a379b1ce05
This protocol documentation is spread out among various functions where it is implemented. This change makes a single README.protocol.md file with a high level overview, referencing the struct names where useful. Test: n/a Change-Id: I83c9f484352b489b4a20cce241d92413f780f9ec
49 lines
1.7 KiB
Markdown
49 lines
1.7 KiB
Markdown
# liblog -> logd
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The data that liblog sends to logd is represented below.
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struct {
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android_log_header_t header;
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union {
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struct {
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char prio;
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char tag[...];
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char message[...];
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} string;
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struct {
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android_event_header_t event_header;
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android_event_*_t payload[...];
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} binary;
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};
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};
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The payload, excluding the header, has a max size of LOGGER_ENTRY_MAX_PAYLOAD.
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## header
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The header is added immediately before sending the log message to logd.
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## `string` payload
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The `string` part of the union is for normal buffers (main, system, radio, etc) and consists of a
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single character priority, followed by a variable length null terminated string for the tag, and
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finally a variable length null terminated string for the message.
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This payload is used for the `__android_log_buf_write()` family of functions.
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## `binary` payload
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The `binary` part of the union is for binary buffers (events, security, etc) and consists of an
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android_event_header_t struct followed by a variable number of android_event_*_t
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(android_event_list_t, android_event_int_t, etc) structs.
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If multiple android_event_*_t elements are present, then they must be in a list and the first
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element in payload must be an android_event_list_t.
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This payload is used for the `__android_log_bwrite()` family of functions. It is additionally used
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for `android_log_write_list()` and the related functions that manipulate event lists.
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# logd -> liblog
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logd sends a `logger_entry` struct to liblog followed by the payload. The payload is identical to
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the payloads defined above. The max size of the entire message from logd is LOGGER_ENTRY_MAX_LEN.
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