(no subject)

Date: Thu, 11 Jun 2020 15:38:38 -0700
From: Nick Desaulniers <ndesaulniers@google.com>
To: Michael Ellerman <redacted>,
	christophe.leroy@c-s.fr, segher@kernel.crashing.org
Cc: Christophe Leroy <redacted>,
	Benjamin Herrenschmidt [off-list ref],
	Paul Mackerras [off-list ref], npiggin@gmail.com,
	segher@kernel.crashing.org, linuxppc-dev@lists.ozlabs.org,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: Re: [PATCH v4 1/2] powerpc/uaccess: Implement unsafe_put_user()
  using 'asm goto'
Message-ID: [off-list ref]
References:  
[ref]
  [ref]
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
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In-Reply-To: [ref]

On Fri, May 29, 2020 at 02:24:16PM +1000, Michael Ellerman wrote:

On Fri, 2020-04-17 at 17:08:51 UTC, Christophe Leroy wrote:

quoted

unsafe_put_user() is designed to take benefit of 'asm goto'.

Instead of using the standard __put_user() approach and branch
based on the returned error, use 'asm goto' and make the
exception code branch directly to the error label. There is
no code anymore in the fixup section.

This change significantly simplifies functions using
unsafe_put_user()

...

quoted

Signed-off-by: Christophe Leroy <redacted>
Reviewed-by: Segher Boessenkool <redacted>

Applied to powerpc topic/uaccess-ppc, thanks.

https://git.kernel.org/powerpc/c/334710b1496af8a0960e70121f850e209c20958f

cheers

Hello!  It seems this patch broke our ppc32 builds, and we had to
disable them [0]. :(

 From what I can tell, though Michael mentioned this was merged on May
29, but our CI of -next was green for ppc32 until June 4, then mainline
went red June 6.  So this patch only got 2 days of soak time before the
merge window opened.

A general issue with the -next workflow seems to be that patches get
different amounts of soak time.  For higher risk patches like this one,
can I please ask that they be help back a release if close to the merge
window?

Segher, Cristophe, I suspect Clang is missing support for the %L and %U
output templates [1]. I've implemented support for some of these before
in Clang via the documentation at [2], but these seem to be machine
specific? Can you please point me to documentation/unit tests/source for
these so that I can figure out what they should be doing, and look into
implementing them in Clang?

(Apologies for the tone off this email; I had typed up a nice fuller
report with links, but it seemed that mutt wrote out an empty postponed
file, and I kind of just want to put my laptop in the garbage right now.
I suspect our internal SMTP tool will also mess up some headers, but
lets see (Also, too lazy+angry right now to solve).)

[0] https://github.com/ClangBuiltLinux/continuous-integration/pull/279
[1] https://bugs.llvm.org/show_bug.cgi?id=46186
[2]  
https://gcc.gnu.org/onlinedocs/gccint/Output-Template.html#Output-Template