Linux 5.0 compat: ASM_BUG macro

[behlendorf]

Motivation and Context

Issue #8545

In file included from /home/fedora/zfs/module/zfs/vdev_raidz_math_aarch64_neon.c:30:
/home/fedora/zfs/module/zfs/vdev_raidz_math_aarch64_neon_common.h:126: error: "ASM_BUG" redefined [-Werror]
 #define ASM_BUG() ASSERT(0)
 
In file included from ./arch/arm64/include/asm/bug.h:23,
                 from ./include/linux/bug.h:5,
                 from ./arch/arm64/include/asm/ptrace.h:93,
                 from ./arch/arm64/include/asm/fpsimd.h:20,
                 from ./arch/arm64/include/asm/neon.h:15,
                 from /home/fedora/zfs/include/linux/simd_aarch64.h:43,
                 from /home/fedora/zfs/module/zfs/vdev_raidz_math_aarch64_neon_common.h:26,
                 from /home/fedora/zfs/module/zfs/vdev_raidz_math_aarch64_neon.c:30:
./arch/arm64/include/asm/asm-bug.h:52: note: this is the location of the previous definition
 #define ASM_BUG() ASM_BUG_FLAGS(0)
 
cc1: all warnings being treated as errors

Description

The 5.0 kernel defines the macro ASM_BUG. In order to prevent a
conflict and build failure rename ASM_BUG to ZFS_ASM_BUG. This
is currently only an issue on aarch64 but all instances of
ASM_BUG we're renamed to avoid any future conflict on x86_64.

How Has This Been Tested?

Compiled on Fedora 29 using the 5.0.10-200.fc29.aarch64 kernel. A subset of the ZTS was then run successfully.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the ZFS on Linux code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• All commit messages are properly formatted and contain Signed-off-by.

[chrisrd]

LGTM

[codecov]

Codecov Report

Merging #8725 into master will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #8725      +/-   ##
==========================================
- Coverage   78.82%   78.77%   -0.06%     
==========================================
  Files         381      381              
  Lines      117630   117630              
==========================================
- Hits        92724    92660      -64     
- Misses      24906    24970      +64

Flag	Coverage Δ
#kernel	79.34% <ø> (ø)	⬆️
#user	67.37% <ø> (-0.26%)	⬇️

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[rlaager]

This change LGTM, and I see the ASM_BUG definition does exist in upstream Linux git.

I do have one question: I'm not a kernel developer, so take this with a big grain of salt, but is this macro doing anything useful (for readability/understandability) over just ASSERT(0)?

[behlendorf]

but is this macro doing anything useful (for readability/understandability) over just ASSERT(0)?

In fact, in the original version of this patch I did just replace ASM_BUG with ASSERT(0). But after further consideration I decided there was value in keeping the macro, since it makes it easy to map ZFS_ASM_BUG to the kernels ASM_BUG which may be useful for different architectures.