• Paul Mackerras's avatar
    powerpc: Don't try to fix up misaligned load-with-reservation instructions · 783494a2
    Paul Mackerras authored
    [ Upstream commit 48fe9e94 ]
    
    In the past, there was only one load-with-reservation instruction,
    lwarx, and if a program attempted a lwarx on a misaligned address, it
    would take an alignment interrupt and the kernel handler would emulate
    it as though it was lwzx, which was not really correct, but benign since
    it is loading the right amount of data, and the lwarx should be paired
    with a stwcx. to the same address, which would also cause an alignment
    interrupt which would result in a SIGBUS being delivered to the process.
    
    We now have 5 different sizes of load-with-reservation instruction. Of
    those, lharx and ldarx cause an immediate SIGBUS by luck since their
    entries in aligninfo[] overlap instructions which were not fixed up, but
    lqarx overlaps with lhz and will be emulated as such. lbarx can never
    generate an alignment interrupt since it only operates on 1 byte.
    
    To straighten this out and fix the lqarx case, this adds code to detect
    the l[hwdq]arx instructions and return without fixing them up, resulting
    in a SIGBUS being delivered to the process.
    
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
    783494a2
align.c 25.5 KB