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Commit f74b7f57 authored by Tom Cherry's avatar Tom Cherry
Browse files

init: add stdio_to_kmsg option 

Some services are not native android services and therefore don't log
via the normal mechanisms.  This gives developers an option to have
their stdout/stderr logs sent directly to kmsg.

Test: see test prints to kernel log
Change-Id: I7973ea74d5cab3a90c2cd9a3d5de2266439d0c01
parent 03642ad8

init/README.md

+9 −0
Original line number Diff line number Diff line
@@ -170,6 +170,8 @@ runs the service. 
  be changed by setting the "androidboot.console" kernel parameter. In

  all cases the leading "/dev/" should be omitted, so "/dev/tty0" would be

  specified as just "console tty0".

  This option connects stdin, stdout, and stderr to the console. It is mutually exclusive with the

  stdio_to_kmsg option, which only connects stdout and stderr to kmsg.



`critical`

> This is a device-critical service. If it exits more than four times in
@@ -313,6 +315,13 @@ runs the service. 
  seclabel or computed based on the service executable file security context.

  For native executables see libcutils android\_get\_control\_socket().



`stdio_to_kmsg`

> Redirect stdout and stderr to /dev/kmsg_debug. This is useful for services that do not use native

  Android logging during early boot and whose logs messages we want to capture. This is only enabled

  when /dev/kmsg_debug is enabled, which is only enabled on userdebug and eng builds.

  This is mutually exclusive with the console option, which additionally connects stdin to the

  given console.



`timeout_period <seconds>`

> Provide a timeout after which point the service will be killed. The oneshot keyword is respected

  here, so oneshot services do not automatically restart, however all other services will.

init/service_parser.cpp

+12 −0
Original line number Diff line number Diff line
@@ -83,6 +83,9 @@ Result<void> ServiceParser::ParseClass(std::vector<std::string>&& args) { 
}



Result<void> ServiceParser::ParseConsole(std::vector<std::string>&& args) {

    if (service_->proc_attr_.stdio_to_kmsg) {

        return Error() << "'console' and 'stdio_to_kmsg' are mutually exclusive";

    }

    service_->flags_ |= SVC_CONSOLE;

    service_->proc_attr_.console = args.size() > 1 ? "/dev/" + args[1] : "";

    return {};
@@ -429,6 +432,14 @@ Result<void> ServiceParser::ParseSocket(std::vector<std::string>&& args) { 
    return {};

}



Result<void> ServiceParser::ParseStdioToKmsg(std::vector<std::string>&& args) {

    if (service_->flags_ & SVC_CONSOLE) {

        return Error() << "'stdio_to_kmsg' and 'console' are mutually exclusive";

    }

    service_->proc_attr_.stdio_to_kmsg = true;

    return {};

}



// name type

Result<void> ServiceParser::ParseFile(std::vector<std::string>&& args) {

    if (args[2] != "r" && args[2] != "w" && args[2] != "rw") {
@@ -514,6 +525,7 @@ const KeywordMap<ServiceParser::OptionParser>& ServiceParser::GetParserMap() con 
        {"shutdown",                {1,     1,    &ServiceParser::ParseShutdown}},

        {"sigstop",                 {0,     0,    &ServiceParser::ParseSigstop}},

        {"socket",                  {3,     6,    &ServiceParser::ParseSocket}},

        {"stdio_to_kmsg",           {0,     0,    &ServiceParser::ParseStdioToKmsg}},

        {"timeout_period",          {1,     1,    &ServiceParser::ParseTimeoutPeriod}},

        {"updatable",               {0,     0,    &ServiceParser::ParseUpdatable}},

        {"user",                    {1,     1,    &ServiceParser::ParseUser}},

init/service_parser.h

+1 −0
Original line number Diff line number Diff line
@@ -75,6 +75,7 @@ class ServiceParser : public SectionParser { 
    Result<void> ParseShutdown(std::vector<std::string>&& args);

    Result<void> ParseSigstop(std::vector<std::string>&& args);

    Result<void> ParseSocket(std::vector<std::string>&& args);

    Result<void> ParseStdioToKmsg(std::vector<std::string>&& args);

    Result<void> ParseTimeoutPeriod(std::vector<std::string>&& args);

    Result<void> ParseFile(std::vector<std::string>&& args);

    Result<void> ParseUser(std::vector<std::string>&& args);

init/service_utils.cpp

+11 −5
Original line number Diff line number Diff line
@@ -16,10 +16,12 @@ 


#include "service_utils.h"



#include <fcntl.h>

#include <grp.h>

#include <sys/mount.h>

#include <sys/prctl.h>

#include <sys/wait.h>

#include <unistd.h>



#include <android-base/file.h>

#include <android-base/logging.h>
@@ -121,11 +123,15 @@ Result<void> SetUpPidNamespace(const char* name) { 
    return {};

}



void ZapStdio() {

void SetupStdio(bool stdio_to_kmsg) {

    auto fd = unique_fd{open("/dev/null", O_RDWR | O_CLOEXEC)};

    dup2(fd, 0);

    dup2(fd, 1);

    dup2(fd, 2);

    dup2(fd, STDIN_FILENO);

    if (stdio_to_kmsg) {

        fd.reset(open("/dev/kmsg_debug", O_WRONLY | O_CLOEXEC));

        if (fd == -1) fd.reset(open("/dev/null", O_WRONLY | O_CLOEXEC));

    }

    dup2(fd, STDOUT_FILENO);

    dup2(fd, STDERR_FILENO);

}



void OpenConsole(const std::string& console) {
@@ -238,7 +244,7 @@ Result<void> SetProcessAttributes(const ProcessAttributes& attr) { 
        if (setpgid(0, getpid()) == -1) {

            return ErrnoError() << "setpgid failed";

        }

        ZapStdio();

        SetupStdio(attr.stdio_to_kmsg);

    }



    for (const auto& rlimit : attr.rlimits) {

init/service_utils.h

+1 −0
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ struct ProcessAttributes { 
    gid_t gid;

    std::vector<gid_t> supp_gids;

    int priority;

    bool stdio_to_kmsg;

};

Result<void> SetProcessAttributes(const ProcessAttributes& attr);