From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/12168 Path: news.gmane.org!.POSTED!not-for-mail From: Nicholas Wilson Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH] Wasm support patch 2 (static syscalls) Date: Tue, 28 Nov 2017 16:20:26 +0000 Message-ID: References: <20171128125948.GK15263@port70.net> <20171128140531.GM15263@port70.net> <20171128143549.GN15263@port70.net> <20171128150806.GO15263@port70.net>,<20171128155014.GA1627@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1511886063 22730 195.159.176.226 (28 Nov 2017 16:21:03 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 28 Nov 2017 16:21:03 +0000 (UTC) To: "musl@lists.openwall.com" Original-X-From: musl-return-12184-gllmg-musl=m.gmane.org@lists.openwall.com Tue Nov 28 17:20:56 2017 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 4.84_2) (envelope-from ) id 1eJich-0004SO-Mg for gllmg-musl@m.gmane.org; Tue, 28 Nov 2017 17:20:40 +0100 Original-Received: (qmail 13557 invoked by uid 550); 28 Nov 2017 16:20:42 -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 13537 invoked from network); 28 Nov 2017 16:20:41 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=realvnc.onmicrosoft.com; s=selector1-realvnc-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=Nb1rU1cYZwXuMllfPRMOybx8Gzwv1ScKbJQ7t6n5nh8=; b=SqhROMHa042Uf61AQ115LEh3izVEzTOTjIATt60Q/cKG7Ww2iCeCSLQPKoP1eeFVvWYFywCacPreYwZisecRIcTFvVbWCLG1syzZGyEzQ5XgLjfxwlANhqPWchxfX0GJid+CPU1RYY4OKBXe6w/3VEODZoKtkg5FNckpZxiGAl4= Thread-Topic: [musl] [PATCH] Wasm support patch 2 (static syscalls) Thread-Index: AQHTaEFVgDgYeA7kVEKWz4n1+gEDaKMpwQcAgAACxiWAAA+XgIAABULSgAADNgCAAAJksIAABqAAgAALxgCAAAfY/A== In-Reply-To: <20171128155014.GA1627@brightrain.aerifal.cx> Accept-Language: en-GB, en-US Content-Language: en-GB X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=nicholas.wilson@realvnc.com; 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received-spf: None (protection.outlook.com: realvnc.com does not designate permitted sender hosts) spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM X-MS-Exchange-CrossTenant-Network-Message-Id: 960d947a-33b1-4ea0-16b0-08d5367bef0d X-MS-Exchange-CrossTenant-originalarrivaltime: 28 Nov 2017 16:20:26.1033 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 9ad766d3-c6a5-4458-8c58-244e7c118728 X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR0502MB3887 X-OriginatorOrg: realvnc.com Xref: news.gmane.org gmane.linux.lib.musl.general:12168 Archived-At: Oh dear, confusion between setuid and getuid is embarrassing! You're quite right, we don't really need to make setuid work well, any appl= ications intend to use it for something useful won't be portable to Wasm wi= thout some modification. The (much slimmer) patch that just turns off __syscall_cp for Wasm is attac= hed below. Thanks for the feedback. Nick diff --git a/src/internal/syscall.h b/src/internal/syscall.h index 6d378a81..bef9fae9 100644 --- a/src/internal/syscall.h +++ b/src/internal/syscall.h @@ -34,15 +34,17 @@ long __syscall_ret(unsigned long), __syscall(syscall_ar= g_t, ...), #define __syscall4(n,a,b,c,d) (__syscall)(n,__scc(a),__scc(b),__scc(c),__s= cc(d)) #define __syscall5(n,a,b,c,d,e) (__syscall)(n,__scc(a),__scc(b),__scc(c),_= _scc(d),__scc(e)) #define __syscall6(n,a,b,c,d,e,f) (__syscall)(n,__scc(a),__scc(b),__scc(c)= ,__scc(d),__scc(e),__scc(f)) +#define __syscall7(n,a,b,c,d,e,f,g) (__syscall)(n,__scc(a),__scc(b),__scc(= c),__scc(d),__scc(e),__scc(f),__scc(g)) #else +#define __syscall0(n) __syscall0(n) #define __syscall1(n,a) __syscall1(n,__scc(a)) #define __syscall2(n,a,b) __syscall2(n,__scc(a),__scc(b)) #define __syscall3(n,a,b,c) __syscall3(n,__scc(a),__scc(b),__scc(c)) #define __syscall4(n,a,b,c,d) __syscall4(n,__scc(a),__scc(b),__scc(c),__sc= c(d)) #define __syscall5(n,a,b,c,d,e) __syscall5(n,__scc(a),__scc(b),__scc(c),__= scc(d),__scc(e)) #define __syscall6(n,a,b,c,d,e,f) __syscall6(n,__scc(a),__scc(b),__scc(c),= __scc(d),__scc(e),__scc(f)) +#define __syscall7(n,a,b,c,d,e,f,g) __syscall7(n,__scc(a),__scc(b),__scc(c= ),__scc(d),__scc(e),__scc(f),__scc(g)) #endif -#define __syscall7(n,a,b,c,d,e,f,g) (__syscall)(n,__scc(a),__scc(b),__scc(= c),__scc(d),__scc(e),__scc(f),__scc(g)) #define __SYSCALL_NARGS_X(a,b,c,d,e,f,g,h,n,...) n #define __SYSCALL_NARGS(...) __SYSCALL_NARGS_X(__VA_ARGS__,7,6,5,4,3,2,1,0= ,) @@ -56,6 +58,18 @@ long __syscall_ret(unsigned long), __syscall(syscall_arg= _t, ...), #define socketcall __socketcall #define socketcall_cp __socketcall_cp +#ifdef SYSCALL_STATIC +// For archs that define SYSCALL_STATIC (wasm), we basically just don't al= low +// for pthread_cancel(). I don't expect wasm will ever allow for cancella= ble +// waits so that's OK. +#define __syscall_cp0(n) __syscall0(n) +#define __syscall_cp1(n,a) __syscall1(n,a) +#define __syscall_cp2(n,a,b) __syscall2(n,a,b) +#define __syscall_cp3(n,a,b,c) __syscall3(n,a,b,c) +#define __syscall_cp4(n,a,b,c,d) __syscall4(n,a,b,c,d) +#define __syscall_cp5(n,a,b,c,d,e) __syscall5(n,a,b,c,d,e) +#define __syscall_cp6(n,a,b,c,d,e,f) __syscall6(n,a,b,c,d,e,f) +#else #define __syscall_cp0(n) (__syscall_cp)(n,0,0,0,0,0,0) #define __syscall_cp1(n,a) (__syscall_cp)(n,__scc(a),0,0,0,0,0) #define __syscall_cp2(n,a,b) (__syscall_cp)(n,__scc(a),__scc(b),0,0,0,0) @@ -63,6 +77,7 @@ long __syscall_ret(unsigned long), __syscall(syscall_arg_= t, ...), #define __syscall_cp4(n,a,b,c,d) (__syscall_cp)(n,__scc(a),__scc(b),__scc(= c),__scc(d),0,0) #define __syscall_cp5(n,a,b,c,d,e) (__syscall_cp)(n,__scc(a),__scc(b),__sc= c(c),__scc(d),__scc(e),0) #define __syscall_cp6(n,a,b,c,d,e,f) (__syscall_cp)(n,__scc(a),__scc(b),__= scc(c),__scc(d),__scc(e),__scc(f)) +#endif #define __syscall_cp(...) __SYSCALL_DISP(__syscall_cp,__VA_ARGS__) #define syscall_cp(...) __syscall_ret(__syscall_cp(__VA_ARGS__)) diff --git a/src/thread/pthread_cancel.c b/src/thread/pthread_cancel.c index 3d229223..d14d96ed 100644 --- a/src/thread/pthread_cancel.c +++ b/src/thread/pthread_cancel.c @@ -20,6 +20,7 @@ long __syscall_cp_asm(volatile void *, syscall_arg_t, syscall_arg_t, syscall_arg_t, syscall_arg_t, syscall_arg_t, syscall_arg_t, syscall_arg_t); +#ifndef SYSCALL_STATIC long __syscall_cp_c(syscall_arg_t nr, syscall_arg_t u, syscall_arg_t v, syscall_arg_t w, syscall_arg_t x, syscall_arg_t y, syscall_arg_t z) @@ -38,6 +39,7 @@ long __syscall_cp_c(syscall_arg_t nr, r =3D __cancel(); return r; } +#endif static void _sigaddset(sigset_t *set, int sig) { ________________________________________ From: Rich Felker on behalf of Rich Felker Sent: 28 November 2017 15:50:14 To: musl@lists.openwall.com Subject: Re: [musl] [PATCH] Wasm support patch 2 (static syscalls) On Tue, Nov 28, 2017 at 04:08:06PM +0100, Szabolcs Nagy wrote: > * Nicholas Wilson [2017-11-28 14:53:58 +000= 0]: > > I think LTO would be required - but I might be missing something > > in your scheme? I'm considering the cases like __setxid and > > pthread_cancel, where the compiler can't work out which syscall > > numbers are possible (because the numbers come from another > > translation unit). In these cases, there's no way to eliminate any > > of the branches in your switch statement. > > > > In particular, getuid() is such a common library call that I think > > we do want to be able to support it on Wasm, without having Musl > > link in everything. I mean, it's not an obscure piece of > > functionality, so it's worth a small refactor to make it usable > > with Wasm. > > getuid is not affected, only __setxid and cancellable syscalls are. > > __setxid is not that important and can be worked around in generic code, > but i don't see an easy solution for syscall_cp except that wasm > probably don't need cancellation at all so it can be just defined > to syscall. I don't think calling __setxid even makes sense in wasm code. Do you actually have a multiuser model with a privileged user who can change uid to other users? Cancellation is actually hard to do via an approach like this, since you need some mechanism for determining the point at which the syscall has atomically succeeded versus being blocked with no side effects yet. Implementing it would probably require doing something similar to what midipix does, but for now it can probably just be omitted. Rich