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Message-ID: <CAKwvOdn-riuzXJWTL08J+qbQkYVzCgBG=XGM9G2TSmA_Kg=hWQ@mail.gmail.com> Date: Tue, 29 Mar 2022 16:03:57 -0700 From: Nick Desaulniers <ndesaulniers@...gle.com> To: Masahiro Yamada <masahiroy@...nel.org>, Arnd Bergmann <arnd@...db.de> Cc: Nathan Chancellor <nathan@...nel.org>, netdev@...r.kernel.org, tipc-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, David Howells <dhowells@...hat.com>, Ying Xue <ying.xue@...driver.com>, Jon Maloy <jmaloy@...hat.com>, David Woodhouse <dwmw2@...radead.org>, Greg KH <gregkh@...uxfoundation.org>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH] net, uapi: remove inclusion of arpa/inet.h On Tue, Mar 29, 2022 at 3:09 PM Nick Desaulniers <ndesaulniers@...gle.com> wrote: > > On Tue, Mar 29, 2022 at 2:50 PM Nick Desaulniers > <ndesaulniers@...gle.com> wrote: > > > > On Tue, Mar 29, 2022 at 2:29 PM Nick Desaulniers > > <ndesaulniers@...gle.com> wrote: > > > > > > Testing out CONFIG_UAPI_HEADER_TEST=y with a prebuilt Bionic sysroot > > > from Android's SDK, I encountered an error: > > > > > > HDRTEST usr/include/linux/fsi.h > > > In file included from <built-in>:1: > > > In file included from ./usr/include/linux/tipc_config.h:46: > > > prebuilts/ndk/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/arpa/inet.h:39:1: > > > error: unknown type name 'in_addr_t' > > > in_addr_t inet_addr(const char* __s); > > > ^ > > > > Oh, this might not quite be the correct fix for this particular issue. > > > > Cherry picking this diff back into my Android kernel tree, I now observe: > > HDRTEST usr/include/linux/tipc_config.h > > In file included from <built-in>:1: > > ./usr/include/linux/tipc_config.h:268:4: error: implicit declaration > > of function 'ntohs' [-Werror,-Wimplicit-function-declaration] > > (ntohs(((struct tlv_desc *)tlv)->tlv_len) <= space); > > ^ > > > > Is there more than one byteorder.h? Oh, I see what I did; ntohs is defined in > > linux/byteorder/generic.h > > not > > usr/include/asm/byteorder.h > > Sorry, I saw `byteorder` and mixed up the path with the filename. > > > > So rather than just remove the latter, I should additionally be adding > > the former. Though that then produces > > > > common/include/linux/byteorder/generic.h:146:9: error: implicit > > declaration of function '__cpu_to_le16' > > [-Werror,-Wimplicit-function-declaration] > > *var = cpu_to_le16(le16_to_cpu(*var) + val); > > ^ > > > > Oh? > > Should there be a definition of ntohs (and friends) under > include/uapi/linux/ somewhere, rather than have the kernel header > include/uapi/linux/tipc_config.h depend on the libc header > arpa/inet.h? > > It looks like we already have > include/uapi/linux/byteorder/{big|little}_endian.h to define > __be16_to_cpu and friends, just no definition of ntohs under > include/uapi/linux/. > > Also, it looks like include/uapi/linux/ has definitions for > __constant_ntohs in > include/uapi/linux/byteorder/{big|little}_endian.h. Should those 2 > headers also define ntohs (and friends) unprefixed, i.e. the versions > that don't depend on constant expressions? > > (I wish there was an entry in MAINTAINERS for UAPI questions like this...) I also think that Documentation/kbuild/headers_install.rst should probably include text from https://lore.kernel.org/all/Pine.LNX.4.58.0411281710490.22796@ppc970.osdl.org/ or something along the lines of "kernel headers MUST NOT depend on userspace headers; any instance of that in tree is a bug that should be fixed." For people I just cc'ed, here's the lore link to this thread: https://lore.kernel.org/lkml/20220329212946.2861648-1-ndesaulniers@google.com/ > > > > > > > > > This is because Bionic has a bug in its inclusion chain. I sent a patch > > > to fix that, but looking closer at include/uapi/linux/tipc_config.h, > > > there's a comment that it includes arpa/inet.h for ntohs; but ntohs is > > > already defined in include/linux/byteorder/generic.h which is already > > > included in include/uapi/linux/tipc_config.h. There are no __KERNEL__ > > > guards on include/linux/byteorder/generic.h's definition of ntohs. So > > > besides fixing Bionic, it looks like we can additionally remove this > > > unnecessary header inclusion. > > > > > > Link: https://android-review.googlesource.com/c/platform/bionic/+/2048127 > > > Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com> > > > --- > > > include/uapi/linux/tipc_config.h | 4 ---- > > > 1 file changed, 4 deletions(-) > > > > > > diff --git a/include/uapi/linux/tipc_config.h b/include/uapi/linux/tipc_config.h > > > index 4dfc05651c98..b38374d5f192 100644 > > > --- a/include/uapi/linux/tipc_config.h > > > +++ b/include/uapi/linux/tipc_config.h > > > @@ -43,10 +43,6 @@ > > > #include <linux/tipc.h> > > > #include <asm/byteorder.h> > > > > > > -#ifndef __KERNEL__ > > > -#include <arpa/inet.h> /* for ntohs etc. */ > > > -#endif > > > - > > > /* > > > * Configuration > > > * > > > > > > base-commit: 5efabdadcf4a5b9a37847ecc85ba71cf2eff0fcf > > > prerequisite-patch-id: 0c2abf2af8051f4b37a70ef11b7d2fc2a3ec7181 > > > -- > > > 2.35.1.1021.g381101b075-goog > > > > > > > > > -- > > Thanks, > > ~Nick Desaulniers > > > > -- > Thanks, > ~Nick Desaulniers -- Thanks, ~Nick Desaulniers
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