linux-toradex.git/tools/include/nolibc/sys.h, branch v6.7

tools/nolibc: automatically detect necessity to use pselect6

2023-10-12T19:14:13+00:00

We can automatically detect if pselect6 is needed or not from the kernel
headers. This removes the need to manually specify it.

Signed-off-by: Thomas Weißschuh 
Acked-by: Willy Tarreau 
Link: https://lore.kernel.org/r/20230917-nolibc-syscall-nr-v2-4-03863d509b9a@weissschuh.net

tools/nolibc: don't define new syscall number

2023-10-12T19:14:12+00:00

All symbols created by nolibc are also visible to user code.
Syscall constants are expected to come from the kernel headers and
should not be made up by nolibc.

Refactor the logic to avoid defining syscall numbers.
Also the new code is easier to understand.

Signed-off-by: Thomas Weißschuh 
Acked-by: Willy Tarreau 
Link: https://lore.kernel.org/r/20230917-nolibc-syscall-nr-v2-3-03863d509b9a@weissschuh.net

tools/nolibc: avoid unused parameter warnings for ENOSYS fallbacks

2023-10-12T19:14:10+00:00

The ENOSYS fallback code does not use its functions parameters.
This can lead to compiler warnings about unused parameters.

Explicitly avoid these warnings.

Signed-off-by: Thomas Weißschuh 
Acked-by: Willy Tarreau 
Link: https://lore.kernel.org/r/20230917-nolibc-syscall-nr-v2-2-03863d509b9a@weissschuh.net

tools/nolibc: add stdarg.h header

2023-10-12T19:13:52+00:00

This allows nolic to work with `-nostdinc` avoiding any reliance on
system headers.

The implementation has been lifted from musl libc 1.2.4.
There is already an implementation of stdarg.h in include/linux/stdarg.h
but that is GPL licensed and therefore not suitable for nolibc.

The used compiler builtins have been validated to be at least available
since GCC 4.1.2 and clang 3.0.0.

Signed-off-by: Thomas Weißschuh 
Signed-off-by: Willy Tarreau

tools/nolibc: avoid undesired casts in the __sysret() macro

2023-08-23T03:17:07+00:00

Having __sysret() as an inline function has the unfortunate effect of
adding casts and large constants comparisons after the syscall returns
that significantly inflate some light code that's otherwise syscall-
heavy. Even nolibc-test grew by ~1%.

Let's switch back to a macro for this, and use it only with signed
arguments. Note that it is also possible to design a slightly more
complex macro covering unsigned and pointers but we only have 3 such
syscalls so it is pointless, and these were just addressed not to use
this macro anymore. Now for the argument (the local variable containing
the syscall return value), any negative value is an error, that results
in -1 being returned and errno to be assigned the opposite value.

This may be revisited again in the future if really needed but for now
let's get back to something sane.

Fixes: 428905da6ec4 ("tools/nolibc: sys.h: add a syscall return helper")
Link: https://lore.kernel.org/lkml/20230806095846.GB10627@1wt.eu/
Link: https://lore.kernel.org/lkml/ZNKOJY+g66nkIyvv@1wt.eu/
Cc: Zhangjin Wu 
Cc: David Laight 
Cc: Thomas Weißschuh 
Signed-off-by: Willy Tarreau

tools/nolibc: keep brk(), sbrk(), mmap() away from __sysret()

2023-08-23T03:19:22+00:00

The __sysret() function causes some undesirable casts so we'll revert
it. In order to keep it simple it will now only support integer return
values like in the past, so we must basically revert the changes that
were made to these 3 syscalls which return a pointer so that they
simply rely on their own test and the SET_ERRNO() macro.

Fixes: 4201cfce15fe ("tools/nolibc: clean up sbrk() routine")
Fixes: 924e9539aeaa ("tools/nolibc: clean up mmap() routine")
Fixes: d27447bc2e0a ("tools/nolibc: sys.h: apply __sysret() helper")
Link: https://lore.kernel.org/lkml/20230806095846.GB10627@1wt.eu/
Link: https://lore.kernel.org/lkml/ZNKOJY+g66nkIyvv@1wt.eu/
Cc: Zhangjin Wu 
Cc: David Laight 
Cc: Thomas Weißschuh 
Signed-off-by: Willy Tarreau

tools/nolibc: sys: avoid implicit sign cast

2023-08-23T03:17:07+00:00

getauxval() returns an unsigned long but the overall type of the ternary
operator needs to be signed.

Signed-off-by: Thomas Weißschuh 
Signed-off-by: Willy Tarreau

tools/nolibc: fix return type of getpagesize()

2023-08-23T03:17:07+00:00

It's documented as returning int which is also implemented by glibc and
musl, so adopt that return type.

Signed-off-by: Thomas Weißschuh 
Signed-off-by: Willy Tarreau

tools/nolibc: drop unused variables

2023-08-23T03:17:07+00:00

Nobody needs it, get rid of it.

Signed-off-by: Thomas Weißschuh 
Signed-off-by: Willy Tarreau

tools/nolibc: add pipe() and pipe2() support

2023-08-23T03:17:07+00:00

According to manual page [1], posix spec [2] and source code like
arch/mips/kernel/syscall.c, for historic reasons, the sys_pipe() syscall
on some architectures has an unusual calling convention.  It returns
results in two registers which means there is no need for it to do
verify the validity of a userspace pointer argument.  Historically that
used to be expensive in Linux.  These days the performance advantage is
negligible.

Nolibc doesn't support the unusual calling convention above, luckily
Linux provides a generic sys_pipe2() with an additional flags argument
from 2.6.27. If flags is 0, then pipe2() is the same as pipe(). So here
we use sys_pipe2() to implement the pipe().

pipe2() is also provided to allow users to use flags argument on demand.

[1]: https://man7.org/linux/man-pages/man2/pipe.2.html
[2]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/pipe.html

Suggested-by: Zhangjin Wu 
Link: https://lore.kernel.org/all/20230729100401.GA4577@1wt.eu/
Signed-off-by: Yuan Tan 
Reviewed-by: Thomas Weißschuh 
Signed-off-by: Willy Tarreau