linux-kernel - [PATCH 5.14 333/334] parisc: Fix unaligned-access crash in bootloader

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Message-Id: <20210913131124.688441395@linuxfoundation.org>
Date:   Mon, 13 Sep 2021 15:16:27 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Helge Deller <deller@....de>,
        Arnd Bergmann <arnd@...nel.org>,
        John David Anglin <dave.anglin@...l.net>
Subject: [PATCH 5.14 333/334] parisc: Fix unaligned-access crash in bootloader

From: Helge Deller <deller@....de>

commit c42813b71a06a2ff4a155aa87ac609feeab76cf3 upstream.

Kernel v5.14 has various changes to optimize unaligned memory accesses,
e.g. commit 0652035a5794 ("asm-generic: unaligned: remove byteshift helpers").

Those changes triggered an unalignment-exception and thus crashed the
bootloader on parisc because the unaligned "output_len" variable now suddenly
was read word-wise while it was read byte-wise in the past.

Fix this issue by declaring the external output_len variable as char which then
forces the compiler to generate byte-accesses.

Signed-off-by: Helge Deller <deller@....de>
Cc: Arnd Bergmann <arnd@...nel.org>
Cc: John David Anglin <dave.anglin@...l.net>
Bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102162
Fixes: 8c031ba63f8f ("parisc: Unbreak bootloader due to gcc-7 optimizations")
Fixes: 0652035a5794 ("asm-generic: unaligned: remove byteshift helpers")
Cc: <stable@...r.kernel.org> # v5.14+
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/parisc/boot/compressed/misc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/parisc/boot/compressed/misc.c
+++ b/arch/parisc/boot/compressed/misc.c
@@ -26,7 +26,7 @@
 extern char input_data[];
 extern int input_len;
 /* output_len is inserted by the linker possibly at an unaligned address */
-extern __le32 output_len __aligned(1);
+extern char output_len;
 extern char _text, _end;
 extern char _bss, _ebss;
 extern char _startcode_end;