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McKenney" To: linux-kernel@vger.kernel.org Cc: gwml@vger.gnuweeb.org, kernel-team@meta.com, w@lwt.eu, =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Willy Tarreau Subject: [PATCH nolibc 17/19] tools/nolibc: add support for constructors and destructors Date: Thu, 12 Oct 2023 12:32:31 -0700 Message-Id: <20231012193233.207857-17-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit List-Id: From: Thomas Weißschuh 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 Acked-by: Willy Tarreau Link: https://lore.kernel.org/lkml/20231007-nolibc-constructors-v2-1-ef84693efbc1@weissschuh.net/ --- tools/include/nolibc/crt.h | 23 +++++++++++++++++++- tools/testing/selftests/nolibc/nolibc-test.c | 17 +++++++++++++++ 2 files changed, 39 insertions(+), 1 deletion(-) diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h index a05655b4ce1d..43b551468c2a 100644 --- a/tools/include/nolibc/crt.h +++ b/tools/include/nolibc/crt.h @@ -13,12 +13,23 @@ 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)); + __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"); @@ -55,8 +66,18 @@ 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; func > __fini_array_start;) + (*--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 7e3936c182dc..8da7f15d010e 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 +597,19 @@ int expect_strne(const char *expr, int llen, const char *cmp) #define CASE_TEST(name) \ case __LINE__: llen += printf("%d %s", test, #name); +/* constructors validate that they are executed in definition order */ +__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; @@ -630,6 +646,7 @@ int run_startup(int min, int max) CASE_TEST(environ_HOME); EXPECT_PTRNZ(1, getenv("HOME")); break; 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(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 */ -- 2.40.1