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author | Yuan Tan <tanyuan@tinylab.org> | 2023-08-01 18:39:54 +0300 |
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committer | Willy Tarreau <w@1wt.eu> | 2023-08-23 06:17:07 +0300 |
commit | 3ec38af6eedb1659f4a2b0350f61782952dd50b7 (patch) | |
tree | bcb709f0dde00a49628945d530c4a90eb5316abb | |
parent | e7d0129df681aa23bb6528f44186accc38d655f0 (diff) | |
download | linux-3ec38af6eedb1659f4a2b0350f61782952dd50b7.tar.xz |
tools/nolibc: add pipe() and pipe2() support
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 <falcon@tinylab.org>
Link: https://lore.kernel.org/all/20230729100401.GA4577@1wt.eu/
Signed-off-by: Yuan Tan <tanyuan@tinylab.org>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
-rw-r--r-- | tools/include/nolibc/sys.h | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h index 8bfe7db20b80..56f63eb48a1b 100644 --- a/tools/include/nolibc/sys.h +++ b/tools/include/nolibc/sys.h @@ -753,6 +753,30 @@ int open(const char *path, int flags, ...) /* + * int pipe2(int pipefd[2], int flags); + * int pipe(int pipefd[2]); + */ + +static __attribute__((unused)) +int sys_pipe2(int pipefd[2], int flags) +{ + return my_syscall2(__NR_pipe2, pipefd, flags); +} + +static __attribute__((unused)) +int pipe2(int pipefd[2], int flags) +{ + return __sysret(sys_pipe2(pipefd, flags)); +} + +static __attribute__((unused)) +int pipe(int pipefd[2]) +{ + return pipe2(pipefd, 0); +} + + +/* * int prctl(int option, unsigned long arg2, unsigned long arg3, * unsigned long arg4, unsigned long arg5); */ |