[U-Boot] [PATCH] SPL: tiny-printf: avoid any BSS usage

[Tom Rini]

On Mon, Jul 04, 2016 at 02:30:20PM +0200, Marek Vasut wrote:
> On 07/04/2016 01:56 AM, Andre Przywara wrote:
> >As printf calls may be executed quite early, we should avoid using any
> >BSS stored variables, since some boards put BSS in DRAM, which may not
> >have been initialised yet.
> >Explicitly mark those "static global" variables as belonging to the
> >.data section, to keep tiny-printf clear of any BSS usage.
> >Please note that this is quite a hack (which may need to be extended to
> >other source files) and more sustainable solutions are warmly welcomed.
> >
> >Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> >---
> >Hi,
> >
> >as mentioned before I don't like this hack very much, but as this fixes
> >the WIP Pine64 SPL code I propose this solution for 2016.07.
> >
> >Cheers,
> >Andre
> >
> > lib/tiny-printf.c | 13 ++++++++++---
> > 1 file changed, 10 insertions(+), 3 deletions(-)
> >
> >diff --git a/lib/tiny-printf.c b/lib/tiny-printf.c
> >index 451f4f7..bc2995b 100644
> >--- a/lib/tiny-printf.c
> >+++ b/lib/tiny-printf.c
> >@@ -13,11 +13,18 @@
> > #include <stdarg.h>
> > #include <serial.h>
> >
> >-static char *bf;
> >-static char zs;
> >+/*
> >+ * This code in here may execute before the DRAM is initialised, so
> >+ * we should make sure that it doesn't touch BSS, which some boards
> >+ * put in DRAM.
> >+ */
> >+#define NO_BSS __attribute__((section(".data")))
> 
> Please don't introduce new macros, it's really not necessary here,
> the comment is enough.

And would also match the other areas where we have to do something
"ugly" like this in order to function within constraints.  Frankly, I
don't see this exactly as a hack, but it should be tested on a few more
platforms just to be safe.

-- 
Tom
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