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Roland McGrath authored
implementing user thread tracing and debugging. This fits on top of the tracehook_* layer, so the new code is well-isolated. The new interface is in <linux/utrace.h> and the DocBook utrace book describes it. It allows for multiple separate tracing engines to work in parallel without interfering with each other. Higher-level tracing facilities can be implemented as loadable kernel modules using this layer. The new facility is made optional under CONFIG_UTRACE. When this is not enabled, no new code is added. It can only be enabled on machines that have all the prerequisites and select CONFIG_HAVE_ARCH_TRACEHOOK. In this initial version, utrace and ptrace do not play together at all. If ptrace is attached to a thread, the attach calls in the utrace kernel API return -EBUSY. If utrace is attached to a thread, the PTRACE_ATTACH or PTRACE_TRACEME request will return EBUSY to userland. The old ptrace code is otherwise unchanged and nothing using ptrace should be affected by this patch as long as utrace is not used at the same time. In the future we can clean up the ptrace implementation and rework it to use the utrace API. [oleg@redhat.com: kill exclude_xtrace logic] Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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