linux-kernel - [PATCH v2] tools/nolibc: completely remove optional environ support

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Message-Id: <20230710-nolibc-environ-v2-1-78b0c465338f@weissschuh.net>
Date:   Mon, 10 Jul 2023 20:01:34 +0200
From:   Thomas Weißschuh <linux@...ssschuh.net>
To:     Willy Tarreau <w@....eu>
Cc:     linux-kernel@...r.kernel.org, Zhangjin Wu <falcon@...ylab.org>,
        Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH v2] tools/nolibc: completely remove optional environ
 support

In commit 52e423f5b93e ("tools/nolibc: export environ as a weak symbol on i386")
and friends the asm startup logic was extended to directly populate the
"environ" array.

This makes it impossible for "environ" to be dropped by the linker.
Therefore also drop the other logic to handle non-present "environ".

Also add a testcase to validate the initialization of environ.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
Changes in v2:
- add testcase to validate initialization and naming of environ as
  suggested by Willy
- Link to v1: https://lore.kernel.org/r/20230710-nolibc-environ-v1-1-173831573af6@weissschuh.net
---
 tools/include/nolibc/stdlib.h                | 12 ++----------
 tools/testing/selftests/nolibc/nolibc-test.c |  7 ++++---
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h
index 902162f80337..bacfd35c5156 100644
--- a/tools/include/nolibc/stdlib.h
+++ b/tools/include/nolibc/stdlib.h
@@ -83,11 +83,10 @@ void free(void *ptr)
  * declared as a char **, and must be terminated by a NULL (it is recommended
  * to set this variable to the "envp" argument of main()). If the requested
  * environment variable exists its value is returned otherwise NULL is
- * returned. getenv() is forcefully inlined so that the reference to "environ"
- * will be dropped if unused, even at -O0.
+ * returned.
  */
 static __attribute__((unused))
-char *_getenv(const char *name, char **environ)
+char *getenv(const char *name)
 {
 	int idx, i;
 
@@ -102,13 +101,6 @@ char *_getenv(const char *name, char **environ)
 	return NULL;
 }
 
-static __inline__ __attribute__((unused,always_inline))
-char *getenv(const char *name)
-{
-	extern char **environ;
-	return _getenv(name, environ);
-}
-
 static __attribute__((unused))
 unsigned long getauxval(unsigned long type)
 {
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index ec0c20df76b2..f357bd815abc 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -44,8 +44,8 @@
 #define SINT_MAX_OF_TYPE(type) (((type)1 << (sizeof(type) * 8 - 2)) - (type)1 + ((type)1 << (sizeof(type) * 8 - 2)))
 #define SINT_MIN_OF_TYPE(type) (-SINT_MAX_OF_TYPE(type) - 1)
 
-/* will be used by nolibc by getenv() */
-char **environ;
+/* will be used to test initialization of environ */
+static char **test_envp;
 
 /* will be used by some test cases as readable file, please don't write it */
 static const char *argv0;
@@ -786,6 +786,7 @@ int run_stdlib(int min, int max)
 		 * test numbers.
 		 */
 		switch (test + __LINE__ + 1) {
+		CASE_TEST(environ);            EXPECT_PTREQ(1, environ, test_envp); break;
 		CASE_TEST(getenv_TERM);        EXPECT_STRNZ(1, getenv("TERM")); break;
 		CASE_TEST(getenv_blah);        EXPECT_STRZR(1, getenv("blah")); break;
 		CASE_TEST(setcmp_blah_blah);   EXPECT_EQ(1, strcmp("blah", "blah"), 0); break;
@@ -1119,7 +1120,7 @@ int main(int argc, char **argv, char **envp)
 	char *test;
 
 	argv0 = argv[0];
-	environ = envp;
+	test_envp = envp;
 
 	/* when called as init, it's possible that no console was opened, for
 	 * example if no /dev file system was provided. We'll check that fd#1

---
base-commit: c9851cc968ac2ed87b83aee0cbec476b07d53a4c
change-id: 20230710-nolibc-environ-79f425ce6354

Best regards,
-- 
Thomas Weißschuh <linux@...ssschuh.net>