kernel/linux.git/tools/include/nolibc/stdlib.h, branch v7.1-rc5

tools/nolibc: check for overflow in calloc() without divisions

2026-04-06T17:46:52+00:00

On some architectures without native division instructions the division can generate calls into libgcc/compiler-rt. This library might not be available, so its use should be avoided. Use the compiler builtin to check for overflows without needing a division. The builtin has been available since GCC 3 and clang 3.8. Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://patch.msgid.link/20260404-nolibc-asprintf-v2-1-17d2d0df9763@weissschuh.net

tools/nolibc: rename sys_foo() functions to _sys_foo()

2026-03-22T10:03:59+00:00

The sys_foo() naming scheme used by the syscall wrappers may collide with application symbols. Especially as 'sys_' is an obvious naming scheme an application may choose for its own custom systemcall wrappers. Avoid these conflicts by using an leading underscore which moves the names into the implementation's namespace. This naming scheme was chosen over a '__nolibc_' prefix, as these functions are not an implementation detail but a documented interface meant to be used by applications. While this may break some existing users, adapting them should be straightforward. Given that nolibc is most-likely vendored, no unexpected breakage should happen. No in-tree users are affected. These conflicts happen when compiling some of the kernel selftests with nolibc. Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://patch.msgid.link/20260319-nolibc-namespacing-v1-1-33c22eaddb5e@weissschuh.net

tools/nolibc: Optimise and common up the number to ascii functions

2026-03-20T16:45:57+00:00

Implement u[64]to[ah]_r() using a common function that uses multiply by reciprocal to generate the least significant digit first and then reverses the string. On 32bit this is five multiplies (with 64bit product) for each output digit. I think the old utoa_r() always did 36 multiplies and a lot of subtracts - so this is likely faster even for 32bit values. Definitely better for 64bit values (especially small ones). Clearly shifts are faster for base 16, but reversing the output buffer makes a big difference. Sharing the code reduces the footprint (unless gcc decides to constant fold the functions). Definitely helps vfprintf() where the constants get loaded and a single call is done. Also makes it cheap to add octal support to vfprintf for completeness. Signed-off-by: David Laight Link: https://patch.msgid.link/20260223101735.2922-3-david.laight.linux@gmail.com Acked-by: Willy Tarreau [Thomas: skip int128 multiplication on SPARC and clang] Signed-off-by: Thomas Weißschuh

tools/nolibc: add option to disable runtime

2025-10-29T15:29:16+00:00

In principle, it is possible to use nolibc for only some object files in a program. In that case, the startup code in _start and _start_c is not going to be used. Add the NOLIBC_NO_RUNTIME compile time option to disable it entirely and also remove anything that depends on it. Doing this avoids warnings from modpost for UML as the _start_c code references the main function from the .init.text section while it is not inside .init itself. Signed-off-by: Benjamin Berg Signed-off-by: Thomas Weißschuh

tools/nolibc: add abs() and friends

2025-05-21T13:32:05+00:00

This is used in various selftests and will be handy when integrating those with nolibc. Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://lore.kernel.org/r/20250428-nolibc-misc-v2-6-3c043eeab06c@linutronix.de Signed-off-by: Thomas Weißschuh

tools/nolibc: include nolibc.h early from all header files

2025-05-21T13:31:50+00:00

Inclusion of any nolibc header file should also bring all other headers. On the other hand it should also be possible to include any nolibc header files in any order. Currently this is implemented by including the catch-all nolibc.h after the headers own definitions. This is problematic if one nolibc header depends on another one. The first header has to include the other one before defining any symbols. That in turn will include the rest of nolibc while the current header has not defined anything yet. If any other part of nolibc depends on definitions from the current header, errors are encountered. This is already the case today. Effectively nolibc can only be included in the order of nolibc.h. Restructure the way "nolibc.h" is included. Move it to the beginning of the header files and before the include guards. Now any header will behave exactly like "nolibc.h" while the include guards prevent any duplicate definitions. Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://lore.kernel.org/r/20250424-nolibc-header-check-v1-2-011576b6ed6f@linutronix.de

tools/nolibc: move getauxval() to sys/auxv.h

2025-04-19T12:22:22+00:00

This is the location regular userspace expects the definition. Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://lore.kernel.org/r/20250416-nolibc-split-sys-v1-4-a069a3f1d145@linutronix.de Signed-off-by: Thomas Weißschuh

tools/nolibc: fix integer overflow in i{64,}toa_r() and

2025-04-19T12:18:05+00:00

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 Acked-by: Willy Tarreau Link: https://lore.kernel.org/r/20250419-nolibc-ubsan-v2-5-060b8a016917@weissschuh.net

tools/nolibc: add prototypes for non-static functions

2025-02-03T19:57:37+00:00

With -Wmissing-prototypes the compiler will warn about non-static functions which don't have a prototype defined. This warning doesn't make much sense for nolibc itself but for user code it is still useful. To pacify the compiler add prototypes next to the function definitions, similar to how it is handled elsewhere in the kernel. Acked-by: Willy Tarreau Link: https://lore.kernel.org/r/20250123-nolibc-prototype-v1-1-e1afc5c1999a@weissschuh.net Signed-off-by: Thomas Weißschuh

tools/nolibc: implement strtol() and friends

2024-06-29T07:44:55+00:00

The implementation always works on uintmax_t values. This is inefficient when only 32bit are needed. However for all functions this only happens for strtol() on 32bit platforms. Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://lore.kernel.org/r/20240425-nolibc-strtol-v1-2-bfeef7846902@weissschuh.net