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Date: Mon, 7 Aug 2023 01:35:12 +0800
From: Zhangjin Wu <falcon@...ylab.org>
To: w@....eu
Cc: falcon@...ylab.org, arnd@...db.de, david.laight@...lab.com,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
thomas@...ch.de
Subject: [PATCH v2] tools/nolibc: fix up size inflate regression
Hi, Willy
> [...]
> before:
>
> // ppc64le
> $ size nolibc-test
> text data bss dec hex filename
> 27916 8 80 28004 6d64 nolibc-test
>
> // mips
> $ size nolibc-test
> text data bss dec hex filename
> 23276 64 64 23404 5b6c nolibc-test
>
> after:
>
> // ppc64le
> $ size nolibc-test
> text data bss dec hex filename
> 27736 8 80 27824 6cb0 nolibc-test
>
> // mips
> $ size nolibc-test
> text data bss dec hex filename
> 23036 64 64 23164 5a7c nolibc-test
>
> Suggested-by: Willy Tarreau <w@....eu>
> Link: https://lore.kernel.org/lkml/20230806095846.GB10627@1wt.eu/
> Link: https://lore.kernel.org/lkml/20230806134348.GA19145@1wt.eu/
> Signed-off-by: Zhangjin Wu <falcon@...ylab.org>
> ---
>
> v2 here is further fix up argument with 'const' in the type and also
> support "void *" argument, v1 is [1].
>
> Tested on many architectures (i386, x86_64, mips, ppc64) and gcc version
> (from gcc 4.8-13.1.0), compiles well without any warning and errors and
> also with smaller size.
>
> [1]: https://lore.kernel.org/lkml/20230806131921.52453-1-falcon@tinylab.org/
>
> ---
> tools/include/nolibc/sys.h | 52 ++++++++++++++++++++++++++++++--------
> 1 file changed, 41 insertions(+), 11 deletions(-)
>
> diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
> index 56f63eb48a1b..9c7448ae19e2 100644
> --- a/tools/include/nolibc/sys.h
> +++ b/tools/include/nolibc/sys.h
> @@ -35,15 +35,45 @@
> * (src/internal/syscall_ret.c) and glibc (sysdeps/unix/sysv/linux/sysdep.h)
> */
>
> -static __inline__ __attribute__((unused, always_inline))
> -long __sysret(unsigned long ret)
> -{
> - if (ret >= (unsigned long)-MAX_ERRNO) {
> - SET_ERRNO(-(long)ret);
> - return -1;
> - }
> - return ret;
> -}
> +/*
> + * Whether 'type' is a signed type or an unsigned type. Supports scalar types,
> + * bool and also pointer types. (from include/linux/compiler.h)
> + */
> +#define __is_signed_type(type) (((type)(-1)) < (type)1)
> +
> +/* __auto_type is used instead of __typeof__ to workaround the build error
> + * 'error: assignment of read-only variable' when the argument has 'const' in
> + * the type, but __auto_type is a new feature from newer version and it only
> + * work with 'const' from gcc 11.0 (__GXX_ABI_VERSION = 1016)
> + * https://gcc.gnu.org/legacy-ml/gcc-patches/2013-11/msg01378.html
> + */
> +
> +#if __GXX_ABI_VERSION < 1016
> +#define __typeofdecl(arg) long
> +#define __typeofconv1(arg) (long)
> +#define __typeofconv2(arg) (long)
> +#else
> +#define __typeofdecl(arg) __auto_type
> +#define __typeofconv1(arg)
> +#define __typeofconv2(arg) (__typeof__(arg))
> +#endif
>
With nolibc-test, we did more tests.
for ppc64le (long better):
// __auto_type
$ size nolibc-test
text data bss dec hex filename
27736 8 80 27824 6cb0 nolibc-test
// long
$ size nolibc-test
text data bss dec hex filename
27612 8 80 27700 6c34 nolibc-test
for ppc64 (long better):
// __auto_type
$ size nolibc-test
text data bss dec hex filename
27136 1880 80 29096 71a8 nolibc-test
// long
$ size nolibc-test
text data bss dec hex filename
27012 1880 80 28972 712c nolibc-test
A further test on x86_64 (__auto_type better):
// __auto_type
$ size nolibc-test
text data bss dec hex filename
22206 8 88 22302 571e nolibc-test
// long
$ size nolibc-test
text data bss dec hex filename
22347 8 88 22443 57ab nolibc-test
And i386 (almost the same):
// __auto_type
$ size nolibc-test
text data bss dec hex filename
19718 4 52 19774 4d3e nolibc-test
// long
$ size nolibc-test
text data bss dec hex filename
19717 4 52 19773 4d3d nolibc-test
arm64 (__auto_type better):
// __auto_type
$ size nolibc-test
text data bss dec hex filename
25764 8 80 25852 64fc nolibc-test
// long
$ size nolibc-test
text data bss dec hex filename
26004 8 80 26092 65ec nolibc-test
arm (the same):
// __auto_type
$ size nolibc-test
text data bss dec hex filename
19595 0 52 19647 4cbf nolibc-test
// long
$ size nolibc-test
text data bss dec hex filename
19595 0 52 19647 4cbf nolibc-test
riscv64 (__auto_type better):
// __auto_type
$ size nolibc-test
text data bss dec hex filename
21814 8 80 21902 558e nolibc-test
// long
$ size nolibc-test
text data bss dec hex filename
21912 8 80 22000 55f0 nolibc-test
s390 (__auto_type better):
// __auto_type
$ size nolibc-test
text data bss dec hex filename
22302 0 80 22382 576e nolibc-test
// long
$ size nolibc-test
text data bss dec hex filename
22438 0 80 22518 57f6 nolibc-test
As a summary, in nolibc-test, for 32-bit architectures, __auto_type has the
same as long, for 64-bit architecture, __auto_type has less size than long,
only ppc64/ppc64le has reverse result.
BR,
Zhangjin
> +#define __sysret(arg) \
> +({ \
> + __typeofdecl(arg) __sysret_arg = __typeofconv1(arg)(arg); \
> + if (__is_signed_type(__typeof__(arg))) { \
> + if (__sysret_arg < 0) { \
> + SET_ERRNO(-(long)__sysret_arg); \
> + __sysret_arg = __typeofconv2(arg)(-1L); \
> + } \
> + } else { \
> + if ((unsigned long)__sysret_arg >= (unsigned long)-MAX_ERRNO) { \
> + SET_ERRNO(-(long)__sysret_arg); \
> + __sysret_arg = __typeofconv2(arg)(-1L); \
> + } \
> + } \
> + (__typeof__(arg))__sysret_arg; \
> +})
>
> /* Functions in this file only describe syscalls. They're declared static so
> * that the compiler usually decides to inline them while still being allowed
> @@ -94,7 +124,7 @@ void *sbrk(intptr_t inc)
> if (ret && sys_brk(ret + inc) == ret + inc)
> return ret + inc;
>
> - return (void *)__sysret(-ENOMEM);
> + return __sysret((void *)-ENOMEM);
> }
>
>
> @@ -682,7 +712,7 @@ void *sys_mmap(void *addr, size_t length, int prot, int flags, int fd,
> static __attribute__((unused))
> void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
> {
> - return (void *)__sysret((unsigned long)sys_mmap(addr, length, prot, flags, fd, offset));
> + return __sysret(sys_mmap(addr, length, prot, flags, fd, offset));
> }
>
> static __attribute__((unused))
> --
> 2.25.1
>
>
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