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Oleg Nesterov authored
SIGILL after the failed arch_uprobe_post_xol() should only be used as a last resort, we should try to restart the probed insn if possible. Currently only adjust_ret_addr() can fail, and this can only happen if another thread unmapped our stack after we executed "call" out-of-line. Most probably the application if buggy, but even in this case it can have a handler for SIGSEGV/etc. And in theory it can be even correct and do something non-trivial with its memory. Of course we can't restart unconditionally, so arch_uprobe_post_xol() does this only if ->post_xol() returns -ERESTART even if currently this is the only possible error. default_post_xol_op(UPROBE_FIX_CALL) can always restart, but as Jim pointed out it should not forget to pop off the return address pushed by this insn executed out-of-line. Note: this is not "perfect", we do not want the extra handler_chain() after restart, but I think this is the best solution we can realistically do without too much uglifications. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
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