From: Peter Oberparleiter <oberpar@linux.ibm.com>
To: Johannes Berg <johannes@sipsolutions.net>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
Arnd Bergmann <arnd@arndb.de>, Jessica Yu <jeyu@kernel.org>,
Johannes Berg <johannes.berg@intel.com>,
linux-um@lists.infradead.org
Subject: Re: [PATCH v2] init/gcov: allow CONFIG_CONSTRUCTORS on UML to fix module gcov
Date: Wed, 20 Jan 2021 18:04:25 +0100 [thread overview]
Message-ID: <ee3bc3bf-9582-d278-5b7a-d9fa27b17800@linux.ibm.com> (raw)
In-Reply-To: <20210120172041.c246a2cac2fb.I1358f584b76f1898373adfed77f4462c8705b736@changeid>
On 20.01.2021 17:20, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@intel.com>
>
> On ARCH=um, loading a module doesn't result in its constructors
> getting called, which breaks module gcov since the debugfs files
> are never registered. On the other hand, in-kernel constructors
> have already been called by the dynamic linker, so we can't call
> them again.
>
> Get out of this conundrum by allowing CONFIG_CONSTRUCTORS to be
> selected, but avoiding the in-kernel constructor calls.
>
> Also remove the "if !UML" from GCOV selecting CONSTRUCTORS now,
> since we really do want CONSTRUCTORS, just not kernel binary
> ones.
>
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Looks good+nicer than v1 to me!
I also tested this patch on s390 and can confirm that it doesn't break
gcov-kernel there.
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Andrew, do we need additional reviews/sign-offs? Could this go in via
your tree?
> ---
> Tested with a kernel configured with CONFIG_GCOV_KERNEL, without
> the patch nothing ever appears in /sys/kernel/debug/gcov/ (apart
> from the reset file), and with it we get the files and they work.
Just to be sure: could you confirm that this test statement for UML also
applies to v2, i.e. that it fixes the original problem you were seeing?
>
> v2:
> * special-case UML instead of splitting the CONSTRUCTORS config
> ---
> init/Kconfig | 1 -
> init/main.c | 8 +++++++-
> kernel/gcov/Kconfig | 2 +-
> 3 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index b77c60f8b963..29ad68325028 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -76,7 +76,6 @@ config CC_HAS_ASM_INLINE
>
> config CONSTRUCTORS
> bool
> - depends on !UML
>
> config IRQ_WORK
> bool
> diff --git a/init/main.c b/init/main.c
> index c68d784376ca..a626e78dbf06 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1066,7 +1066,13 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
> /* Call all constructor functions linked into the kernel. */
> static void __init do_ctors(void)
> {
> -#ifdef CONFIG_CONSTRUCTORS
> +/*
> + * For UML, the constructors have already been called by the
> + * normal setup code as it's just a normal ELF binary, so we
> + * cannot do it again - but we do need CONFIG_CONSTRUCTORS
> + * even on UML for modules.
> + */
> +#if defined(CONFIG_CONSTRUCTORS) && !defined(CONFIG_UML)
> ctor_fn_t *fn = (ctor_fn_t *) __ctors_start;
>
> for (; fn < (ctor_fn_t *) __ctors_end; fn++)
> diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig
> index 3110c77230c7..f62de2dea8a3 100644
> --- a/kernel/gcov/Kconfig
> +++ b/kernel/gcov/Kconfig
> @@ -4,7 +4,7 @@ menu "GCOV-based kernel profiling"
> config GCOV_KERNEL
> bool "Enable gcov-based kernel profiling"
> depends on DEBUG_FS
> - select CONSTRUCTORS if !UML
> + select CONSTRUCTORS
> default n
> help
> This option enables gcov-based code profiling (e.g. for code coverage
>
--
Peter Oberparleiter
Linux on Z Development - IBM Germany
next prev parent reply other threads:[~2021-01-20 17:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 11:18 [PATCH] init/module: split CONFIG_CONSTRUCTORS to fix module gcov on UML Johannes Berg
2021-01-20 16:07 ` Peter Oberparleiter
2021-01-20 16:09 ` Johannes Berg
2021-01-20 16:20 ` Peter Oberparleiter
2021-01-20 16:20 ` [PATCH v2] init/gcov: allow CONFIG_CONSTRUCTORS on UML to fix module gcov Johannes Berg
2021-01-20 17:04 ` Peter Oberparleiter [this message]
2021-01-20 17:38 ` Johannes Berg
[not found] ` <tencent_99073B61C8137C88B76C231139F94EFB3805@qq.com>
2021-05-10 11:37 ` Johannes Berg
2021-05-10 13:31 ` lambertdev
2021-05-14 13:55 ` Peter Oberparleiter
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ee3bc3bf-9582-d278-5b7a-d9fa27b17800@linux.ibm.com \
--to=oberpar@linux.ibm.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=jeyu@kernel.org \
--cc=johannes.berg@intel.com \
--cc=johannes@sipsolutions.net \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-um@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).