Now one can specify the log level of the LibOS by setting `OCCLUM_LOG_LEVEL`
environment variable. The possible values are "off", "error", "warn",
"info", and "trace".
However, for the sake of security, the log level of a release enclave
(DisableDebug = 1 in Enclave.xml) is always "off" (i.e., no log) regardless of
the log level specified by the untrusted environment.
It is slow to allocate big buffers using SGX SDK's malloc. Even worse, it
consumes a large amount of precious trusted memory inside enclaves. This
commit avoids using trusted buffers and allocates untrusted buffers for
sendmsg/recvmsg directly via OCall, thus improving the performance of
sendmsg/recvmsg. Note that this optimization does not affect the security of
network data as it has to be sent/received via OCalls.
Before this commit, using custom C types in ECalls/OCalls defined in Occlum's
EDL is cumbersme. Now this issue is resolved by providing `occlum_edl_types.h`
header file. There are two versions of this file: one is under
`src/libos/include/edl/` for LibOS, the other is under
`src/pal/include/edl/` for PAL. So now to define a new custom C type, just
edit the two versions of `occlum_edl_types.h` to define the type.
