[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-Id: <20231005-nolibc-constructors-v1-1-776d56bbe917@weissschuh.net>
Date: Thu, 05 Oct 2023 18:45:07 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Willy Tarreau <w@....eu>, Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH RFC] tools/nolibc: add support for constructors and
destructors
With the startup code moved to C, implementing support for
constructors and deconstructors is fairly easy to implement.
Examples for code size impact:
text data bss dec hex filename
21837 104 88 22029 560d nolibc-test.before
22135 120 88 22343 5747 nolibc-test.after
21970 104 88 22162 5692 nolibc-test.after-only-crt.h-changes
The sections are defined by [0].
[0] https://refspecs.linuxfoundation.org/elf/gabi4+/ch5.dynamic.html
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
Note:
This is only an RFC as I'm not 100% sure it belong into nolibc.
But at least the code is visible as an example.
Also it is one prerequisite for full ksefltest_harness.h support in
nolibc, should we want that.
---
tools/include/nolibc/crt.h | 23 ++++++++++++++++++++++-
tools/testing/selftests/nolibc/nolibc-test.c | 16 ++++++++++++++++
2 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h
index a5f33fef1672..c1176611d9a9 100644
--- a/tools/include/nolibc/crt.h
+++ b/tools/include/nolibc/crt.h
@@ -13,11 +13,22 @@ const unsigned long *_auxv __attribute__((weak));
static void __stack_chk_init(void);
static void exit(int);
+extern void (*const __preinit_array_start[])(void) __attribute__((weak));
+extern void (*const __preinit_array_end[])(void) __attribute__((weak));
+
+extern void (*const __init_array_start[])(void) __attribute__((weak));
+extern void (*const __init_array_end[])(void) __attribute__((weak));
+
+extern void (*const __fini_array_start[])(void) __attribute__((weak));
+extern void (*const __fini_array_end[])(void) __attribute__((weak));
+
void _start_c(long *sp)
{
long argc;
char **argv;
char **envp;
+ int exitcode;
+ void (* const *func)(void);
const unsigned long *auxv;
/* silence potential warning: conflicting types for 'main' */
int _nolibc_main(int, char **, char **) __asm__ ("main");
@@ -54,8 +65,18 @@ void _start_c(long *sp)
;
_auxv = auxv;
+ for (func = __preinit_array_start; func < __preinit_array_end; func++)
+ (*func)();
+ for (func = __init_array_start; func < __init_array_end; func++)
+ (*func)();
+
/* go to application */
- exit(_nolibc_main(argc, argv, envp));
+ exitcode = _nolibc_main(argc, argv, envp);
+
+ for (func = __fini_array_end - 1; func >= __fini_array_start; func--)
+ (*func)();
+
+ exit(exitcode);
}
#endif /* _NOLIBC_CRT_H */
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index a3ee4496bf0a..f166b425613a 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -57,6 +57,9 @@ static int test_argc;
/* will be used by some test cases as readable file, please don't write it */
static const char *argv0;
+/* will be used by constructor tests */
+static int constructor_test_value;
+
/* definition of a series of tests */
struct test {
const char *name; /* test name */
@@ -594,6 +597,18 @@ int expect_strne(const char *expr, int llen, const char *cmp)
#define CASE_TEST(name) \
case __LINE__: llen += printf("%d %s", test, #name);
+__attribute__((constructor))
+static void constructor1(void)
+{
+ constructor_test_value = 1;
+}
+
+__attribute__((constructor))
+static void constructor2(void)
+{
+ constructor_test_value *= 2;
+}
+
int run_startup(int min, int max)
{
int test;
@@ -631,6 +646,7 @@ int run_startup(int min, int max)
CASE_TEST(auxv_addr); EXPECT_PTRGT(test_auxv != (void *)-1, test_auxv, brk); break;
CASE_TEST(auxv_AT_UID); EXPECT_EQ(1, getauxval(AT_UID), getuid()); break;
CASE_TEST(auxv_AT_PAGESZ); EXPECT_GE(1, getauxval(AT_PAGESZ), 4096); break;
+ CASE_TEST(constructor); EXPECT_EQ(1, constructor_test_value, 2); break;
case __LINE__:
return ret; /* must be last */
/* note: do not set any defaults so as to permit holes above */
---
base-commit: ab663cc32912914258bc8a2fbd0e753f552ee9d8
change-id: 20231005-nolibc-constructors-b2aebffe9b65
Best regards,
--
Thomas Weißschuh <linux@...ssschuh.net>
Powered by blists - more mailing lists