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SubjectRe: [PATCH 8/9] syslog_ns: implement ns_printk for specific syslog_ns
On 2013/7/29 18:37, Gu Zheng wrote:
> Hi Rui,
>
> On 07/29/2013 10:31 AM, Rui Xiang wrote:
>
>> Add a new interface named ns_printk, and assign an
>> patamater ns. Log which belong to a container can
>> be printed by ns_printk.
>
> One question, with the syslog_ns used, do the log we print by *printk* in the
> host contains the log in each syslog_ns(print out with ns_printk) or not?
>

No. While using ns_printk, a parameter ns shouled be passed to identify syslog_ns.
If this ns has been created, it has a own log_buf to store logs. Otherwise this ns
comes from current->user_ns. When it is inis_syslog_ns the logs will be printed
out in host.

> Thanks,
> Gu
>
>>
>> Signed-off-by: Rui Xiang <rui.xiang@huawei.com>
>> ---
>> include/linux/printk.h | 4 ++++
>> kernel/printk.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++----
>> 2 files changed, 53 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/linux/printk.h b/include/linux/printk.h
>> index 29e3f85..bf83ad9 100644
>> --- a/include/linux/printk.h
>> +++ b/include/linux/printk.h
>> @@ -6,6 +6,7 @@
>> #include <linux/kern_levels.h>
>> #include <linux/linkage.h>
>>
>> +struct syslog_namespace;
>> extern const char linux_banner[];
>> extern const char linux_proc_banner[];
>>
>> @@ -123,6 +124,9 @@ asmlinkage int printk_emit(int facility, int level,
>> asmlinkage __printf(1, 2) __cold
>> int printk(const char *fmt, ...);
>>
>> +asmlinkage __printf(2, 3) __cold
>> +int ns_printk(struct syslog_namespace *ns, const char *fmt, ...);
>> +
>> /*
>> * Special printk facility for scheduler use only, _DO_NOT_USE_ !
>> */
>> diff --git a/kernel/printk.c b/kernel/printk.c
>> index 6b561db..56a8b27 100644
>> --- a/kernel/printk.c
>> +++ b/kernel/printk.c
>> @@ -1554,9 +1554,10 @@ static size_t cont_print_text(char *text, size_t size)
>> return textlen;
>> }
>>
>> -asmlinkage int vprintk_emit(int facility, int level,
>> - const char *dict, size_t dictlen,
>> - const char *fmt, va_list args)
>> +static int ns_vprintk_emit(int facility, int level,
>> + const char *dict, size_t dictlen,
>> + const char *fmt, va_list args,
>> + struct syslog_namespace *ns)
>> {
>> static int recursion_bug;
>> static char textbuf[LOG_LINE_MAX];
>> @@ -1566,7 +1567,6 @@ asmlinkage int vprintk_emit(int facility, int level,
>> unsigned long flags;
>> int this_cpu;
>> int printed_len = 0;
>> - struct syslog_namespace *ns = &init_syslog_ns;
>>
>> boot_delay_msec(level);
>> printk_delay();
>> @@ -1697,6 +1697,14 @@ out_restore_irqs:
>>
>> return printed_len;
>> }
>> +
>> +asmlinkage int vprintk_emit(int facility, int level,
>> + const char *dict, size_t dictlen,
>> + const char *fmt, va_list args)
>> +{
>> + return ns_vprintk_emit(facility, level, dict, dictlen, fmt, args,
>> + &init_syslog_ns);
>> +}
>> EXPORT_SYMBOL(vprintk_emit);
>>
>> asmlinkage int vprintk(const char *fmt, va_list args)
>> @@ -1762,6 +1770,43 @@ asmlinkage int printk(const char *fmt, ...)
>> }
>> EXPORT_SYMBOL(printk);
>>
>> +/**
>> + * ns_printk - print a kernel message in syslog_ns
>> + * @ns: syslog namespace
>> + * @fmt: format string
>> + *
>> + * This is ns_printk().
>> + * It can be called from container context. We add a param
>> + * ns to record current syslog namespace, because we need to
>> + * print some log which are not generated by host, but contaner.
>> + *
>> + * See the vsnprintf() documentation for format string extensions over C99.
>> + **/
>> +asmlinkage int ns_printk(struct syslog_namespace *ns,
>> + const char *fmt, ...)
>> +{
>> + va_list args;
>> + int r;
>> +
>> + if (!ns)
>> + ns = current_user_ns()->syslog_ns;
>> +
>> +#ifdef CONFIG_KGDB_KDB
>> + if (unlikely(kdb_trap_printk)) {
>> + va_start(args, fmt);
>> + r = vkdb_printf(fmt, args);
>> + va_end(args);
>> + return r;
>> + }
>> +#endif
>> + va_start(args, fmt);
>> + r = ns_vprintk_emit(0, -1, NULL, 0, fmt, args, ns);
>> + va_end(args);
>> +
>> + return r;
>> +}
>> +EXPORT_SYMBOL(ns_printk);
>> +
>
> Here can we do some clean up to printk using ns_printk?
>

ok, I will have a try to do it.:)

Thanks.




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