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Date: Tue, 9 Jan 2024 20:05:04 +0000
From: Carlos Llamas <cmllamas@google.com>
To: Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Tom Rix <trix@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, kernel-team@android.com,
	Will Deacon <will@kernel.org>, John Stultz <jstultz@google.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] scripts/decode_stacktrace.sh: optionally use LLVM
 utilities
Message-ID: <ZZ2m8PO92oCF-uO-@google.com>
References: <20230929034836.403735-1-cmllamas@google.com>
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In-Reply-To: <20230929034836.403735-1-cmllamas@google.com>

On Fri, Sep 29, 2023 at 03:48:17AM +0000, Carlos Llamas wrote:
> GNU's addr2line can have problems parsing a vmlinux built with LLVM,
> particularly when LTO was used. In order to decode the traces correctly
> this patch adds the ability to switch to LLVM's utilities readelf and
> addr2line. The same approach is followed by Will in [1].
> 
> Before:
>   $ scripts/decode_stacktrace.sh vmlinux < kernel.log
>   [17716.240635] Call trace:
>   [17716.240646] skb_cow_data (??:?)
>   [17716.240654] esp6_input (ld-temp.o:?)
>   [17716.240666] xfrm_input (ld-temp.o:?)
>   [17716.240674] xfrm6_rcv (??:?)
>   [...]
> 
> After:
>   $ LLVM=1 scripts/decode_stacktrace.sh vmlinux < kernel.log
>   [17716.240635] Call trace:
>   [17716.240646] skb_cow_data (include/linux/skbuff.h:2172 net/core/skbuff.c:4503)
>   [17716.240654] esp6_input (net/ipv6/esp6.c:977)
>   [17716.240666] xfrm_input (net/xfrm/xfrm_input.c:659)
>   [17716.240674] xfrm6_rcv (net/ipv6/xfrm6_input.c:172)
>   [...]
> 
> Note that one could set CROSS_COMPILE=llvm- instead to hack around this
> issue. However, doing so can break the decodecode routine as it will
> force the selection of other LLVM utilities down the line e.g. llvm-as.
> 
> [1] https://lore.kernel.org/all/20230914131225.13415-3-will@kernel.org/
> 
> Cc: Will Deacon <will@kernel.org>
> Cc: John Stultz <jstultz@google.com>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Carlos Llamas <cmllamas@google.com>
> ---

There is no clear maintainer for this script. However, I had a look at
git history and it seems this might need to be picked up by Andrew.

Cc: Andrew Morton <akpm@linux-foundation.org>

Andrew can you please pick this up?

--
Carlos Llamas