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Message-ID: <20250612163408.GF6263@brightrain.aerifal.cx>
Date: Thu, 12 Jun 2025 12:34:08 -0400
From: Rich Felker <dalias@...c.org>
To: enh <enh@...gle.com>
Cc: musl@...ts.openwall.com, Namhyung Kim <namhyung@...nel.org>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: sys/prctl.h differences vs man page
On Thu, Jun 12, 2025 at 12:28:24PM -0400, enh wrote:
> https://man7.org/linux/man-pages/man2/prctl.2.html
OK, apparently this is either a regression since the man-pages 6.8-r0
package I have here on Alpine, or an old version. Guess we should look
at the git history and how that happened...
> On Thu, Jun 12, 2025 at 12:26 PM Rich Felker <dalias@...c.org> wrote:
> >
> > On Thu, Jun 12, 2025 at 10:31:03AM -0400, enh wrote:
> > > yeah, apologies that i don't think i reported this to the list before,
> > > but android also hit various prctl portability issues trying to use
> > > musl as the host libc and added this ahead of the musl <sys/prctl.h>
> > > as our workaround:
> > >
> > > #ifndef _SYS_PRCTL_H
> > > #define _SYS_PRCTL_H
> > >
> > > #ifdef __cplusplus
> > > extern "C" {
> > > #endif
> > >
> > > #include <stdint.h>
> > >
> > > /*
> > > * Get the constants and structs from uapi so that code that
> > > * includes <linux/prctl.h> doesn't conflict with <sys/prctl.h>.
> > > */
> > > #include <linux/prctl.h>
> > >
> > > int prctl (int, ...);
> > >
> > > #ifdef __cplusplus
> > > }
> > > #endif
> > >
> > > #endif
> > >
> > > "we don't duplicate anything that's in a uapi header" is just what
> > > bionic does for everything, all the time, but interestingly
> > > <sys/prctl.h> is a rare header where glibc also doesn't do their usual
> > > copy & paste and just includes <linux/prctl.h> instead. (which is why
> > > this is an issue unique to musl, not one shared with glibc.)
> >
> > musl policy is generally the opposite; we don't include any linux uapi
> > headers and don't expect them to be namespace-safe to include from
> > userspace headers. Many historically haven't been, and aside from
> > namespace violations, they made conflicting definitions with userspace
> > types.
> >
> > glibc is more in the middle on this, usually not including linux uapi
> > headers, but sometimes doing it.
> >
> > I don't see where it's documented that one should include
> > <linux/prctl.h> to use the prctl API. It's not in my copy of the man
> > page.
> >
> > Rich
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