linux_dsm_epyc7002/arch/arm64/include
Will Deacon 4230509978 arm64: cmpxchg: Use "K" instead of "L" for ll/sc immediate constraint
The "L" AArch64 machine constraint, which we use for the "old" value in
an LL/SC cmpxchg(), generates an immediate that is suitable for a 64-bit
logical instruction. However, for cmpxchg() operations on types smaller
than 64 bits, this constraint can result in an invalid instruction which
is correctly rejected by GAS, such as EOR W1, W1, #0xffffffff.

Whilst we could special-case the constraint based on the cmpxchg size,
it's far easier to change the constraint to "K" and put up with using
a register for large 64-bit immediates. For out-of-line LL/SC atomics,
this is all moot anyway.

Reported-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2018-12-07 17:28:13 +00:00
..
asm arm64: cmpxchg: Use "K" instead of "L" for ll/sc immediate constraint 2018-12-07 17:28:13 +00:00
uapi/asm arm64: Add support for SB barrier and patch in over DSB; ISB sequences 2018-12-06 16:47:04 +00:00