May 26, 2017 at 11:17:26AM +0300, Adrian Hunter escreveu:
> >> Add definitions for synthesized Intel PT events for power and ptwrite.
> >
> >> +++ b/tools/perf/util/event.h
> >> +/*
> >> + * Raw data formats for synthesized events. Note that raw data
> >> +plus the raw data
> >> + * size (4 bytes) must align to 8-bytes.
> >> + */
> >> +
> >> +struct perf_synth_intel_ptwrite {
> >> + union {
> >> + struct {
> >> + u32 ip : 1,
> >> + reserved : 31;
> >> + };
> >> + u32 flags;
> >> + };
> >> + u64 payload;
> >> +} __packed;
> >
> >
> > some versions of clang and gcc dislike this __packed here:
> >
> > In file included from builtin-script.c:5:
> > In file included from /git/linux/tools/perf/util/debug.h:8:
> > /git/linux/tools/perf/util/event.h:274:2: error: packed attribute is
> > unnecessary for (null) [-Werror,-Wpacked]
> > union {
> > ^
> > /git/linux/tools/perf/util/event.h:285:6: error: packed attribute is
> > unnecessary for 'reserved' [-Werror,-Wpacked]
> > u32 reserved;
> > ^
> > /git/linux/tools/perf/util/event.h:298:6: error: packed attribute is
> > unnecessary for 'reserved' [-Werror,-Wpacked]
> > u32 reserved;
> > ^
> > /git/linux/tools/perf/util/event.h:322:6: error: packed attribute is
> > unnecessary for 'reserved' [-Werror,-Wpacked]
> > u32 reserved;
> > ^
> > 4 errors generated.
> > mv: can't rename '/tmp/build/perf/.builtin-script.o.tmp': No such
> > file or directory
> >
> > /git/linux/tools/build/Makefile.build:101: recipe for target
> > '/tmp/build/perf/builtin-script.o' failed
> >
> > Failing in various distros:
> >
> > [root@jouet ~]# waitp 3940 ; time dm
> > 1 92.3684147260 alpine:3.4: FAIL
> > 2 95.9136365930 alpine:3.5: FAIL
> > 3 104.8328303770 alpine:3.6: FAIL
> > 4 121.6584964930 alpine:edge: FAIL
> > 5 37.2536373490 android-ndk:r12b-arm: Ok
> > 6 83.9077612370 archlinux:latest: Ok
> > 7 14.7094639200 centos:5: FAIL
> > 8 16.6371634320 centos:6: FAIL
> >
> > Investigating...
>
> Re-reading the documentation for __packed, it seems like the following
> might be better:
Humm, can you provide the URL for such docs? I always saw packed as an
attribute for a struct, not for a member... For members "aligned" is what I'm
used to see:
__attribute__ ((aligned (8)))
In the kernel sources there are a few such cases as you suggest:
[acme@jouet linux]$ find include/ -name "*.h"| xargs grep -w __packed | grep -v
} | grep -v "struct __packed" | wc -l
12
[acme@jouet linux]$
But most are the other way, i.e. tagging the packed attribute to the whole
struct, as you originally did :-\
- Arnaldo
> diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h index
> c283603f59c7..a7547cb3b760 100644
> --- a/tools/perf/util/event.h
> +++ b/tools/perf/util/event.h
> @@ -278,8 +278,8 @@ struct perf_synth_intel_ptwrite {
> };
> u32 flags;
> };
> - u64 payload;
> -} __packed;
> + u64 payload __packed;
> +};
>
> struct perf_synth_intel_mwait {
> u32 reserved;
> @@ -291,8 +291,8 @@ struct perf_synth_intel_mwait {
> reserved2 : 30;
> };
> u64 payload;
> - };
> -} __packed;
> + } __packed;
> +};
>
> struct perf_synth_intel_pwre {
> u32 reserved;
> @@ -305,8 +305,8 @@ struct perf_synth_intel_pwre {
> reserved2 : 48;
> };
> u64 payload;
> - };
> -} __packed;
> + } __packed;
> +};
>
> struct perf_synth_intel_exstop {
> union {
> @@ -328,8 +328,8 @@ struct perf_synth_intel_pwrx {
> reserved1 : 52;
> };
> u64 payload;
> - };
> -} __packed;
> + } __packed;
> +};
>
> struct perf_synth_intel_cbr {
> union {
