• Christian Borntraeger's avatar
    [S390] s390: fix single stepping on svc0 · bcc6525f
    Christian Borntraeger authored
    On s390 there are two ways of specifying the system call number for
    the svc instruction. The standard way is to use the immediate field
    in the instruction (or to use EXecute for values unknown during
    assemble time). This can encode 256 system calls.
    The kernel ABI also allows to put the system call number in r1 and
    then execute svc 0 to enable system call numbers > 255.
    
    It turns out that single stepping svc 0 is broken, since the PER
    program check handler uses r1. We have to use a different register.
    Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
    Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
    bcc6525f
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