From 2177dd375d087012907e389f787b21ac38bb1785 Mon Sep 17 00:00:00 2001 From: David Laight Date: Sun, 8 Mar 2026 11:37:28 +0000 Subject: tools/nolibc: Implement strerror() in terms of strerror_r() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit strerror() can be the only part of a program that has a .data section. This requires 4k in the program file. Add a simple implementation of strerror_r() and use that in strerror() so that the "errno=" string is copied at run-time. Use __builtin_memcpy() because that optimises away the input string and just writes the required constants to the target buffer. Code size change largely depends on whether the inlining decision for strerror() changes. Change the tests to use the normal EXPECT_VFPRINTF() when testing %m. Skip the tests when !is_nolibc. Signed-off-by: David Laight Acked-by: Willy Tarreau Link: https://patch.msgid.link/20260308113742.12649-4-david.laight.linux@gmail.com Signed-off-by: Thomas Weißschuh --- tools/include/nolibc/stdio.h | 22 +++++++++++++++++++--- tools/testing/selftests/nolibc/nolibc-test.c | 20 ++------------------ 2 files changed, 21 insertions(+), 21 deletions(-) (limited to 'tools') diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h index a4df72d9a2d3..b324fc438ea0 100644 --- a/tools/include/nolibc/stdio.h +++ b/tools/include/nolibc/stdio.h @@ -722,14 +722,30 @@ int setvbuf(FILE *stream __attribute__((unused)), return 0; } +static __attribute__((unused)) +int strerror_r(int errnum, char *buf, size_t buflen) +{ + if (buflen < 18) + return ERANGE; + + __builtin_memcpy(buf, "errno=", 6); + i64toa_r(errnum, buf + 6); + return 0; +} + static __attribute__((unused)) const char *strerror(int errno) { - static char buf[18] = "errno="; + static char buf[18]; + char *b = buf; + + /* Force gcc to use 'register offset' to access buf[]. */ + _NOLIBC_OPTIMIZER_HIDE_VAR(b); - i64toa_r(errno, &buf[6]); + /* Use strerror_r() to avoid having the only .data in small programs. */ + strerror_r(errno, b, sizeof(buf)); - return buf; + return b; } #endif /* _NOLIBC_STDIO_H */ diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index 5c3bf96f57bb..d8949aa1dee3 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -1794,23 +1794,6 @@ static int test_scanf(void) return 0; } -int test_strerror(void) -{ - char buf[100]; - ssize_t ret; - - memset(buf, 'A', sizeof(buf)); - - errno = EINVAL; - ret = snprintf(buf, sizeof(buf), "%m"); - if (is_nolibc) { - if (ret < 6 || memcmp(buf, "errno=", 6)) - return 1; - } - - return 0; -} - static int test_printf_error(void) { int fd, ret, saved_errno; @@ -1860,8 +1843,9 @@ static int run_printf(int min, int max) CASE_TEST(string_width); EXPECT_VFPRINTF(1, " 1", "%10s", "1"); break; CASE_TEST(number_width); EXPECT_VFPRINTF(1, " 1", "%10d", 1); break; CASE_TEST(width_trunc); EXPECT_VFPRINTF(1, " 1", "%25d", 1); break; + CASE_TEST(errno); errno = 22; EXPECT_VFPRINTF(is_nolibc, "errno=22", "%m"); break; + CASE_TEST(errno-neg); errno = -22; EXPECT_VFPRINTF(is_nolibc, " errno=-22", "%12m"); break; CASE_TEST(scanf); EXPECT_ZR(1, test_scanf()); break; - CASE_TEST(strerror); EXPECT_ZR(1, test_strerror()); break; CASE_TEST(printf_error); EXPECT_ZR(1, test_printf_error()); break; case __LINE__: return ret; /* must be last */ -- cgit v1.2.3