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Subject[PATCH] add a printk_init variant storing format strings in __initdata
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[As gcc seems unable to help us out selecting the appropriate data segment
for the code, how about we did something like this?]

When using printk from __init functions it would be desirable to place
the printk format strings in __initdata. Add a printk_init() variant
which does this.

This printk_init() is necessarily a #define so that we can declare the
format string in static scope and mark it __initdata. We then call a
newly introduced __printk_init() variant which is identicle to printk() but
marked __init itself. By ensuring that an __init variant of printk is used
we get proper section violation warnings when this is used incorrectly:

WARNING: vmlinux.o(.text+0x3): Section mismatch in reference from the
function something() to the variable .init.data:__printk_init_fmt.31426
The function something() references
the variable __initdata __printk_init_fmt.31426.
This is often because something lacks a __initdata
annotation or the annotation of __printk_init_fmt.31426 is wrong.

Note I have followed printk's pattern for __cold annotations.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
---
include/linux/kernel.h | 10 ++++++++++
kernel/printk.c | 12 ++++++++++++
2 files changed, 22 insertions(+), 0 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 792bf0a..7754196 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -180,6 +180,13 @@ struct pid;
extern struct pid *session_of_pgrp(struct pid *pgrp);

#ifdef CONFIG_PRINTK
+#define printk_init(fmt, args...) \
+do { \
+ static char __printk_init_fmt[] __initdata = fmt; \
+ __printk_init(__printk_init_fmt, ##args); \
+} while (0)
+asmlinkage int __printk_init(const char * fmt, ...)
+ __attribute__ ((format (printf, 1, 2))) __cold;
asmlinkage int vprintk(const char *fmt, va_list args)
__attribute__ ((format (printf, 1, 0)));
asmlinkage int printk(const char * fmt, ...)
@@ -196,6 +203,9 @@ extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
unsigned int interval_msec);
#else
+asmlinkage int printk_init(const char * fmt, ...)
+ __attribute__ ((format (printf, 1, 2))) __cold;
+static inline int __cold printk_init(const char *s, ...) { return 0; }
static inline int vprintk(const char *s, va_list args)
__attribute__ ((format (printf, 1, 0)));
static inline int vprintk(const char *s, va_list args) { return 0; }
diff --git a/kernel/printk.c b/kernel/printk.c
index 8fb01c3..992a5c0 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -616,6 +616,18 @@ asmlinkage int printk(const char *fmt, ...)
return r;
}

+asmlinkage __init int __printk_init(const char *fmt, ...)
+{
+ va_list args;
+ int r;
+
+ va_start(args, fmt);
+ r = vprintk(fmt, args);
+ va_end(args);
+
+ return r;
+}
+
/* cpu currently holding logbuf_lock */
static volatile unsigned int printk_cpu = UINT_MAX;


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