From: Andi Kleen <ak@linux.intel.com>
To: Nick Desaulniers <ndesaulniers@google.com>,
Arnd Bergmann <arnd@arndb.de>
Cc: linux-fsdevel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Hellwig <hch@lst.de>,
Eric Dumazet <edumazet@google.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH] fs/select: avoid clang stack usage warning
Date: Fri, 7 Oct 2022 18:46:48 -0700 [thread overview]
Message-ID: <f0dbc406-11b4-90f7-52fd-ce79f842c356@linux.intel.com> (raw)
In-Reply-To: <20221006222124.aabaemy7ofop7ccz@google.com>
On 10/6/2022 3:21 PM, Nick Desaulniers wrote:
> On Thu, Mar 07, 2019 at 10:01:36AM +0100, Arnd Bergmann wrote:
>> The select() implementation is carefully tuned to put a sensible amount
>> of data on the stack for holding a copy of the user space fd_set,
>> but not too large to risk overflowing the kernel stack.
>>
>> When building a 32-bit kernel with clang, we need a little more space
>> than with gcc, which often triggers a warning:
>>
>> fs/select.c:619:5: error: stack frame size of 1048 bytes in function 'core_sys_select' [-Werror,-Wframe-larger-than=]
>> int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
>>
>> I experimentally found that for 32-bit ARM, reducing the maximum
>> stack usage by 64 bytes keeps us reliably under the warning limit
>> again.
>>
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> ---
>> include/linux/poll.h | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/include/linux/poll.h b/include/linux/poll.h
>> index 7e0fdcf905d2..1cdc32b1f1b0 100644
>> --- a/include/linux/poll.h
>> +++ b/include/linux/poll.h
>> @@ -16,7 +16,11 @@
>> extern struct ctl_table epoll_table[]; /* for sysctl */
>> /* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
>> additional memory. */
>> +#ifdef __clang__
>> +#define MAX_STACK_ALLOC 768
> Hi Arnd,
> Upon a toolchain upgrade for Android, our 32b x86 image used for
> first-party developer VMs started tripping -Wframe-larger-than= again
> (thanks -Werror) which is blocking our ability to upgrade our toolchain.
I wonder if there is a way to disable the warning or increase the
threshold just for this function. I don't think attribute optimize would
work, but perhaps some pragma?
-Andi
next prev parent reply other threads:[~2022-10-08 1:46 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-07 9:01 [PATCH] fs/select: avoid clang stack usage warning Arnd Bergmann
2019-03-07 16:19 ` Andi Kleen
2022-10-06 22:21 ` Nick Desaulniers
2022-10-07 8:28 ` Arnd Bergmann
2022-10-07 19:04 ` Nick Desaulniers
2022-10-07 20:11 ` [PATCH] fs/select: mark do_select noinline_for_stack for 32b Nick Desaulniers
2022-10-10 7:44 ` Christoph Hellwig
2022-10-10 16:42 ` Nick Desaulniers
2022-10-10 19:55 ` Arnd Bergmann
2022-10-13 18:52 ` kernel test robot
2022-10-07 21:42 ` [PATCH] fs/select: avoid clang stack usage warning Arnd Bergmann
2022-10-07 22:54 ` Nick Desaulniers
2022-10-10 18:40 ` Nick Desaulniers
2022-10-11 12:46 ` Arnd Bergmann
2022-10-11 20:55 ` [PATCH v2] fs/select: mark do_select noinline_for_stack Nick Desaulniers
2022-10-14 22:39 ` Nathan Chancellor
2022-10-07 23:17 ` [PATCH] fs/select: avoid clang stack usage warning Kees Cook
2022-10-09 10:49 ` David Laight
2022-10-08 1:46 ` Andi Kleen [this message]
2022-10-11 20:50 ` Nick Desaulniers
2022-10-13 20:52 ` Andi Kleen
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=f0dbc406-11b4-90f7-52fd-ce79f842c356@linux.intel.com \
--to=ak@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=darrick.wong@oracle.com \
--cc=edumazet@google.com \
--cc=gregkh@linuxfoundation.org \
--cc=hch@lst.de \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=llvm@lists.linux.dev \
--cc=ndesaulniers@google.com \
--cc=viro@zeniv.linux.org.uk \
/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).