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 <benjamin.berg@intel.com>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Use the version of the attribute with underscores to avoid issues if
fallthrough has been defined by another header file already.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
For improved compatibility, print %m as "unknown error" when nolibc is
compiled using NOLIBC_IGNORE_ERRNO.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Using errno is not possible when NOLIBC_IGNORE_ERRNO is set. Use
sys_lseek instead of lseek as that avoids using errno.
Fixes: 665fa8dea9 ("tools/nolibc: add support for directory access")
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
There is no errno variable when NOLIBC_IGNORE_ERRNO is defined. As such,
simply print the message with "unknown error" rather than the integer
value of errno.
Fixes: acab7bcdb1 ("tools/nolibc/stdio: add perror() to report the errno value")
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Since commit fb01ff635e ("tools/nolibc: keep brk(), sbrk(), mmap()
away from __sysret()") the implementation of mmap() does not use the
__sysret() macro anymore.
Remove the outdated comment.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
I recently got occasional build failures at -Os or -Oz that would always
involve waitpid(), where the assembler would complain about this:
init.s: Error: .size expression for waitpid.constprop.0 does not evaluate to a constant
And without -fno-asynchronous-unwind-tables it could also spit such
errors:
init.s:836: Error: CFI instruction used without previous .cfi_startproc
init.s:838: Error: .cfi_endproc without corresponding .cfi_startproc
init.s: Error: open CFI at the end of file; missing .cfi_endproc directive
A trimmed down reproducer is as simple as this:
int main(int argc, char **argv)
{
int ret, status;
if (argc == 0)
ret = waitpid(-1, &status, 0);
else
ret = waitpid(-1, &status, 0);
return status;
}
It produces the following asm code on x86_64:
.text
.section .text.nolibc_memmove_memcpy
.weak memmove
.weak memcpy
memmove:
memcpy:
movq %rdx, %rcx
(...)
retq
.section .text.nolibc_memset
.weak memset
memset:
xchgl %eax, %esi
movq %rdx, %rcx
pushq %rdi
rep stosb
popq %rax
retq
.type waitpid.constprop.0.isra.0, @function
waitpid.constprop.0.isra.0:
subq $8, %rsp
(...)
jmp *.L5(,%rax,8)
.section .rodata
.align 8
.align 4
.L5:
.quad .L10
(...)
.quad .L4
.text
.L10:
(...)
.cfi_def_cfa_offset 8
ret
.cfi_endproc
.LFE273:
.size waitpid.constprop.0.isra.0, .-waitpid.constprop.0.isra.0
It's a bit dense, but here's the explanation: the compiler has emitted a
".text" statement because it knows it's working in the .text section.
Then, our hand-written asm code for the mem* functions forced the section
to .text.something without the compiler knowing about it, so it thinks
the code is still being emitted for .text. As such, without any .section
statement, the waitpid.constprop.0.isra.0 label is in fact placed in the
previously created section, here .text.nolibc_memset.
The waitpid() function involves a switch/case statement that can be
turned to a jump table, which is what the compiler does with the .rodata
section, and after that it restores .text, which is no longer the
previous .text.nolibc_memset section. Then the CFI statements cross a
section, so does the .size calculation, which explains the error.
While a first approach consisting in placing an explicit ".text" at the
end of these functions was verified to work, it's still unreliable as
it depends on what the compiler remembers having emitted previously. A
better approach is to replace the ".section" with ".pushsection", and
place a ".popsection" at the end, so that these code blocks are agnostic
to where they're placed relative to other blocks.
Fixes: 553845eebd ("tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()`")
Fixes: 12108aa8c1 ("tools/nolibc: x86-64: Use `rep stosb` for `memset()`")
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
wstatus is allowed to be NULL. Avoid a segmentation fault in this case.
Fixes: 0c89abf5ab ("tools/nolibc: implement waitpid() in terms of waitid()")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Commit d5094bcb5b ("tools/nolibc: define time_t in terms of
__kernel_old_time_t") made nolibc use the kernel's time type so that
`time_t` matches `timespec::tv_sec` on all ABIs (notably x32).
But since __kernel_old_time_t is fairly new, notably from 2020 in commit
94c467ddb2 ("y2038: add __kernel_old_timespec and __kernel_old_time_t"),
nolibc builds that rely on host headers may fail.
Switch to __kernel_time_t, which is the same as __kernel_old_time_t and
has existed for longer.
Tested in PPC VM of Open Source Lab of Oregon State University
(./tools/testing/selftests/rcutorture/bin/mkinitrd.sh)
Fixes: d5094bcb5b ("tools/nolibc: define time_t in terms of __kernel_old_time_t")
Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
[Thomas: Reformat commit and its message a bit]
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Nolibc assumes that the kernel ABI is using a time values that are as
large as a long integer. For most ABIs this holds true.
But for x32 this is not correct, as it uses 32bit longs but 64bit times.
Also the 'struct stat' implementation of nolibc relies on timespec::tv_sec
and time_t being the same type. While timespec::tv_sec comes from the
kernel and is of type __kernel_old_time_t, time_t is defined within nolibc.
Switch to the __kernel_old_time_t to always get the correct type.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20250712-nolibc-x32-v1-1-6d81cb798710@weissschuh.net
Acked-by: Willy Tarreau <w@1wt.eu>
The compiler does not know that waitid() will only ever return 0 or -1.
If waitid() would return a positive value than waitpid() would return that
same value and *status would not be initialized.
However users calling waitpid() know that the only possible return values
of it are 0 or -1. They therefore might check for errors with
'ret == -1' or 'ret < 0' and use *status otherwise. The compiler will then
warn about the usage of a potentially uninitialized variable.
Example:
$ cat test.c
#include <stdio.h>
#include <unistd.h>
int main(void)
{
int ret, status;
ret = waitpid(0, &status, 0);
if (ret == -1)
return 0;
printf("status %x\n", status);
return 0;
}
$ gcc --version
gcc (GCC) 15.1.1 20250425
$ gcc -Wall -Os -Werror -nostdlib -nostdinc -static -Iusr/include -Itools/include/nolibc/ -o /dev/null test.c
test.c: In function ‘main’:
test.c:12:9: error: ‘status’ may be used uninitialized [-Werror=maybe-uninitialized]
12 | printf("status %x\n", status);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test.c:6:18: note: ‘status’ was declared here
6 | int ret, status;
| ^~~~~~
cc1: all warnings being treated as errors
Avoid the warning by normalizing waitid() errors to '-1' in waitpid().
Fixes: 0c89abf5ab ("tools/nolibc: implement waitpid() in terms of waitid()")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250707-nolibc-waitpid-uninitialized-v1-1-dcd4e70bcd8f@linutronix.de
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
To allow testing of vfork() support in the arm64 basic-gcs test provide an
implementation for nolibc, using the vfork() syscall if one is available
and otherwise clone3(). We implement in terms of clone3() since the order
of the arguments for clone() varies between architectures.
As for fork() SPARC returns the parent PID rather than 0 in the child
for vfork() so needs custom handling.
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250703-arm64-gcs-vfork-exit-v3-2-1e9a9d2ddbbe@kernel.org
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Add support for SuperH/"sh" to nolibc.
Only sh4 is tested for now.
The startup code is special:
__nolibc_entrypoint_epilogue() calls __builtin_unreachable() which emits
a call to abort(). To make this work a function prologue is generated to
set up a GOT pointer which corrupts "sp".
__builtin_unreachable() is necessary for __attribute__((noreturn)).
Also depending on compiler flags (for example -fPIC) even more prologue
is generated.
Work around this by defining a nested function in asm.
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70216
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Acked-by: Rob Landley <rob@landley.net>
Acked-by: D. Jeff Dionne <jeff@coresemi.io>
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://lore.kernel.org/r/20250623-nolibc-sh-v2-3-0f5b4b303025@weissschuh.net
This remained the only exception to the kernel's architectures
organization and it's always a bit cumbersome to deal with. Let's merge
i386 and x86_64 into x86. This will result in a single arch-x86.h file
by default, and we'll no longer need to merge the two manually during
installation. Requesting either i386 or x86_64 will also result in
installing x86.
Acked-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
While nolibc-test does test syscalls, it doesn't test as much the rest
of the macros, and a wrong spelling of FD_SETBITMASK in commit
feaf756587 broke programs using either FD_SET() or FD_CLR() without
being noticed. Let's fix these macros.
Fixes: feaf756587 ("nolibc: fix fd_set type")
Cc: stable@vger.kernel.org # v6.2+
Acked-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
This is used in various selftests and will be handy when integrating
those with nolibc.
Not all configurations support namespaces, so skip the tests where
necessary. Also if the tests are running without privileges.
Enable the namespace configuration for those architectures where it is not
enabled by default.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250428-nolibc-misc-v2-12-3c043eeab06c@linutronix.de
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
