From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/13769 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH] powerpc64: use a type for mcontext_t regs field Date: Tue, 12 Feb 2019 13:21:01 -0500 Message-ID: <20190212182101.GM23599@brightrain.aerifal.cx> References: <20190212153522.2371-1-AWilcox@Wilcox-Tech.com> <20190212161800.GJ23599@brightrain.aerifal.cx> <20190212172338.GL23599@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="109340"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-13785-gllmg-musl=m.gmane.org@lists.openwall.com Tue Feb 12 19:21:18 2019 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.89) (envelope-from ) id 1gtcgF-000SKZ-V3 for gllmg-musl@m.gmane.org; Tue, 12 Feb 2019 19:21:16 +0100 Original-Received: (qmail 20451 invoked by uid 550); 12 Feb 2019 18:21:14 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 20431 invoked from network); 12 Feb 2019 18:21:13 -0000 Content-Disposition: inline In-Reply-To: Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:13769 Archived-At: On Tue, Feb 12, 2019 at 01:17:34PM -0500, David Edelsohn wrote: > On Tue, Feb 12, 2019 at 12:23 PM Rich Felker wrote: > > > > On Tue, Feb 12, 2019 at 12:05:17PM -0500, David Edelsohn wrote: > > > On Tue, Feb 12, 2019 at 11:18 AM Rich Felker wrote: > > > > > > > > On Tue, Feb 12, 2019 at 09:35:22AM -0600, A. Wilcox wrote: > > > > > GCC Go dereferences `regs` for `nip`. Without this change, compilation > > > > > fails with the following message: > > > > > > > > > > .../../../libgo/runtime/go-signal.c: In function ‘getSiginfo’: > > > > > .../../../libgo/runtime/go-signal.c:225:56: warning: dereferencing ‘void *’ pointer > > > > > ret.sigpc = ((ucontext_t*)(context))->uc_mcontext.regs->nip; > > > > > ^~ > > > > > .../../../libgo/runtime/go-signal.c:225:56: error: request for member ‘nip’ in something not a structure or union > > > > > --- > > > > > arch/powerpc64/bits/signal.h | 4 +++- > > > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/arch/powerpc64/bits/signal.h b/arch/powerpc64/bits/signal.h > > > > > index 34693a68..6736c69a 100644 > > > > > --- a/arch/powerpc64/bits/signal.h > > > > > +++ b/arch/powerpc64/bits/signal.h > > > > > @@ -8,6 +8,8 @@ > > > > > > > > > > #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE) > > > > > > > > > > +#include > > > > > + > > > > > > > > This is almost surely not right. You can never use a bits/* header > > > > except from the corresponding public header that includes it. They do > > > > not have multiple-inclusion guards and are not designed to be usable > > > > independently. And including sys/user.h is also almost surely wrong > > > > since it's a problematic header you don't want getting included > > > > (conflicts with linux/*.h stuff). > > > > > > > > > typedef unsigned long greg_t, gregset_t[48]; > > > > > > > > > > typedef struct { > > > > > @@ -29,7 +31,7 @@ typedef struct sigcontext { > > > > > int _pad0; > > > > > unsigned long handler; > > > > > unsigned long oldmask; > > > > > - void *regs; > > > > > + struct pt_regs *regs; > > > > > gregset_t gp_regs; > > > > > fpregset_t fp_regs; > > > > > vrregset_t *v_regs; > > > > > -- > > > > > 2.19.2 > > > > > > > > Do you know if there's a reason Go is trying to use this regs member > > > > rather than gp_regs? I think that's the real issue here. > > > > > > Apparently GCCGo runtime has dependencies on GLibc and has not been > > > ported to Musl Libc. The GCCGo runtime is trying to obtain the PC for > > > a signal. > > > > > > #ifdef __PPC__ > > > #ifdef __linux__ > > > ret.sigpc = ((ucontext_t*)(context))->uc_mcontext.regs->nip; > > > #endif > > > #ifdef _AIX > > > ret.sigpc = ((ucontext_t*)(context))->uc_mcontext.jmp_context.iar; > > > #endif > > > #endif > > > > > > The program counter is not part of gp_regs. > > > > Yes it is, as musl already depends on having access to the program > > counter for thread cancellation. See arch/powerpc64/pthread_arch.h: > > > > // the kernel calls the ip "nip", it's the first saved value after the 32 > > // GPRs. > > #define MC_PC gp_regs[32] > > Apparently Ian Taylor now is aware of this and investigating a > solution -- possibly another ifdef in the above for PPC Musl Libc. This is not a public #define that you could #ifdef on. It's part of musl thread implementation internals and only present in the musl source tree, not anywhere installed. I just showed it to demonstrate that the NIP register (as well as 15 other registers that are just not the 32 numbered GPRs) is part of the gp_regs array. Rich