[PATCH v5 1/1] u-boot-initial-env: rework make 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>
Acked-by: Pali Rohár <pali@kernel.org>

---

Changes in v5:
- don't build the printinitialenv tool unconditionally but build it
  only as part of the u-boot-initial-env target.
  This no longer fails the 'make tools-only_defconfig tools-only'
  use-case which is reported by Tom Rini.
  Adding the $(env_h) dependencies to the tools target might give
  circular dependencies issues with some future tool.
- add Acked-by: Pali Rohár <pali@kernel.org>

Changes in v4:
- add '(objtree)/' when calling the tool. Suggested by Pali Rohár.
- renamed patch, as more than just the Makefile has changes

Changes in v3:
- moved the tool from scripts/ to tools/. Suggested by Tom Rini
- changed the dependencies to '$(env_h)' and 'tools'.
  Suggested by Tom Rini and Pali Rohár.
- removed the sed rule which replaces \x00 with \x0A as this is already
  done by the tool. Suggested by Pali Rohár.

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                | 10 ++++++----
 tools/.gitignore        |  1 +
 tools/Makefile          |  4 ++++
 tools/printinitialenv.c | 44 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 55 insertions(+), 4 deletions(-)
 create mode 100644 tools/printinitialenv.c

diff --git a/Makefile b/Makefile
index 2d24ac3959f..32e4bef10f5 100644
--- a/Makefile
+++ b/Makefile
@@ -2439,11 +2439,13 @@ 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*$$/d' $@; \
-	sort --field-separator== -k1,1 --stable $@ -o $@
+cmd_genenv = \
+	$(objtree)/tools/printinitialenv | \
+	sed -e '/^\s*$$/d' | \
+	sort --field-separator== -k1,1 --stable -o $@
 
-u-boot-initial-env: u-boot.bin
+u-boot-initial-env: $(env_h) FORCE
+	$(Q)$(MAKE) $(build)=tools $(objtree)/tools/printinitialenv
 	$(call if_changed,genenv)
 
 # Consistency checks
diff --git a/tools/.gitignore b/tools/.gitignore
index d3a93ff294a..28e8ce2a07a 100644
--- a/tools/.gitignore
+++ b/tools/.gitignore
@@ -28,6 +28,7 @@
 /mxsboot
 /ncb
 /prelink-riscv
+/printinitialenv
 /proftool
 /relocate-rela
 /spl_size_limit
diff --git a/tools/Makefile b/tools/Makefile
index 26be0a7ba2e..80bc62befcb 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -275,6 +275,10 @@ clean-dirs := lib common
 
 always := $(hostprogs-y)
 
+# Host tool to dump the currently configured default environment,
+# build it on demand, i.e. not add it to 'always'.
+hostprogs-y += printinitialenv
+
 # Generated LCD/video logo
 LOGO_H = $(objtree)/include/bmp_logo.h
 LOGO_DATA_H = $(objtree)/include/bmp_logo_data.h
diff --git a/tools/printinitialenv.c b/tools/printinitialenv.c
new file mode 100644
index 00000000000..c58b234d679
--- /dev/null
+++ b/tools/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