Le 04/02/2020 à 03:55, Josh Kunz a écrit :
> On Tue, Jan 28, 2020 at 7:07 AM Laurent Vivier <laur...@vivier.eu> wrote:
>>
>> Le 17/01/2020 à 20:28, Josh Kunz a écrit :
>>> This change switches linux-user strace logging to use the newer `qemu_log`
>>> logging subsystem rather than the older `gemu_log` (notice the "g")
>>> logger. `qemu_log` has several advantages, namely that it allows logging
>>> to a file, and provides a more unified interface for configuration
>>> of logging (via the QEMU_LOG environment variable or options).
>>>
>>> This change introduces a new log mask: `LOG_STRACE` which is used for
>>> logging of user-mode strace messages.
>>>
>>> Signed-off-by: Josh Kunz <j...@google.com>
>>> ---
>>> include/qemu/log.h | 2 +
>>> linux-user/main.c | 30 ++-
>>> linux-user/qemu.h | 1 -
>>> linux-user/signal.c | 2 +-
>>> linux-user/strace.c | 479 ++++++++++++++++++++++---------------------
>>> linux-user/syscall.c | 13 +-
>>> util/log.c | 2 +
>>> 7 files changed, 278 insertions(+), 251 deletions(-)
>>>
>> ...
>>> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
>>> index 629f3a21b5..54e60f3807 100644
>>> --- a/linux-user/syscall.c
>>> +++ b/linux-user/syscall.c
>>> @@ -12098,14 +12098,15 @@ abi_long do_syscall(void *cpu_env, int num,
>>> abi_long arg1,
>>> record_syscall_start(cpu, num, arg1,
>>> arg2, arg3, arg4, arg5, arg6, arg7, arg8);
>>>
>>> - if (unlikely(do_strace)) {
>>> + if (unlikely(qemu_loglevel_mask(LOG_STRACE))) {
>>> print_syscall(num, arg1, arg2, arg3, arg4, arg5, arg6);
>>> - ret = do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4,
>>> - arg5, arg6, arg7, arg8);
>>> + }
>>> +
>>> + ret = do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4,
>>> + arg5, arg6, arg7, arg8);
>>> +
>>> + if (unlikely(qemu_loglevel_mask(LOG_STRACE))) {
>>> print_syscall_ret(num, ret);
>>> - } else {
>>> - ret = do_syscall1(cpu_env, num, arg1, arg2, arg3, arg4,
>>> - arg5, arg6, arg7, arg8);
>>> }
>>>
>>> record_syscall_return(cpu, num, ret);
>>
>> In term of performance perhaps it sould be better to only test once for
>> the mask as it is done before?
>
> Modern compilers will generate functionally identical sequences for
> test once or testing twice (which is to say, they recognize they are
> the same compare: https://godbolt.org/z/VyrMHf IMO testing twice is
> nicer to read, so I'm leaving it that way for now unless you object.
>
If generated code is the same, I have no objection.
Thanks,
Laurent
