Both constructors and main() may be executed with different function signatures than they are actually using. This is intentional but trips up UBSAN.

Disable the function sanitizer of UBSAN in _start_c().

Signed-off-by: Thomas Weißschuh linux@weissschuh.net --- tools/include/nolibc/crt.h | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h index c4b10103bbec50f1a3a0a4562e34fdbd1b43ce6f..961cfe777c3564e705dfdd581de828b374d05b0b 100644 --- a/tools/include/nolibc/crt.h +++ b/tools/include/nolibc/crt.h @@ -7,6 +7,8 @@ #ifndef _NOLIBC_CRT_H #define _NOLIBC_CRT_H

+#include "compiler.h" + char **environ __attribute__((weak)); const unsigned long *_auxv __attribute__((weak));

@@ -25,6 +27,9 @@ extern void (*const __fini_array_end[])(void) __attribute__((weak));

void _start_c(long *sp); __attribute__((weak,used)) +#if __nolibc_has_feature(undefined_behavior_sanitizer) + __attribute__((no_sanitize("function"))) +#endif void _start_c(long *sp) { long argc;

In twos complement the most negative number can not be negated.

Fixes: b1c21e7d99cd ("tools/nolibc/stdlib: add i64toa() and u64toa()") Fixes: 66c397c4d2e1 ("tools/nolibc/stdlib: replace the ltoa() function with more efficient ones") Signed-off-by: Thomas Weißschuh linux@weissschuh.net --- tools/include/nolibc/stdlib.h | 24 ++++++++---------------- 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h index 86ad378ab1ea220559d5ab1adc4bb9972977ba9e..5e4b97810d49ac1b1bd79d6f779f6a748f188a39 100644 --- a/tools/include/nolibc/stdlib.h +++ b/tools/include/nolibc/stdlib.h @@ -271,16 +271,12 @@ int utoa_r(unsigned long in, char *buffer) static __attribute__((unused)) int itoa_r(long in, char *buffer) { - char *ptr = buffer; - int len = 0; - if (in < 0) { - in = -in; - *(ptr++) = '-'; - len++; + *(buffer++) = '-'; + return 1 + utoa_r(-(unsigned long)in, buffer); } - len += utoa_r(in, ptr); - return len; + + return utoa_r(in, buffer); }

/* for historical compatibility, same as above but returns the pointer to the @@ -407,16 +403,12 @@ int u64toa_r(uint64_t in, char *buffer) static __attribute__((unused)) int i64toa_r(int64_t in, char *buffer) { - char *ptr = buffer; - int len = 0; - if (in < 0) { - in = -in; - *(ptr++) = '-'; - len++; + *(buffer++) = '-'; + return 1 + u64toa_r(-(unsigned long long)in, buffer); } - len += u64toa_r(in, ptr); - return len; + + return u64toa_r(in, buffer); }

/* converts int64_t <in> to a string using the static itoa_buffer and returns

UBSAN detects undefined behaviour at runtime. To avoid introduction of new UB, enable UBSAN for nolibc-test.

By signalling detected errors through traps no runtime dependency is necessary.

Signed-off-by: Thomas Weißschuh linux@weissschuh.net --- tools/testing/selftests/nolibc/Makefile | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile index aa05c1faac20d3054b231090b939d050b0231d40..94f3e8be7a68f63ecd639c4f283b3cd10764ce74 100644 --- a/tools/testing/selftests/nolibc/Makefile +++ b/tools/testing/selftests/nolibc/Makefile @@ -189,9 +189,10 @@ ifeq ($(origin XARCH),command line) CFLAGS_XARCH = $(CFLAGS_$(XARCH)) endif CFLAGS_STACKPROTECTOR ?= $(call cc-option,-mstack-protector-guard=global $(call cc-option,-fstack-protector-all)) +CFLAGS_SANITIZER ?= $(call cc-option,-fsanitize=undefined -fsanitize-trap=all) CFLAGS ?= -Os -fno-ident -fno-asynchronous-unwind-tables -std=c89 -W -Wall -Wextra \ $(call cc-option,-fno-stack-protector) $(call cc-option,-Wmissing-prototypes) \ - $(CFLAGS_XARCH) $(CFLAGS_STACKPROTECTOR) $(CFLAGS_EXTRA) + $(CFLAGS_XARCH) $(CFLAGS_STACKPROTECTOR) $(CFLAGS_SANITIZER) $(CFLAGS_EXTRA) LDFLAGS :=

LIBGCC := -lgcc