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Date:   Mon, 29 May 2023 21:23:39 -0700
From:   Kees Cook <kees@kernel.org>
To:     =?ISO-8859-1?Q?Joan_Bruguera_Mic=F3?= <joanbrugueram@gmail.com>,
        Thorsten Leemhuis <linux@leemhuis.info>
CC:     Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        linux-crypto@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Linux Next Mailing List <linux-next@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>
Subject: =?US-ASCII?Q?Re=3A_build_error_while_building_arch/x86/purgatory/sha256?= =?US-ASCII?Q?=2Eo=3A_invalid_=27asm=27=3A_operand_i?= =?US-ASCII?Q?s_not_a_condition_code_=5B=2E=2E=2E=5D?=
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On May 28, 2023 9:40:31 AM PDT, "Joan Bruguera Mic=C3=B3" <joanbrugueram@gm=
ail=2Ecom> wrote:
>I can also reproduce the problem with Arch's linux-next-git, see config:
>https://aur=2Earchlinux=2Eorg/cgit/aur=2Egit/tree/config?h=3Dlinux-next-g=
it&id=3Df9a384e1c582321651fb613782ebc5a581146af0
>
>I've bisected it to df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3D=
3"),
>which explains why it only happens on GCC13=2E
>
>The problematic expansion that causes the error seems to be this fragment
>from `_BUG_FLAGS` in `arch/x86/include/asm/bug=2Eh`:
>    asm("=2Elong %c0 - =2E\n": : "i" (__FILE__));
>
>Along with the fact that this file is built with `-mcmodel=3Dlarge`
>(see `PURGATORY_CFLAGS` in `arch/x86/purgatory/Makefile`)=2E

I haven't reproduced this yet, but the error implies that the asm input "i=
"mmediate value of the __FILE__ string address cannot be used with the asm =
template format "%c0" (a constant value)=2E

https://gcc=2Egnu=2Eorg/onlinedocs/gcc/Extended-Asm=2Ehtml#Generic-Operand=
-Modifiers

I cannot fathom why struct flex array logic would change that=2E=2E=2E

I'll take a closer look in the morning=2E

-Kees


--=20
Kees Cook