[PATCH v3 08/18] Android: add support for dynamically enable/disable tracing

[Imre Deak]

On Wed, 2012-05-23 at 12:05 +0300, Imre Deak wrote:
> To trace applications started by the Dalvik VM we have to wrap the main
> Dalvik process zygote (or app_process) which is started at boot time and
> never stopped afterwards. We would still want to restrict tracing to a
> single process which will be forked by zygote.
> 
> To achieve this we'll use the fact that the forked process image is
> contained in the same file as zygote, pointed to by /proc/self/exe. So
> if this is 'app_process' we know it's a zygote process. To distinguish
> between zygote processes we'll check /proc/self/cmdline which will in
> turn be set to a unique application specific string (for example
> com.android.settings). The user has to set the debug.apitrace.procname
> to this string in order to enable tracing.
> 
> For non-zygote processes tracing will be always enabled.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  common/os.hpp       |    9 +++++++
>  common/os_posix.cpp |   66 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  wrappers/trace.py   |    8 ++++++
>  3 files changed, 83 insertions(+), 0 deletions(-)
> 
> diff --git a/common/os.hpp b/common/os.hpp
> index cc72a0e..7f62451 100644
> --- a/common/os.hpp
> +++ b/common/os.hpp
> @@ -70,6 +70,15 @@ void log(const char *format, ...)
>    #endif
>  #endif
>  
> +#ifdef ANDROID
> +bool apitrace_enabled(void);
> +#else
> +static inline bool apitrace_enabled(void)
> +{
> +    return true;
> +}
> +#endif
> +
>  void abort(void);
>  
>  void setExceptionCallback(void (*callback)(void));
> diff --git a/common/os_posix.cpp b/common/os_posix.cpp
> index 7d39d8a..d348ace 100644
> --- a/common/os_posix.cpp
> +++ b/common/os_posix.cpp
> @@ -46,6 +46,10 @@
>  
>  #ifdef ANDROID
>  #include <android/log.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <sys/system_properties.h>
>  #endif
>  
>  #ifndef PATH_MAX
> @@ -97,6 +101,68 @@ getProcessName(void)
>      return path;
>  }
>  
> +#ifdef ANDROID
> +static String
> +getZygoteProcessName(void)
> +{
> +    String path;
> +    size_t size = PATH_MAX;
> +    char *buf = path.buf(size);
> +    ssize_t len;
> +
> +    int fd = open("/proc/self/cmdline", O_RDONLY);
> +
> +    assert(fd >= 0);
> +    len = read(fd, buf, size - 1);
> +    close(fd);
> +    path.truncate(len);
> +
> +    return path;
> +}
> +
> +static bool isZygoteProcess(void)
> +{
> +    os::String proc_name;
> +
> +    proc_name = getProcessName();
> +    proc_name.trimDirectory();
> +
> +    return strcmp(proc_name, "app_process") == 0;
> +}
> +
> +bool apitrace_enabled(void)
> +{
> +    static pid_t cached_pid;
> +    static bool enabled;
> +    pid_t pid;
> +
> +    pid = getpid();
> +    if (cached_pid == pid)
> +        return enabled;
> +    cached_pid = pid;
> +
> +    if (!isZygoteProcess()) {
> +        os::log("apitrace[%d]: enabled for standalone %s", pid,
> +                (const char *)proc_name);

Doh, there is an error here due to a last minute change :/ proc_name
should be getProcessName() .

--Imre