Date:   Mon, 7 Feb 2022 16:00:28 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Willy Tarreau <w@....eu>
Cc:     Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/42] nolibc: update to resync with out-of-tree project

On Mon, Feb 07, 2022 at 05:23:12PM +0100, Willy Tarreau wrote:
> Hello Paul,
> 
> Here comes an update to the nolibc subsystem to keep it in sync with
> the out-of-tree project and to bring a number of usability improvements.
> 
> The approach here consists in better splitting the layers so that
> arch-specific syscall functions are now in their own files (one per
> arch), then syscalls are implemented on top of this in a generic file,
> then the generic libc stuff is exposed. This way it becomes easier to
> add support for new architectures if needed.
> 
> I exported 3 functions as weak symbols: memset(), memmove() and abort().
> For the first two ones, gcc/clang may issue calls to them and will not
> always fall back to the builtin equivalent. For abort(), I've seen it
> referenced by libgcc from some divide functions.
> 
> A few stdio-level functions were added (unbuffered), including a quite
> limited but usable printf() which significantly eases debugging of test
> programs by allowing to print return codes or pointers for example.
> 
> A few functions and syscalls like abort(), raise(), time() and usleep()
> were added. More str* functions were added as well. open() now takes a
> vararg on the 3rd argument so as to ease porting of existing programs.
> 
> Finally, the functions and definitions were moved to the appropriate
> files as documented in their man pages when relevant, so that simple
> programs which only use a few include files among stdio.h, stdlib.h,
> string.h, unistd.h, errno.h, ctype.h, signal.h, time.h or types.h can
> build without modification. Obviously this remains fairly limited in
> scope, but for test programs that's usually fine.
> 
> I could verify that a few of my programs and that your rcutorture test
> continue to work (not much surprising since most of the work only
> consists in moving functions between files).
> 
> There's obviously no rush, but I preferred to resync the version here
> given that Mark expressed some interest recently, and I'd hate it if
> he had to add new syscalls that already existed out of tree! Comments,
> suggestions and feature requests welcome as usual. If you prefer to
> pull, it's also available here, on top of 5.17-rc3:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/wtarreau/nolibc.git 20220206-nolibc-split-2

I queued these from email to get some time on them.  If an update is
needed (for example, based on discussion with David Laight), please feel
free to send me an update and I can drop the current set in favor of a
new version.

Good stuff, by the way, thank you!!!

Hmmm...  I should make rcutorture able to smoke-test this.  My thought
would be to add some code to rcutorture's init.c that tried out the
system calls.  But I bet that you already have some test code.  ;-)

One approach would be to place the test code in tools/nolibc, and
have rcutorture's init.c either #include that or link to it.

Thoughts?  Especially thoughts about better testing approaches?

							Thanx, Paul

> Thank you!
> Willy
> 
> ---
> Willy Tarreau (42):
>   tools/nolibc: use pselect6 on RISCV
>   tools/nolibc: guard the main file against multiple inclusion
>   tools/nolibc/std: move the standard type definitions to std.h
>   tools/nolibc/types: split syscall-specific definitions into their own files
>   tools/nolibc/arch: split arch-specific code into individual files
>   tools/nolibc/sys: split the syscall definitions into their own file
>   tools/nolibc/stdlib: extract the stdlib-specific functions to their own file
>   tools/nolibc/string: split the string functions into string.h
>   tools/nolibc/ctype: split the is* functions to ctype.h
>   tools/nolibc/ctype: add the missing is* functions
>   tools/nolibc/types: move the FD_* functions to macros in types.h
>   tools/nolibc/types: make FD_SETSIZE configurable
>   tools/nolibc/types: move makedev to types.h and make it a macro
>   tools/nolibc/stdlib: move ltoa() to stdlib.h
>   tools/nolibc/stdlib: replace the ltoa() function with more efficient ones
>   tools/nolibc/stdlib: add i64toa() and u64toa()
>   tools/nolibc/stdlib: add utoh() and u64toh()
>   tools/nolibc/stdio: add a minimal set of stdio functions
>   tools/nolibc/stdio: add stdin/stdout/stderr and fget*/fput* functions
>   tools/nolibc/stdio: add fwrite() to stdio
>   tools/nolibc/stdio: add a minimal [vf]printf() implementation
>   tools/nolibc/types: define EXIT_SUCCESS and EXIT_FAILURE
>   tools/nolibc/stdio: add perror() to report the errno value
>   tools/nolibc/sys: make open() take a vararg on the 3rd argument
>   tools/nolibc/stdlib: avoid a 64-bit shift in u64toh_r()
>   tools/nolibc/stdlib: make raise() use the lower level syscalls only
>   tools/nolibc/sys: make getpgrp(), getpid(), gettid() not set errno
>   tools/nolibc/string: use unidirectional variants for memcpy()
>   tools/nolibc/string: slightly simplify memmove()
>   tools/nolibc/string: add strncpy() and strlcpy()
>   tools/nolibc/string: add tiny versions of strncat() and strlcat()
>   tools/nolibc: move exported functions to their own section
>   tools/nolibc/arch: mark the _start symbol as weak
>   tools/nolibc/types: define PATH_MAX and MAXPATHLEN
>   tools/nolibc/string: export memset() and memmove()
>   tools/nolibc/errno: extract errno.h from sys.h
>   tools/nolibc/unistd: extract msleep(), sleep(), tcsetpgrp() to unistd.h
>   tools/nolibc/unistd: add usleep()
>   tools/nolibc/signal: move raise() to signal.h
>   tools/nolibc/time: create time.h with time()
>   tools/nolibc: also mention how to build by just setting the include path
>   tools/nolibc/stdlib: implement abort()
> 
>  tools/include/nolibc/arch-aarch64.h |  200 +++
>  tools/include/nolibc/arch-arm.h     |  205 +++
>  tools/include/nolibc/arch-i386.h    |  197 +++
>  tools/include/nolibc/arch-mips.h    |  216 +++
>  tools/include/nolibc/arch-riscv.h   |  205 +++
>  tools/include/nolibc/arch-x86_64.h  |  216 +++
>  tools/include/nolibc/arch.h         |   32 +
>  tools/include/nolibc/ctype.h        |   99 ++
>  tools/include/nolibc/errno.h        |   27 +
>  tools/include/nolibc/nolibc.h       | 2540 +--------------------------
>  tools/include/nolibc/signal.h       |   22 +
>  tools/include/nolibc/std.h          |   49 +
>  tools/include/nolibc/stdio.h        |  296 ++++
>  tools/include/nolibc/stdlib.h       |  311 ++++
>  tools/include/nolibc/string.h       |  212 +++
>  tools/include/nolibc/sys.h          | 1168 ++++++++++++
>  tools/include/nolibc/time.h         |   28 +
>  tools/include/nolibc/types.h        |  184 ++
>  tools/include/nolibc/unistd.h       |   54 +
>  19 files changed, 3756 insertions(+), 2505 deletions(-)
>  create mode 100644 tools/include/nolibc/arch-aarch64.h
>  create mode 100644 tools/include/nolibc/arch-arm.h
>  create mode 100644 tools/include/nolibc/arch-i386.h
>  create mode 100644 tools/include/nolibc/arch-mips.h
>  create mode 100644 tools/include/nolibc/arch-riscv.h
>  create mode 100644 tools/include/nolibc/arch-x86_64.h
>  create mode 100644 tools/include/nolibc/arch.h
>  create mode 100644 tools/include/nolibc/ctype.h
>  create mode 100644 tools/include/nolibc/errno.h
>  create mode 100644 tools/include/nolibc/signal.h
>  create mode 100644 tools/include/nolibc/std.h
>  create mode 100644 tools/include/nolibc/stdio.h
>  create mode 100644 tools/include/nolibc/stdlib.h
>  create mode 100644 tools/include/nolibc/string.h
>  create mode 100644 tools/include/nolibc/sys.h
>  create mode 100644 tools/include/nolibc/time.h
>  create mode 100644 tools/include/nolibc/types.h
>  create mode 100644 tools/include/nolibc/unistd.h
> 
> -- 
> 2.35.1
> 

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