s390/entry: avoid setting up backchain in ext|io handlers
Currently when interrupt arrives to cpu while in kernel context INT_HANDLER macro (used for ext_int_handler and io_int_handler) allocates new stack frame and pt_regs on the kernel stack and sets up the backchain to jump over the pt_regs to the frame which has been interrupted. This is not ideal to two reasons: 1. This hides the fact that kernel stack contains interrupt frame in it and hence breaks arch_stack_walk_reliable(), which needs to know that to guarantee "reliability" and checks that there are no pt_regs on the way. 2. It breaks the backchain unwinder logic, which assumes that the next stack frame after an interrupt frame is reliable, while it is not. In some cases (when r14 contains garbage) this leads to early unwinding termination with an error, instead of marking frame as unreliable and continuing. To address that, only set backchain to 0. Fixes: 56e62a73 ("s390: convert to generic entry") Reviewed-by:Sven Schnelle <svens@linux.ibm.com> Signed-off-by:
Vasily Gorbik <gor@linux.ibm.com> Signed-off-by:
Heiko Carstens <hca@linux.ibm.com>
parent
ad31a8c0
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