musl - socketcall syscall on x32 ABI producing incorrect results

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Message-ID: <RVjBr0Pxqg5uJL0_Sh1AEYZ8LsOUXKnYP3JJb11MQWe_PgjBn3jhM7BG5ih11jrtgBFClxHX-7AKBNh2dNaFAOGkuToDv1BfHZvpW-Zs_60=@protonmail.ch>
Date: Sun, 26 Mar 2023 21:12:41 +0000
From: ca0 <ca0@...tonmail.ch>
To: "musl@...ts.openwall.com" <musl@...ts.openwall.com>
Subject: socketcall syscall on x32 ABI producing incorrect results

I am running busybox with musl-1.2.3 on x32 linux with gcc-12.2.0.

The syscall returns bad address in the case of the bind call. I have traced this down to the pointer being 0xf...... in 32bits being sign extended to 32bits in the syscall.

Here is the code:
0xf7f687ec	65		else r = __syscall(sys, a, b, c, d, e, f);
0xf7f687e9 <__alt_socketcall+178>:	48 63 d0           	movslq %eax,%rdx

I can see the address being sign extended as intended by the movslq instruction.

If I change the bind implementation to cast this address I do not see this issue, but other issues arise with the soecket call

ie. in bind 
int bind(int fd, const struct sockaddr *addr, socklen_t len)
{
    long b = ((unsigned long)(addr)  & 0xffffffff);
    freturn socketcall(bind, fd, b, len, 0, 0, 0);
}

Is this a known issue as x32 is marked as experimental.

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