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Subject[PATCH 8/9] syslog_ns: implement ns_printk for specific syslog_ns
Date
Add a new interface named ns_printk, and assign an
patamater ns. Log which belong to a container can
be printed by ns_printk.

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);
+
#else /* CONFIG_PRINTK */

#define LOG_LINE_MAX 0
--
1.8.2.2



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