From 75f9ef0b7f1aae33b7be7ba8d9c23c8cb48c2212 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 3 Apr 2014 20:52:19 +0200 Subject: [PATCH] uprobes/x86: Teach arch_uprobe_post_xol() to restart if possible 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 Reviewed-by: Masami Hiramatsu Reviewed-by: Jim Keniston --- Reading git-format-patch failed