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List: musl
Subject: [musl] [PATCH] use new socket syscalls, fallback to socketcall
From: Rich Felker <dalias () libc ! org>
Date: 2020-08-06 2:18:47
Message-ID: 20200806021844.GK6949 () brightrain ! aerifal ! cx
[Download RAW message or body]
On Tue, Aug 04, 2020 at 03:15:06PM -0400, Rich Felker wrote:
> On Tue, Aug 04, 2020 at 08:56:42PM +0200, Markus Wichmann wrote:
> > On Tue, Aug 04, 2020 at 02:18:45PM -0400, Rich Felker wrote:
> > > Of these, only ppc, ppc64, sh, and possibly s390 (we only support
> > > 64-bit "s390x" and I'm not sure if it ever lacked the broken-down
> > > syscalls) are relevant. The rest are either unsupported by musl
> > > (including pre-EABI arm) or already using SYS_socketcall.
> >
> > According to musl source, all currently supported architectures have
> > __NR_socket (I didn't check the other calls; I just assumed that
> > __NR_socket was a stand-in for all the other ones).
> >
> > Therefore the required change can be performed by changing the
> > __socketcall macro (and __socketcall_cp of course). Something like this,
> > maybe? (If using GCC statement expressions is alright):
> >
> > #ifdef __NR_socketcall
> > #define __socketcall(nm, a, b, c, d, e, f) \
> > ({int r = __syscall(__NR_ ## nm, a, b, c, d, e, f); \
> > if (r == -ENOSYS) \
> > r = __syscall(__NR_socketcall, __SC_ ## nm, \
> > (long[6]){(long)a, (long) b, (long)c, (long)d, (long)e, (long) f});
> > r;})
> > #else
> > #define __socketcall(nm, a, b, c, d, e, f) __syscall(__NR_ ## nm, a, b, c, d, e, f)
> > #endif
>
> This would work, but we don't use statement-expressions in musl. I
> think an alternative with an inline function would be trivial, though:
>
> static inline long __socketcall(int sys, int sock, long a, long b, long c, long d, long e, long f)
> {
> long r = __syscall(sys, a, b, c, d, e, f);
> if (r != -ENOSYS) return r;
> return __syscall(SYS_socketcall, sock, ((long[6]){a, b, c, d, e, f}));
> }
> #define __socketcall(nm, a, b, c, d, e, f) __socketcall(SYS_##nm, __SC_##nm, \
> (long)(a), (long)(b), (long)(c), (long)(d), (long)(e), (long)(f))
>
> However it may (will?) end up including SYS_socketcall fallback code
> even on archs that never need it if SYS_socketcall is defined.
> Probably arch/*/syscall_arch.h should #undef SYS_socketcall if it's
> never needed. I'm not sure if there are any such archs.
>
> I kinda just thought of getting rid of the __socketcall abstraction,
> but indeed it looks like a lot of ugly boilerplate to duplicate across
> ~15 functions, so I think keeping it in src/internal/syscall.h makes
> the most sense.
OK, that roughly works. Special care is needed for SYS_accept since it
doesn't exist on i386, m68k, or s390x and needs to be emulated with
SYS_accept4. microblaze and mips (plain o32) seem to be the only archs
that define SYS_socketcall but don't ever need to use it.
Attached is a patch that seems to work implementing the above idea
with fixups. It's not heavily tested yet.
Rich
["socketcall_fallback.diff" (text/plain)]
diff --git a/arch/i386/syscall_arch.h b/arch/i386/syscall_arch.h
index 69642e57..f92b7aa9 100644
--- a/arch/i386/syscall_arch.h
+++ b/arch/i386/syscall_arch.h
@@ -87,5 +87,3 @@ static inline long __syscall6(long n, long a1, long a2, long a3, \
long a4, long a #define VDSO_CGT32_VER "LINUX_2.6"
#define VDSO_CGT_SYM "__vdso_clock_gettime64"
#define VDSO_CGT_VER "LINUX_2.6"
-
-#define SYSCALL_USE_SOCKETCALL
diff --git a/arch/m68k/syscall_arch.h b/arch/m68k/syscall_arch.h
index af79c306..6a9d0ae8 100644
--- a/arch/m68k/syscall_arch.h
+++ b/arch/m68k/syscall_arch.h
@@ -87,5 +87,4 @@ static inline long __syscall6(long n, long a, long b, long c, long \
d, long e, lo return d0;
}
-#define SYSCALL_USE_SOCKETCALL
#define SYSCALL_IPC_BROKEN_MODE
diff --git a/arch/microblaze/syscall_arch.h b/arch/microblaze/syscall_arch.h
index 169013f8..61d8248e 100644
--- a/arch/microblaze/syscall_arch.h
+++ b/arch/microblaze/syscall_arch.h
@@ -95,3 +95,5 @@ static inline long __syscall6(long n, long a, long b, long c, long \
d, long e, lo }
#define SYSCALL_IPC_BROKEN_MODE
+
+#undef SYS_socketcall
diff --git a/arch/mips/syscall_arch.h b/arch/mips/syscall_arch.h
index 380a94b3..5b7c38de 100644
--- a/arch/mips/syscall_arch.h
+++ b/arch/mips/syscall_arch.h
@@ -149,3 +149,5 @@ static inline long __syscall7(long n, long a, long b, long c, \
long d, long e, lo
#define SO_SNDTIMEO_OLD 0x1005
#define SO_RCVTIMEO_OLD 0x1006
+
+#undef SYS_socketcall
diff --git a/arch/s390x/syscall_arch.h b/arch/s390x/syscall_arch.h
index afb99852..83cc9a27 100644
--- a/arch/s390x/syscall_arch.h
+++ b/arch/s390x/syscall_arch.h
@@ -72,5 +72,3 @@ static inline long __syscall6(long n, long a, long b, long c, long \
d, long e, lo register long r7 __asm__("r7") = f;
__asm_syscall("+r"(r2), "r"(r1), "r"(r3), "r"(r4), "r"(r5), "r"(r6), "r"(r7));
}
-
-#define SYSCALL_USE_SOCKETCALL
diff --git a/src/internal/syscall.h b/src/internal/syscall.h
index 975a0031..bd073c1a 100644
--- a/src/internal/syscall.h
+++ b/src/internal/syscall.h
@@ -2,6 +2,7 @@
#define _INTERNAL_SYSCALL_H
#include <features.h>
+#include <errno.h>
#include <sys/syscall.h>
#include "syscall_arch.h"
@@ -57,15 +58,23 @@ hidden long __syscall_ret(unsigned long),
#define __syscall_cp(...) __SYSCALL_DISP(__syscall_cp,__VA_ARGS__)
#define syscall_cp(...) __syscall_ret(__syscall_cp(__VA_ARGS__))
-#ifndef SYSCALL_USE_SOCKETCALL
-#define __socketcall(nm,a,b,c,d,e,f) __syscall(SYS_##nm, a, b, c, d, e, f)
-#define __socketcall_cp(nm,a,b,c,d,e,f) __syscall_cp(SYS_##nm, a, b, c, d, e, f)
+static inline long __alt_socketcall(int sys, int sock, int cp, long a, long b, long \
c, long d, long e, long f) +{
+ long r;
+ if (cp) r = __syscall_cp(sys, a, b, c, d, e, f);
+ else r = __syscall(sys, a, b, c, d, e, f);
+ if (r != -ENOSYS) return r;
+#ifndef SYS_socketcall
+ return r;
#else
-#define __socketcall(nm,a,b,c,d,e,f) __syscall(SYS_socketcall, __SC_##nm, \
- ((long [6]){ (long)a, (long)b, (long)c, (long)d, (long)e, (long)f }))
-#define __socketcall_cp(nm,a,b,c,d,e,f) __syscall_cp(SYS_socketcall, __SC_##nm, \
- ((long [6]){ (long)a, (long)b, (long)c, (long)d, (long)e, (long)f }))
+ if (cp) return __syscall_cp(SYS_socketcall, sock, ((long[6]){a, b, c, d, e, f}));
+ else return __syscall(SYS_socketcall, sock, ((long[6]){a, b, c, d, e, f}));
#endif
+}
+#define __socketcall(nm, a, b, c, d, e, f) __alt_socketcall(SYS_##nm, __SC_##nm, 0, \
\ + (long)(a), (long)(b), (long)(c), (long)(d), (long)(e), (long)(f))
+#define __socketcall_cp(nm, a, b, c, d, e, f) __alt_socketcall(SYS_##nm, __SC_##nm, \
1, \ + (long)(a), (long)(b), (long)(c), (long)(d), (long)(e), (long)(f))
/* fixup legacy 16-bit junk */
@@ -338,6 +347,10 @@ hidden long __syscall_ret(unsigned long),
#define __SC_recvmmsg 19
#define __SC_sendmmsg 20
+#ifndef SYS_accept
+#define SYS_accept SYS_accept4
+#endif
+
#ifndef SO_RCVTIMEO_OLD
#define SO_RCVTIMEO_OLD 20
#endif
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