[microdump] Move microdump writes to the crash ring-buffer log

[microdump] Move microdump writes to the crash ring-buffer log

So far the microdump_writer dumped the log in logcat using the default
system log. This is simple to achieve but has some drawbacks:
 1. Creates spam in the system log, pushing back other eventual useful
    messages.
 2. There is a high chance that the microdump gets lost if some log
    spam storm happens immediately after a crash and before the log
    is collected by the feedback client.
 3. Since Android L, the logger is smartly throttling messages (to
    reduce logcat spam). Throttling brekpad logs defeats the all
    point of microdumps.

This change is conceptually very simple. Replace the use of
__android_log_write() with __android_log_buf_write(), which takes
an extra bufID argument. The main drawback is that the
__android_log_buf_write is not exported in the NDK and needs to be
dynamically looked up via dlsym.
This choice has been discussed and advocated by Android owners.
See the internal bug b/21753476.

BUG=chromium:512755
R=thestig@chromium.org

Committed: https://code.google.com/p/google-breakpad/source/detail?r=1490

[Primiano Tucci (use gerrit), 2015-08-13 11:08:36]

primiano@chromium.org changed reviewers:
+ thestig@chromium.org

[Primiano Tucci (use gerrit), 2015-08-13 11:08:37]

Lei, can I ask a review on this?

Torne, would you mind give it an end-to-end try to this in WebView.
I did already test locally on Chrome and seems to work fine.

[Lei Zhang, 2015-08-13 21:07:57]

lgtm

All the comments are nitty.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
File src/client/linux/log/log.cc (right):

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:36: // From Android system/core/include/log/log.h
nit: Move these out of a #if block for #includes.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:36: // From Android system/core/include/log/log.h
Might be good to mention __android_log_buf_write() is not exported in the NDK.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:55: namespace {
nit: blank lines after the start of the namespace and before the end.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:69: // Try writing to the crash log ring buffer. If
not available, fall back using
nit: "fall back to" parses slightly better in my mind.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:71: if (g_crash_log_initialized &&
g_android_log_buf_write) {
Do you really need to check |g_crash_log_initialized| ?

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:72: const int kAndroidCrashLogId = 4;
Where did this magical value come from? Add a comment?

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/microd...
File src/client/linux/microdump_writer/microdump_writer.cc (right):

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/microd...
src/client/linux/microdump_writer/microdump_writer.cc:109:
logger::writeToCrashLog(msg);
nit: indentation

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/microd...
src/client/linux/microdump_writer/microdump_writer.cc:112: logger::write("\n",
1);  // Android logger appends the \n. Linux's doesn't.
You can probably omit or shorten the comment now?

[Primiano Tucci (use gerrit), 2015-08-14 09:16:45]

primiano@chromium.org changed reviewers:
+ simonb@chromium.org

[Primiano Tucci (use gerrit), 2015-08-14 09:16:46]

Thanks.
simonb@ can I ask you,, as owner of all the linkers, just a quick eye on the
dlsym black magic?

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
File src/client/linux/log/log.cc (right):

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:36: // From Android system/core/include/log/log.h
On 2015/08/13 21:07:57, Lei Zhang wrote:
> Might be good to mention __android_log_buf_write() is not exported in the NDK.

Done.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:36: // From Android system/core/include/log/log.h
On 2015/08/13 21:07:57, Lei Zhang wrote:
> nit: Move these out of a #if block for #includes.

Done.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:36: // From Android system/core/include/log/log.h
On 2015/08/13 21:07:57, Lei Zhang wrote:
> nit: Move these out of a #if block for #includes.

Moved below in the anonymous namespace

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:55: namespace {
On 2015/08/13 21:07:57, Lei Zhang wrote:
> nit: blank lines after the start of the namespace and before the end.

Done.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:69: // Try writing to the crash log ring buffer. If
not available, fall back using
On 2015/08/13 21:07:57, Lei Zhang wrote:
> nit: "fall back to" parses slightly better in my mind.

Done.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:71: if (g_crash_log_initialized &&
g_android_log_buf_write) {
On 2015/08/13 21:07:57, Lei Zhang wrote:
> Do you really need to check |g_crash_log_initialized| ?

Nah not really. Done.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/log/lo...
src/client/linux/log/log.cc:72: const int kAndroidCrashLogId = 4;
On 2015/08/13 21:07:57, Lei Zhang wrote:
> Where did this magical value come from? Add a comment?

Done.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/microd...
File src/client/linux/microdump_writer/microdump_writer.cc (right):

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/microd...
src/client/linux/microdump_writer/microdump_writer.cc:109:
logger::writeToCrashLog(msg);
On 2015/08/13 21:07:57, Lei Zhang wrote:
> nit: indentation

Done.

https://codereview.chromium.org/1286063003/diff/20001/src/client/linux/microd...
src/client/linux/microdump_writer/microdump_writer.cc:112: logger::write("\n",
1);  // Android logger appends the \n. Linux's doesn't.
On 2015/08/13 21:07:57, Lei Zhang wrote:
> You can probably omit or shorten the comment now?

Done.

[Torne, 2015-08-14 12:36:06]

On 2015/08/13 11:08:37, Primiano Tucci wrote:
> Torne, would you mind give it an end-to-end try to this in WebView.
> I did already test locally on Chrome and seems to work fine.

Tested in webview and it seems to be fine. The "Chrome build fingerprint"
section is still being printed to main, but that part is still useless for
webview anyway afaict, so that seems fine.

Code also LGTM.

[Primiano Tucci (use gerrit), 2015-08-17 10:32:34]

Committed patchset #3 (id:40001) manually as 1490 (presubmit successful).