bpf: Support writable context for bare tracepoint

mainline inclusion
from mainline-5.16
commit 65223741
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4H3JT


CVE: NA

---------------------------

Commit 9df1c28b ("bpf: add writable context for raw tracepoints")
supports writable context for tracepoint, but it misses the support
for bare tracepoint which has no associated trace event.

Bare tracepoint is defined by DECLARE_TRACE(), so adding a corresponding
DECLARE_TRACE_WRITABLE() macro to generate a definition in __bpf_raw_tp_map
section for bare tracepoint in a similar way to DEFINE_TRACE_WRITABLE().

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211004094857.30868-2-hotforest@gmail.com


Reviewed-by: Kuohai Xu <xukuohai@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>