common: env_embedded: allow fine placement of environment object

Commit 7653942b ("common/env_embedded.c: drop support for
CONFIG_SYS_USE_PPCENV") dropped the .ppcenv section which was
used in linking scripts to allow fine placement of embedded
environment sections.

This implies that GCC randomly places objects from env/embedded.o
and environment is not guaranteed to be located at the correct address:

04003df8 g     F .text  00000038 mii_init
04004000 g     O .text  00000004 env_size
04004004 g     O .text  00002000 environment
04006004 g     F .text  00000040 .hidden __lshrdi3

This patch restores this capability by allocating each object marked
with __UBOOT_ENV_SECTION__ into a different section. Hence
'environment' will be alone in .text.environment, allowing a
fine placement in u-boot.lds with:

		. = DEFINED(env_offset) ? env_offset : .;
		env/embedded.o			(.text.environment)

Fixes: 7653942b ("common/env_embedded.c: drop support for CONFIG_SYS_USE_PPCENV")
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

env/embedded.c

@@ -35,11 +35,11 @@
  * a seperate section.
  */
 #if defined(USE_HOSTCC) /* Native for 'tools/envcrc' */
-#  define __UBOOT_ENV_SECTION__	/*XXX DO_NOT_DEL_THIS_COMMENT*/
+#  define __UBOOT_ENV_SECTION__(name)	/*XXX DO_NOT_DEL_THIS_COMMENT*/
 
 #else /* Environment is embedded in U-Boot's .text section */
 /* XXX - This only works with GNU C */
-#  define __UBOOT_ENV_SECTION__	__attribute__ ((section(".text")))
+#  define __UBOOT_ENV_SECTION__(name)	__attribute__ ((section(".text."#name)))
 #endif
 
 /*
@@ -70,7 +70,7 @@
 #include <env_default.h>
 
 #ifdef CONFIG_ENV_ADDR_REDUND
-env_t redundand_environment __UBOOT_ENV_SECTION__ = {
+env_t redundand_environment __UBOOT_ENV_SECTION__(redundand_environment) = {
 	0,		/* CRC Sum: invalid */
 	0,		/* Flags:   invalid */
 	{
@@ -87,7 +87,7 @@ env_t redundand_environment __UBOOT_ENV_SECTION__ = {
  * .data/.sdata section.
  *
  */
-unsigned long env_size __UBOOT_ENV_SECTION__ = sizeof(env_t);
+unsigned long env_size __UBOOT_ENV_SECTION__(env_size) = sizeof(env_t);
 
 /*
  * Add in absolutes.

include/env_default.h

@@ -11,7 +11,7 @@
 #include <env_callback.h>
 
 #ifdef DEFAULT_ENV_INSTANCE_EMBEDDED
-env_t environment __UBOOT_ENV_SECTION__ = {
+env_t environment __UBOOT_ENV_SECTION__(environment) = {
 	ENV_CRC,	/* CRC Sum */
 #ifdef CONFIG_SYS_REDUNDAND_ENVIRONMENT
 	1,		/* Flags: valid */