[U-Boot] [RFC] bug.h: Drop filename from BUG/WARNING logs if building for TPL/SPL

[Andreas Dannenberg]

On several platforms space is very tight when building for SPL or TPL.
To claw back a few bytes to be used for code remove the __FILE__ name
from the BUG() and WARN() type macros. Since those macros still print
the function name plus a line number this should not really affect
the ability to backtrace an actual BUG/WARN message to a specific
piece of code.

Signed-off-by: Andreas Dannenberg <dannenberg at ti.com>
---

I was looking for a way to shave off a few bytes from the SPL code size
(TI AM335x) and looking at the hexdump of the SPL I found well why not
further reduce some strings down in size... I was already aware of the
recent compiler optimizations to drop some of the irrelevant path from
the __FILE__ macro but I wanted to go one step beyond this. Dropping
all the path from __FILE__ via preprocessor macro can't be easily done
as others have already found so I decided to drop __FILE__ altogether
(code below) and was excited about the improvements I got...

Then of course using Google I found there was prior art, specifically
this discussion here:

"[U-Boot] __FILE__ usage and and SPL limits for SRAM"
https://patchwork.ozlabs.org/patch/746922/


So I made this submission to "RFC" to simply re-ignite the subject to
see if we can somehow find some path to proceed with such a change...

I like about the proposal referenced above that it touches more places
than what I came up with, however it is missing the TPL/SPL aspect
which I thought would be a good way to alleviate some of the concerns
raised (Wolfgang) around not having __FILE__ in the log...

Maybe a combination of the approaches could be workable?

At the end of the day SPL/TPL are intended for very memory-constrained
environments, so I feel changes like the proposed that don't really
affect any of the existing functionality are good candidates to
consider...

Regards,
Andreas

 include/linux/bug.h | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/bug.h b/include/linux/bug.h
index 29f84168a3..36b5fddfae 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -5,9 +5,22 @@
 #include <linux/build_bug.h>
 #include <linux/compiler.h>
 #include <linux/printk.h>
+#include <linux/kconfig.h>
+
+#if defined(CONFIG_TPL_BUILD) || defined(CONFIG_SPL_BUILD)
+/*
+ * In case of TPL/SPL use a short format not including __FILE__
+ * to reduce image size
+ */
+#define BUG_WARN_LOC_FMT	"%d@%s()"
+#define BUG_WARN_LOC_ARGS	__LINE__, __func__
+#else
+#define BUG_WARN_LOC_FMT	"%s:%d/%s()"
+#define BUG_WARN_LOC_ARGS	__FILE__, __LINE__, __func__
+#endif
 
 #define BUG() do { \
-	printk("BUG at %s:%d/%s()!\n", __FILE__, __LINE__, __func__); \
+	printk("BUG at " BUG_WARN_LOC_FMT "!\n", BUG_WARN_LOC_ARGS);	\
 	panic("BUG!"); \
 } while (0)
 
@@ -16,7 +29,7 @@
 #define WARN_ON(condition) ({						\
 	int __ret_warn_on = !!(condition);				\
 	if (unlikely(__ret_warn_on))					\
-		printk("WARNING at %s:%d/%s()!\n", __FILE__, __LINE__, __func__); \
+		printk("WARNING at " BUG_WARN_LOC_FMT "!\n", BUG_WARN_LOC_ARGS); \
 	unlikely(__ret_warn_on);					\
 })
 
-- 
2.17.1