linux-kernel - improve compat handling for the i386 u64 alignment quirk

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Message-Id: <20200726160401.311569-1-hch@lst.de>
Date:   Sun, 26 Jul 2020 18:03:57 +0200
From:   Christoph Hellwig <hch@....de>
To:     x86@...nel.org, Jan Kara <jack@...e.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-arch@...r.kernel.org
Subject: improve compat handling for the i386 u64 alignment quirk

Hi all,

the i386 ABI is a little special in that it uses less than natural
alignment for 64-bit integer types (u64 and s64), and a significant
amount of our compat handlers deals with just that.  Unfortunately
there is no good way to check for this specific quirk at runtime,
similar how in_compat_syscall() checks for a compat syscall.  This
series adds such a check, and then uses the quota code as an example
of how this improves the compat handling.  I have a few other places
in mind where this will also be useful going forward.

Diffstat:
 b/arch/arm64/include/asm/compat.h        |    2 
 b/arch/arm64/include/asm/stat.h          |    2 
 b/arch/arm64/kernel/process.c            |    1 
 b/arch/arm64/kernel/ptrace.c             |    1 
 b/arch/mips/include/asm/compat.h         |    2 
 b/arch/parisc/include/asm/compat.h       |    2 
 b/arch/powerpc/include/asm/compat.h      |    2 
 b/arch/s390/include/asm/compat.h         |    2 
 b/arch/sparc/include/asm/compat.h        |    3 
 b/arch/x86/entry/syscalls/syscall_32.tbl |    2 
 b/arch/x86/include/asm/compat.h          |    3 
 b/fs/quota/Kconfig                       |    5 -
 b/fs/quota/Makefile                      |    1 
 b/fs/quota/compat.h                      |   34 ++++++++
 b/fs/quota/quota.c                       |   73 +++++++++++++++---
 b/include/linux/compat.h                 |   17 ++++
 b/include/linux/quotaops.h               |    3 
 b/kernel/sys_ni.c                        |    1 
 fs/quota/compat.c                        |  120 -------------------------------
 19 files changed, 114 insertions(+), 162 deletions(-)