Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Ard Biesheuvel <ardb@kernel.org>
To:     linux-efi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Cc:     Ard Biesheuvel <ardb@kernel.org>, linux-kernel@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        Borislav Petkov <bp@suse.de>,
        Colin Ian King <colin.king@canonical.com>,
        Gary Lin <glin@suse.com>, Jiri Slaby <jslaby@suse.cz>,
        Sergey Shatunov <me@prok.pw>, Takashi Iwai <tiwai@suse.de>
Subject: [PATCH 5/9] efi/arm: Deal with ADR going out of range in efi_enter_kernel()
Date:   Thu,  9 Apr 2020 15:04:30 +0200
Message-Id: <20200409130434.6736-6-ardb@kernel.org>
In-Reply-To: <20200409130434.6736-1-ardb@kernel.org>
References: <20200409130434.6736-1-ardb@kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Commit

  0698fac4ac2a ("efi/arm: Clean EFI stub exit code from cache instead of avoiding it")

introduced a PC-relative reference to 'call_cache_fn' into
efi_enter_kernel(), which lives way at the end of head.S. In some cases,
the ARM version of the ADR instruction does not have sufficient range,
resulting in a build error:

  arch/arm/boot/compressed/head.S:1453: Error: invalid constant (fffffffffffffbe4) after fixup

ARM defines an alternative with a wider range, called ADRL, but this does
not exist for Thumb-2. At the same time, the ADR instruction in Thumb-2
has a wider range, and so it does not suffer from the same issue.

So let's switch to ADRL for ARM builds, and keep the ADR for Thumb-2 builds.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm/boot/compressed/head.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 04f77214f050..61e6ee3ba75f 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -1454,7 +1454,8 @@ ENTRY(efi_enter_kernel)
 		@ running beyond the PoU, and so calling cache_off below from
 		@ inside the PE/COFF loader allocated region is unsafe unless
 		@ we explicitly clean it to the PoC.
-		adr	r0, call_cache_fn		@ region of code we will
+ ARM(		adrl	r0, call_cache_fn	)
+ THUMB(		adr	r0, call_cache_fn	)	@ region of code we will
 		adr	r1, 0f				@ run with MMU off
 		bl	cache_clean_flush
 		bl	cache_off
-- 
2.17.1