[PATCH v2 1/1] Makefile: rework u-boot-initial-env target

[Max Krummenacher <max.oss.09@gmail.com>]

From: Max Krummenacher <max.krummenacher@toradex.com>

With LTO enabled the U-Boot initial environment is no longer stored
in an easy accessible section in env/common.o. I.e. the section name
changes from build to build, its content maybe compressed and it is
annotated with additional data.

Drop trying to read the initial env with elf tools from the compiler
specific object file in favour of adding and using a host tool with
the only functionality of printing the initial env to stdout.

See also:
https://lore.kernel.org/all/927b122e-1f62-e790-f5ca-30bae4332c77@foss.st.com/

Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>

---

Changes in v2:
- reworked to build a host tool which prints the configured
  environment as proposed by Pali Rohár
  https://lore.kernel.org/u-boot/20221018174827.1393211-1-max.oss.09@gmail.com/
- renamed patch, v1 used "Makefile: fix u-boot-initial-env target if lto is enabled"

 Makefile                  |  7 ++++---
 scripts/.gitignore        |  1 +
 scripts/Makefile          |  5 +++++
 scripts/printinitialenv.c | 44 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 54 insertions(+), 3 deletions(-)
 create mode 100644 scripts/printinitialenv.c

diff --git a/Makefile b/Makefile
index 0f1174718f7..2f97d63c398 100644
--- a/Makefile
+++ b/Makefile
@@ -2442,9 +2442,10 @@ endif
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 
 quiet_cmd_genenv = GENENV  $@
-cmd_genenv = $(OBJCOPY) --dump-section .rodata.default_environment=$@ env/common.o; \
-	sed --in-place -e 's/\x00/\x0A/g' $@; sed --in-place -e '/^\s*$$/d' $@; \
-	sort --field-separator== -k1,1 --stable $@ -o $@
+cmd_genenv = \
+	scripts/printinitialenv | \
+	sed -e 's/\x00/\x0A/g' -e '/^\s*$$/d' | \
+	sort --field-separator== -k1,1 --stable -o $@
 
 u-boot-initial-env: u-boot.bin
 	$(call if_changed,genenv)
diff --git a/scripts/.gitignore b/scripts/.gitignore
index 08cc824bac3..6068724a0d4 100644
--- a/scripts/.gitignore
+++ b/scripts/.gitignore
@@ -2,3 +2,4 @@
 # Generated files
 #
 bin2c
+printinitialenv
diff --git a/scripts/Makefile b/scripts/Makefile
index 8731e6cecd7..ba993820571 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -5,8 +5,13 @@
 # ---------------------------------------------------------------------------
 
 hostprogs-$(CONFIG_BUILD_BIN2C)		+= bin2c
+hostprogs-y				+= printinitialenv
 
 always		:= $(hostprogs-y)
 
+HOSTCFLAGS_printinitialenv.o += \
+		$(patsubst -I%,-idirafter%, $(filter -I%, $(UBOOTINCLUDE))) \
+		-DUSE_HOSTCC
+
 # Let clean descend into subdirs
 subdir-	+= basic kconfig dtc
diff --git a/scripts/printinitialenv.c b/scripts/printinitialenv.c
new file mode 100644
index 00000000000..c58b234d679
--- /dev/null
+++ b/scripts/printinitialenv.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2022
+ * Max Krummenacher, Toradex
+ *
+ * Snippets taken from tools/env/fw_env.c
+ *
+ * This prints the list of default environment variables as currently
+ * configured.
+ *
+ */
+
+#include <stdio.h>
+
+/* Pull in the current config to define the default environment */
+#include <linux/kconfig.h>
+
+#ifndef __ASSEMBLY__
+#define __ASSEMBLY__ /* get only #defines from config.h */
+#include <config.h>
+#undef	__ASSEMBLY__
+#else
+#include <config.h>
+#endif
+
+#define DEFAULT_ENV_INSTANCE_STATIC
+#include <generated/environment.h>
+#include <env_default.h>
+
+int main(void)
+{
+	char *env, *nxt;
+
+	for (env = default_environment; *env; env = nxt + 1) {
+		for (nxt = env; *nxt; ++nxt) {
+			if (nxt >= &default_environment[sizeof(default_environment)]) {
+				fprintf(stderr, "## Error: environment not terminated\n");
+				return -1;
+			}
+		}
+		printf("%s\n", env);
+	}
+	return 0;
+}
-- 
2.35.3