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Date: Sun, 26 Mar 2023 17:16:24 -0400
From: Rich Felker <dalias@...c.org>
To: ca0 <ca0@...tonmail.ch>
Cc: "musl@...ts.openwall.com" <musl@...ts.openwall.com>
Subject: Re: socketcall syscall on x32 ABI producing incorrect results
On Sun, Mar 26, 2023 at 09:12:41PM +0000, ca0 wrote:
> 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.
>
> Sent with Proton Mail secure email.
Thanks! I think this is fixed upstream already (not in a release) in
commit 2404d9d643763e6eceafa9a1918925d80a84ad44. Let us know if you
think that doesn't solve it.
Rich
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