Add and consistently use wrapper macro for romstage static variables

x86 systems run their romstage as execute-in-place from flash, which
prevents them from having writable data segments. In several code pieces
that get linked into both romstage and ramstage, this has been worked
around by using a local variable and having the 'static' storage class
guarded by #ifndef __PRE_RAM__.

However, x86 is the only architecture using execute-in-place (for now),
so it does not make sense to impose the restriction globally. Rather
than fixing the #ifdef at every occurrence, this should really be
wrapped in a way that makes it easier to modify in a single place. The
chromeos/cros_vpd.c file already had a nice approach for a wrapper
macro, but unfortunately restricted it to one file... this patch moves
it to stddef.h and employs it consistently throughout coreboot.

BRANCH=nyan
BUG=None
TEST=Measured boot time on Nyan_Big before and after, confirmed that it
gained 6ms from caching the FMAP in vboot_loader.c.

Original-Change-Id: Ia53b94ab9c6a303b979db7ff20b79e14bc51f9f8
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/203033
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
(cherry picked from commit c8127e4ac9811517f6147cf019ba6a948cdaa4a5)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I44dacc10214351992b775aca52d6b776a74ee922
Reviewed-on: http://review.coreboot.org/8055
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)

4 files changed, 13 insertions, 24 deletions

diff --git a/src/include/stddef.h b/src/include/stddef.h
index 3a030e14a1..60e34595ee 100644
--- a/src/include/stddef.h
+++ b/src/include/stddef.h
@@ -49,4 +49,11 @@ typedef unsigned int wint_t;
 #define ROMSTAGE_CONST
 #endif
 
+/* Work around non-writable data segment in execute-in-place romstage on x86. */
+#if defined(__PRE_RAM__) && CONFIG_ARCH_X86
+#define MAYBE_STATIC
+#else
+#define MAYBE_STATIC static
+#endif
+
 #endif /* STDDEF_H */
diff --git a/src/lib/lzma.c b/src/lib/lzma.c
index ea5f15f2d1..8efa1e6e1a 100644
--- a/src/lib/lzma.c
+++ b/src/lib/lzma.c
@@ -24,12 +24,7 @@ unsigned long ulzma(unsigned char * src, unsigned char * dst)
 	int res;
 	CLzmaDecoderState state;
 	SizeT mallocneeds;
-#if !defined(__PRE_RAM__)
-	/* in ramstage, this can go in BSS */
-	static
-#endif
-	/* in pre-ram, it must go on the stack */
-	unsigned char scratchpad[15980];
+	MAYBE_STATIC unsigned char scratchpad[15980];
 	unsigned char *cp;
 
 	memcpy(properties, src, LZMA_PROPERTIES_SIZE);
diff --git a/src/vendorcode/google/chromeos/cros_vpd.c b/src/vendorcode/google/chromeos/cros_vpd.c
index 26b01ee7a3..df2b5bf667 100644
--- a/src/vendorcode/google/chromeos/cros_vpd.c
+++ b/src/vendorcode/google/chromeos/cros_vpd.c
@@ -15,16 +15,6 @@
 #include "lib_vpd.h"
 #include "vpd_tables.h"
 
-/*
- * Static variables are available in ramstage (all platforms), and romstage for
- * some platforms (ex, ARM, which uses SRAM).
- */
-#if defined(__PRE_RAM__) && CONFIG_ARCH_X86
-#define STATIC_VAR
-#else
-#define STATIC_VAR	static
-#endif
-
 /* Currently we only support Google VPD 2.0, which has a fixed offset. */
 enum {
 	GOOGLE_VPD_2_0_OFFSET = 0x600,
@@ -39,10 +29,10 @@ struct vpd_gets_arg {
 
 static int cros_vpd_load(uint8_t **vpd_address, int32_t *vpd_size)
 {
-	STATIC_VAR int cached = 0;
-	STATIC_VAR uint8_t *cached_address = NULL;
-	STATIC_VAR int32_t cached_size = 0;
-	STATIC_VAR int result = -1;
+	MAYBE_STATIC int cached = 0;
+	MAYBE_STATIC uint8_t *cached_address = NULL;
+	MAYBE_STATIC int32_t cached_size = 0;
+	MAYBE_STATIC int result = -1;
 	struct google_vpd_info info;
 	int32_t base;
 
diff --git a/src/vendorcode/google/chromeos/fmap.c b/src/vendorcode/google/chromeos/fmap.c
index d758f57a20..a8425c0d10 100644
--- a/src/vendorcode/google/chromeos/fmap.c
+++ b/src/vendorcode/google/chromeos/fmap.c
@@ -92,10 +92,7 @@ const struct fmap_area *find_fmap_area(const struct fmap *fmap,
 
 int find_fmap_entry(const char name[], void **pointer)
 {
-#ifndef __PRE_RAM__
-	static
-#endif
-	const struct fmap *fmap = NULL;
+	MAYBE_STATIC const struct fmap *fmap = NULL;
 	const struct fmap_area *area;
 	void *base = NULL;