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authorPaul Burton <paul.burton@mips.com>2018-08-17 15:36:24 -0700
committerPaul Burton <paul.burton@mips.com>2018-08-17 16:40:11 -0700
commitcfd54de3b0e4f82b3f2b80230726f74a6bec964f (patch)
treea39924a60e70e0a93f6eab4f1f9caf71f26b5593 /arch/Kconfig
parent4bcb4ad6634ea1084faa630fe35d72f75b5e80fa (diff)
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MIPS: Avoid move psuedo-instruction whilst using MIPS_ISA_LEVEL
MIPS_ISA_LEVEL is always defined as the 64 bit ISA that is a compatible superset of the ISA that the kernel build is targeting, and is used to allow us to emit instructions that we may detect support for at runtime. When we use a .set MIPS_ISA_LEVEL directive & are building a 32-bit kernel, we therefore are temporarily allowing the assembler to generate MIPS64 instructions. Using the move pseudo-instruction whilst this is the case is problematic because the assembler is likely to emit a daddu instruction which will generate a reserved instruction exception when executed on a MIPS32 machine. Unfortunately the combination of commit a0a5ac3ce8fe ("MIPS: Fix delay slot bug in `atomic*_sub_if_positive' for R10000_LLSC_WAR") and commit 4936084c2ee2 ("MIPS: Cleanup R10000_LLSC_WAR logic in atomic.h") causes us to do exactly this in atomic_sub_if_positive(), and the result is MIPS64 daddu instructions in 32-bit kernels. Fix this by using .set mips0 to restore the default ISA after the ll instruction, and use .set MIPS_ISA_LEVEL again prior to the sc. This ensures everything but the ll & sc are assembled using the default ISA for the kernel build & the move pseudo-instruction is emitted as a MIPS32 addu instruction. We appear to have another pre-existing instance of the same issue in our atomic_fetch_*_relaxed() functions, and fix that up too by moving our .set move0 such that it occurs prior to use of the move pseudo-instruction. Signed-off-by: Paul Burton <paul.burton@mips.com> Fixes: a0a5ac3ce8fe ("MIPS: Fix delay slot bug in `atomic*_sub_if_positive' for R10000_LLSC_WAR") Fixes: 4936084c2ee2 ("MIPS: Cleanup R10000_LLSC_WAR logic in atomic.h") Patchwork: https://patchwork.linux-mips.org/patch/20253/ Cc: James Hogan <jhogan@kernel.org> Cc: Joshua Kinard <kumba@gentoo.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: linux-mips@linux-mips.org
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