4.20-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 33309ecda0070506c49182530abe7728850ebe78 ]
The dcache_by_line_op macro suffers from a couple of small problems:
First, the GAS directives that are currently being used rely on assembler behavior that is not documented, and probably not guaranteed to produce the correct behavior going forward. As a result, we end up with some undefined symbols in cache.o:
$ nm arch/arm64/mm/cache.o ... U civac ... U cvac U cvap U cvau
This is due to the fact that the comparisons used to select the operation type in the dcache_by_line_op macro are comparing symbols not strings, and even though it seems that GAS is doing the right thing here (undefined symbols by the same name are equal to each other), it seems unwise to rely on this.
Second, when patching in a DC CVAP instruction on CPUs that support it, the fallback path consists of a DC CVAU instruction which may be affected by CPU errata that require ARM64_WORKAROUND_CLEAN_CACHE.
Solve these issues by unrolling the various maintenance routines and using the conditional directives that are documented as operating on strings. To avoid the complexity of nested alternatives, we move the DC CVAP patching to __clean_dcache_area_pop, falling back to a branch to __clean_dcache_area_poc if DCPOP is not supported by the CPU.
Reported-by: Ard Biesheuvel ard.biesheuvel@linaro.org Suggested-by: Robin Murphy robin.murphy@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/include/asm/assembler.h | 30 ++++++++++++++++++------------ arch/arm64/mm/cache.S | 3 +++ 2 files changed, 21 insertions(+), 12 deletions(-)
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h index 6142402c2eb4..08b216c200c9 100644 --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -377,27 +377,33 @@ alternative_endif * size: size of the region * Corrupts: kaddr, size, tmp1, tmp2 */ + .macro __dcache_op_workaround_clean_cache, op, kaddr +alternative_if_not ARM64_WORKAROUND_CLEAN_CACHE + dc \op, \kaddr +alternative_else + dc civac, \kaddr +alternative_endif + .endm + .macro dcache_by_line_op op, domain, kaddr, size, tmp1, tmp2 dcache_line_size \tmp1, \tmp2 add \size, \kaddr, \size sub \tmp2, \tmp1, #1 bic \kaddr, \kaddr, \tmp2 9998: - .if (\op == cvau || \op == cvac) -alternative_if_not ARM64_WORKAROUND_CLEAN_CACHE - dc \op, \kaddr -alternative_else - dc civac, \kaddr -alternative_endif - .elseif (\op == cvap) -alternative_if ARM64_HAS_DCPOP - sys 3, c7, c12, 1, \kaddr // dc cvap -alternative_else - dc cvac, \kaddr -alternative_endif + .ifc \op, cvau + __dcache_op_workaround_clean_cache \op, \kaddr + .else + .ifc \op, cvac + __dcache_op_workaround_clean_cache \op, \kaddr + .else + .ifc \op, cvap + sys 3, c7, c12, 1, \kaddr // dc cvap .else dc \op, \kaddr .endif + .endif + .endif add \kaddr, \kaddr, \tmp1 cmp \kaddr, \size b.lo 9998b diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S index 0c22ede52f90..a194fd0e837f 100644 --- a/arch/arm64/mm/cache.S +++ b/arch/arm64/mm/cache.S @@ -212,6 +212,9 @@ ENDPROC(__dma_clean_area) * - size - size in question */ ENTRY(__clean_dcache_area_pop) + alternative_if_not ARM64_HAS_DCPOP + b __clean_dcache_area_poc + alternative_else_nop_endif dcache_by_line_op cvap, sy, x0, x1, x2, x3 ret ENDPIPROC(__clean_dcache_area_pop)